Utility of off-axis rebound tonometry in children with glaucoma

Utility of off-axis rebound tonometry in children with glaucoma | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Utility of off-axis rebound tonometry in children with glaucoma Nicola Sabokbar, Leon N. Davies, Nicola S. Logan, Joseph Abbott This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7608247/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose To evaluate the validity and reliability of off-axis rebound tonometry (RBT) measurements in children with glaucoma, and the utility of these off-axis measurements in ocular and systemic conditions. Methods RBT measurements were taken at the optical centre (RBT on ) and 3 mm temporally (RBT off ) from one eye of children with glaucoma who visited the Eye Department of Birmingham Women’s and Children’s Hospital. Goldmann applanation tonometer (GAT) measurements were subsequently obtained. Co-existing factors were analysed including age, sex, ethnicity, type of glaucoma, treatment, general health, nystagmus, strabismus, corneal scars, spectacle prescription (Rx) and best corrected visual acuity (BCVA). Results Thirty-four children aged 4–15 years (mean age 9.2 (SD 3.5) years, 14 female) with glaucoma were evaluated. RBT on measurements (mean 20.0 (SD 9.1) mmHg) overestimated GAT IOP (mean 17.6 (SD 7.1) mmHg) by 2.4 (SD 3.0) mmHg (p = 0.000), with bias increasing above 28 mmHg. To a lesser extent, RBT off overestimated IOP by 1.7 (SD 3.5) mmHg compared to GAT (p < 0.01). In absolute terms, mean RBT off was closer to GAT than the mean RBT on . Notably, RBT on agreed better with GAT in younger children (< 9 years old), while differences were independent of coexisting factors such as sex or ethnicity. Conclusions Rebound tonometry consistently overestimated IOP relative to GAT, particularly at higher pressures, but within clinically acceptable limits. Whilst the bias was more pronounced in older children, underscoring the need for paediatric-specific calibration, peripheral RBT measures were closer to GAT than those taken centrally. Although a useful measure in this population, these findings advocate for caution when interpreting rebound readings, to ensure appropriate glaucoma management in children. paediatric glaucoma intraocular pressure tonometry Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Key Points Temporal off-axis RBT measurements are clinically useful in children with glaucoma, regardless of age, sex, ethnicity, type of glaucoma, treatment, general health, nystagmus, strabismus, corneal scars, spectacle prescription (Rx) and best corrected visual acuity (BCVA). RBT tends to underestimate GAT in children under 9 years old and overestimate in children over 9 years of age. RBT is good alternative to GAT in children with glaucoma, however, when making clinical decisions IOPs should be checked with another tonometer. Introduction Although glaucoma is a rare disease in children, it often occurs in neonates and infants 1 , with an incidence of 1:18,500 births in Europe. Globally, Saudi Arabia has the highest glaucoma incidence, 1:2,500 2 . Increased intraocular pressure (IOP) can cause progressive optic nerve atrophy, which, if left untreated, can lead to irreversible loss of vision and blindness 3 . Thus, IOP reduction is the most important modifiable factor in disease treatment 4 . Goldmann applanation tonometry (GAT; Keeler, Windsor, UK) is the gold standard clinical method for measuring IOP 5 . This involves the use of a topical anaesthetic and contact applanation of the cornea. Additionally, general anaesthesia is often required as GAT is not well tolerated by young children and infants 6 . However, the advent of the iCare rebound tonometer (RBT; Tiolat Oy, Helsinki, Finland) has changed this paradigm 7 . Herein, a lightweight magnetic probe with a plastic tip is propelled towards the cornea by a magnetic force created within a solenoid by a 30 ms current which induces a voltage. Following impact with the cornea, the probe decelerates and rebounds back into the solenoid, modifying the voltage 8 . The rebound speed of the probe determines the voltage, which is analysed using a microprocessor; higher rebound speeds with shorter contact times result in higher IOP readings 9 . This technique is generally well tolerated by young children and neonates without topical anaesthesia and has therefore reduced the need for general anaesthetics in paediatric eye clinics 10 . Although studies in adults have indicated that RBT measurements may overestimate IOP compared with GAT 8 , 11 , 12 , there is a paucity of data regarding the validity and reliability of RBT measurements in children 10 , 13 – 15 . RBT readings should ideally be taken from the geometric centre of the cornea 16 . However, children often avert their gaze during IOP measurements with upward eye movements due to Bell’s phenomenon, leading to off-axis RBT measurements 17 . Limited information is available regarding the validity of these off-axis measurements in children with glaucoma. Although previous studies in adults have indicated that temporal measurements are close in value to the central and GAT measurements 18 , 19 , it remains unclear whether these findings are similar in children with glaucoma. Furthermore, co-existing conditions such as nystagmus and corneal scars can make IOP measurement more challenging 13 . Additionally, little is known regarding the association between these co-existing conditions and off-axis RBT measurements. Therefore, this study aimed to determine whether RBT is an appropriate substitute for GAT in children with glaucoma, whether RBT off measurements are valid compared to RBT on and whether co-existing factors affect these measurements. Methods Intraocular pressure measurements were obtained from patients aged 4–15 years who visited the Eye Department of Birmingham Women’s and Children’s Hospital (BWCH), a specialist centre for paediatric glaucoma. Assents were provided by the children and informed consent was obtained from the parent/guardian prior to measurement. This study was conducted in accordance with the tenets of the Declaration of Helsinki and Good Clinical Practice guidelines. The study protocol was approved by the National Health Service (NHS) North West Liverpool East Research Ethics Committee (16/NW/0237), the Research and Development Department of BWCH, and the Ethics Committee of Aston University. The study was also registered with ISRCTN ( https://doi.org/10.1186/ISRCTN15954407 ). RBT readings were measured first to mitigate the reduction in IOP caused by aqueous displacement by the GAT 11 . Data were randomly collected from one eye. If glaucoma was present in only one eye, that eye was selected 20 . An Oculus UB 3 Universal Trial Frame (OCULUS Optikgeräte GmbH, Münchholzhäuser Str, Germany) with the monocular interpupillary distance set at the geometric corneal centre (RBT on ) or 3 mm temporally (RBT off ) was placed onto the child’s face and adjusted to fit comfortably 16 . RBT off was measured at a point 3 mm temporal to the centre because it was easily accessible. The iCare tonometer probe was aligned with an indicator on the trial frame, and six readings were recorded at each location (Fig. 1 ). All measurements, except those generating the “P top” readout on the iCare, were recorded 13 . The trial frame was then removed, and the child was prepared for GAT. One drop of Minims® Proxymetacaine Hydrochloride 0.5% (Bausch & Lomb U.K Limited) was instilled into the eye under investigation, followed by one drop of sodium fluorescein delivered using BioGlo Fluorescein Strips (Accutome, Inc., PA 19355 USA) wetted with sterile saline (Bausch & Lomb U.K Limited). The corneal integrity was assessed using a slit lamp before the first GAT reading 8 . The GAT digital display was set to 10 mmHg, and a Tonosafe disposable probe (Haag-Streit, Harlow, UK) was placed at the centre of the cornea. In instances where the GAT mire oscillated with the arterial pulse, the middle oscillation was used as the endpoint 21 . Corneal integrity was rechecked after applanation 8 . In most cases (97%), both measurements were performed by the same observer 22 . The following co-existing characteristics of the participants were noted: age, sex, ethnicity, ocular history, glaucoma treatment, strabismus, nystagmus, corneal defects, general health, refractive error (Rx) and best corrected visual acuity (BCVA). Statistical Analysis The number of participants required for the study was calculated using G*Power 3.1.5 software (Franz Faul, Universität Kiel, Germany). A priori power analysis was selected for a two tailed t-test for the difference between two dependent means, with an 80% power, Pearson correlation coefficient of 0.5 for medium effect size, and an alpha level of 5%, which indicated a sample size of 34. Data were analysed using SPSS for Windows (IBM SPSS Statistics, v21) and tested for normality using the Kolmogorov–Smirnov test (K-S test). A probability of < 0.05% was considered statistically significant. Where appropriate, data that were not normally distributed were transformed into log _10 units and retested for normality. As the GAT, RBT on and RBT off values were not normally distributed, the non-parametric Wilcoxon signed-rank test was used to indicate whether there was a useful level of agreement between GAT and RBT on , between RBT off and RBT on or between RBT off and GAT. Fisher’s exact test was used to examine the association between age and (RBT on – GAT). The association between RBT off - RBT on and age, sex, ethnicity, ocular history, glaucoma treatment, nystagmus, strabismus, corneal defects, general health, Rx and BCVA was also examined. Results Thirty-four children with glaucoma aged 4–15 years, with a mean age of 9.2 (SD 3.5) years, of whom 14 were female, were included in the study. Children self-classified their ethnicity as white (n = 21), Asian-British (n = 12), or mixed (n = 1; Gov. uk.2024). The right and left eye was selected in 21 and 13 children, respectively. Comparison between RBT and GAT GAT measurements ranged between 9–38 mmHg and RBT on ranged between 9–48 mmHg. The mean IOP measured by RBT on was 20.0 (SD 9.1) mmHg compared to 17.6 (SD 7.1) mmHg as measured by GAT. A significant positive correlation (r = .67, n = 34, p = 0.01) was observed, with a significant overestimate of 2.4 (SD 3.0) mmHg (Z = -3.741, p = 0.000) with 95% limits of agreement of -3.8–8.28 mmHg, the bias of which increased significantly with higher IOPs above 28 mmHg. The median bias (3.00 mmHg) and the 2.5% (-3.35 mmHg) and 97.5% (7.70 mmHg) quartiles between measures are shown in Fig. 2 . RBT on measurements were within ± 3, ± 2, ± 1 mmHg of GAT in 62%, 41% and 32% of the study population, respectively. Approximately one third (38%) RBT on measurements were > 3mmHg and 15% of them were ≥ 5 mmHg than GAT. Differences between RBT on and GAT varied according to patient age. Fisher’s exact test indicated a significant association between the age groups and status A ( p = 0.02 (Table 1 )). The younger age group (4– 9 years) had more (RBT on - GAT) measurements between − 5–2 mmHg compared with the older age group (10–15 years). RBT on was closer to the GAT in the younger age group. The effects of both GAT and RBT on IOPs increased marginally with age, however, this increase was not dependent on age (Fig. 3.0). Conversely, Fisher’s Exact Test indicated no significant association between age groups and IOP status B ( p = 0.29 (Table 1 ). Table 1 IOP status groups: A B and C represent the IOP range. A was divided into two groups according to the median of the range of RBT on – GAT. B represents the division of RBT on – GAT used by Flemmons et al . 11 . Status C represents RBT off - RBT on differences that are clinically acceptable ( 3 mmHg C RBT off - RBT on < 3 mmHg ≥ 3 mmHg Comparison between RBT and GAT The GAT measurements ranged between 9–38 mmHg, and the RBT off measurements ranged between 9–52 mmHg. The mean IOP measured by RBT off and GAT was 19.3 (SD 9.4) mmHg and 17.6 (SD 7.1) mmHg, respectively. A significant positive correlation (r = 0.66, n = 34, p = 0.01) was observed with a significant overestimate of 1.7 (SD 3.5) mmHg (Z = -2.679, p = 0.007) with 95% limits of agreement of -5.21–8.51 mmHg, the bias of which increased significantly with IOPs > 27 mmHg. The median bias (1.00) and the 2.5% (-4.00 mmHg) and 97.5% (8.4 mmHg) quartiles between measures are shown in Fig. 4 . Comparison between RBT and RBT and the association of coexisting factors RBT off measurements ranged between 9–52 mmHg and RBT on measurements ranged between 9–48 mmHg. The mean IOP measured by RBT off and RBT on was 19.3 (SD 9.4) mmHg and 20.0 (SD 9.1) mmHg, respectively, which represents a positive correlation ( r = 0.112, n = 34, p = 0.01) with an insignificant underestimate of -0.7 (SD 2.7) mmHg (Z = -1.647, p = 0.10) with 95% limits of agreement of -8.56–5.16mmHg, the bias of which only increased slightly with higher IOPs > 35 mmHg. The median bias (-1.00 mmHg) and the 2.5% (-6.00 mmHg) and 97.5% (4.16 mmHg) quartiles between measurements are shown in Fig. 5 . Table 2 Results of the association among coexisting conditions and (RBT off -RBT on ). IOP status C groups (see Table 1 ) represent the IOP limits selected in this study to represent clinically acceptable (< 3 mmHg) and unacceptable (≥ 3 mmHg) differences between RBT off and RBT on . Co-existing condition Association with age group status C Age None, p = 0.725 Sex None, p = 1.000 Ethnicity None, p = 0.46 Glaucoma treatment None, p = 0.40 Corneal defects None, p = 1.000 Strabismus None, p = 0.157 Nystagmus None, p = 1.000 General Health None, p = 1.000 Type of Glaucoma None, p = 0.165 Spectacle Rx None, p = 0.728 BCVA None, p = 0.481 The difference between RBT off and RBT on was within ± 1 mmHg, < 3 mmHg and < 3 mmHg in 41.2%, 62% and 38% measurements, respectively. No statistical difference was observed between this status and age, sex, nystagmus, strabismus, corneal defect, general health, Rx, or BCVA when examining the association between RBT off and RBT on (IOP status C). However, no differences were observed for glaucoma type, ethnicity, and treatment (Table 2 ). Discussion The study demonstrated that rebound tonometry (RBT) is a viable alternative to Goldmann applanation tonometry (GAT) for assessing intraocular pressure in paediatric glaucoma. A novel observation was that RBT measurements obtained 3 mm temporal to the corneal optical centre (i.e., RBT off ) corresponded closely with those recorded at the centre (i.e., RBT on ), with off-axis readings aligning more closely with GAT. Furthermore, RBT off tended to underestimate GAT in children under 9 years and overestimate it in older children. To our knowledge, this is the first study to explore the relationship between RBT off , RBT on and coexisting characteristics, revealing no significant associations, thereby supporting the use of RBT 3 mm temporally irrespective of age, sex, ethnicity, ocular history, glaucoma treatment, strabismus, nystagmus, corneal defects, refractive correction or best-corrected visual acuity. Over the past few years, rebound tonometry has become a popular method for screening children’s IOPs hospital settings. This is consistent with a recent review of IOP measurement in children with glaucoma by Yulia and Tan 23 , who found that RBT has become the preferred method because of its ease of use and non-invasive nature. RBT vs GAT This study found that RBT measurements taken at the geometric centre of the cornea (RBT on ) were significantly higher than those of GAT for IOPs between 8–38 mmHg, with the difference increasing for IOPs > 28 mmHg. RBT on overestimated GAT by an average of 2.4 (SD 3.0) mmHg which compares favourably with previous studies in children and adults 7 , 10 , 13 , 16 , 24 , 25 . Although this is a statistically significant difference, it is not clinically significant because differences of ± 3 mmHg do not generally impact the management of the disease 10 , 13 . In the present study, 62% children had RBT on readings within ± 3 mmHg of GAT, which is consistent with the 63% reported by Flemmons et al. 11 . However, other studies have reported contrasting results. Rosentreter et al. 26 found that RBT overestimated GAT by < 2 mmHg in two thirds of children with glaucoma who underwent measurement under general anaesthetic (EUA). Whereas Esmael et al. 14 found that RBT overestimated the Perkins tonometer by 0.59 (SD 2.59) mmHg. However, in their study several children received an EUA, which could have affected the measurements 27 . More recently, Strzalkowska et al. 15 examined the effects of the EUA on the differences between RBT and Perkins tonometry. They found that IOP decreased with time after anaesthesia initiation, but RBT measurements remained higher than those reported by Perkins. Thus, this is a complex area with a myriad of physiological and pharmacological factors that must be controlled for meaningful studies. Association between difference in RBT vs GAT and patient age The association between age and the difference between RBT on and GAT (IOP status A, Table 1 ) was examined and a significant association between the child’s age group and IOP status A was found ( p = 0.02). RBT on was significantly different from GAT in both age groups. However, the mean difference between RBT on and GAT was smaller in the younger age group (4–9 years), and RBT on underestimated GAT in this group. Conversely, the older age group (10–15 years) had a larger mean difference, wider limits of agreement, higher standard deviations, and tended to overestimate the GAT. This may be because the older group had higher IOPs, in which larger differences between the RBT and GAT may be expected 13 , 28 . Whereas the underestimation of GAT by RBT in the younger age group may be associated with lower IOPs, which is consistent with the findings of Takagi et al. 29 . No association was found between IOP status B (Table 1 ) and age, which is consistent with findings by Flemmons et al., 13 . This association was examined because Flemmons et al. 13 divided IOP status in this way. RBT off vs. RBT on RBT off was not significantly different from RBT on . A good agreement was found between RBT off and RBT on from 9–48 mmHg (Fig. 5 ) for the entire cohort (r 2 = 0.923), which is consistent with previous studies 30 , 31 . Mean RBT off underestimated RBT on by an average of -1.70 (SD 3.5) mmHg with upper (97.5%) and lower quartiles (2.5%) of -6.00 to 4.16mmHg (Fig. 5 ). This is in line with previous adult studies, where RBT taken at the temporal periphery of the cornea was found to be lower than the central RBT 12 , 16 , 31 . However, the previous results varied according to the method in which the RBT device was used (either fixed to a slit lamp or freely held). A smaller insignificant difference (0.37 mmHg was found by Queirós et al. 31 with a freely handheld RBT, whereas a larger significant difference of 3–4 mmHg was found by Muttuvelu et al. 12 with a fixed device. Conversely, Beasley et al. 16 did not find a significant difference between RBT peripheral readings or a 5º tilt and those taken at the centre of the cornea. However, a statistically significant difference was found when the probe was tilted by10º nasally, although this was < 1 mm Hg and was not clinically significant. Yamashita et al., 19 examined nasal, temporal, superior, and inferior peripheral corneal measurements and found that nasal and superior values were significantly higher than the central RBT. Although inferior and temporal RBT measurements were higher than GAT measurements, the difference was not statistically significant. An Ocular Hypertension Treatment Study found that GAT measurements were greater in thicker corneas 32 . Therefore, it was expected that IOP would be higher at the periphery of the cornea owing to the 25% increase in thickness 33 however, the reverse was observed. Previous studies have examined the effect of central corneal thickness (CCT) on RBT, with varying results. Martinez-de-la-Casa et al . 34 found a strong correlation between RBT and CCT. However, Queirós et al . 31 , Chui et al . 18 , and Takenaka et al . 35 did not observe this phenomenon. As mentioned previously, several studies have found that peripheral RBT measurements are lower than central measurements. Takenaka et al . 36 argued that this may be due to the angle of the probe when it hits the peripheral cornea from a straight position because of the curvature of the cornea. The force of the probe was the greatest when it was perpendicular to the cornea. Therefore, the temporal probe exerted less force when it hit the corneal surface because it was not perpendicular to the cornea. Consequently, as the mass of the probe remains unchanged, less force will produce less deceleration as the probe rebounds, which will in turn register as a lower IOP by the RBT device (Fig. 1 ). Additionally, variations in the peripheral corneal area affected by the probe may also be a factor 10 . The difference between RBT off and RBT on was within ± 1 mmHg in 41.2% of measurements, < 3 mmHg in 62% of measurements and ≥ 3 mmHg in 38% of measurements, which is different from those in adult studies. Queirós et al . 31 found that 73.2% of temporal RBT values were within ± 1 mmHg of central RBT, 80% of nasal values were within ± 1 mmHg of central RBT and 82.3% of temporal values were within ± 1 mmHg of nasal RBT. This may be due to a lack of cooperation among children and inconsistent RBT positioning, leading to lower precision and accuracy. Thus, to the best of our knowledge, this is the first study to evaluate suboptimal RBT measurements in children with glaucoma. Based on our results, additional research is required to determine how far out of the cornea toward the limbus can reliable RBT measurements be obtained. RBT off vs. GAT RBT off measurements were compared with the GAT to further investigate their validity. The mean RBT off was significantly higher 1.7 (SD 3.5 mmHg) than that of the GAT. As previously discussed, RBT off was expected to be higher than RBT on because of the increase in corneal thickness towards the periphery of the cornea. However, the reverse was observed, with the mean RBT off readings underestimating the mean RBT on . The reasons for this have been discussed previously. This resulted in an unexpected anomaly, where the mean RBT off was closer to the GAT than the mean RBT on . Yamashita et al., 19 in their study on adults found that temporal RBT was closer to GAT than nasal, inferior, and superior peripheral cornea. Temporal RBT also had the highest correlation coefficient with the GAT. Therefore, further investigation of the relationship between the temporal RBT and GAT in children with glaucoma is warranted. RBT off vs. RBT on and co existing conditions A high frequency of co-existing conditions was observed in the children with glaucoma who participated in this study which is consistent with Flemmons et al . 13 . However, none of the co-existing factors were associated with an increase in the (RBT off – RBT on ) value. Age was important because a wide age range of children with varying levels of cooperation and experience was recruited. General health was also an important factor, because half of the children had health conditions that influenced how well they felt on the day of participation, which may have affected their cooperation. Additionally, the children received different treatments for glaucoma: medical, surgical, or both. The majority (68%) underwent both medical and surgical treatments. Surgical treatments varied from shunt to cataract surgery, and medical treatments include a range of medications. Surgery sometimes results in corneal changes; however, these changes are mostly peripheral. Whereas the various topical medications (e.g., Brimonidine, Travoprost, Brinzolamide and Timolol) used, all of which are associated with keratoepitheliopathy due to tear insufficiency and instability 37 , may have influenced IOP measurement. This study did have limitations, one of which was the relatively small sample size. The research participants were children with a rare disease, which made recruitment within a timely manner challenging. Protocols were designed with previous studies in mind. Masking was not possible. One examiner did most of the measurements, however, in two cases, for clinical reasons, the readings had to be taken by a consultant ophthalmologist. Conclusion RBT on was significantly higher than the GAT, with the difference increasing > 28 mmHg. Approximately two-thirds of RBT on measurements were < 3 mmHg from GAT and were clinically useful. However, one-third were not within this range; therefore, when making clinical decisions, this study recommends measuring IOPs with a second contact applanation tonometer, such as Perkins or GAT, for confirmation. Additionally, the relationship between RBT on and GAT varies with the patient’s age, possibly due to the differences in IOPs between age groups, which may benefit from further investigation. Temporal RBT measurements taken 3 mm from the optical centre of the cornea are clinically useful in children with glaucoma who also have a range of co-existing conditions. RBT off measurements taken 3 mm temporally to RBT on were found to be closer to the GAT than to the RBT on ; this incidental finding may be useful and warrants further investigation. Declarations Conflicts of interest statement The authors confirm that there are no conflicting interests and no external funding or sponsorship. Author Contribution NK , LD, NS wrote the main manuscript. 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Sullivan-Mee M, Pham F. Correspondence of Tono–Pen® intraocular pressure measurements performed at the central cornea and mid-peripheral cornea. Optometry 2004;75:26–32. Queiros A, Gonzalez-Meijome JM, Fernandes P, et al. A comparison of central and peripheral intraocular pressure using rebound tonometry. Ophthalmic Physiol Opt 2007;27:506–511. Brandt JD, Beiser JA, Kass MA, et al. Central corneal thickness in the ocular hypertension treatment study (OHTS). Ophthalmology 2001;108:1779–1788. Martola EL, Baum JL. Central and peripheral corneal thickness: a clinical study. Arch Ophthalmol 1968;79:28–30. Martinez-de-la-Casa JM, Garcia-Feijoo J, Castillo A, et al. Reproducibility and clinical evaluation of rebound tonometry. Invest Ophthalmol Vis Sci 2005;46:4578–4580. Takenaka J, Mochizuki H, Kunihara E, et al. Evaluation of rebound tonometer for measuring intraocular pressure at deviated angle and position. Curr Eye Res 2011;36:422–428. Takenaka J, Mochizuki H, Kunihara E, et al. Intraocular pressure measurement using rebound tonometer for deviated angles and positions in human eyes. Curr Eye Res 2012;37:109–114. Fraunfelder FW. Corneal toxicity from topical ocular and systemic medications. Cornea 2006;25:1133–1138. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7608247","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":518887523,"identity":"afbbc709-7292-4dbf-a6ce-1c2508de7146","order_by":0,"name":"Nicola Sabokbar","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8UlEQVRIiWNgGAWjYDACZiAEAQMGNjYgZQNkkKglDaolgYAmJC2HCWsxZ2d+bMzDUCdvzt6W9uDnnvN55vwH2B58/IFbi2Uzm3EyD8Nhw509x44b9jy7XWw5I4HdcAYeWwwO8zAf5mE4wLjhRnqbBM+B24kbbjCwSfMQ1lJnD9Ii+efAucQN5w+wSf8hoAXoMGag4WnHpHkOHEjccCCBTRqf9w0OsxkbzjE4nAz0S7qxzIFkoN7ENsmeNDxazh9+LPGmos52O3ub2cM3B+yADjt8TOKHDW4tIMDEgxrjjA341YOU4ImEUTAKRsEoGAUMDAD4xFFDzukRwAAAAABJRU5ErkJggg==","orcid":"","institution":"Aston University","correspondingAuthor":true,"prefix":"","firstName":"Nicola","middleName":"","lastName":"Sabokbar","suffix":""},{"id":518887524,"identity":"f3f235e1-c023-4e54-a733-503b3f4f6b32","order_by":1,"name":"Leon N. Davies","email":"","orcid":"","institution":"Aston University","correspondingAuthor":false,"prefix":"","firstName":"Leon","middleName":"N.","lastName":"Davies","suffix":""},{"id":518887525,"identity":"5d8393b8-269b-49d6-a0f3-386ec3d3bfe7","order_by":2,"name":"Nicola S. Logan","email":"","orcid":"","institution":"Aston University","correspondingAuthor":false,"prefix":"","firstName":"Nicola","middleName":"S.","lastName":"Logan","suffix":""},{"id":518887526,"identity":"322240f6-3806-4d26-85ca-762b162faf9c","order_by":3,"name":"Joseph Abbott","email":"","orcid":"","institution":"Birmingham Women’s and Children’s Hospital","correspondingAuthor":false,"prefix":"","firstName":"Joseph","middleName":"","lastName":"Abbott","suffix":""}],"badges":[],"createdAt":"2025-09-13 15:23:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7608247/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7608247/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":92196869,"identity":"76257a83-36ce-4315-bf1d-b8e881eb5d18","added_by":"auto","created_at":"2025-09-25 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15:47:46","extension":"html","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":90056,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7608247/v1/1ba90ae6662375de29640599.html"},{"id":92194556,"identity":"5af06655-6757-4b45-a141-9219317ddf85","added_by":"auto","created_at":"2025-09-25 15:39:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":65058,"visible":true,"origin":"","legend":"\u003cp\u003eProbe alignment schematic demonstrating the angle of corneal touch by the probe central (A) and temporally (B).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7608247/v1/e5c62ab8c1b5b7ec104fd3d9.png"},{"id":92194557,"identity":"c1c96f9d-0949-480a-9357-d4b1f720baf0","added_by":"auto","created_at":"2025-09-25 15:39:45","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":26093,"visible":true,"origin":"","legend":"\u003cp\u003eDifference versus the mean plot demonstrating the comparison of RBT\u003csub\u003eon \u003c/sub\u003eand GAT. The dotted line indicates the median bias (3.00 mmHg), the upper and lower dashed lines indicate the 2.5% (-3.35 mmHg) and 97.5% (7.70 mmHg) quartiles. Linear regression statistics \u003cem\u003ey\u003c/em\u003e = 0.25\u003cem\u003ex\u003c/em\u003e - 2.29; r=0.67, r\u003csup\u003e2\u003c/sup\u003e= 0.44.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7608247/v1/0eba8d1ee1c30c377b663a52.png"},{"id":92196870,"identity":"f6e09551-5e91-48c9-8b98-ccc73b6e25e0","added_by":"auto","created_at":"2025-09-25 16:03:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":193751,"visible":true,"origin":"","legend":"\u003cp\u003eFrequency chart showing the range of difference between RBT\u003csub\u003eon\u003c/sub\u003e and GAT for IOP Status A (see Table 1).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7608247/v1/f4da75571239a8b3504f1485.png"},{"id":92194563,"identity":"08814728-dc40-42bf-93d3-ad28284f1277","added_by":"auto","created_at":"2025-09-25 15:39:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":28058,"visible":true,"origin":"","legend":"\u003cp\u003eDifference versus the mean plot demonstrating the comparison of RBT\u003csub\u003eoff \u003c/sub\u003eand GAT. The dotted line indicates the median bias (1.00 mmHg), the upper and lower dashed lines indicate the 2.5% (-4.00 mmHg) and 97.5% (8.40 mmHg) quartiles. Linear regression statistics \u003cem\u003ey\u003c/em\u003e = 0.28\u003cem\u003ex\u003c/em\u003e – 3.59; r=0.66, r\u003csup\u003e2\u003c/sup\u003e= 0.44.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7608247/v1/c56c55c6a662c116aa175b99.png"},{"id":92194560,"identity":"00c57a29-6225-43ad-b470-3561ba6b279d","added_by":"auto","created_at":"2025-09-25 15:39:45","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":26148,"visible":true,"origin":"","legend":"\u003cp\u003eDifference versus the mean plot demonstrating the comparison of RBT\u003csub\u003eoff \u003c/sub\u003eand RBT\u003csub\u003eon\u003c/sub\u003e. The dotted line indicates the median bias (-1.00 mmHg), the upper and lower dashed lines indicate the 2.5% (-6.00 mmHg) and 97.5% (4.16 mmHg) quartiles. Linear regression statistics \u003cem\u003ey\u003c/em\u003e = 0.03\u003cem\u003ex\u003c/em\u003e - 1.41; r = 0.11; r\u003csup\u003e2\u003c/sup\u003e = 0.013.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7608247/v1/d6daa70ce891298d379d44f5.png"},{"id":102297619,"identity":"16349b28-db9b-4e47-a03b-45b8ccff4030","added_by":"auto","created_at":"2026-02-10 10:28:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":944341,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7608247/v1/a9472a6a-8110-40a4-83ee-73fc1146cb42.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Utility of off-axis rebound tonometry in children with glaucoma","fulltext":[{"header":"Key Points","content":"\u003col\u003e\n \u003cli\u003eTemporal off-axis RBT measurements are clinically useful in children with glaucoma, regardless of\u0026nbsp;age, sex, ethnicity, type of glaucoma, treatment, general health, nystagmus, strabismus, corneal scars, spectacle prescription (Rx) and best corrected visual acuity (BCVA).\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eRBT tends to underestimate GAT in children under 9 years old and overestimate in children over 9 years of age.\u003c/li\u003e\n \u003cli\u003eRBT is good alternative to GAT in children with glaucoma, however, when making clinical decisions IOPs should be checked with another tonometer.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Introduction","content":"\u003cp\u003eAlthough glaucoma is a rare disease in children, it often occurs in neonates and infants\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, with an incidence of 1:18,500 births in Europe. Globally, Saudi Arabia has the highest glaucoma incidence, 1:2,500\u003csup\u003e2\u003c/sup\u003e. Increased intraocular pressure (IOP) can cause progressive optic nerve atrophy, which, if left untreated, can lead to irreversible loss of vision and blindness\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Thus, IOP reduction is the most important modifiable factor in disease treatment\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Goldmann applanation tonometry (GAT; Keeler, Windsor, UK) is the gold standard clinical method for measuring IOP\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. This involves the use of a topical anaesthetic and contact applanation of the cornea. Additionally, general anaesthesia is often required as GAT is not well tolerated by young children and infants\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. However, the advent of the iCare rebound tonometer (RBT; Tiolat Oy, Helsinki, Finland) has changed this paradigm\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Herein, a lightweight magnetic probe with a plastic tip is propelled towards the cornea by a magnetic force created within a solenoid by a 30 ms current which induces a voltage. Following impact with the cornea, the probe decelerates and rebounds back into the solenoid, modifying the voltage\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. The rebound speed of the probe determines the voltage, which is analysed using a microprocessor; higher rebound speeds with shorter contact times result in higher IOP readings\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. This technique is generally well tolerated by young children and neonates without topical anaesthesia and has therefore reduced the need for general anaesthetics in paediatric eye clinics\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Although studies in adults have indicated that RBT measurements may overestimate IOP compared with GAT\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, there is a paucity of data regarding the validity and reliability of RBT measurements in children\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eRBT readings should ideally be taken from the geometric centre of the cornea\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. However, children often avert their gaze during IOP measurements with upward eye movements due to Bell\u0026rsquo;s phenomenon, leading to off-axis RBT measurements\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Limited information is available regarding the validity of these off-axis measurements in children with glaucoma. Although previous studies in adults have indicated that temporal measurements are close in value to the central and GAT measurements\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e, it remains unclear whether these findings are similar in children with glaucoma. Furthermore, co-existing conditions such as nystagmus and corneal scars can make IOP measurement more challenging\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Additionally, little is known regarding the association between these co-existing conditions and off-axis RBT measurements.\u003c/p\u003e\u003cp\u003eTherefore, this study aimed to determine whether RBT is an appropriate substitute for GAT in children with glaucoma, whether RBT\u003csub\u003eoff\u003c/sub\u003e measurements are valid compared to RBT\u003csub\u003eon\u003c/sub\u003e and whether co-existing factors affect these measurements.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eIntraocular pressure measurements were obtained from patients aged 4\u0026ndash;15 years who visited the Eye Department of Birmingham Women\u0026rsquo;s and Children\u0026rsquo;s Hospital (BWCH), a specialist centre for paediatric glaucoma. Assents were provided by the children and informed consent was obtained from the parent/guardian prior to measurement. This study was conducted in accordance with the tenets of the Declaration of Helsinki and Good Clinical Practice guidelines. The study protocol was approved by the National Health Service (NHS) North West Liverpool East Research Ethics Committee (16/NW/0237), the Research and Development Department of BWCH, and the Ethics Committee of Aston University. The study was also registered with ISRCTN (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/ISRCTN15954407\u003c/span\u003e\u003cspan address=\"10.1186/ISRCTN15954407\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eRBT readings were measured first to mitigate the reduction in IOP caused by aqueous displacement by the GAT\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Data were randomly collected from one eye. If glaucoma was present in only one eye, that eye was selected\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAn Oculus UB 3 Universal Trial Frame (OCULUS Optikger\u0026auml;te GmbH, M\u0026uuml;nchholzh\u0026auml;user Str, Germany) with the monocular interpupillary distance set at the geometric corneal centre (RBT\u003csub\u003eon\u003c/sub\u003e) or 3 mm temporally (RBT\u003csub\u003eoff\u003c/sub\u003e) was placed onto the child\u0026rsquo;s face and adjusted to fit comfortably \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. RBT\u003csub\u003eoff\u003c/sub\u003e was measured at a point 3 mm temporal to the centre because it was easily accessible. The iCare tonometer probe was aligned with an indicator on the trial frame, and six readings were recorded at each location (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). All measurements, except those generating the \u0026ldquo;P top\u0026rdquo; readout on the iCare, were recorded\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. The trial frame was then removed, and the child was prepared for GAT. One drop of Minims\u0026reg; Proxymetacaine Hydrochloride 0.5% (Bausch \u0026amp; Lomb U.K Limited) was instilled into the eye under investigation, followed by one drop of sodium fluorescein delivered using BioGlo Fluorescein Strips (Accutome, Inc., PA 19355 USA) wetted with sterile saline (Bausch \u0026amp; Lomb U.K Limited). The corneal integrity was assessed using a slit lamp before the first GAT reading \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe GAT digital display was set to 10 mmHg, and a \u003cem\u003eTonosafe\u003c/em\u003e disposable probe (Haag-Streit, Harlow, UK) was placed at the centre of the cornea. In instances where the GAT mire oscillated with the arterial pulse, the middle oscillation was used as the endpoint\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Corneal integrity was rechecked after applanation\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. In most cases (97%), both measurements were performed by the same observer\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. The following co-existing characteristics of the participants were noted: age, sex, ethnicity, ocular history, glaucoma treatment, strabismus, nystagmus, corneal defects, general health, refractive error (Rx) and best corrected visual acuity (BCVA).\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis\u003c/h2\u003e\u003cp\u003eThe number of participants required for the study was calculated using G*Power 3.1.5 software (Franz Faul, \u003cem\u003eUniversit\u0026auml;t\u003c/em\u003e Kiel, Germany). A priori power analysis was selected for a two tailed t-test for the difference between two dependent means, with an 80% power, Pearson correlation coefficient of 0.5 for medium effect size, and an alpha level of 5%, which indicated a sample size of 34. Data were analysed using SPSS for Windows (IBM SPSS Statistics, v21) and tested for normality using the Kolmogorov\u0026ndash;Smirnov test (K-S test). A probability of \u0026lt;\u0026thinsp;0.05% was considered statistically significant. Where appropriate, data that were not normally distributed were transformed into log _10 units and retested for normality. As the GAT, RBT\u003csub\u003eon\u003c/sub\u003e and RBT\u003csub\u003eoff\u003c/sub\u003e values were not normally distributed, the non-parametric Wilcoxon signed-rank test was used to indicate whether there was a useful level of agreement between GAT and RBT\u003csub\u003eon\u003c/sub\u003e, between RBT\u003csub\u003eoff\u003c/sub\u003e and RBT\u003csub\u003eon\u003c/sub\u003e or between RBT\u003csub\u003eoff and\u003c/sub\u003e GAT. Fisher\u0026rsquo;s exact test was used to examine the association between age and (RBT\u003csub\u003eon\u003c/sub\u003e \u0026ndash; GAT). The association between RBT\u003csub\u003eoff\u003c/sub\u003e - RBT\u003csub\u003eon\u003c/sub\u003e and age, sex, ethnicity, ocular history, glaucoma treatment, nystagmus, strabismus, corneal defects, general health, Rx and BCVA was also examined.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThirty-four children with glaucoma aged 4\u0026ndash;15 years, with a mean age of 9.2 (SD 3.5) years, of whom 14 were female, were included in the study. Children self-classified their ethnicity as white (n\u0026thinsp;=\u0026thinsp;21), Asian-British (n\u0026thinsp;=\u0026thinsp;12), or mixed (n\u0026thinsp;=\u0026thinsp;1; Gov. uk.2024). The right and left eye was selected in 21 and 13 children, respectively.\u003c/p\u003e\n\u003ch3\u003eComparison between RBT and GAT\u003c/h3\u003e\n\u003cp\u003eGAT measurements ranged between 9\u0026ndash;38 mmHg and RBT\u003csub\u003eon\u003c/sub\u003e ranged between 9\u0026ndash;48 mmHg. The mean IOP measured by RBT\u003csub\u003eon\u003c/sub\u003e was 20.0 (SD 9.1) mmHg compared to 17.6 (SD 7.1) mmHg as measured by GAT. A significant positive correlation (r\u0026thinsp;=\u0026thinsp;.67, n\u0026thinsp;=\u0026thinsp;34, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01) was observed, with a significant overestimate of 2.4 (SD 3.0) mmHg (Z = -3.741, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.000) with 95% limits of agreement of -3.8\u0026ndash;8.28 mmHg, the bias of which increased significantly with higher IOPs above 28 mmHg.\u003c/p\u003e\u003cp\u003eThe median bias (3.00 mmHg) and the 2.5% (-3.35 mmHg) and 97.5% (7.70 mmHg) quartiles between measures are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eRBT\u003csub\u003eon\u003c/sub\u003e measurements were within \u0026plusmn;\u0026thinsp;3, \u0026plusmn; 2, \u0026plusmn; 1 mmHg of GAT in 62%, 41% and 32% of the study population, respectively. Approximately one third (38%) RBT\u003csub\u003eon\u003c/sub\u003e measurements were \u0026gt;\u0026thinsp;3mmHg and 15% of them were \u0026ge;\u0026thinsp;5 mmHg than GAT. Differences between RBT\u003csub\u003eon\u003c/sub\u003e and GAT varied according to patient age. Fisher\u0026rsquo;s exact test indicated a significant association between the age groups and status A (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.02 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)). The younger age group (4\u0026ndash; 9 years) had more (RBT\u003csub\u003eon\u003c/sub\u003e - GAT) measurements between \u0026minus;\u0026thinsp;5\u0026ndash;2 mmHg compared with the older age group (10\u0026ndash;15 years). RBT\u003csub\u003eon\u003c/sub\u003e was closer to the GAT in the younger age group. The effects of both GAT and RBT\u003csub\u003eon\u003c/sub\u003e IOPs increased marginally with age, however, this increase was not dependent on age (Fig.\u0026nbsp;3.0). Conversely, Fisher\u0026rsquo;s Exact Test indicated no significant association between age groups and IOP status B (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.29 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eIOP status groups: A B and C represent the IOP range. A was divided into two groups according to the median of the range of RBT\u003csub\u003eon\u003c/sub\u003e \u0026ndash; GAT. B represents the division of RBT\u003csub\u003eon\u003c/sub\u003e \u0026ndash; GAT used by Flemmons \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e11\u003c/sup\u003e. Status C represents RBT\u003csub\u003eoff\u003c/sub\u003e - RBT\u003csub\u003eon\u003c/sub\u003e differences that are clinically acceptable (\u0026lt;\u0026thinsp;3 mmHg) or unacceptable (\u0026ge;\u0026thinsp;3 mmHg)\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIOP status\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGroup 1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup 2\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA: RBT\u003csub\u003eon\u003c/sub\u003e - GAT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-5\u0026ndash;2 mmHg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3\u0026ndash;11 mmHg\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB RBT\u003csub\u003eon\u003c/sub\u003e - GAT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;3 mmHg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;3 mmHg\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC RBT\u003csub\u003eoff\u003c/sub\u003e - RBT\u003csub\u003eon\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;3 mmHg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;3 mmHg\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003eComparison between RBT and GAT\u003c/h3\u003e\n\u003cp\u003eThe GAT measurements ranged between 9\u0026ndash;38 mmHg, and the RBT\u003csub\u003eoff\u003c/sub\u003e measurements ranged between 9\u0026ndash;52 mmHg. The mean IOP measured by RBT\u003csub\u003eoff\u003c/sub\u003e and GAT was 19.3 (SD 9.4) mmHg and 17.6 (SD 7.1) mmHg, respectively. A significant positive correlation (r\u0026thinsp;=\u0026thinsp;0.66, n\u0026thinsp;=\u0026thinsp;34, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01) was observed with a significant overestimate of 1.7 (SD 3.5) mmHg (Z = -2.679, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.007) with 95% limits of agreement of -5.21\u0026ndash;8.51 mmHg, the bias of which increased significantly with IOPs\u0026thinsp;\u0026gt;\u0026thinsp;27 mmHg. The median bias (1.00) and the 2.5% (-4.00 mmHg) and 97.5% (8.4 mmHg) quartiles between measures are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eComparison between RBT and RBT and the association of coexisting factors\u003c/h3\u003e\n\u003cp\u003eRBT\u003csub\u003eoff\u003c/sub\u003e measurements ranged between 9\u0026ndash;52 mmHg and RBT\u003csub\u003eon\u003c/sub\u003e measurements ranged between 9\u0026ndash;48 mmHg. The mean IOP measured by RBT\u003csub\u003eoff\u003c/sub\u003e and RBT\u003csub\u003eon\u003c/sub\u003e was 19.3 (SD 9.4) mmHg and 20.0 (SD 9.1) mmHg, respectively, which represents a positive correlation (\u003cem\u003er\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.112, \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;34, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01) with an insignificant underestimate of -0.7 (SD 2.7) mmHg (Z = -1.647, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.10) with 95% limits of agreement of -8.56\u0026ndash;5.16mmHg, the bias of which only increased slightly with higher IOPs\u0026thinsp;\u0026gt;\u0026thinsp;35 mmHg. The median bias (-1.00 mmHg) and the 2.5% (-6.00 mmHg) and 97.5% (4.16 mmHg) quartiles between measurements are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eResults of the association among coexisting conditions and (RBT\u003csub\u003eoff\u003c/sub\u003e -RBT\u003csub\u003eon\u003c/sub\u003e). IOP status C groups (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) represent the IOP limits selected in this study to represent clinically acceptable (\u0026lt;\u0026thinsp;3 mmHg) and unacceptable (\u0026ge;\u0026thinsp;3 mmHg) differences between RBT\u003csub\u003eoff\u003c/sub\u003e and RBT\u003csub\u003eon\u003c/sub\u003e.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCo-existing condition\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAssociation with age group status C\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.725\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEthnicity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGlaucoma treatment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCorneal defects\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStrabismus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.157\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNystagmus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGeneral Health\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eType of Glaucoma\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.165\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpectacle Rx\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.728\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBCVA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.481\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe difference between RBT\u003csub\u003eoff\u003c/sub\u003e and RBT\u003csub\u003eon\u003c/sub\u003e was within \u0026plusmn;\u0026thinsp;1 mmHg, \u0026lt; 3 mmHg and \u0026lt;\u0026thinsp;3 mmHg in 41.2%, 62% and 38% measurements, respectively. No statistical difference was observed between this status and age, sex, nystagmus, strabismus, corneal defect, general health, Rx, or BCVA when examining the association between RBT\u003csub\u003eoff\u003c/sub\u003e and RBT\u003csub\u003eon\u003c/sub\u003e (IOP status C). However, no differences were observed for glaucoma type, ethnicity, and treatment (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe study demonstrated that rebound tonometry (RBT) is a viable alternative to Goldmann applanation tonometry (GAT) for assessing intraocular pressure in paediatric glaucoma. A novel observation was that RBT measurements obtained 3 mm temporal to the corneal optical centre (i.e., RBT\u003csub\u003eoff\u003c/sub\u003e) corresponded closely with those recorded at the centre (i.e., RBT\u003csub\u003eon\u003c/sub\u003e), with off-axis readings aligning more closely with GAT. Furthermore, RBT\u003csub\u003eoff\u003c/sub\u003e tended to underestimate GAT in children under 9 years and overestimate it in older children. To our knowledge, this is the first study to explore the relationship between RBT\u003csub\u003eoff\u003c/sub\u003e, RBT\u003csub\u003eon\u003c/sub\u003e and coexisting characteristics, revealing no significant associations, thereby supporting the use of RBT 3 mm temporally irrespective of age, sex, ethnicity, ocular history, glaucoma treatment, strabismus, nystagmus, corneal defects, refractive correction or best-corrected visual acuity.\u003c/p\u003e\u003cp\u003eOver the past few years, rebound tonometry has become a popular method for screening children\u0026rsquo;s IOPs hospital settings. This is consistent with a recent review of IOP measurement in children with glaucoma by Yulia and Tan\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, who found that RBT has become the preferred method because of its ease of use and non-invasive nature.\u003c/p\u003e\n\u003ch3\u003eRBT vs GAT\u003c/h3\u003e\n\u003cp\u003eThis study found that RBT measurements taken at the geometric centre of the cornea (RBT\u003csub\u003eon\u003c/sub\u003e) were significantly higher than those of GAT for IOPs between 8\u0026ndash;38 mmHg, with the difference increasing for IOPs\u0026thinsp;\u0026gt;\u0026thinsp;28 mmHg. RBT\u003csub\u003eon\u003c/sub\u003e overestimated GAT by an average of 2.4 (SD 3.0) mmHg which compares favourably with previous studies in children and adults \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Although this is a statistically significant difference, it is not clinically significant because differences of \u0026plusmn;\u0026thinsp;3 mmHg do not generally impact the management of the disease\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. In the present study, 62% children had RBT\u003csub\u003eon\u003c/sub\u003e readings within \u0026plusmn;\u0026thinsp;3 mmHg of GAT, which is consistent with the 63% reported by Flemmons et al.\u003csup\u003e11\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eHowever, other studies have reported contrasting results. Rosentreter et al.\u003csup\u003e26\u003c/sup\u003e found that RBT overestimated GAT by \u0026lt;\u0026thinsp;2 mmHg in two thirds of children with glaucoma who underwent measurement under general anaesthetic (EUA). Whereas Esmael et al.\u003csup\u003e14\u003c/sup\u003e found that RBT overestimated the Perkins tonometer by 0.59 (SD 2.59) mmHg. However, in their study several children received an EUA, which could have affected the measurements\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. More recently, Strzalkowska et al.\u003csup\u003e15\u003c/sup\u003e examined the effects of the EUA on the differences between RBT and Perkins tonometry. They found that IOP decreased with time after anaesthesia initiation, but RBT measurements remained higher than those reported by Perkins. Thus, this is a complex area with a myriad of physiological and pharmacological factors that must be controlled for meaningful studies.\u003c/p\u003e\n\u003ch3\u003eAssociation between difference in RBT vs GAT and patient age\u003c/h3\u003e\n\u003cp\u003eThe association between age and the difference between RBT\u003csub\u003eon\u003c/sub\u003e and GAT (IOP status A, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) was examined and a significant association between the child\u0026rsquo;s age group and IOP status A was found (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.02). RBT\u003csub\u003eon\u003c/sub\u003e was significantly different from GAT in both age groups. However, the mean difference between RBT\u003csub\u003eon\u003c/sub\u003e and GAT was smaller in the younger age group (4\u0026ndash;9 years), and RBT\u003csub\u003eon\u003c/sub\u003e underestimated GAT in this group. Conversely, the older age group (10\u0026ndash;15 years) had a larger mean difference, wider limits of agreement, higher standard deviations, and tended to overestimate the GAT. This may be because the older group had higher IOPs, in which larger differences between the RBT and GAT may be expected\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Whereas the underestimation of GAT by RBT in the younger age group may be associated with lower IOPs, which is consistent with the findings of Takagi et al.\u003csup\u003e29\u003c/sup\u003e. No association was found between IOP status B (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and age, which is consistent with findings by Flemmons et al.,\u003csup\u003e13\u003c/sup\u003e. This association was examined because Flemmons et al.\u003csup\u003e13\u003c/sup\u003e divided IOP status in this way.\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eRBT\u003csub\u003eoff\u003c/sub\u003e vs. RBT\u003csub\u003eon\u003c/sub\u003e\u003c/h2\u003e\u003cp\u003eRBT\u003csub\u003eoff\u003c/sub\u003e was not significantly different from RBT\u003csub\u003eon\u003c/sub\u003e. A good agreement was found between RBT\u003csub\u003eoff\u003c/sub\u003e and RBT\u003csub\u003eon\u003c/sub\u003e from 9\u0026ndash;48 mmHg (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) for the entire cohort (r\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.923), which is consistent with previous studies\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Mean RBT\u003csub\u003eoff\u003c/sub\u003e underestimated RBT\u003csub\u003eon\u003c/sub\u003e by an average of -1.70 (SD 3.5) mmHg with upper (97.5%) and lower quartiles (2.5%) of -6.00 to 4.16mmHg (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). This is in line with previous adult studies, where RBT taken at the temporal periphery of the cornea was found to be lower than the central RBT\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. However, the previous results varied according to the method in which the RBT device was used (either fixed to a slit lamp or freely held). A smaller insignificant difference (0.37 mmHg was found by Queir\u0026oacute;s et al.\u003csup\u003e31\u003c/sup\u003e with a freely handheld RBT, whereas a larger significant difference of 3\u0026ndash;4 mmHg was found by Muttuvelu et al.\u003csup\u003e12\u003c/sup\u003e with a fixed device. Conversely, Beasley et al.\u003csup\u003e16\u003c/sup\u003e did not find a significant difference between RBT peripheral readings or a 5\u0026ordm; tilt and those taken at the centre of the cornea. However, a statistically significant difference was found when the probe was tilted by10\u0026ordm; nasally, although this was \u0026lt;\u0026thinsp;1 mm Hg and was not clinically significant. Yamashita et al.,\u003csup\u003e19\u003c/sup\u003e examined nasal, temporal, superior, and inferior peripheral corneal measurements and found that nasal and superior values were significantly higher than the central RBT. Although inferior and temporal RBT measurements were higher than GAT measurements, the difference was not statistically significant.\u003c/p\u003e\u003cp\u003eAn Ocular Hypertension Treatment Study found that GAT measurements were greater in thicker corneas\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. Therefore, it was expected that IOP would be higher at the periphery of the cornea owing to the 25% increase in thickness\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e however, the reverse was observed. Previous studies have examined the effect of central corneal thickness (CCT) on RBT, with varying results. Martinez-de-la-Casa \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e34\u003c/sup\u003e found a strong correlation between RBT and CCT. However, Queir\u0026oacute;s \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e31\u003c/sup\u003e, Chui \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e18\u003c/sup\u003e, and Takenaka \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e35\u003c/sup\u003e did not observe this phenomenon. As mentioned previously, several studies have found that peripheral RBT measurements are lower than central measurements. Takenaka \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e36\u003c/sup\u003e argued that this may be due to the angle of the probe when it hits the peripheral cornea from a straight position because of the curvature of the cornea. The force of the probe was the greatest when it was perpendicular to the cornea. Therefore, the temporal probe exerted less force when it hit the corneal surface because it was not perpendicular to the cornea. Consequently, as the mass of the probe remains unchanged, less force will produce less deceleration as the probe rebounds, which will in turn register as a lower IOP by the RBT device (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Additionally, variations in the peripheral corneal area affected by the probe may also be a factor\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The difference between RBT\u003csub\u003eoff\u003c/sub\u003e and RBT\u003csub\u003eon\u003c/sub\u003e was within \u0026plusmn;\u0026thinsp;1 mmHg in 41.2% of measurements, \u0026lt; 3 mmHg in 62% of measurements and \u0026ge;\u0026thinsp;3 mmHg in 38% of measurements, which is different from those in adult studies. Queir\u0026oacute;s \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e31\u003c/sup\u003e found that 73.2% of temporal RBT values were within \u0026plusmn;\u0026thinsp;1 mmHg of central RBT, 80% of nasal values were within \u0026plusmn;\u0026thinsp;1 mmHg of central RBT and 82.3% of temporal values were within \u0026plusmn;\u0026thinsp;1 mmHg of nasal RBT. This may be due to a lack of cooperation among children and inconsistent RBT positioning, leading to lower precision and accuracy. Thus, to the best of our knowledge, this is the first study to evaluate suboptimal RBT measurements in children with glaucoma. Based on our results, additional research is required to determine how far out of the cornea toward the limbus can reliable RBT measurements be obtained.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eRBT\u003csub\u003eoff\u003c/sub\u003e vs. GAT\u003c/h2\u003e\u003cp\u003eRBT\u003csub\u003eoff\u003c/sub\u003e measurements were compared with the GAT to further investigate their validity. The mean RBT\u003csub\u003eoff\u003c/sub\u003e was significantly higher 1.7 (SD 3.5 mmHg) than that of the GAT. As previously discussed, RBT\u003csub\u003eoff\u003c/sub\u003e was expected to be higher than RBT\u003csub\u003eon\u003c/sub\u003e because of the increase in corneal thickness towards the periphery of the cornea. However, the reverse was observed, with the mean RBT\u003csub\u003eoff\u003c/sub\u003e readings underestimating the mean RBT\u003csub\u003eon\u003c/sub\u003e. The reasons for this have been discussed previously. This resulted in an unexpected anomaly, where the mean RBT\u003csub\u003eoff\u003c/sub\u003e was closer to the GAT than the mean RBT\u003csub\u003eon\u003c/sub\u003e. Yamashita et al.,\u003csup\u003e19\u003c/sup\u003ein their study on adults found that temporal RBT was closer to GAT than nasal, inferior, and superior peripheral cornea. Temporal RBT also had the highest correlation coefficient with the GAT. Therefore, further investigation of the relationship between the temporal RBT and GAT in children with glaucoma is warranted.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eRBT\u003csub\u003eoff\u003c/sub\u003e vs. RBT\u003csub\u003eon\u003c/sub\u003e and co existing conditions\u003c/h2\u003e\u003cp\u003eA high frequency of co-existing conditions was observed in the children with glaucoma who participated in this study which is consistent with Flemmons \u003cem\u003eet al\u003c/em\u003e.\u003csup\u003e13\u003c/sup\u003e. However, none of the co-existing factors were associated with an increase in the (RBT\u003csub\u003eoff\u003c/sub\u003e \u0026ndash; RBT\u003csub\u003eon\u003c/sub\u003e) value. Age was important because a wide age range of children with varying levels of cooperation and experience was recruited. General health was also an important factor, because half of the children had health conditions that influenced how well they felt on the day of participation, which may have affected their cooperation. Additionally, the children received different treatments for glaucoma: medical, surgical, or both. The majority (68%) underwent both medical and surgical treatments. Surgical treatments varied from shunt to cataract surgery, and medical treatments include a range of medications. Surgery sometimes results in corneal changes; however, these changes are mostly peripheral. Whereas the various topical medications (e.g., Brimonidine, Travoprost, Brinzolamide and Timolol) used, all of which are associated with keratoepitheliopathy due to tear insufficiency and instability\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e, may have influenced IOP measurement.\u003c/p\u003e\u003cp\u003eThis study did have limitations, one of which was the relatively small sample size. The research participants were children with a rare disease, which made recruitment within a timely manner challenging. Protocols were designed with previous studies in mind. Masking was not possible. One examiner did most of the measurements, however, in two cases, for clinical reasons, the readings had to be taken by a consultant ophthalmologist.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eRBT\u003csub\u003eon\u003c/sub\u003e was significantly higher than the GAT, with the difference increasing\u0026thinsp;\u0026gt;\u0026thinsp;28 mmHg. Approximately two-thirds of RBT\u003csub\u003eon\u003c/sub\u003e measurements were \u0026lt;\u0026thinsp;3 mmHg from GAT and were clinically useful. However, one-third were not within this range; therefore, when making clinical decisions, this study recommends measuring IOPs with a second contact applanation tonometer, such as Perkins or GAT, for confirmation. Additionally, the relationship between RBT\u003csub\u003eon\u003c/sub\u003e and GAT varies with the patient\u0026rsquo;s age, possibly due to the differences in IOPs between age groups, which may benefit from further investigation. Temporal RBT measurements taken 3 mm from the optical centre of the cornea are clinically useful in children with glaucoma who also have a range of co-existing conditions. RBT\u003csub\u003eoff\u003c/sub\u003e measurements taken 3 mm temporally to RBT\u003csub\u003eon\u003c/sub\u003e were found to be closer to the GAT than to the RBT\u003csub\u003eon\u003c/sub\u003e; this incidental finding may be useful and warrants further investigation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflicts of interest statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors confirm that there are no conflicting interests and no external funding or sponsorship.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eNK , LD, NS wrote the main manuscript. JA commented.All authors reviewed the manuscript\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data that support the findings of this study are available from the authors upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBadawi AH, Al-Muhaylib AA, Al Owaifeer AM, et al. Primary congenital glaucoma: An updated review. Saudi J Ophthalmol 2019;33:382\u0026ndash;388.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAziz A, Fakhoury O, Matonti F, et al. Epidemiology and clinical characteristics of primary congenital glaucoma. J Fr Ophtalmol 2015;38:960\u0026ndash;966.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTham YC, Li X, Wong TY, et al. Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. Ophthalmology 2014;121:2081\u0026ndash;2090.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWeinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma: a review. JAMA 2014;311:1901\u0026ndash;1911.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMunkwitz S, Elkarmouty A, Hoffmann EM, et al. Comparison of the iCare rebound tonometer and the Goldmann applanation tonometer over a wide IOP range. Graefe's Arch Clin Exp Ophthalmol 2008;246:875\u0026ndash;879.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFayed, M.A. and Chen, T.C. Pediatric intraocular pressure measurements: tonometers, central corneal thickness, and anesthesia. Survey of Ophthalmology 2019;64:810\u0026ndash;825.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGrigorian F, Grigorian AP, Li A, et al. Comparison of the Icare rebound tonometry with the Goldmann applanation tonometry in a pediatric population. J AAPOS 2015;19:572\u0026ndash;574.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDavies LN, Bartlett H, Mallen EA, et al. Clinical evaluation of rebound tonometer. Acta Ophthalmol Scand 2006;84:206\u0026ndash;209.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKontiola, AI. A new induction-based impact method for measuring intraocular pressure. Acta Ophthalmol Scand 2000;78:142\u0026ndash;145.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDahlmann-Noor AH, Puertas R, Tabasa-Lim S, et al. Comparison of handheld rebound tonometry with Goldmann applanation tonometry in children with glaucoma: a cohort study. BMJ Open 2013;3:e001788.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFernandes P, D\u0026iacute;az-Rey JA, Queiros A, et al. Comparison of the ICare\u0026reg; rebound tonometer with the Goldmann tonometer in a normal population. Ophthalmic Physiol Opt 2005;25:436\u0026ndash;440.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMuttuvelu DV, Baggesen K, Ehlers N. Precision and accuracy of the ICare tonometer\u0026ndash;peripheral and central IOP measurements by rebound tonometry. Acta Ophthalmol 2012;90:322\u0026ndash;326.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFlemmons MS, Hsiao YC, Dzau J, et al. Icare rebound tonometry in children with known and suspected glaucoma. J AAPOS 2011;15:153\u0026ndash;157.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEsmael A, Ismail YM, Elhusseiny AM, et al. Agreement profiles for rebound and applanation tonometry in normal and glaucomatous children. Eur J Ophthalmo 2019;29:379\u0026ndash;385.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStrzalkowska A, Pirlich N, Stingl JV, et al. Intraocular pressure measurement in childhood glaucoma under standardized general anaesthesia: the prospective eyeBIS study. J Clin Med 2022;11:2846.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBeasley IG, Laughton DS, Coldrick BJ, et al. Does rebound tonometry probe misalignment modify intraocular pressure measurements in human eyes J Ophthalmol 2013;2013:791084\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMustafa TA. The Bell\u0026rsquo;s phenomenon in newborns. Neurosciences 2005;10:41\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChui WS, Lam A, Chen D, et al. The influence of corneal properties on rebound tonometry. Ophthalmology 2008;115:80\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYamashita T, Miki A, Ieki Y, et al. Central and peripheral intraocular pressure measured by a rebound tonometer. Clin Ophthalmol 2011;5:1113\u0026ndash;1118.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGandhi NG, Prakalapakorn SG, El-Dairi MA, et al. Icare ONE rebound versus Goldmann applanation tonometry in children with known or suspected glaucoma. Am J Ophthalmol 2012;154:843\u0026ndash;849.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDielemans I, Vingerling JR, Hofman A, et al. Reliability of intraocular pressure measurement with the Goldmann applanation tonometer in epidemiological studies. Graefe's Arch Clin Exp Ophthal 1994;232:141\u0026ndash;144.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKageyama M, Hirooka K, Baba T, et al. Comparison of ICare rebound tonometer with noncontact tonometer in healthy children. J Glaucoma 2011;20:63\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYulia DE, Tan S. Intraocular pressure measurements in paediatric glaucoma: A narrative review on accuracy, tolerability, and ease of use. Med J Malaysia 2023;79:207\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePoostchi A, Mitchell R, Nicholas S, Purdie, G. and Wells, A. The iCare rebound tonometer: comparisons with Goldmann tonometry, and influence of central corneal thickness. Clin Exp ophthal 2009;37:687\u0026ndash;691.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim K N, Jeoung J W, Park K H, Yang M K and Kim D M, 2013. Comparison of the new rebound tonometer with Goldmann applanation tonometer in a clinical setting. Acta ophthalmol; 91:e392-e396.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRosentreter A, Jablonski KS, Mellein AC, et al. A new rebound tonometer for home monitoring of intraocular pressure. Graefe's Arch Clin Exp Ophthalmol 2011;249:1713\u0026ndash;1719.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMurgatroyd H, Bembridge J. Intraocular pressure. Continuing Education in Anaesthesia, Critical Care \u0026amp; Pain 2008;8:100\u0026ndash;103.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFeng CS, Jin KW, Yi K, et al. Comparison of intraocular pressure measurements obtained by rebound, noncontact, and Goldmann applanation tonometry in children. Am J Ophthalmol 2015;160:937\u0026ndash;943.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTakagi D, Sawada A, Yamamoto T. Evaluation of a new rebound self-tonometer, Icare HOME: comparison with Goldmann applanation tonometer. J Glaucoma 2017;26:613\u0026ndash;618.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSullivan-Mee M, Pham F. Correspondence of Tono\u0026ndash;Pen\u0026reg; intraocular pressure measurements performed at the central cornea and mid-peripheral cornea. Optometry 2004;75:26\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eQueiros A, Gonzalez-Meijome JM, Fernandes P, et al. A comparison of central and peripheral intraocular pressure using rebound tonometry. Ophthalmic Physiol Opt 2007;27:506\u0026ndash;511.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBrandt JD, Beiser JA, Kass MA, et al. Central corneal thickness in the ocular hypertension treatment study (OHTS). Ophthalmology 2001;108:1779\u0026ndash;1788.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMartola EL, Baum JL. Central and peripheral corneal thickness: a clinical study. Arch Ophthalmol 1968;79:28\u0026ndash;30.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMartinez-de-la-Casa JM, Garcia-Feijoo J, Castillo A, et al. Reproducibility and clinical evaluation of rebound tonometry. Invest Ophthalmol Vis Sci 2005;46:4578\u0026ndash;4580.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTakenaka J, Mochizuki H, Kunihara E, et al. Evaluation of rebound tonometer for measuring intraocular pressure at deviated angle and position. Curr Eye Res 2011;36:422\u0026ndash;428.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTakenaka J, Mochizuki H, Kunihara E, et al. Intraocular pressure measurement using rebound tonometer for deviated angles and positions in human eyes. Curr Eye Res 2012;37:109\u0026ndash;114.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFraunfelder FW. Corneal toxicity from topical ocular and systemic medications. Cornea 2006;25:1133\u0026ndash;1138.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"paediatric glaucoma, intraocular pressure, tonometry","lastPublishedDoi":"10.21203/rs.3.rs-7608247/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7608247/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo evaluate the validity and reliability of off-axis rebound tonometry (RBT) measurements in children with glaucoma, and the utility of these off-axis measurements in ocular and systemic conditions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRBT measurements were taken at the optical centre (RBT\u003csub\u003eon\u003c/sub\u003e) and 3 mm temporally (RBT\u003csub\u003eoff\u003c/sub\u003e) from one eye of children with glaucoma who visited the Eye Department of Birmingham Women’s and Children’s Hospital. Goldmann applanation tonometer (GAT) measurements were subsequently obtained. Co-existing factors were analysed including age, sex, ethnicity, type of glaucoma, treatment, general health, nystagmus, strabismus, corneal scars, spectacle prescription (Rx) and best corrected visual acuity (BCVA).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThirty-four children aged 4–15 years (mean age 9.2 (SD 3.5) years, 14 female) with glaucoma were evaluated. RBT\u003csub\u003eon\u003c/sub\u003e measurements (mean 20.0 (SD 9.1) mmHg) overestimated GAT IOP (mean 17.6 (SD 7.1) mmHg) by 2.4 (SD 3.0) mmHg (p = 0.000), with bias increasing above 28 mmHg. To a lesser extent, RBT\u003csub\u003eoff\u003c/sub\u003e overestimated IOP by 1.7 (SD 3.5) mmHg compared to GAT (p \u0026lt; 0.01). In absolute terms, mean RBT\u003csub\u003eoff \u003c/sub\u003ewas closer to GAT than the mean RBT\u003csub\u003eon\u003c/sub\u003e. Notably, RBT\u003csub\u003eon\u003c/sub\u003e agreed better with GAT in younger children (\u0026lt; 9 years old), while differences were independent of coexisting factors such as sex or ethnicity.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRebound tonometry consistently overestimated IOP relative to GAT, particularly at higher pressures, but within clinically acceptable limits. Whilst the bias was more pronounced in older children, underscoring the need for paediatric-specific calibration, peripheral RBT measures were closer to GAT than those taken centrally. Although a useful measure in this population, these findings advocate for caution when interpreting rebound readings, to ensure appropriate glaucoma management in children.\u003c/p\u003e","manuscriptTitle":"Utility of off-axis rebound tonometry in children with glaucoma","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-25 15:39:41","doi":"10.21203/rs.3.rs-7608247/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"57ac9cb5-07d0-409c-92be-285bc9fa3c32","owner":[],"postedDate":"September 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-09T20:25:01+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-25 15:39:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7608247","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7608247","identity":"rs-7608247","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}