Novel Syringe Handle for One-Handed Anterior Chamber Paracentesis

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Stewart, Mitchel A. Cole, Madelynn E. Mackenzie, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6934401/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 28 Nov, 2025 Read the published version in BMC Ophthalmology → Version 1 posted 12 You are reading this latest preprint version Abstract Background: Anterior chamber (AC) paracentesis is a valuable diagnostic and therapeutic ophthalmic procedure, but the conventional technique poses ergonomic and safety challenges. Methods: We developed a custom, low-cost, 3D-printed syringe handle that enables one-handed AC paracentesis using standard 1-mL syringes by allowing single-finger plunger retraction. In a randomized controlled wet-lab study, ten ophthalmology residents each performed four AC paracentesis procedures (two with the novel device, two with the conventional technique) on porcine eyes. The primary outcome was successful aspiration of ≥100 μL of aqueous humor. Secondary outcomes included intraocular injury, aspirated volume, procedure time, and responses to an anonymous post-procedure survey. Results: All AC paracentesis procedures achieved ≥100 μL of fluid. No intraocular injuries occurred with the novel device, compared to 2 intraocular tissue contacts with the conventional method. The median aspirated volume was 120 μL (interquartile range [IQR]: 110–150 μL) with the novel device, close to the 100 μL threshold, with no extractions exceeding 200 μL. In contrast, the conventional method yielded a significantly higher median volume of 200 μL (IQR 140–270 μL; P < 0.001), with 25% of procedures exceeding 250 μL. The median procedure time was 26.9 seconds with the novel device versus 35.7 seconds with the conventional method, a 8.8 seconds (25%) reduction (P = 0.13). Participants generally preferred the novel device for ease of use, control, and perceived safety. Nine of 10 participants reported feeling more or much more confident about performing AC paracentesis safely with the novel syringe handle than with the conventional technique. Conclusions: We developed a novel syringe handle for one-handed AC paracentesis, which improved the safety and precision of the procedure while reducing procedural time. Its low-cost, reusable design and compatibility with standard syringes make it a practical tool for the procedure. Further clinical studies are warranted to explore broader applications. Anterior chamber paracentesis new instrument syringe Figures Figure 1 Figure 2 Figure 3 Background Anterior chamber (AC) paracentesis is a routine in-office ophthalmic procedure with important diagnostic and therapeutic applications. It involves inserting a fine needle into the anterior chamber to collect aqueous humor. 1 Clinically, it is used for diagnosing uveitis, endophthalmitis, or lymphoma and for rapidly lowering intraocular pressure in glaucoma or perioperatively for intravitreal injections. 1 – 4 Though generally safe, complications such as trauma to the cornea, iris, or lens, hyphema, keratitis, and endophthalmitis have been reported. 1 5 6 Precision and safety are therefore essential. Conventional AC paracentesis techniques pose ergonomic and safety challenges. Passive aspiration by removing the syringe plunger offers no control over flow rate and makes fluid transfer for testing difficult. Sudden egress can lead to unpredictable intraocular pressure drops, AC shallowing, and complications such as gas entering the AC after pneumatic retinopexy or iris plugging the needle. Alternatively, using both hands—one to hold the syringe, the other to pull the plunger—limits the ability to stabilize the globe or adjust the slit lamp. This often forces the operator to look away from the needle to check volume, increasing the risk of over-aspiration or injury if the patient moves. A third method involves an assistant pulling the plunger while the ophthalmologist inserts the needle with one hand while using the other hand to stabilize the eye or to adjust the slit lamp, but this requires additional personnel and can result in inconsistent aspiration force, collapsed anterior chamber, or unintended trauma. Previous efforts have aimed to improve safety and ease of use. The aqueous pipette, introduced 20 years ago, allows one-handed aspiration with a squeeze bulb. 7 However, it requires users to adapt to a new tool, and the extracted fluid can return to the chamber, which has limited its adoption in clinics. More recently, a plungerless AC paracentesis technique using an adhesive film dressing and a vacutainer was described, but passive collection may yield insufficient volumes, fluid extraction speed cannot be controlled, and vacutainers are not universally accessible. 8 To address these limitations, we developed a 3D-printed syringe handle that allows one-handed AC paracentesis using standard syringes. This snap-on device enables plunger retraction with a finger while the other hand stabilizes the globe. We evaluated its performance against the conventional technique in a randomized controlled wet-lab study using porcine eyes, followed by a post-procedure survey. Methods Syringe Handle Design We designed the syringe handle using Autodesk Fusion 360 (Autodesk Inc., San Francisco, CA, USA) and 3D printed it with polylactic acid material. The 7-gram handle consists of a slider and a housing (Fig. 1 A), with an estimated material cost of $ 0.14. Once assembled, the slider locks into the housing, which snaps onto a a 1-mL BD® Tuberculin Syringe (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) (Fig. 1 B). A hard stop at the 0.2-mL syringe marker prevents over-extraction. We also created a one-piece version with the same function (eFigure 1). We uploaded the models to the National Institutes of Health 3D model repository (3DPX ID: 022172; https://3d.nih.gov/entries/3DPX-022172 ). Wet-lab Study Design and Participants A pilot randomized controlled wet-lab study was conducted using porcine eyes under institutional review board exemption from the University of California, San Francisco (reference number: 24-42297; clinical trial number: not applicable). Ten ophthalmology residents were recruited with informed consent. Each performed four AC paracentesis procedures—two with the novel device and two with the conventional method—for a total of 40 procedures. To reduce bias, participants were randomly assigned in a 1:1 ratio to start with either the novel or conventional method. Fresh porcine eyes were mounted in Styrofoam head models secured to a slit lamp stand (Fig. 1 C, 1 D). Prior to each procedure, the anterior chamber was inflated with balanced salt solution. A 30-gauge needle attached to a 1-mL BD® Syringe was used in all procedures. Each participant first performed the procedure on the left eye with the right hand, then on the right eye with the left hand. In the novel method, participants held the syringe in one hand and retracted the plunger with their index finger until it reached the 0.2 mL stop, stabilizing the globe with the other hand using a cotton-tipped applicator (Fig. 1 C; Supplemental Video). In the conventional method, one hand held the syringe while the other retracted the plunger (Fig. 1 D). In both methods, participants were instructed to aspirate ≥ 100 µL of aqueous humor while avoiding intraocular structures. Statistical Analysis The primary outcome was success rate, defined as aspiration of ≥ 100 µL. Secondary outcomes included intraocular contact, aspirated volume, and procedure time. Participants completed an five-question anonymous post-procedure survey (Supplemental Methods). Data were analyzed in R 4.0.4 (R Foundation for Statistical Computing). We performed a linear mixed-effects model, including procedure method and eye laterality as fixed effects and participant as a random effect. Results All 40 procedures achieved ≥ 100 µL fluid aspiration. No intraocular injuries occurred with the novel method. Two contacts occurred in the conventional group: one with the corneal endothelium and another involving both iris and cornea. Significant needle movement was also observed when participants looked away from the slit lamp to check volume. With the novel device, the median aspirated volume was 120 µL (interquartile range [IQR]: 110–150 µL), close to the 100 µL threshold, with no extractions exceeding 200 µL. In contrast, the conventional method aspirated a median of 200 µL (IQR 140–270 µL), significantly higher than the novel method (P 250 µL. The median procedure time was 26.9 (IQR 22.5–33.1) seconds with the novel device versus 35.7 (IQR 22.3–41.6) seconds with the conventional method (Fig. 2 B), a median reduction of 8.8 seconds (25% reduction), though not statistically significant (P = 0.13). Figure 3 presents the post-procedure survey results. All 10 participants rated the novel device between 3 and 5 (with 5 indicating the greatest preference towards the novel method) for ease of use, control, safety, and satisfaction. Nine of 10 reported feeling more confident about safety with the novel device, and 7 of 10 said it would likely reduce their procedural time. Discussion In this study, we developed a novel syringe handle that works with standard 1-mL syringes for one-handed AC paracentesis, which improved safety and precision compared to the conventional method while reducing procedural time in a randomized controlled wet-lab study. In all 20 uses, participants successfully extracted at least 100 µL of aqueous humor by retracting the plunger to the hard stop at 0.2 mL, without looking away from the slit lamp. This improves control and safety by eliminating the need to monitor volume mid-procedure, unlike the conventional two-handed technique. The anonymous post-study survey demonstrated participants’ preference towards the novel device. Our device may benefit other ophthalmic and medical procedures requiring aspiration or injection. In ophthalmology, it may assist with intracameral gas injection at the slit lamp 9 . It could also be applied to large-volume aspiration or injection in non-ophthalmic procedures such as joint aspiration, abscess drainage, or epidural injections—situations where one hand operates the syringe while the other stabilizes the site. Future studies should investigate these potential applications. Study limitations include the single-center design, modest sample size, and use of porcine eyes, which do not mimic human eye movement. Conclusions We developed a novel syringe handle that enhances the safety and accuracy of AC paracentesis without compromising efficiency. Its simple design and compatibility with standard syringes make it a practical tool with potential to enhance the procedure. Further studies may explore broader medical applications. Abbreviations AC, Anterior Chamber; IQR, Interquartile Range. Declarations Ethics approval and consent to participate: This study involves human participants and was performed in accordance with the ethical principles of the Declaration of Helsinki. The study was exempted by the institutional review board at University of California, San Francisco (Reference number: 24-42297). Participants gave informed consent to participate in the study before taking part. Consent for publication: Not applicable. Availability of data and materials: The 3D printing file for the anterior chamber syringe handle is available at the National Institutes of Health 3D model repository (3DPX ID: 022172; https://3d.nih.gov/entries/3DPX-022172). All data generated or analysed during this study are included in this published article [and its supplementary information files]. Competing Interests: L. L. Shen : Provisional patent related to the device used in this study, Consultant – Boehringer Ingelheim, Sanofi; J. M. Stewart : Consultant – Carl Zeiss, Merck, Valitor, Long Bridge, Twenty Twenty, Oculgen, Science; Personal Financial Interest – Long Bridge, Valitor, Science; M. A. Cole : None; M. E. Mackenzie : None. F. Brodie : Provisional patent related to the device used in this study, Consultant: Genentech, Long Bridge Medical, Science Corporation; Financial Interest: Long Bridge Medical, Science Corporation, RxSight. Funding: National Eye Institute Core Grant for Vision Research (EY002162), Research to Prevent Blindness Unrestricted Grant to the UCSF Department of Ophthalmology, All May See Foundation, San Francisco, CA. The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication. Authors’ contributions: Conception and design: LLS. Data collection: LLS, MAC, MEM. Data analysis: LLS. Data interpretation, LLS, JMS, FB. Obtained funding: LLS, FB. Manuscript writing: LLS, JMS, MAC, MEM, FB. References Saxena S, Lai TY, Koizumi H, et al. Anterior chamber paracentesis during intravitreal injections in observational trials: effectiveness and safety and effects. Int J Retina Vitreous. 2019;5:8. Finger PT, Papp C, Latkany P, Kurli M, Iacob CE. Anterior chamber paracentesis cytology (cytospin technique) for the diagnosis of intraocular lymphoma. Br J Ophthalmol. 2006;90(6):690–2. Chen X, Li C, Peng X, Lum F, McLeod SD, Acharya NR. Use of Anterior Chamber Paracentesis for Diagnosis in Viral Anterior Uveitis. Ophthalmology. 2024;131(5):634–36. Lam DSC, Chua JKH, Tham CCY, Lai JSM. Efficacy and safety of immediate anterior chamber paracentesis in the treatment of acute primary angle-closure glaucoma: A pilot study. Ophthalmology. 2002;109(1):64–70. Helbig H, Noske W, Kleineidam M, Kellner U, Foerster MH. Bacterial endophthalmitis after anterior chamber paracentesis. Br J Ophthalmol. 1995;79(9):866. Yannuzzi NA, Relhan N, Schimel A, FlynnJr HW. Lens Capsule Violation During Anterior Chamber Paracentesis in Pneumatic Retinopexy. J VitreoRetinal Dis. 2018;2(3):176–78. Cheung CM, Durrani OM, Murray PI. The safety of anterior chamber paracentesis in patients with uveitis. Br J Ophthalmol. 2004;88(4):582–3. Ji MH, Uwaydat SH, Sallam AB. Plungerless Diagnostic Anterior Chamber Paracentesis Technique. Ophthalmol Retina. 2024;8(2):136. Kim T, Hasan SA. A new technique for repairing descemet membrane detachments using intracameral gas injection. Arch Ophthalmol. 2002;120(2):181–3. Additional Declarations Competing interest reported. L. L. Shen: Provisional patent related to the device used in this study, Consultant – Boehringer Ingelheim, Sanofi; J. M. Stewart: Consultant – Carl Zeiss, Merck, Valitor, Long Bridge, Twenty Twenty, Oculgen, Science; Personal Financial Interest – Long Bridge, Valitor, Science; M. A. Cole: None; M. E. Mackenzie: None. F. Brodie: Provisional patent related to the device used in this study, Consultant: Genentech, Long Bridge Medical, Science Corporation; Financial Interest: Long Bridge Medical, Science Corporation, RxSight. Supplementary Files SupplementalMethods.pdf SupplementalFigure1.pdf SupplementalVideo.mp4 Cite Share Download PDF Status: Published Journal Publication published 28 Nov, 2025 Read the published version in BMC Ophthalmology → Version 1 posted Editorial decision: Revision requested 09 Oct, 2025 Reviews received at journal 28 Sep, 2025 Reviews received at journal 18 Sep, 2025 Reviewers agreed at journal 16 Sep, 2025 Reviewers agreed at journal 06 Sep, 2025 Reviewers agreed at journal 20 Aug, 2025 Reviews received at journal 07 Jul, 2025 Reviewers agreed at journal 07 Jul, 2025 Reviewers invited by journal 03 Jul, 2025 Editor assigned by journal 27 Jun, 2025 Submission checks completed at journal 26 Jun, 2025 First submitted to journal 26 Jun, 2025 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. 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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-6934401","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":480222625,"identity":"4cb7e728-65c1-407f-adeb-36c32e02ef95","order_by":0,"name":"Liangbo Linus Shen","email":"","orcid":"","institution":"University of California, San Francisco","correspondingAuthor":false,"prefix":"","firstName":"Liangbo","middleName":"Linus","lastName":"Shen","suffix":""},{"id":480222626,"identity":"7eae8d68-e66b-4665-b5cf-84556f81bbf9","order_by":1,"name":"Jay M. 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(A) The 3D-printed syringe handle comprises a slider and a housing. (B) The assembled syringe handle features a hard stop at the 0.2 mL syringe mark (red arrow), preventing the extraction of more than 0.2 mL of aqueous fluid. (C) A photograph illustrating the syringe handle in use during anterior chamber paracentesis, where the user performs one-handed paracentesis with the right hand while stabilizing the eye using a cotton-tip applicator in the left hand. (D) The two-handed anterior chamber paracentesis technique used in the wet lab study, where one hand holds the syringe barrel while the other pulls the plunger.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6934401/v1/02e88573a29e26ace1403e6e.png"},{"id":86218395,"identity":"867c0a28-66f9-4f1e-bcae-3bbafd45258a","added_by":"auto","created_at":"2025-07-08 06:31:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":7839298,"visible":true,"origin":"","legend":"\u003cp\u003eWet lab study results comparing the novel syringe handle to the conventional two-handed anterior chamber paracentesis technique (40 procedures, 10 participants). A, Boxplot of extracted aqueous volume. All participants successfully extracted at least 100 µL using both methods. The novel handle had a median [interquartile range (IQR)] of 120 [110–150] µL, close to the 100 µL target, with no extractions exceeding 200 µL. In contrast, the conventional method yielded significantly higher volumes (200 [140–270] µL, P \u0026lt; 0.001), with 25% of procedures exceeding 250 µL. B, Boxplot comparing procedure time between the two methods. The median and IQR for the novel method was 26.9 [22.5–33.1] seconds, while the conventional method took 35.7 [22.3–41.6] seconds (P = 0.13).\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-6934401/v1/019db6d3947501508c4e1b2b.png"},{"id":86217713,"identity":"626c0804-aeac-4979-bb40-beb61c82d7d8","added_by":"auto","created_at":"2025-07-08 06:23:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":16846473,"visible":true,"origin":"","legend":"\u003cp\u003eResults of the anonymous survey from 10 participants after the wet lab study. Participants rated each question on a scale from 1 to 5, with 5 indicating the most favorable response toward the novel syringe handle. All responses ranged from 3 to 5.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-6934401/v1/64bed64776da8198cc2748a0.png"},{"id":97178576,"identity":"46c1c4b4-19f7-4c04-99fb-2ea822b20c05","added_by":"auto","created_at":"2025-12-01 16:10:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":28269165,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6934401/v1/982ef730-92cc-49fe-a9d3-f30f1e8d77b8.pdf"},{"id":86217708,"identity":"0d5f531e-b41a-427b-bcc6-4869bd75760b","added_by":"auto","created_at":"2025-07-08 06:23:05","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":10158,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementalMethods.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6934401/v1/4356fc5923ca30a07791081f.pdf"},{"id":86217710,"identity":"0304eb31-f29f-4d67-b025-b45d89c4fcf8","added_by":"auto","created_at":"2025-07-08 06:23:06","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":43808,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementalFigure1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6934401/v1/339274ca170b79a0c6125a50.pdf"},{"id":86217723,"identity":"92fbbed2-201e-4334-af74-fe2da62d819e","added_by":"auto","created_at":"2025-07-08 06:23:06","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":10115572,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementalVideo.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6934401/v1/4725244e05712ff32646dd5c.mp4"}],"financialInterests":"Competing interest reported. L. L. Shen: Provisional patent related to the device used in this study, Consultant – Boehringer Ingelheim, Sanofi; J. M. Stewart: Consultant – Carl Zeiss, Merck, Valitor, Long Bridge, Twenty Twenty, Oculgen, Science; Personal Financial Interest – Long Bridge, Valitor, Science; M. A. Cole: None; M. E. Mackenzie: None. F. Brodie: Provisional patent related to the device used in this study, Consultant: Genentech, Long Bridge Medical, Science Corporation; Financial Interest: Long Bridge Medical, Science Corporation, RxSight.","formattedTitle":"Novel Syringe Handle for One-Handed Anterior Chamber Paracentesis","fulltext":[{"header":"Background","content":"\u003cp\u003eAnterior chamber (AC) paracentesis is a routine in-office ophthalmic procedure with important diagnostic and therapeutic applications. It involves inserting a fine needle into the anterior chamber to collect aqueous humor.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e Clinically, it is used for diagnosing uveitis, endophthalmitis, or lymphoma and for rapidly lowering intraocular pressure in glaucoma or perioperatively for intravitreal injections.\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e Though generally safe, complications such as trauma to the cornea, iris, or lens, hyphema, keratitis, and endophthalmitis have been reported.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e Precision and safety are therefore essential.\u003c/p\u003e\u003cp\u003eConventional AC paracentesis techniques pose ergonomic and safety challenges. Passive aspiration by removing the syringe plunger offers no control over flow rate and makes fluid transfer for testing difficult. Sudden egress can lead to unpredictable intraocular pressure drops, AC shallowing, and complications such as gas entering the AC after pneumatic retinopexy or iris plugging the needle. Alternatively, using both hands\u0026mdash;one to hold the syringe, the other to pull the plunger\u0026mdash;limits the ability to stabilize the globe or adjust the slit lamp. This often forces the operator to look away from the needle to check volume, increasing the risk of over-aspiration or injury if the patient moves. A third method involves an assistant pulling the plunger while the ophthalmologist inserts the needle with one hand while using the other hand to stabilize the eye or to adjust the slit lamp, but this requires additional personnel and can result in inconsistent aspiration force, collapsed anterior chamber, or unintended trauma.\u003c/p\u003e\u003cp\u003ePrevious efforts have aimed to improve safety and ease of use. The aqueous pipette, introduced 20 years ago, allows one-handed aspiration with a squeeze bulb.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e However, it requires users to adapt to a new tool, and the extracted fluid can return to the chamber, which has limited its adoption in clinics. More recently, a plungerless AC paracentesis technique using an adhesive film dressing and a vacutainer was described, but passive collection may yield insufficient volumes, fluid extraction speed cannot be controlled, and vacutainers are not universally accessible.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eTo address these limitations, we developed a 3D-printed syringe handle that allows one-handed AC paracentesis using standard syringes. This snap-on device enables plunger retraction with a finger while the other hand stabilizes the globe. We evaluated its performance against the conventional technique in a randomized controlled wet-lab study using porcine eyes, followed by a post-procedure survey.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSyringe Handle Design\u003c/h2\u003e\u003cp\u003eWe designed the syringe handle using Autodesk Fusion 360 (Autodesk Inc., San Francisco, CA, USA) and 3D printed it with polylactic acid material. The 7-gram handle consists of a slider and a housing (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA), with an estimated material cost of \u003cspan\u003e$\u003c/span\u003e0.14. Once assembled, the slider locks into the housing, which snaps onto a a 1-mL BD\u0026reg; Tuberculin Syringe (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). A hard stop at the 0.2-mL syringe marker prevents over-extraction. We also created a one-piece version with the same function (eFigure 1). We uploaded the models to the National Institutes of Health 3D model repository (3DPX ID: 022172; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://3d.nih.gov/entries/3DPX-022172\u003c/span\u003e\u003cspan address=\"https://3d.nih.gov/entries/3DPX-022172\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eWet-lab Study Design and Participants\u003c/h3\u003e\n\u003cp\u003eA pilot randomized controlled wet-lab study was conducted using porcine eyes under institutional review board exemption from the University of California, San Francisco (reference number: 24-42297; clinical trial number: not applicable). Ten ophthalmology residents were recruited with informed consent. Each performed four AC paracentesis procedures\u0026mdash;two with the novel device and two with the conventional method\u0026mdash;for a total of 40 procedures. To reduce bias, participants were randomly assigned in a 1:1 ratio to start with either the novel or conventional method.\u003c/p\u003e\u003cp\u003eFresh porcine eyes were mounted in Styrofoam head models secured to a slit lamp stand (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD). Prior to each procedure, the anterior chamber was inflated with balanced salt solution. A 30-gauge needle attached to a 1-mL BD\u0026reg; Syringe was used in all procedures. Each participant first performed the procedure on the left eye with the right hand, then on the right eye with the left hand.\u003c/p\u003e\u003cp\u003eIn the novel method, participants held the syringe in one hand and retracted the plunger with their index finger until it reached the 0.2 mL stop, stabilizing the globe with the other hand using a cotton-tipped applicator (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC; Supplemental Video). In the conventional method, one hand held the syringe while the other retracted the plunger (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD). In both methods, participants were instructed to aspirate\u0026thinsp;\u0026ge;\u0026thinsp;100 \u0026micro;L of aqueous humor while avoiding intraocular structures.\u003c/p\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis\u003c/h2\u003e\u003cp\u003eThe primary outcome was success rate, defined as aspiration of \u0026ge;\u0026thinsp;100 \u0026micro;L. Secondary outcomes included intraocular contact, aspirated volume, and procedure time. Participants completed an five-question anonymous post-procedure survey (Supplemental Methods). Data were analyzed in R 4.0.4 (R Foundation for Statistical Computing). We performed a linear mixed-effects model, including procedure method and eye laterality as fixed effects and participant as a random effect.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eAll 40 procedures achieved\u0026thinsp;\u0026ge;\u0026thinsp;100 \u0026micro;L fluid aspiration. No intraocular injuries occurred with the novel method. Two contacts occurred in the conventional group: one with the corneal endothelium and another involving both iris and cornea. Significant needle movement was also observed when participants looked away from the slit lamp to check volume.\u003c/p\u003e\u003cp\u003eWith the novel device, the median aspirated volume was 120 \u0026micro;L (interquartile range [IQR]: 110\u0026ndash;150 \u0026micro;L), close to the 100 \u0026micro;L threshold, with no extractions exceeding 200 \u0026micro;L. In contrast, the conventional method aspirated a median of 200 \u0026micro;L (IQR 140\u0026ndash;270 \u0026micro;L), significantly higher than the novel method (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). Five (25%) of 20 conventional procedures extracted\u0026thinsp;\u0026gt;\u0026thinsp;250 \u0026micro;L.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe median procedure time was 26.9 (IQR 22.5\u0026ndash;33.1) seconds with the novel device versus 35.7 (IQR 22.3\u0026ndash;41.6) seconds with the conventional method (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), a median reduction of 8.8 seconds (25% reduction), though not statistically significant (P\u0026thinsp;=\u0026thinsp;0.13).\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the post-procedure survey results. All 10 participants rated the novel device between 3 and 5 (with 5 indicating the greatest preference towards the novel method) for ease of use, control, safety, and satisfaction. Nine of 10 reported feeling more confident about safety with the novel device, and 7 of 10 said it would likely reduce their procedural time.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, we developed a novel syringe handle that works with standard 1-mL syringes for one-handed AC paracentesis, which improved safety and precision compared to the conventional method while reducing procedural time in a randomized controlled wet-lab study. In all 20 uses, participants successfully extracted at least 100 \u0026micro;L of aqueous humor by retracting the plunger to the hard stop at 0.2 mL, without looking away from the slit lamp. This improves control and safety by eliminating the need to monitor volume mid-procedure, unlike the conventional two-handed technique. The anonymous post-study survey demonstrated participants\u0026rsquo; preference towards the novel device.\u003c/p\u003e\u003cp\u003eOur device may benefit other ophthalmic and medical procedures requiring aspiration or injection. In ophthalmology, it may assist with intracameral gas injection at the slit lamp\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. It could also be applied to large-volume aspiration or injection in non-ophthalmic procedures such as joint aspiration, abscess drainage, or epidural injections\u0026mdash;situations where one hand operates the syringe while the other stabilizes the site. Future studies should investigate these potential applications.\u003c/p\u003e\u003cp\u003eStudy limitations include the single-center design, modest sample size, and use of porcine eyes, which do not mimic human eye movement.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eWe developed a novel syringe handle that enhances the safety and accuracy of AC paracentesis without compromising efficiency. Its simple design and compatibility with standard syringes make it a practical tool with potential to enhance the procedure. Further studies may explore broader medical applications.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAC, Anterior Chamber; IQR, Interquartile Range.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study involves human participants and was performed in accordance with the ethical principles of the Declaration of Helsinki. The study was exempted by the institutional review board at University of California, San Francisco (Reference number: 24-42297). Participants gave informed consent to participate in the study before taking part.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe 3D printing file for the anterior chamber syringe handle is available at the National Institutes of Health 3D model repository (3DPX ID: 022172; https://3d.nih.gov/entries/3DPX-022172). All data generated or analysed during this study are included in this published article [and its supplementary information files].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests: L. L. Shen\u003c/strong\u003e: Provisional patent related to the device used in this study, Consultant \u0026ndash; Boehringer Ingelheim, Sanofi; \u003cstrong\u003eJ. M. Stewart\u003c/strong\u003e: Consultant \u0026ndash; Carl Zeiss, Merck, Valitor, Long Bridge, Twenty Twenty, Oculgen, Science; Personal Financial Interest \u0026ndash; Long Bridge, Valitor, Science; \u003cstrong\u003eM. A. Cole\u003c/strong\u003e: None; \u003cstrong\u003eM. E. Mackenzie\u003c/strong\u003e: None. \u003cstrong\u003eF. Brodie\u003c/strong\u003e: Provisional patent related to the device used in this study, Consultant: Genentech, Long Bridge Medical, Science Corporation; Financial Interest: Long Bridge Medical, Science Corporation, RxSight.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eNational Eye Institute Core Grant for Vision Research (EY002162), Research to Prevent Blindness Unrestricted Grant to the UCSF Department of Ophthalmology, All May See Foundation, San Francisco, CA. The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions:\u0026nbsp;\u003c/strong\u003eConception and design: LLS. Data collection: LLS, MAC, MEM. Data analysis: LLS. Data interpretation, LLS, JMS, FB. Obtained funding: LLS, FB. Manuscript writing: LLS, JMS, MAC, MEM, FB.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSaxena S, Lai TY, Koizumi H, et al. Anterior chamber paracentesis during intravitreal injections in observational trials: effectiveness and safety and effects. Int J Retina Vitreous. 2019;5:8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFinger PT, Papp C, Latkany P, Kurli M, Iacob CE. Anterior chamber paracentesis cytology (cytospin technique) for the diagnosis of intraocular lymphoma. Br J Ophthalmol. 2006;90(6):690\u0026ndash;2.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen X, Li C, Peng X, Lum F, McLeod SD, Acharya NR. Use of Anterior Chamber Paracentesis for Diagnosis in Viral Anterior Uveitis. Ophthalmology. 2024;131(5):634\u0026ndash;36.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLam DSC, Chua JKH, Tham CCY, Lai JSM. Efficacy and safety of immediate anterior chamber paracentesis in the treatment of acute primary angle-closure glaucoma: A pilot study. Ophthalmology. 2002;109(1):64\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHelbig H, Noske W, Kleineidam M, Kellner U, Foerster MH. Bacterial endophthalmitis after anterior chamber paracentesis. Br J Ophthalmol. 1995;79(9):866.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYannuzzi NA, Relhan N, Schimel A, FlynnJr HW. Lens Capsule Violation During Anterior Chamber Paracentesis in Pneumatic Retinopexy. J VitreoRetinal Dis. 2018;2(3):176\u0026ndash;78.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCheung CM, Durrani OM, Murray PI. The safety of anterior chamber paracentesis in patients with uveitis. Br J Ophthalmol. 2004;88(4):582\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJi MH, Uwaydat SH, Sallam AB. Plungerless Diagnostic Anterior Chamber Paracentesis Technique. Ophthalmol Retina. 2024;8(2):136.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim T, Hasan SA. A new technique for repairing descemet membrane detachments using intracameral gas injection. Arch Ophthalmol. 2002;120(2):181\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Anterior chamber paracentesis, new instrument, syringe ","lastPublishedDoi":"10.21203/rs.3.rs-6934401/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6934401/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e Anterior chamber (AC) paracentesis is a valuable diagnostic and therapeutic ophthalmic procedure, but the conventional technique poses ergonomic and safety challenges.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eWe developed a custom, low-cost, 3D-printed syringe handle that enables one-handed AC paracentesis using standard 1-mL syringes by allowing single-finger plunger retraction. In a randomized controlled wet-lab study, ten ophthalmology residents each performed four AC paracentesis procedures (two with the novel device, two with the conventional technique) on porcine eyes. The primary outcome was successful aspiration of ≥100 μL of aqueous humor. Secondary outcomes included intraocular injury, aspirated volume, procedure time, and responses to an anonymous post-procedure survey.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eAll AC paracentesis procedures achieved ≥100 μL of fluid. No intraocular injuries occurred with the novel device, compared to 2 intraocular tissue contacts with the conventional method. The median aspirated volume was 120 μL (interquartile range [IQR]: 110–150 μL) with the novel device, close to the 100 μL threshold, with no extractions exceeding 200 μL. In contrast, the conventional method yielded a significantly higher median volume of 200 μL (IQR 140–270 μL; P \u0026lt; 0.001), with 25% of procedures exceeding 250 μL. The median procedure time was 26.9 seconds with the novel device versus 35.7 seconds with the conventional method, a 8.8 seconds (25%) reduction (P = 0.13). Participants generally preferred the novel device for ease of use, control, and perceived safety. Nine of 10 participants reported feeling more or much more confident about performing AC paracentesis safely with the novel syringe handle than with the conventional technique.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions: \u003c/strong\u003eWe developed a novel syringe handle for one-handed AC paracentesis, which improved the safety and precision of the procedure while reducing procedural time. Its low-cost, reusable design and compatibility with standard syringes make it a practical tool for the procedure. Further clinical studies are warranted to explore broader applications.\u003c/p\u003e","manuscriptTitle":"Novel Syringe Handle for One-Handed Anterior Chamber Paracentesis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-08 06:23:00","doi":"10.21203/rs.3.rs-6934401/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-09T08:50:21+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-29T02:24:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-18T13:36:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"188353748619494313922050334496224344053","date":"2025-09-16T08:38:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"290530879915614699662509719602177662778","date":"2025-09-06T12:55:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"72651741011855667776028773996459169806","date":"2025-08-21T01:55:05+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-07T05:27:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"24224867814532560386987100080207925740","date":"2025-07-07T05:10:05+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-03T13:28:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-27T07:07:08+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-26T04:52:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Ophthalmology","date":"2025-06-26T04:49:45+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"84c26e2d-ff30-4d31-a053-dc571b04fa54","owner":[],"postedDate":"July 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-01T16:03:53+00:00","versionOfRecord":{"articleIdentity":"rs-6934401","link":"https://doi.org/10.1186/s12886-025-04503-z","journal":{"identity":"bmc-ophthalmology","isVorOnly":false,"title":"BMC Ophthalmology"},"publishedOn":"2025-11-28 15:58:16","publishedOnDateReadable":"November 28th, 2025"},"versionCreatedAt":"2025-07-08 06:23:00","video":"","vorDoi":"10.1186/s12886-025-04503-z","vorDoiUrl":"https://doi.org/10.1186/s12886-025-04503-z","workflowStages":[]},"version":"v1","identity":"rs-6934401","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6934401","identity":"rs-6934401","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}