SD-OCT Diagnosis of Optic Nerve Head Drusen and Pseudopapilledema Associated With Advanced Chorioretinopathy in a Dog: Case Report

SD-OCT Diagnosis of Optic Nerve Head Drusen and Pseudopapilledema Associated With Advanced Chorioretinopathy in a Dog: Case Report | 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 Case Report SD-OCT Diagnosis of Optic Nerve Head Drusen and Pseudopapilledema Associated With Advanced Chorioretinopathy in a Dog: Case Report Jowita Zwolska, Wiktoria Teodorowska, Barbara Kuduk, Martyna Padjasek, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8509002/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract Background Unilateral pseudopapilledema and optic nerve head drusen (ONHD) are uncommon findings in dogs and can closely mimic true optic disc edema, which may lead to diagnostic uncertainty and ineffective anti-inflammatory treatment. Spectral-domain optical coherence tomography (SD-OCT) has emerged as a valuable tool for differentiating pseudopapilledema from papilledema by enabling detailed in vivo assessment of the optic nerve head. This case report presents a young mixed-breed dog with suspected retinal detachment and apparent optic disc swelling, in which SD-OCT supported the diagnosis of unilateral pseudopapilledema/ONHD, with advanced chorioretinopathy documented as an additional, case-specific finding. Two complete ophthalmic examinations were performed 10 months apart, including funduscopy and spectral-domain optical coherence tomography (SD-OCT). In addition, electroretinography (ERG) was performed twice, 14 months apart, while ultrasonography (USG) and magnetic resonance imaging (MRI) were each conducted once. Results Funduscopic evaluation revealed multiple chorioretinal lesions and optic disc elevation with blurred margins. SD-OCT identified hyperreflective drusen within the optic nerve head (ONHD), peripapillary hyperreflective ovoid mass-like structures (PHOMS), and localized retinal thinning. SD-OCT based morphometric analysis revealed retinal thinning, while ERG demonstrated photoreceptor dysfunction. Ocular B-scan ultrasonography demonstrated a well-defined hyperechoic lesion within the optic nerve head of the left eye, consistent with optic nerve head drusen, with no analogous findings in the right eye. MRI showed no evidence of disturbed cerebrospinal fluid flow, and no inflammatory or structural abnormalities were detected within the brain or optic nerves. Conclusion This is the first canine case in which ONHD was primarily detected and characterized using SD-OCT. The modality enabled precise, non-invasive longitudinal monitoring of structural and morphometric retinal changes, allowed differentiation of ONHD from true optic disc edema and other optic neuropathies. SD-OCT represents a valuable tool for veterinary ophthalmology, particularly in cases of unexplained optic disc elevation. optic nerve head drusen pseudopapilledema chorioretinopathy SD-OCT dog Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Optic disc elevation is a frequent clinical finding that may result from true optic disc edema or from pseudopapilledema, commonly caused by optic nerve head drusen (ONHD). Distinguishing between these two entities can be challenging, as both may present with blurred disc margins and elevation of the optic nerve head on funduscopic examination. Relying solely on funduscopic appearance and patient history often leads to diagnostic uncertainty, since the key differentiating features - such as disc color, vascular congestion, or subtle topographical variations - may be difficult to evaluate without advanced imaging. 1 , 2 , 3 Accurate differentiation is crucial, however, as true papilledema usually indicates increased intracranial pressure and requires urgent investigation, whereas pseudopapilledema is a benign condition associated with deposits within the optic nerve head. 4 , 5 Optic nerve head drusen are acellular deposits composed primarily of calcium, mucopolysaccharides, and amino acids such as arginine, tryptophan, and tyrosine. 1 , 6 They can occur superficially, where they are visible upon ophthalmoscopic examination, or deeply within the optic disc, where they may mimic papilledema. 5 , 7 The pathogenesis remains uncertain, though impaired axoplasmic transport and subsequent mitochondrial calcification have been proposed as potential mechanisms. 8 Over the years, several diagnostic modalities have been employed to identify and differentiate ONHD from true optic disc edema. B-scan ultrasonography has traditionally been used for the detection of calcified optic nerve head drusen owing to its ability to demonstrate hyperreflective foci with posterior acoustic shadowing, while its utility in identifying non-calcified drusen is limited. 9 , 10 Other techniques, including fluorescein angiography, scanning laser ophthalmoscopy, and computed tomography, have also contributed to diagnostic accuracy, particularly in detecting superficial drusen. However, the sensitivity of fluorescein angiography for the detection of optic nerve head drusen is lower than that of ultrasonography. 2,3,11 More recently, optical coherence tomography, particularly in its spectral-domain form, has emerged as a valuable non-invasive imaging tool capable of visualizing both superficial and buried drusen, as well as quantifying retinal nerve fiber layer thickness, and is currently regarded as the gold standard for the evaluation of optic nerve head drusen. 5 , 12 In veterinary ophthalmology, reports of optic nerve head drusen remain exceedingly rare. To date, ONHD in dogs have primarily been described using computed tomography or ultrasonography, but not with SD-OCT. 13 This case report describes a dog with optic nerve head drusen (ONHD) in which advanced chorioretinopathy was additionally identified and was considered presumptively unrelated to the ONHD, based on spectral-domain optical coherence tomography (SD-OCT) findings. Case report A 3-year-old male mixed-breed dog weighing 21 kg, of unknown medical history, adopted from a shelter, was presented with suspected retinal detachment and optic disc edema. The dog showed no improvement after anti-inflammatory therapy. Treatment consisted of systemic corticosteroid therapy using prednisone at a dose of 1 mg/kg body weight per day, administered orally for two weeks, followed by a gradual taper. According to the owner, the initial clinical concern was night vision impairment. Two complete ophthalmic examinations were performed 10 months apart. Each examination included funduscopy (using a binocular indirect ophthalmoscope [Keeler, UK], a direct ophthalmoscope [Welch Allyn, USA], and a PanOptic ophthalmoscope [Welch Allyn, USA]) and SD-OCT (Topcon 3D OCT-2000, Topcon, Japan). In addition, electroretinography (ERG), with the use of the LKC RETevet system (LKC Technologies, USA), was performed twice, 14 months apart. Ultrasonography (USG) [Vinno G65, Norax] and magnetic resonance imaging (MRI) [GE Optima MR450w 1.5T, GE Medical Systems Polska Sp. z o.o., Warsaw, Poland] were each performed once. Animal owner provided written informed consent for enrollment in the study, procedures and therapy undertaken, and publication of data and images. SD-OCT-based retinal morphology and morphometry were compared with data obtained from 11 healthy control mixed-breed dogs of comparable body weight (18-24 kg) and age (2-4 years). Complete blood count and serum biochemistry results were within normal limits. The ophthalmic evaluation included assessments of menace response, dazzle reflex, tracking reflex, and visual placing reflex, as well as an obstacle course test. The obstacle course was conducted first under scotopic and then under photopic conditions. Chromatic pupillary light reflexes were tested using a BPI-50 Precision Illuminator (RetinoGraphics Inc., USA). All the aforementioned reflexes and responses were intact. Schirmer’s Tear Test (Eickemeyer, Germany) and intraocular pressure measurements obtained with a TonoVet rebound tonometer (iCare, Finland) were within normal ranges in both eyes. Slit-lamp biomicroscopy revealed no abnormalities in the anterior segment of either eye. Funduscopic findings: Funduscopic examination revealed chorioretinal lesions that differed slightly between the right and left eyes (Figure 1). In the right eye, two areas of well-demarcated areas of tapetal hyperreflectivity with a pigmented center were observed. Additionally, two further oval hyperreflective areas were present in the dorsotemporal region. Abnormal retinal pigmentation was also noted within the tapetal fundus. Two well-demarcated areas of depigmentation were present: one at the tapetal-non-tapetal border within the non-tapetal fundus of the ventrotemporal region, and the other within the non-tapetal fundus of the ventronasal region. In the left eye, three areas of tapetal hyperreflectivity with a pigmented center were identified in the dorsotemporal region. As in the right eye, abnormal retinal pigmentation was evident in the tapetal fundus. Furthermore, elevation and blurring of the optic disc margins were observed. During the subsequent funduscopic examination, in the right eye slight thinning of the retinal blood vessels was observed compared to the previous examination. The chorioretinal lesions appearance remained comparable, although progression of abnormal tapetal pigmentation was noted. In the left eye, the funduscopic findings were comparable to those observed during the previous examination. Electroretinography: Two ERG examinations were performed using the LKC RETevet system (LKC Technologies, USA) in accordance with the ECVO 5-step protocol. Electroretinography (ERG) was performed twice, at a 14-month interval, as part of the diagnostic evaluation and longitudinal follow-up of suspected retinopathy to assess changes in retinal function over time. Prior to testing, the pupils were dilated with topical tropicamide (Tropicamidum WZF 1%, Polfa Warszawa S.A., Poland). Anesthesia was induced using intramuscular dexmedetomidine (Dexdomitor, Orion Pharma, Espoo, Finland) at 2.5 µg/kg and butorphanol (Butomidor, Richter Pharma AG, Wels, Austria) at 0.2 mg/kg, followed by intravenous propofol (Propofol-Lipuro, B. Braun Melsungen AG, Melsungen, Germany) at 1 mg/kg for induction. After endotracheal intubation, general anesthesia was maintained with 1% isoflurane (IsoFlo, Zoetis, Louvain-la-Neuve, Belgium). Corneal anesthesia was achieved using 0.5% proxymetacaine hydrochloride (Alcaine 5 mg/mL, Alcon, Warsaw, Poland). The right eye was examined first. In the rod response protocol (white flash, 0.01 cd·s/m², 0.2 Hz, dark adaptation 20 min, no background), both eyes demonstrated reduced amplitudes with normal implicit times. Compared with the initial ERG, the amplitude in the right eye decreased by approximately 70% from baseline, while the left eye showed a reduction of around 20%. A similar amplitude reduction was observed in the cone response protocol (white flash, 3.0 cd·s/m², 2 Hz, light adaptation 10 min, background 30 cd/m²), with approximately 80% reduction in the right eye and 20% in the left eye. These findings indicated bilateral photoreceptor dysfunction, more pronounced in the right eye (Figure 2). Optical coherence tomography: SD-OCT examinations were performed twice-initially on the day of the first visit and again 10 months later. Pupillary dilation was achieved using tropicamide (Tropicamidum WZF 1%, Polfa Warszawa S.A., Poland). The procedure was carried out under sedation using intramuscular medetomidine at a dose of 15 μg/kg body weight (Domitor 1 mg/mL, Orion Pharma, Finland). Topical anesthesia of the cornea and conjunctiva was induced using 0.5% proxymetacaine hydrochloride (Alcaine 5 mg/mL, Alcon, Warsaw, Poland). The eye was stabilized by gently grasping the bulbar conjunctiva with thumb forceps. For detailed evaluation of retinal and optic disc structures, linear, 6-line radial, cross-sectional, and 3D scans (λ = 840 nm; enhanced depth imaging mode; Topcon 3D OCT-2000; Topcon, Japan) were obtained. During imaging, the cornea was kept moist with saline drops applied every 30 seconds to prevent desiccation and ensure optimal image quality. Measurements of retinal layers were performed in the left eye, where ONHD were present in the peripapillary region. The following retinal layers were analyzed: internal limiting membrane + nerve fiber layer (ILM+NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor layers including external limiting membrane (ELM), myoid zone (MZ), ellipsoid zone (EZ), outer photoreceptor segment (OPRS), and interdigitation zone (IZ), outer retina (OR; OPL + ONL + ELM + MZ + EZ + OPRS + IZ), and total retinal thickness (TRT), measured from the internal limiting membrane to the interdigitation zone, excluding the retinal pigment epithelium–Bruch’s membrane–choriocapillaris complex (RPE–BmCc). During the first SD-OCT examination, multiple chorioretinal lesions were detected in the right eye, localized in the temporal tapetal region and at the tapetal–non-tapetal border. Within these chorioretinal lesions, advanced retinal atrophy with thinning and disorganization of the retinal layers was observed. Segmental thinning of the outer nuclear layer (ONL) was noted, accompanied by loss and disorganization of the inner retinal layers (MZ, EZ, OPRS, IZ) in the dorsotemporal and non-tapetal fundus. A lamellar retinal tear and an adjacent retinal hole were identified in the dorsotemporal region of the left eye. The retina in the area surrounding the hole was thickened. The retinal layers adjacent to the retinal tear and hole were disorganized. Both the hole and tear extended to the outer nuclear layer (ONL). In the case of the retinal tear, the ONL, ellipsoid zone (EZ), outer photoreceptor segments (OPRS), and interdigitation zone (IZ) were disorganized (Figures 3A and 3B). In the left eye, multiple chorioretinal lesions were detected in the dorsal region. The retina surrounding the lesions exhibited ongoing disorganization and thinning of retinal layers. SD-OCT performed during the first examination revealed multiple hyperreflective structures within the optic nerve head consistent with optic nerve head drusen (ONHD), located both superficially and at deeper levels of the prelaminar region. The internal contour of the optic nerve head was irregular, with elevation and blurred margins, findings consistent with pseudopapilledema rather than true optic disc edema. Peripapillary retinal nerve fiber layer (RNFL) thickness measurements were obtained, allowing quantitative assessment of neuroaxonal integrity (Figure 4). Retinal schisis between the ILM/NFL and GCL layers was observed in the peripapillary region. A Bergmeister’s papilla was visible at the optic nerve apex, representing a physiological finding. The optic nerve head appeared elevated, with an irregular internal contour consistent with pseudopapilledema (Figure 4A). In the follow-up SD-OCT examination, the right eye exhibited areas of advanced retinal atrophy in the non-tapetal regions. Segmental thinning of the ONL and progressive disorganization of the retinal layers were also evident in the peripapillary region. Both the retinal tear and the retinal hole increased in size. Temporally beyond the hole, the retina exhibited advanced thinning and disorganization of the retinal layers. (Figure 3C). On follow-up SD-OCT examination, persistent optic nerve head elevation was observed. In addition, a peripapillary hyperreflective ovoid mass-like structure (PHOMS) was identified adjacent to the optic nerve head. The overall OCT appearance remained stable over time, supporting a non-inflammatory and non-progressive process (Figure 4). SD-OCT assessment of the choroid in well-demarcated areas of tapetal hyperreflectivity with central pigmentation in the tapetal fundus, as well as in areas of depigmentation in the non- tapetal fundus, was associated with retinal and choroidal atrophy in both eyes. The choroid was thinner than in surrounding regions, particularly in the large vessel layer. Morphometric analysis of retinal layers in the left eye with ONHD revealed thinning of the peripapillary retina after 10 months, with a 14% reduction in the ILM+NFL+GCL layers and a 12.5% decrease in the IPL thickness (Table 1). Ultrasonography: Ocular ultrasonography (Vinno G65, Norax) was performed immediately after the initial SD-OCT examination. During the examination, the optic nerve head region was carefully assessed for the presence of hyperechoic structures and lesions protruding toward the vitreous cavity, which are characteristic features of optic nerve head drusen. In the left eye, a well-defined hyperechoic structure was identified within the optic nerve head, causing focal protrusion toward the vitreous cavity (Figure 5). These ultrasonographic findings were consistent with optic nerve head drusen. No hyperechoic lesions were detected in the optic nerve head region of the right eye. Magnetic resonance imaging: Magnetic resonance imaging (MRI) of the head was performed two weeks after the initial OCT examination using a high-field 1.5 T GE system [GE Optima MR450w 1.5T, GE Medical Systems Polska Sp. z o.o., Warsaw, Poland]. The protocol included FSE sequences in T1-weighted (sagittal, coronal, and transverse planes), T2-weighted (sagittal, coronal, and transverse planes), T2*-weighted (transverse plane), FLAIR (coronal plane), DWI (transverse plane), and ADC (transverse plane) images. Post-contrast imaging was obtained using T1-weighted (sagittal, coronal, and transverse planes) and FLAIR (coronal plane) sequences following intravenous administration of contrast medium (Dotagraf, 0.5 mmol/ml; Bayer Pharma AG, Berlin, Germany). The retrobulbar spaces were unremarkable, and both optic nerves showed no detectable abnormalities. The cerebrospinal fluid–filled perineural subarachnoid spaces surrounding the optic nerves were of normal width throughout their visible course. Mild asymmetry of the lateral cerebral ventricles was observed, without evidence of disturbed cerebrospinal fluid flow, most likely representing a normal anatomic variant. No inflammatory or structural abnormalities were identified within the brain or optic nerves. Discussion Optic nerve head drusen are acellular, usually calcified deposits located anterior to the lamina cribrosa, commonly associated with pseudopapilledema. Visual field defects are a common consequence of ONHD in humans. Studies report that 63.2% of eyes with ONHD exhibit visual field deficits, while abnormal visual evoked potentials are observed in 44.7% of eyes with visible drusen and 20% with buried drusen. Although most eyes with ONHD progress slowly, approximately 12% may show moderate to rapid visual field loss. 14 In the present case, ERG revealed a 20% reduction in photoreceptor cell function in the eye affected by drusen. However, due to the presence of concurrent chorioretinal lesions of unknown origin, it is not possible to determine to what extent the observed ERG abnormalities were directly attributable to the drusen themselves. In the present case, ophthalmic examination revealed preserved visual function, with intact menace response, dazzle reflex, tracking and visual placing reflexes, as well as normal performance on an obstacle course under both scotopic and photopic conditions. Chromatic pupillary light reflexes were within normal limits bilaterally. It should be emphasized that the absence of visual deficits and normal pupillary light reflexes (PLRs) does not exclude papilledema, particularly when associated with intracranial hypertension. In contrast to optic neuritis, papilledema represents a passive swelling of the optic nerve head secondary to increased intracranial pressure and may initially occur without functional impairment of the optic nerve. Consequently, visual deficits and PLR abnormalities are not obligatory findings, especially in early or moderate stages of the disease. 4 , 5 , 7 In the present case, preserved chromatic PLRs argue against a primary inflammatory optic neuropathy. The observed visual dysfunction was instead supported by abnormal electroretinography findings consistent with chorioretinopathy, indicating a retinal rather than optic nerve origin of visual impairment. Therefore, normal PLRs do not rule out papilledema but rather support the absence of clinically significant optic nerve dysfunction. Morphometric analysis of the retinal layers over 10 months demonstrated thinning of the peripapillary retina, with a 14% reduction in ILM + NFL + GCL layers and a 12.5% reduction in IPL thickness. These findings parallel observations in humans with ONHD, where peripapillary NFL thinning progresses in correlation with age. 15 Differentiation between true optic disc edema and pseudopapilledema is critical, as it has significant implications for patient management. Misdiagnosis may lead to unnecessary and potentially invasive diagnostic procedures. Superficial drusen are occasionally visible during ophthalmoscopy, yet deeply buried ones may remain undetected without the aid of advanced imaging modalities. In our case, ocular B-scan ultrasonography identified a well-defined hyperechoic structure within the optic nerve head of the left eye, causing focal protrusion toward the vitreous cavity, consistent with optic nerve head drusen, while no such lesions were observed in the right eye. It is observed that in patients with intracranial hypertension, OCT can demonstrate a deflection of Bruch’s membrane toward the vitreous, which helps differentiate papilledema from pseudopapilledema. However, in our clinical case no displacement of Bruch’s membrane was observed. True optic disc edema is characterized by an elevated optic nerve head with a smooth internal contour, whereas pseudopapilledema associated with ONHD presents as an elevated optic nerve head with irregular internal contour on SD-OCT imaging. 16 In the present case, SD-OCT revealed the presence of ONHD, identified as sharply demarcated hyperreflective deposits within the optic nerve head, as well as PHOMS visualized as ovoid hyperreflective formations in the peripapillary area. Moreover, SD-OCT confirmed the presence of an irregular internal contour, consistent with pseudopapilledema. In veterinary medicine, the diagnosis of ONHD has been rare and dependent on ultrasonography or computed tomography. Ramírez et al. (1983) were among the first to describe calcified drusen in a dog using CT, where they appeared as hyperdense foci consistent with optic nerve calcification. 17 Comparable hyperdense calcified deposits have been documented in human studies, reinforcing the morphological similarities between species. 18 , 19 More recently, Niranjana et al. (2023) reported the incidental discovery of bilateral optic nerve head drusen in a six-year-old Rottweiler during head CT examination. 13 Characteristic discrete hyperdense areas were identified within the optic nerve head. In contrast, the present case represents the first report of ONHD in a dog confirmed and characterized using the non-invasive SD-OCT, which enabled precise longitudinal monitoring of structural changes not achievable with previously available imaging methods. Conclusion The peripapillary retinal thinning coexisting with optic nerve head drusen (ONHD) and peripapillary hyperreflective ovoid mass-like structures (PHOMS) underscores the similarity of pathological changes observed in this dog to those described in humans. This case represents the first canine report in which ONHD was primarily detected and comprehensively characterized using spectral-domain optical coherence tomography (SD-OCT). The modality enabled precise, non-invasive qualitative and quantitative assessment of ONHD and associated retinal alterations, facilitated differentiation of ONHD from true optic disc edema and other optic neuropathies, and allowed detailed longitudinal monitoring of structural and morphometric retinal changes over time. These findings highlight SD-OCT as a valuable diagnostic and monitoring tool in veterinary ophthalmology, particularly in cases of unexplained optic disc elevation. Declarations Ethics Statement This was a client-owned animal, and the client provided written informed consent for using any information from examinations, procedures, and publication of data and images. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. Funding Not applicable. Authors' contributions JZ conceived and designed the study, conducted the investigation, performed the formal analysis, and was responsible for project administration and supervision. JZ also wrote the original draft and contributed to the review and editing of the manuscript, as well as to the validation of the results. WT took part in the investigation, formal analysis, and validation of the study, was a major contributor in writing the original draft, and participated in reviewing and editing the manuscript. BK contributed to the investigation, software development, data visualization, and formal analysis, and participated in reviewing and editing the manuscript. MP was involved in the investigation, formal analysis, validation, and provided essential resources for the study. IB contributed to data curation, resource management, project administration, and conceptualization. IB also participated in the investigation, methodology design, formal analysis, visualization, validation, and was a contributor in writing the original draft. All authors read and approved the final manuscript. Acknowledgments The results of this study were presented as an abstract during the European Society of Veterinary Ophthalmology (ESVO) Meeting, held from 2–5 October 2025. 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Arch Ophthalmol. 2009 Jan;127(1):45-9. PMID: 19139337. doi: 10.1001/archophthalmol.2008.524. Ramirez H, Blatt ES, Hibri NS. Computed tomographic identification of calcified optic nerve drusen. Radiology. 1983 Jul;148(1):137-9. PMID: 6856823. doi: 10.1148/radiology.148.1.6856823. Bidot S, Lamirel C. Asymptomatic swollen optic discs and CT scan. Neurol Clin Pract. 2012 Jun;2(2):165-166. PMID: 29443292; PMCID: PMC5798212. doi: 10.1212/CPJ.0b013e31825a61cc. Wang DD, Leong JCY, Gale J, Wells AP. Multimodal imaging of buried optic nerve head drusen. Eye (Lond). 2018 Jun;32(6):1145-1146. Epub 2018 Jan 30. PMID: 29379102; PMCID: PMC5997681. doi: 10.1038/s41433-017-0009-8. Table Table 1. Measurements of individual retinal layers and total retinal thickness in the peripapillary region in the control group and in the clinical case during the first and second SD-OCT examinations. ILM+ NFL GCL ILM +NFL +GCL IPL INL OPL ONL ELM MZ EZ IZ PR+ TRT Control 12 18 35 40 17 13 56 9 10 12 16 46 201 SD-OCT 1 15 20 35 40 12 13 62 10 11 17 16 54 214 SD-OCT 2 12 18 30 35 14 14 62 9 9 15 16 49 204 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 29 Apr, 2026 Reviews received at journal 22 Apr, 2026 Reviewers agreed at journal 18 Apr, 2026 Reviewers invited by journal 21 Jan, 2026 Editor invited by journal 09 Jan, 2026 Editor assigned by journal 06 Jan, 2026 Submission checks completed at journal 06 Jan, 2026 First submitted to journal 03 Jan, 2026 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. 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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-8509002","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":578358630,"identity":"4a93be13-53dd-4349-b756-9b62478959ed","order_by":0,"name":"Jowita Zwolska","email":"","orcid":"","institution":"University of Life Sciences in Lublin","correspondingAuthor":false,"prefix":"","firstName":"Jowita","middleName":"","lastName":"Zwolska","suffix":""},{"id":578358631,"identity":"51b134d5-3000-4100-b4f3-9bdadb4f3673","order_by":1,"name":"Wiktoria Teodorowska","email":"","orcid":"","institution":"Klinika 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Padjasek","email":"","orcid":"","institution":"International Institute of Translational Medicine (MIMT)","correspondingAuthor":false,"prefix":"","firstName":"Martyna","middleName":"","lastName":"Padjasek","suffix":""},{"id":578358634,"identity":"f957f3c4-7be5-407f-bcd3-fb2906c8860c","order_by":4,"name":"Ireneusz Balicki","email":"","orcid":"","institution":"University of Life Sciences in Lublin","correspondingAuthor":false,"prefix":"","firstName":"Ireneusz","middleName":"","lastName":"Balicki","suffix":""}],"badges":[],"createdAt":"2026-01-03 20:53:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8509002/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8509002/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":100930655,"identity":"d2338398-7d85-44b7-8f38-44d46025fe92","added_by":"auto","created_at":"2026-01-23 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00:41:36","extension":"html","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":86938,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8509002/v1/d746b20cd00ac6986acc373b.html"},{"id":100930657,"identity":"0a0c7190-797f-4594-b9a0-2a23dca04b2a","added_by":"auto","created_at":"2026-01-23 00:41:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1700174,"visible":true,"origin":"","legend":"\u003cp\u003eFundus photographs of the right (A) and left (B) eyes obtained during the first (1) and second (2) examinations.\u003c/p\u003e","description":"","filename":"Fig.1.png","url":"https://assets-eu.researchsquare.com/files/rs-8509002/v1/327731f19936967c0b0e3d2a.png"},{"id":100930661,"identity":"a8b55430-4f3c-4318-b8bb-6901a39e8b11","added_by":"auto","created_at":"2026-01-23 00:41:36","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":262840,"visible":true,"origin":"","legend":"\u003cp\u003eScotopic single-flash rod responses (A), photopic single-flash cone responses (B), and cone flicker responses (C) recorded from the right and left eyes during two electroretinographic examinations performed 14 months apart.\u003c/p\u003e","description":"","filename":"Fig.2.png","url":"https://assets-eu.researchsquare.com/files/rs-8509002/v1/a71ce727bde940593db8d49d.png"},{"id":100930665,"identity":"00aaef54-c939-4dcf-bd6b-4dfdaf7d8577","added_by":"auto","created_at":"2026-01-23 00:41:36","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":5886584,"visible":true,"origin":"","legend":"\u003cp\u003eRetinal tear (A) and adjacent retinal hole (B) located in the dorsotemporal region of the left eye. Enlargement of both the tear and the hole was documented during the second SD-OCT examination (C).\u003c/p\u003e","description":"","filename":"Fig.3.png","url":"https://assets-eu.researchsquare.com/files/rs-8509002/v1/f5d51f142c73f047c6bb0de9.png"},{"id":100930664,"identity":"d7c77042-9d4a-4e3f-b8b0-26f464bd428c","added_by":"auto","created_at":"2026-01-23 00:41:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1882283,"visible":true,"origin":"","legend":"\u003cp\u003eSpectral-domain optical coherence tomography (SD-OCT) scans from the first (A, B) and second (C) examinations. Optic nerve head drusen (ONHD) within the optic nerve head are indicated by white arrows in images A and B. A peripapillary hyperreflective ovoid mass-like structure (PHOMS) is marked by a white arrow in image C. The irregular internal contour of the optic nerve head, outlined by a white line in image A, is consistent with pseudopapilledema.\u003c/p\u003e","description":"","filename":"Fig.4.png","url":"https://assets-eu.researchsquare.com/files/rs-8509002/v1/3e4bc08e5d8c8eae85a8d0a1.png"},{"id":100951998,"identity":"0710acd6-b0d5-451a-8a97-75c7c6b71471","added_by":"auto","created_at":"2026-01-23 07:11:40","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":148371,"visible":true,"origin":"","legend":"\u003cp\u003eUltrasonography of the left eye, in which optic nerve head drusen were diagnosed. A hyperechoic lesion within the optic nerve head protruding toward the vitreous cavity is visible (white arrow).\u003c/p\u003e","description":"","filename":"Fig.5.png","url":"https://assets-eu.researchsquare.com/files/rs-8509002/v1/f4753d6dd2ba2676d0f57cca.png"},{"id":101207499,"identity":"f9ab01c3-8cf3-4549-8dde-80d0d1ef8605","added_by":"auto","created_at":"2026-01-27 10:05:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11444072,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8509002/v1/7a94805d-cf3f-4ab3-a69c-3ae39b1f38a5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"SD-OCT Diagnosis of Optic Nerve Head Drusen and Pseudopapilledema Associated With Advanced Chorioretinopathy in a Dog: Case Report","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOptic disc elevation is a frequent clinical finding that may result from true optic disc edema or from pseudopapilledema, commonly caused by optic nerve head drusen (ONHD). Distinguishing between these two entities can be challenging, as both may present with blurred disc margins and elevation of the optic nerve head on funduscopic examination. Relying solely on funduscopic appearance and patient history often leads to diagnostic uncertainty, since the key differentiating features - such as disc color, vascular congestion, or subtle topographical variations - may be difficult to evaluate without advanced imaging.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e Accurate differentiation is crucial, however, as true papilledema usually indicates increased intracranial pressure and requires urgent investigation, whereas pseudopapilledema is a benign condition associated with deposits within the optic nerve head.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eOptic nerve head drusen are acellular deposits composed primarily of calcium, mucopolysaccharides, and amino acids such as arginine, tryptophan, and tyrosine.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e They can occur superficially, where they are visible upon ophthalmoscopic examination, or deeply within the optic disc, where they may mimic papilledema.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e The pathogenesis remains uncertain, though impaired axoplasmic transport and subsequent mitochondrial calcification have been proposed as potential mechanisms.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eOver the years, several diagnostic modalities have been employed to identify and differentiate ONHD from true optic disc edema. B-scan ultrasonography has traditionally been used for the detection of calcified optic nerve head drusen owing to its ability to demonstrate hyperreflective foci with posterior acoustic shadowing, while its utility in identifying non-calcified drusen is limited.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e Other techniques, including fluorescein angiography, scanning laser ophthalmoscopy, and computed tomography, have also contributed to diagnostic accuracy, particularly in detecting superficial drusen. However, the sensitivity of fluorescein angiography for the detection of optic nerve head drusen is lower than that of ultrasonography. \u003csup\u003e2,3,11\u003c/sup\u003e More recently, optical coherence tomography, particularly in its spectral-domain form, has emerged as a valuable non-invasive imaging tool capable of visualizing both superficial and buried drusen, as well as quantifying retinal nerve fiber layer thickness, and is currently regarded as the gold standard for the evaluation of optic nerve head drusen.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eIn veterinary ophthalmology, reports of optic nerve head drusen remain exceedingly rare. To date, ONHD in dogs have primarily been described using computed tomography or ultrasonography, but not with SD-OCT.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e This case report describes a dog with optic nerve head drusen (ONHD) in which advanced chorioretinopathy was additionally identified and was considered presumptively unrelated to the ONHD, based on spectral-domain optical coherence tomography (SD-OCT) findings.\u003c/p\u003e"},{"header":"Case report","content":"\u003cp\u003eA 3-year-old male mixed-breed dog weighing 21 kg, of unknown medical history, adopted from a shelter, was presented with suspected retinal detachment and optic disc edema. The dog showed no improvement after anti-inflammatory therapy. Treatment consisted of systemic corticosteroid therapy using prednisone at a dose of 1 mg/kg body weight per day, administered orally for two weeks, followed by a gradual taper. According to the owner, the initial clinical concern was night vision impairment. Two complete ophthalmic examinations were performed 10 months apart. Each examination included funduscopy (using a binocular indirect ophthalmoscope [Keeler, UK], a direct ophthalmoscope [Welch Allyn, USA], and a PanOptic ophthalmoscope [Welch Allyn, USA]) and SD-OCT (Topcon 3D OCT-2000, Topcon, Japan). In addition, electroretinography (ERG), with the use of the LKC RETevet system (LKC Technologies, USA), was performed twice, 14 months apart. Ultrasonography (USG) [Vinno G65, Norax] and magnetic resonance imaging (MRI) [GE Optima MR450w 1.5T, GE Medical Systems Polska Sp. z o.o., Warsaw, Poland] were each performed once. Animal owner provided written informed consent for enrollment in the study, procedures and therapy undertaken, and publication of data and images. SD-OCT-based retinal morphology and morphometry were compared with data obtained from 11 healthy control mixed-breed dogs of comparable body weight (18-24 kg) and age (2-4 years). Complete blood count and serum biochemistry results were within normal limits.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe ophthalmic evaluation included assessments of menace response, dazzle reflex, tracking reflex, and visual placing reflex, as well as an obstacle course test. The obstacle course was conducted first under scotopic and then under photopic conditions. Chromatic pupillary light reflexes were tested using a BPI-50 Precision Illuminator (RetinoGraphics Inc., USA). All the aforementioned reflexes and responses were intact. Schirmer\u0026rsquo;s Tear Test (Eickemeyer, Germany) and intraocular pressure measurements obtained with a TonoVet rebound tonometer (iCare, Finland) were within normal ranges in both eyes. Slit-lamp biomicroscopy revealed no abnormalities in the anterior segment of either eye.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunduscopic findings:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFunduscopic examination revealed chorioretinal lesions that differed slightly between the right and left eyes (Figure 1). In the right eye, two areas of well-demarcated areas of tapetal hyperreflectivity with a pigmented center were observed. Additionally, two further oval hyperreflective areas were present in the dorsotemporal region. Abnormal retinal pigmentation was also noted within the tapetal fundus. Two well-demarcated areas of depigmentation were present: one at the tapetal-non-tapetal border within the non-tapetal fundus of the ventrotemporal region, and the other within the non-tapetal fundus of the ventronasal region. \u0026nbsp;In the left eye, three areas of tapetal hyperreflectivity with a pigmented center were identified in the dorsotemporal region. As in the right eye, abnormal retinal pigmentation was evident in the tapetal fundus. Furthermore, elevation and blurring of the optic disc margins were observed. During the subsequent funduscopic examination, in the right eye slight thinning of the retinal blood vessels was observed compared to the previous examination. The chorioretinal lesions appearance remained comparable, although progression of abnormal tapetal pigmentation was noted. In the left eye, the funduscopic findings were comparable to those observed during the previous examination.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectroretinography:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTwo ERG examinations were performed using the LKC RETevet system (LKC Technologies, USA) in accordance with the ECVO 5-step protocol. Electroretinography (ERG) was performed twice, at a 14-month interval, as part of the diagnostic evaluation and longitudinal follow-up of suspected retinopathy to assess changes in retinal function over time. Prior to testing, the pupils were dilated with topical tropicamide (Tropicamidum WZF 1%, Polfa Warszawa S.A., Poland). Anesthesia was induced using intramuscular dexmedetomidine (Dexdomitor, Orion Pharma, Espoo, Finland) at 2.5 \u0026micro;g/kg and butorphanol (Butomidor, Richter Pharma AG, Wels, Austria) at 0.2 mg/kg, followed by intravenous propofol (Propofol-Lipuro, B. Braun Melsungen AG, Melsungen, Germany) at 1 mg/kg for induction. After endotracheal intubation, general anesthesia was maintained with 1% isoflurane (IsoFlo, Zoetis, Louvain-la-Neuve, Belgium). Corneal anesthesia was achieved using 0.5% proxymetacaine hydrochloride (Alcaine 5 mg/mL, Alcon, Warsaw, Poland). The right eye was examined first. In the rod response protocol (white flash, 0.01 cd\u0026middot;s/m\u0026sup2;, 0.2 Hz, dark adaptation 20 min, no background), both eyes demonstrated reduced amplitudes with normal implicit times. Compared with the initial ERG, the amplitude in the right eye decreased by approximately 70% from baseline, while the left eye showed a reduction of around 20%. A similar amplitude reduction was observed in the cone response protocol (white flash, 3.0 cd\u0026middot;s/m\u0026sup2;, 2 Hz, light adaptation 10 min, background 30 cd/m\u0026sup2;), with approximately 80% reduction in the right eye and 20% in the left eye. These findings indicated bilateral photoreceptor dysfunction, more pronounced in the right eye (Figure 2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOptical coherence tomography:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSD-OCT examinations were performed twice-initially on the day of the first visit and again 10 months later. Pupillary dilation was achieved using tropicamide (Tropicamidum WZF 1%, Polfa Warszawa S.A., Poland). The procedure was carried out under sedation using intramuscular medetomidine at a dose of 15 \u0026mu;g/kg body weight (Domitor 1 mg/mL, Orion Pharma, Finland). Topical anesthesia of the cornea and conjunctiva was induced using 0.5% proxymetacaine hydrochloride (Alcaine 5 mg/mL, Alcon, Warsaw, Poland). The eye was stabilized by gently grasping the bulbar conjunctiva with thumb forceps. For detailed evaluation of retinal and optic disc structures, linear, 6-line radial, cross-sectional, and 3D scans (\u0026lambda; = 840 nm; enhanced depth imaging mode; Topcon 3D OCT-2000; Topcon, Japan) were obtained. During imaging, the cornea was kept moist with saline drops applied every 30 seconds to prevent desiccation and ensure optimal image quality.\u003c/p\u003e\n\u003cp\u003eMeasurements of retinal layers were performed in the left eye, where ONHD were present in the peripapillary region. The following retinal layers were analyzed: internal limiting membrane + nerve fiber layer (ILM+NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor layers including external limiting membrane (ELM), myoid zone (MZ), ellipsoid zone (EZ), outer photoreceptor segment (OPRS), and interdigitation zone (IZ), outer retina (OR; OPL + ONL + ELM + MZ + EZ + OPRS + IZ), and total retinal thickness (TRT), measured from the internal limiting membrane to the interdigitation zone, excluding the retinal pigment epithelium\u0026ndash;Bruch\u0026rsquo;s membrane\u0026ndash;choriocapillaris complex (RPE\u0026ndash;BmCc).\u003c/p\u003e\n\u003cp\u003eDuring the first SD-OCT examination, multiple chorioretinal lesions were detected in the right eye, localized in the temporal tapetal region and at the tapetal\u0026ndash;non-tapetal border. Within these chorioretinal lesions, advanced retinal atrophy with thinning and disorganization of the retinal layers was observed. Segmental thinning of the outer nuclear layer (ONL) was noted, accompanied by loss and disorganization of the inner retinal layers (MZ, EZ, OPRS, IZ) in the dorsotemporal and non-tapetal fundus. A lamellar retinal tear and an adjacent retinal hole were identified in the dorsotemporal region of the left eye. The retina in the area surrounding the hole was thickened. The retinal layers adjacent to the retinal tear and hole were disorganized. Both the hole and tear extended to the outer nuclear layer (ONL). In the case of the retinal tear, the ONL, ellipsoid zone (EZ), outer photoreceptor segments (OPRS), and interdigitation zone (IZ) were disorganized (Figures 3A and 3B).\u003c/p\u003e\n\u003cp\u003eIn the left eye, multiple chorioretinal lesions were detected in the dorsal region. The retina surrounding the lesions exhibited ongoing disorganization and thinning of retinal layers. SD-OCT performed during the first examination revealed multiple hyperreflective structures within the optic nerve head consistent with optic nerve head drusen (ONHD), located both superficially and at deeper levels of the prelaminar region. The internal contour of the optic nerve head was irregular, with elevation and blurred margins, findings consistent with pseudopapilledema rather than true optic disc edema. Peripapillary retinal nerve fiber layer (RNFL) thickness measurements were obtained, allowing quantitative assessment of neuroaxonal integrity (Figure 4). Retinal schisis between the ILM/NFL and GCL layers was observed in the peripapillary region. A Bergmeister\u0026rsquo;s papilla was visible at the optic nerve apex, representing a physiological finding. The optic nerve head appeared elevated, with an irregular internal contour consistent with pseudopapilledema (Figure 4A).\u003c/p\u003e\n\u003cp\u003eIn the follow-up SD-OCT examination, the right eye exhibited areas of advanced retinal atrophy in the non-tapetal regions. Segmental thinning of the ONL and progressive disorganization of the retinal layers were also evident in the peripapillary region. Both the retinal tear and the retinal hole increased in size. Temporally beyond the hole, the retina exhibited advanced thinning and disorganization of the retinal layers. (Figure 3C). On follow-up SD-OCT examination, persistent optic nerve head elevation was observed. In addition, a peripapillary hyperreflective ovoid mass-like structure (PHOMS) was identified adjacent to the optic nerve head. The overall OCT appearance remained stable over time, supporting a non-inflammatory and non-progressive process (Figure 4). SD-OCT assessment of the choroid in well-demarcated areas of tapetal hyperreflectivity with central pigmentation in the tapetal fundus, as well as in areas of depigmentation in the non- tapetal fundus, was associated with retinal and choroidal atrophy in both eyes. The choroid was thinner than in surrounding regions, particularly in the large vessel layer. Morphometric analysis of retinal layers in the left eye with ONHD revealed thinning of the peripapillary retina after 10 months, with a 14% reduction in the ILM+NFL+GCL layers and a 12.5% decrease in the IPL thickness (Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eUltrasonography:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOcular ultrasonography (Vinno G65, Norax) was performed immediately after the initial SD-OCT examination. During the examination, the optic nerve head region was carefully assessed for the presence of hyperechoic structures and lesions protruding toward the vitreous cavity, which are characteristic features of optic nerve head drusen. In the left eye, a well-defined hyperechoic structure was identified within the optic nerve head, causing focal protrusion toward the vitreous cavity (Figure 5). These ultrasonographic findings were consistent with optic nerve head drusen. No hyperechoic lesions were detected in the optic nerve head region of the right eye.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMagnetic resonance imaging:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMagnetic resonance imaging (MRI) of the head was performed two weeks after the initial OCT examination using a high-field 1.5 T GE system [GE Optima MR450w 1.5T, GE Medical Systems Polska Sp. z o.o., Warsaw, Poland]. The protocol included FSE sequences in T1-weighted (sagittal, coronal, and transverse planes), T2-weighted (sagittal, coronal, and transverse planes), T2*-weighted (transverse plane), FLAIR (coronal plane), DWI (transverse plane), and ADC (transverse plane) images. Post-contrast imaging was obtained using T1-weighted (sagittal, coronal, and transverse planes) and FLAIR (coronal plane) sequences following intravenous administration of contrast medium (Dotagraf, 0.5 mmol/ml; Bayer Pharma AG, Berlin, Germany). The retrobulbar spaces were unremarkable, and both optic nerves showed no detectable abnormalities. The cerebrospinal fluid\u0026ndash;filled perineural subarachnoid spaces surrounding the optic nerves were of normal width throughout their visible course. Mild asymmetry of the lateral cerebral ventricles was observed, without evidence of disturbed cerebrospinal fluid flow, most likely representing a normal anatomic variant. No inflammatory or structural abnormalities were identified within the brain or optic nerves.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOptic nerve head drusen are acellular, usually calcified deposits located anterior to the lamina cribrosa, commonly associated with pseudopapilledema. Visual field defects are a common consequence of ONHD in humans. Studies report that 63.2% of eyes with ONHD exhibit visual field deficits, while abnormal visual evoked potentials are observed in 44.7% of eyes with visible drusen and 20% with buried drusen. Although most eyes with ONHD progress slowly, approximately 12% may show moderate to rapid visual field loss.\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e In the present case, ERG revealed a 20% reduction in photoreceptor cell function in the eye affected by drusen. However, due to the presence of concurrent chorioretinal lesions of unknown origin, it is not possible to determine to what extent the observed ERG abnormalities were directly attributable to the drusen themselves.\u003c/p\u003e \u003cp\u003eIn the present case, ophthalmic examination revealed preserved visual function, with intact menace response, dazzle reflex, tracking and visual placing reflexes, as well as normal performance on an obstacle course under both scotopic and photopic conditions. Chromatic pupillary light reflexes were within normal limits bilaterally. It should be emphasized that the absence of visual deficits and normal pupillary light reflexes (PLRs) does not exclude papilledema, particularly when associated with intracranial hypertension. In contrast to optic neuritis, papilledema represents a passive swelling of the optic nerve head secondary to increased intracranial pressure and may initially occur without functional impairment of the optic nerve. Consequently, visual deficits and PLR abnormalities are not obligatory findings, especially in early or moderate stages of the disease.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e In the present case, preserved chromatic PLRs argue against a primary inflammatory optic neuropathy. The observed visual dysfunction was instead supported by abnormal electroretinography findings consistent with chorioretinopathy, indicating a retinal rather than optic nerve origin of visual impairment. Therefore, normal PLRs do not rule out papilledema but rather support the absence of clinically significant optic nerve dysfunction.\u003c/p\u003e \u003cp\u003eMorphometric analysis of the retinal layers over 10 months demonstrated thinning of the peripapillary retina, with a 14% reduction in ILM\u0026thinsp;+\u0026thinsp;NFL\u0026thinsp;+\u0026thinsp;GCL layers and a 12.5% reduction in IPL thickness. These findings parallel observations in humans with ONHD, where peripapillary NFL thinning progresses in correlation with age.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eDifferentiation between true optic disc edema and pseudopapilledema is critical, as it has significant implications for patient management. Misdiagnosis may lead to unnecessary and potentially invasive diagnostic procedures. Superficial drusen are occasionally visible during ophthalmoscopy, yet deeply buried ones may remain undetected without the aid of advanced imaging modalities. In our case, ocular B-scan ultrasonography identified a well-defined hyperechoic structure within the optic nerve head of the left eye, causing focal protrusion toward the vitreous cavity, consistent with optic nerve head drusen, while no such lesions were observed in the right eye. It is observed that in patients with intracranial hypertension, OCT can demonstrate a deflection of Bruch\u0026rsquo;s membrane toward the vitreous, which helps differentiate papilledema from pseudopapilledema. However, in our clinical case no displacement of Bruch\u0026rsquo;s membrane was observed. True optic disc edema is characterized by an elevated optic nerve head with a smooth internal contour, whereas pseudopapilledema associated with ONHD presents as an elevated optic nerve head with irregular internal contour on SD-OCT imaging.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e In the present case, SD-OCT revealed the presence of ONHD, identified as sharply demarcated hyperreflective deposits within the optic nerve head, as well as PHOMS visualized as ovoid hyperreflective formations in the peripapillary area. Moreover, SD-OCT confirmed the presence of an irregular internal contour, consistent with pseudopapilledema.\u003c/p\u003e \u003cp\u003eIn veterinary medicine, the diagnosis of ONHD has been rare and dependent on ultrasonography or computed tomography. Ram\u0026iacute;rez et al. (1983) were among the first to describe calcified drusen in a dog using CT, where they appeared as hyperdense foci consistent with optic nerve calcification.\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e Comparable hyperdense calcified deposits have been documented in human studies, reinforcing the morphological similarities between species.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e More recently, Niranjana et al. (2023) reported the incidental discovery of bilateral optic nerve head drusen in a six-year-old Rottweiler during head CT examination.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e Characteristic discrete hyperdense areas were identified within the optic nerve head. In contrast, the present case represents the first report of ONHD in a dog confirmed and characterized using the non-invasive SD-OCT, which enabled precise longitudinal monitoring of structural changes not achievable with previously available imaging methods.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe peripapillary retinal thinning coexisting with optic nerve head drusen (ONHD) and peripapillary hyperreflective ovoid mass-like structures (PHOMS) underscores the similarity of pathological changes observed in this dog to those described in humans. This case represents the first canine report in which ONHD was primarily detected and comprehensively characterized using spectral-domain optical coherence tomography (SD-OCT). The modality enabled precise, non-invasive qualitative and quantitative assessment of ONHD and associated retinal alterations, facilitated differentiation of ONHD from true optic disc edema and other optic neuropathies, and allowed detailed longitudinal monitoring of structural and morphometric retinal changes over time. These findings highlight SD-OCT as a valuable diagnostic and monitoring tool in veterinary ophthalmology, particularly in cases of unexplained optic disc elevation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis was a client-owned animal, and the client provided written informed consent for using\u003c/p\u003e\n\u003cp\u003eany information from examinations, procedures, and publication of data and images.\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 datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors report no conflicts of interest. The authors alone are responsible for the content\u003c/p\u003e\n\u003cp\u003eand writing of the paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJZ conceived and designed the study, conducted the investigation, performed the formal analysis, and was responsible for project administration and supervision. JZ also wrote the original draft and contributed to the review and editing of the manuscript, as well as to the validation of the results. WT took part in the investigation, formal analysis, and validation of the study, was a major contributor in writing the original draft, and participated in reviewing and editing the manuscript. BK contributed to the investigation, software development, data visualization, and formal analysis, and participated in reviewing and editing the manuscript. \u0026nbsp;MP was involved in the investigation, formal analysis, validation, and provided essential resources for the study. IB contributed to data curation, resource management, project administration, and conceptualization. IB also participated in the investigation, methodology design, formal analysis, visualization, validation, and was a contributor in writing the original draft. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe results of this study were presented as an abstract during the European Society of Veterinary Ophthalmology (ESVO) Meeting, held from 2\u0026ndash;5 October 2025.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDisclosure\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eArtificial Intelligence (AI) Generated Content: The authors have not used AI to generate any part of the manuscript.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eFriedman AH, Beckerman B, Gold DH, Walsh JB, Gartner S. Drusen of the optic disc. Surv Ophthalmol. 1977 Mar-Apr;21(5):373-90. PMID: 68551. doi: 10.1016/0039-6257(77)90041-8.\u003c/li\u003e\n \u003cli\u003eAllegrini D, Pagano L, Ferrara M, Borgia A, Sorrentino T, Montesano G, Angi M, Romano MR. Optic disc drusen: a systematic review: Up-to-date and future perspective. Int Ophthalmol. 2020 Aug;40(8):2119-2127. Epub 2020 May 7. PMID: 32383130. doi: 10.1007/s10792-020-01365-w.\u003c/li\u003e\n \u003cli\u003ePineles SL, Arnold AC. Fluorescein angiographic identification of optic disc drusen with and without optic disc edema. J Neuroophthalmol. 2012 Mar;32(1):17-22. PMID: 21926917; PMCID: PMC3713807. doi: 10.1097/WNO.0b013e31823010b8.\u003c/li\u003e\n \u003cli\u003eChang MY, Pineles SL. Optic disk drusen in children. Surv Ophthalmol. 2016 Nov-Dec;61(6):745-758. Epub 2016 Mar 29. PMID: 27033945; PMCID: PMC5042815. doi: 10.1016/j.survophthal.2016.03.007.\u003c/li\u003e\n \u003cli\u003eRosa N, De Bernardo M, Abbinante G, Vecchio G, Cione F, Capasso L. Optic Nerve Drusen Evaluation: A Comparison between Ultrasound and OCT. J Clin Med. 2022 Jun 27;11(13):3715. PMID: 35806999; PMCID: PMC9267746. doi: 10.3390/jcm11133715.\u003c/li\u003e\n \u003cli\u003eTso MO. Pathology and pathogenesis of drusen of the optic nervehead. Ophthalmology. 1981 Oct;88(10):1066-80. PMID: 7335311. doi: 10.1016/s0161-6420(81)80038-3.\u003c/li\u003e\n \u003cli\u003eObuchowska I, Mariak Z. Zaburzenia pola widzenia w druzach tarczy nerwu wzrokowego [Visual field defects in the optic disc drusen]. Klin Oczna. 2008; Polish. PMID: 19195165. doi: 110(10-12):357-60.\u003c/li\u003e\n \u003cli\u003eHamann S, Malmqvist L, Costello F. Optic disc drusen: understanding an old problem from a new perspective. Acta Ophthalmol. 2018 Nov;96(7):673-684. Epub 2018 Apr 16. PMID: 29659172. doi: 10.1111/aos.13748.\u003c/li\u003e\n \u003cli\u003eAlmog Y, Nemet A, Nemet AY. Optic disc drusen demonstrate a hyperechogenic artifact in B mode ultrasound. J Clin Neurosci. 2016 Jan;23:111-119. Epub 2015 Sep 26. PMID: 26412252. doi: 10.1016/j.jocn.2015.08.005.\u003c/li\u003e\n \u003cli\u003eMorris RW, Ellerbrock JM, Hamp AM, Joy JT, Roels P, Davis CN Jr. Advanced visual field loss secondary to optic nerve head drusen: case report and literature review. Optometry. 2009 Feb;80(2):83-100. PMID: 19187896. doi: 10.1016/j.optm.2008.11.004.\u003c/li\u003e\n \u003cli\u003eChang MY, Velez FG, Demer JL, Bonelli L, Quiros PA, Arnold AC, Sadun AA, Pineles SL. Accuracy of Diagnostic Imaging Modalities for Classifying Pediatric Eyes as Papilledema Versus Pseudopapilledema. Ophthalmology. 2017 Dec;124(12):1839-1848. Epub 2017 Jul 18. PMID: 28732589. doi: 10.1016/j.ophtha.2017.06.016.\u003c/li\u003e\n \u003cli\u003eCarta A, Mora P, Aldigeri R, Gozzi F, Favilla S, Tedesco S, Calzetti G, Farci R, Barboni P, Bianchi-Marzoli S, Fossarello M, Gandolfi S, Sadun AA. Optical coherence tomography is a useful tool in the differentiation between true edema and pseudoedema of the optic disc. PLoS One. 2018 Nov 29;13(11):e0208145. PMID: 30496251; PMCID: PMC6264818. doi: 10.1371/journal.pone.0208145.\u003c/li\u003e\n \u003cli\u003eNiranjana, C., Shafiuzama, M. and Iyer, R.C. (2023) \u0026lsquo;Computed tomographic finding of bilateral optic nerve head drusen in a dog \u0026ndash; a case report\u0026rsquo;, \u003cem\u003eVeterinarski Arhiv\u003c/em\u003e, 93, pp. 491\u0026ndash;494. doi: 10.24099/vet.arhiv.1774\u003c/li\u003e\n \u003cli\u003eEstrela T, Jammal AA, El-Dairi M, Medeiros FA. Rates of Visual Field Change in Eyes With Optic Disc Drusen. J Neuroophthalmol. 2023 Sep 1;43(3):353-358. Epub 2023 Jan 18. PMID: 36728098; PMCID: PMC10352462. doi: 10.1097/WNO.0000000000001801.\u003c/li\u003e\n \u003cli\u003eVienne-Jumeau A, Lebranchu P, Akhenak I, Bremond-Gignac D, Robert MP. Peripapillary hyperreflective ovoid mass-like structure (PHOMS) and optic disc drusen in pediatric pseudo-papilledema. Graefes Arch Clin Exp Ophthalmol. 2025 Jun;263(6):1725-1732. Epub 2025 Mar 18. PMID: 40102220. doi: 10.1007/s00417-025-06799-5.\u003c/li\u003e\n \u003cli\u003eJohnson LN, Diehl ML, Hamm CW, Sommerville DN, Petroski GF. Differentiating optic disc edema from optic nerve head drusen on optical coherence tomography. Arch Ophthalmol. 2009 Jan;127(1):45-9. PMID: 19139337. doi: 10.1001/archophthalmol.2008.524.\u003c/li\u003e\n \u003cli\u003eRamirez H, Blatt ES, Hibri NS. Computed tomographic identification of calcified optic nerve drusen. Radiology. 1983 Jul;148(1):137-9. PMID: 6856823. doi: 10.1148/radiology.148.1.6856823.\u003c/li\u003e\n \u003cli\u003eBidot S, Lamirel C. Asymptomatic swollen optic discs and CT scan. Neurol Clin Pract. 2012 Jun;2(2):165-166. PMID: 29443292; PMCID: PMC5798212. doi: 10.1212/CPJ.0b013e31825a61cc.\u003c/li\u003e\n \u003cli\u003eWang DD, Leong JCY, Gale J, Wells AP. Multimodal imaging of buried optic nerve head drusen. Eye (Lond). 2018 Jun;32(6):1145-1146. Epub 2018 Jan 30. PMID: 29379102; PMCID: PMC5997681. doi: 10.1038/s41433-017-0009-8.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Measurements of individual retinal layers and total retinal thickness in the peripapillary region in the control group and in the clinical case during the first and second SD-OCT examinations.\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"602\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 79px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 53px;\"\u003e\n \u003cp\u003eILM+\u003cbr\u003e\u0026nbsp;NFL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eGCL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003eILM\u003cbr\u003e\u0026nbsp;+NFL\u003cbr\u003e\u0026nbsp;+GCL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 35px;\"\u003e\n \u003cp\u003eIPL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eINL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003eOPL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003eONL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 50px;\"\u003e\n \u003cp\u003eELM\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003eMZ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003eEZ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 26px;\"\u003e\n \u003cp\u003eIZ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003ePR+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003eTRT\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 79px;\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 53px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 35px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 50px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 26px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e201\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 79px;\"\u003e\n \u003cp\u003eSD-OCT 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 53px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 35px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 50px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 26px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e214\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 79px;\"\u003e\n \u003cp\u003eSD-OCT 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 53px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 35px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 43px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 46px;\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 50px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 26px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 34px;\"\u003e\n \u003cp\u003e49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 38px;\"\u003e\n \u003cp\u003e204\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"bmc-veterinary-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [BMC Veterinary Research](http://bmcvetres.biomedcentral.com/)","snPcode":"12917","submissionUrl":"https://submission.nature.com/new-submission/12917/3?","title":"BMC Veterinary Research","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"optic nerve head drusen, pseudopapilledema, chorioretinopathy, SD-OCT, dog","lastPublishedDoi":"10.21203/rs.3.rs-8509002/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8509002/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eUnilateral pseudopapilledema and optic nerve head drusen (ONHD) are uncommon findings in dogs and can closely mimic true optic disc edema, which may lead to diagnostic uncertainty and ineffective anti-inflammatory treatment. Spectral-domain optical coherence tomography (SD-OCT) has emerged as a valuable tool for differentiating pseudopapilledema from papilledema by enabling detailed in vivo assessment of the optic nerve head. This case report presents a young mixed-breed dog with suspected retinal detachment and apparent optic disc swelling, in which SD-OCT supported the diagnosis of unilateral pseudopapilledema/ONHD, with advanced chorioretinopathy documented as an additional, case-specific finding. Two complete ophthalmic examinations were performed 10 months apart, including funduscopy and spectral-domain optical coherence tomography (SD-OCT). In addition, electroretinography (ERG) was performed twice, 14 months apart, while ultrasonography (USG) and magnetic resonance imaging (MRI) were each conducted once.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eFunduscopic evaluation revealed multiple chorioretinal lesions and optic disc elevation with blurred margins. SD-OCT identified hyperreflective drusen within the optic nerve head (ONHD), peripapillary hyperreflective ovoid mass-like structures (PHOMS), and localized retinal thinning. SD-OCT based morphometric analysis revealed retinal thinning, while ERG demonstrated photoreceptor dysfunction. Ocular B-scan ultrasonography demonstrated a well-defined hyperechoic lesion within the optic nerve head of the left eye, consistent with optic nerve head drusen, with no analogous findings in the right eye. MRI showed no evidence of disturbed cerebrospinal fluid flow, and no inflammatory or structural abnormalities were detected within the brain or optic nerves.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThis is the first canine case in which ONHD was primarily detected and characterized using SD-OCT. The modality enabled precise, non-invasive longitudinal monitoring of structural and morphometric retinal changes, allowed differentiation of ONHD from true optic disc edema and other optic neuropathies. SD-OCT represents a valuable tool for veterinary ophthalmology, particularly in cases of unexplained optic disc elevation.\u003c/p\u003e","manuscriptTitle":"SD-OCT Diagnosis of Optic Nerve Head Drusen and Pseudopapilledema Associated With Advanced Chorioretinopathy in a Dog: Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-23 00:41:19","doi":"10.21203/rs.3.rs-8509002/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"44902655144031931615037220794087483197","date":"2026-04-29T06:31:32+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-22T21:38:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"271526964489618145409250794385722477523","date":"2026-04-18T15:08:40+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-21T08:09:13+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-09T09:06:55+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-06T09:18:20+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-06T09:15:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Veterinary Research","date":"2026-01-03T20:47:47+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-veterinary-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [BMC Veterinary Research](http://bmcvetres.biomedcentral.com/)","snPcode":"12917","submissionUrl":"https://submission.nature.com/new-submission/12917/3?","title":"BMC Veterinary Research","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"daa33139-6e7c-43e6-8177-8e5ab440d5da","owner":[],"postedDate":"January 23rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-23T00:41:20+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-23 00:41:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8509002","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8509002","identity":"rs-8509002","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}