SD-OCT diagnosis of optic nerve head drusen and pseudopapilledema associated with advanced chorioretinopathy in a dog: case report

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. 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. 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.