A 25-year-old male patient underwent a routine ophthalmic examination. Best-corrected visual acuity was 20/20 in both eyes.
During routine fundus examination, a striking asymmetry in optic disc size was noted. The right optic disc was more than 1.5 times larger than the left optic disc, making the asymmetry particularly apparent when both eyes were compared. Based on the fundus appearance and comparison with the fellow eye, the diameter of the right optic disc was estimated to be > 2.5 mm.
The patient had no visual complaints, and the finding was discovered incidentally during the examination. The overall appearance was consistent with megalopapilla, a congenital variant characterized by an abnormally large optic disc.
Color fundus photograph demonstrating megalopapilla in the right eye
Color fundus photograph of the left eye with normal-sized optic disc 
Megalopapilla
Megalopapilla refers to an unusually large optic nerve head with otherwise relatively preserved optic disc architecture. It is important to recognize this anatomical variant because a large optic disc may naturally have a relatively large physiological cup, potentially leading to an erroneous suspicion of glaucoma based solely on the cup-to-disc ratio. The assessment should therefore focus on the overall disc size, neuroretinal rim configuration, retinal nerve fiber layer, visual field, and—most importantly—evidence of structural or functional progression over time. In a patient with normal visual function and stable structural findings, a large cup in the setting of a large optic disc may represent anatomical variation rather than glaucomatous optic neuropathy.
This case highlights an important clinical principle: before interpreting a large cup as glaucomatous, always look at the size of the optic disc itself.
Credit: M. Giray Ersoz, MD, FEBO, Retina Specialist
Memorial Bahçelievler Hospital, Department of Ophthalmology, Istanbul, Turkey
Arel University School of Medicine, Department of Ophthalmology, Istanbul, Turkey
Instagram accounts: @retina.review and @retina.dr.girayersoz
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