A 6-month-old infant presents with nystagmus, photophobia, and poor visual fixation from birth. The mother has albinism. On slit-lamp, the iris transilluminates fully. OCT of the macula shows absence of the foveal pit (foveal hypoplasia). The nystagmus is best explained by:

• A Cerebellar vermis dysfunction from associated neurological abnormality
• B Chiasmal misrouting of retinogeniculate fibers causing defective binocular development ✓
• C Central scotoma driving jerk nystagmus pattern
• D Strabismic amblyopia causing optokinetic nystagmus asymmetry

Explanation

In oculocutaneous albinism, reduced melanin in the RPE during fetal development leads to abnormal decussation at the optic chiasm — a larger-than-normal proportion of temporal fibers cross inappropriately, reducing the ipsilateral visual pathway. This misrouting disrupts normal binocular cortical development and normal VEP asymmetry, leading to infantile nystagmus syndrome. Foveal hypoplasia (absence of foveal pit) is a consistent OCT feature and contributes to reduced acuity. The nystagmus in albinism is due to this abnormal visual pathway development, not a primary cerebellar or strabismic cause.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.