A patient with suspected retinitis pigmentosa undergoes full-field electroretinography (ERG). The 30 Hz flicker response is markedly reduced with an increased implicit time (peak time). This pattern is most characteristic of:

• A Cone-rod dystrophy
• B X-linked juvenile retinoschisis
• C Rod-cone dystrophy (typical retinitis pigmentosa) ✓
• D Cancer-associated retinopathy (CAR)

Explanation

In rod-cone dystrophy (typical RP), rod responses are severely reduced or extinguished early, while cone responses (30 Hz flicker) are relatively preserved initially but eventually show reduced amplitude and prolonged implicit time. X-linked retinoschisis shows a negative waveform (normal a-wave, reduced b-wave); CAR shows reduced b-wave with normal a-wave.

Reference: Principles and Practice of Clinical Electrophysiology of Vision, 2nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.