An elderly patient reports that he can now read newspaper print without his distance glasses, although his distance vision has worsened over recent years. Which mechanism explains this 'second sight' phenomenon?

• A Cortical spokes clearing from the visual axis
• B Pupillary miosis improving depth of focus
• C Index myopia from increased refractive index of the sclerosing nucleus ✓
• D Posterior capsule thinning allowing better light transmission

Explanation

As the nucleus becomes progressively more sclerosed in nuclear sclerosis, its refractive index rises, producing acquired index myopia. The resulting myopic shift allows the patient to read at near without glasses even while distance vision deteriorates. Cortical cataracts do not produce this shift, miosis is not the primary driver here, and the posterior capsule remains intact in an unoperated cataractous lens.

Reference: Khurana, Comprehensive Ophthalmology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.