A 7-year-old child is diagnosed with bilateral posterior subcapsular cataracts after prolonged use of systemic corticosteroids for nephrotic syndrome. What is the primary mechanism of steroid-induced cataract formation?

• A Covalent binding of steroids to lens crystallins altering their solubility ✓
• B Inhibition of Na-K ATPase at the lens epithelium causing ionic imbalance
• C Direct oxidative damage to lens fiber DNA
• D Accumulation of sorbitol through the polyol pathway

Explanation

Corticosteroids form covalent adducts with the lysine residues of lens crystallin proteins (particularly alpha-crystallin), altering their conformation and reducing their water solubility; these modified proteins aggregate and scatter light, producing posterior subcapsular opacity. The posterior subcapsular location is characteristic because epithelial cells migrating posteriorly along the capsule under steroid influence accumulate there. Sorbitol accumulation is the mechanism in diabetic cataracts.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.