Which mechanism best explains lens-induced (phacoanaphylactic) endophthalmitis following accidental rupture of the lens capsule during cataract surgery?

• A Direct bacterial contamination of the aqueous humour
• B Type III hypersensitivity reaction with circulating immune complexes
• C Type I IgE-mediated mast cell degranulation within the uveal tract
• D Type IV delayed hypersensitivity to sequestered lens protein released into the eye ✓

Explanation

Lens protein is normally sequestered behind the capsule and never exposed to the immune system. When capsular rupture releases it, a T-cell mediated delayed-type (type IV) hypersensitivity response develops, producing a zonal granulomatous inflammation centred on exposed lens matter, usually after a latent interval of days. Bacterial endophthalmitis presents within hours to days with hypopyon and marked toxicity, which is the key distractor to exclude.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.