A 40-year-old patient with type 1 diabetes mellitus presents with bilateral cataracts showing snowflake opacities in the subcapsular region. This type of cataract is also called 'metabolic cataract' and is associated with which biochemical pathway?
- A Sorbitol accumulation in the lens via the polyol pathway due to excess glucose converted by aldose reductase ✓
- B Nonenzymatic glycation of lens crystallins causing protein cross-linking and Maillard reaction products
- C Advanced glycation end-products (AGEs) binding to RAGE receptors on lens epithelial cells
- D Oxidative stress from superoxide dismutase deficiency in the lens cortex
Explanation
Diabetic 'snowflake' cataract occurs due to the polyol (sorbitol) pathway: excess intralenticular glucose → aldose reductase (in lens) converts glucose to sorbitol → sorbitol poorly membrane-permeable accumulates in lens fiber cells → osmotic water influx → lens fiber swelling, membrane disruption, and vacuole formation → subcapsular white opacities with snowflake appearance. This is true 'metabolic cataract' classically seen in young type 1 diabetics with poor control. The common nuclear sclerotic cataract in older diabetics is more related to glycation and oxidative mechanisms.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.