A 30-year-old woman on long-term treatment following total thyroidectomy develops perioral tingling and a bilateral cataract composed of small multicoloured punctate opacities in the anterior and posterior subcapsular cortex. The underlying metabolic abnormality is:
- A Hypocalcaemia ✓
- B Hypokalaemia
- C Hypercalcaemia
- D Hypernatraemia
Correct answer: A. Hypocalcaemia
Explanation
Hypocalcaemia from parathyroid insufficiency causes the tetanic cataract: numerous small punctate, iridescent cortical opacities lying just beneath the capsule, separated from it by a zone of clear lens. Calcium levels must fall markedly before the cataract appears. Hypercalcaemia does not produce this pattern, and the punctate polychromatic subcapsular morphology is the discriminating feature.
Reference: Parsons' Diseases of the Eye, 23rd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.