On slit-lamp examination of a patient with a nasal pterygium, a fine golden-brown line is seen in the corneal epithelium just anterior to the advancing head of the growth. This finding represents:

• A Calcium salt deposition in sun-damaged epithelium
• B Copper deposition secondary to impaired biliary excretion
• C Haemosiderin from recurrent microhaemorrhages at the cap
• D Iron deposition caused by pooling of tears in front of the elevated lesion ✓

Explanation

The line described is Stocker's line, an iron deposit in the corneal epithelium lying just in front of the head of a pterygium. The elevated apex of the pterygium disturbs the precorneal tear film, tears pool there, and iron from the tears deposits in the epithelium. Copper deposition at the corneal periphery describes the Kayser-Fleischer ring, and calcium band keratopathy lies in the interpalpebral zone, so options B and A describe unrelated entities.

Reference: Parsons' Diseases of the Eye, 23rd ed.

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Written and medically reviewed by the StethoPrep medical team.