Corneal topographic changes in a case of limbal conjunctival carcinoma.

PURPOSE To describe topographic changes in a case of limbal conjunctival carcinoma. METHODS Corneal topography was performed before and 3 months after excision. RESULTS Preoperative topography revealed a localized flattening (37.1 diopters [D]) adjacent to the tumor and extending to the corneal apex, causing a 3-diopter asymmetric with-the-rule astigmatism. Preoperative corneal curvature was abnormally flat in all hemimeridians (average 40.8 D). During surgical excision, no corneal infiltration was found. Three months later, the astigmatism was 0.3 D, and corneal curvature had increased to normal values in all hemimeridians (45.5 D in the tumor area; average of all hemimeridians 45.5 D). Corneal steepening after tumor excision measured by topography almost doubled that observed in refraction. CONCLUSION The similarity with the patterns induced by pterygia, the lack of corneal infiltration, and the complete reversal of astigmatism after excision support the theory that tear pooling at the tumor apex is responsible for secondary astigmatism and diffuse corneal flattening. However, the irregularity induced by the tumor may affect the precision of topographic measurements.