Trick of the Light Through the Cornea

      A 70-year-old man with aqueous-deficient dry eye presented for regular examination. Diffuse illumination slit-lamp imaging revealed an abnormal dark lesion in the nasal-inferior iris of his left eye (Fig A). The temporal view of the nasal-inferior cornea revealed a delle (a localized saucer-shaped corneal thinning due to dehydration). Light passing through the concave lens caused by the delle was diffused, resulting in a dark lesion on the iris underneath (Fig B; right). The nasal view to avoid the optical artifact by the delle demonstrated no dark lesion (Fig B; left), which was confirmed by cross-sectional anterior-segment OCT imaging (Fig C). (Magnified version of Fig A-C is available online at
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