Pellucid-like keratoconus

To study the tomographic features of pellucid-like keratoconus (PLK), and to report a new sign on the pachymetry map (PM) in pellucid marginal degeneration (PMD).

A retrospective descriptive case series was performed in Damascus University in 2011. Clinical and tomographic findings of 15 eyes (9 patients) that had the claw pattern of the anterior sagital map (ASM) were reviewed. Patients were distributed into two groups: (1) 4 eyes were considered PMD since they had inferior corneal thinning on both slitlamp biomicroscopy and PM; (2) 11 eyes were considered as PLK since they did not show inferior corneal thinning. Patients were studied using slitlamp biomicroscopy and Scheimpflug-based tomography (Pentacam HR). The ASM, anterior elevation map (AEM) and PM were analyzed and compared to study the "kissing birds" sign, the "bell" sign, and cone location.

Patients' average age was 25.93±8.05 (16-44 years). In total, 60% of patients were male. In group 1, the AEM in the best fit sphere (BFS) mode revealed no kissing birds sign, and the cone was central in 1 eye (25%) and paracentral in 3 eyes (75%). PM showed the bell sign in 4 eyes (100%). In group 2, the AEM in the BFS mode revealed the kissing birds sign in 2 eyes (18.2%), and the cone was central in 1 eye (9.1%), paracentral in 8 eyes (72.7%) and peripheral in 2 eyes (18.2%). PM didn't show the bell sign in any eye.

The claw pattern on the ASM is not a hallmark of PMD; it can be seen in PLK. Cone location does not relate to diagnosis. The "bell" sign on the PM is a deferential diagnostic sign in PMD.