A retrospective evaluation
In light of this, she and her colleagues retrospectively analyzed the ETMs, topographies (Atlas 9000, Zeiss), and tomographies (OCULUS Pentacam) in normal eyes compared with eyes with mild topographic and tomographic abnormalities.
Two hundred ninety-eight eyes of 149 consecutive patients were included who were myopic and stopped wearing soft contacts a week before the scans, which were part of their preoperative workup. Only patients with normal-appearing corneas and normal tear film on slit-lamp examinations were included in the evaluation. Patients with corneal scars, epithelial basement membrane dystrophy, superficial punctate keratitis, and decreased tear break-up time were excluded.
The analysis showed that 190 eyes (95 patients) (group 1) had normal topography and tomography scans; 89 eyes (49 patients) (group 2) had one of the following: pachymetry 475 to 510 μm (10 eyes/five patients), 1.50 D or less of inferior steepening (35 eyes/22 patients), 1.50 D or less of superior steepening (16 eyes/eight patients), central steepening (eight eyes/four patients), claw shape (14 eyes/seven patients), and posterior float (six eyes/three patients).
The minimal pachymetry thickness, central epithelial thickness, ratio of inferior epithelial thickness to the superior epithelial thickness, minimal epithelial thickness, the difference between the maximal and minimal epithelial thickness were compared between the two groups.
When the investigators compared the ETM patterns in the two groups, they found no differences in any parameters between the normal eyes and those with one mild topographic or tomographic abnormality. The retrospective chart review also identified 10 eyes (five patients) with a thin cornea (475 to 500 μm) and an additional mild abnormality, i.e., central steepening, a corneal thickness less than 475 μm, or a slightly skewed astigmatic axis.
Dr. Faktorovich recounted that the 10 eyes had epithelial thinning over the thinnest corneal spot, consistent with one of the possible ETM findings in patients with forme fruste keratoconus.
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