Characteristics of corneal topographic and pachymetric patterns in patients with pellucid marginal corneal degeneration.

PURPOSE: To determine the characteristics of the shape of the cornea in patients with pellucid marginal corneal degeneration (PMD) and to compare these characteristics to those of eyes with keratoconus and eyes of normal subjects. METHODS: This was a retrospective, cross-sectional case-series in which 49 eyes of 33 patients with PMD, 51 eyes of 51 patients with keratoconus and 53 eyes of 53 subjects with normal corneas (controls) were examined and compared. For all eyes, we obtained the topographic patterns of the axial power maps, anterior and posterior elevation maps and pachymetric maps using a rotating Scheimpflug camera. The eyes were classified into the respective patterns by visual inspection of these maps. RESULTS: In eyes with PMD, the most common axial power map pattern was the crab claw pattern (78 %) followed by the inferior steepening pattern (18 %). In eyes with keratoconus, the most common pattern was the inferior steepening pattern (67 %). The most common pattern in the elevation maps for both surfaces was the asymmetric island in eyes with PMD and keratoconus. Although the decentered pattern, including the decentered oval (27 %) and decentered round (20 %) pattern, on pachymetric map was specific to eyes with PMD, the incidence of these patterns was relatively low. CONCLUSIONS: The similarity in the topographic and pachymetric patterns in eyes with PMD and keratoconus suggests that they may be a continuity of the same disorder with different phenotypes.

Gender differences in corneal thickness values

The aim was to study gender differences in corneal thickness. We analysed the corneal thickness of 100 corneas of 100 healthy subjects (mean age 30.87±7.76 years; range, 19 to 54 years old) with the Orbscan Topography System II (Orbscan, Inc., Salt Lake City, UT. USA). The means of five consecutive measurements of the central and paracentral corneal thickness were obtained. No significant differences in mean corneal thickness between women and men at central (p=0.477), nasal (p=0.247), superonasal (p=0.242), inferonasal (p=0.554), temporal (p=0.538), superotemporal (p=0.524) and inferotemporal (p=0.860) corneal locations were found. In sum, there are no differences in mean central and paracentral corneal thickness values between women and men (AU)

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Human corneal thickness using a noncontact specular microscope

The aim of this work was to study the central corneal thickness values and interobserver variability using a noncontact specular microscope. Methods: 62 eyes from 31 healthy subjects were studied with the Topcon SP-2000P noncontact specular microscope (Topcon Corp., Tokyo, Japan). 16 (51.61%) were females, and 15 (48.38%) were males. The mean age of the sample was 31.83±5.68 years. The mean of three consecutive measurements of the central corneal thickness was recorded by two investigators. Results: Mean central corneal thickness was 497±53 ?m for physician I and 497±51 ?m for physician II (p=0.982). No significant differences were found between the left and right corneas (p=0.999), between females and males (p=0.756), between ? 29-years-olds and ? 30-years-olds (p=0.945) or between myopic and hyperopic eyes (p=0.994). Conclusion: Noncontact specular microscopy is a recently introduced anatomical tool that can be used to study the human cornea in vivo (AU)

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Assessment of central corneal thickness in extreme myopic eyes

Purpose: To study the central corneal thickness values in two groups of extreme myopic patients (cycloplegic spherical equivalent refraction >=-12 diopters) and in a control group. Methods: We carried out ultrasonic pachymetry with the DGH 2000 AP ultrasonic pachymeter (DGH Technology, Inc., San Diego, CA, USA). Group I (n=45) was made up of patients with spherical equivalent refraction ranging from -12.00 to -18.00 diopters; group II (n=25) with spherical equivalent refraction > -18.00 diopters, and the control group (n = 34) was made up of patients with spherical equivalent refraction ranging from -0.25 to -3.00 diopters. Results: Mean central corneal thickness (mean±SD) was 531±42 ?m, 551±52 ?m and 538±35 ?m in groups I, II and controls, respectively (p=0.193). No significant differences between women and men were found in group I (p=0.314), group II (p=0.071) and the control group (p=0.113). No significant differences among age subgroups were found in group I (p=0.989), group II (p=0.641) or in the control group (p=0.397). Conclusions: In extreme myopic eyes there is a slight tendency for central corneal thickness to increase in the presence of higher degrees of myopia. Nevertheless, central corneal thickness in extreme myopic patients is similar to that noted in non-extreme myopic patients (AU)

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