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A. Sahin, H. Basmak, N. Yildirim; Evaluation of Topographic Characteristics and Progression of Keratoconus Patients Using Orbscan Topography System . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1308.
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© ARVO (1962-2015); The Authors (2016-present)
To define topographic characteristics and to evaluate progression in a series of keratoconus patients using the Orbscan II Topography System.
The corneal topographic maps of 217 eyes in 112 patients with keratoconus were evaluated. Quantitative topographic parameters including location–radius, elevation–compared to a best–fit sphere (BFS), mean tangential curvature, mean spheric curvature, and pachymetry were evaluated with special reference to the central point of the cornea, the apex, and the thinnest point. The correlation between the following parameters was investigated: apex elevation and apex tangential curvature; apex elevation and apex mean curvature; apex elevation and apex pachymetry; and apex elevation and thinnest point pachymetry. In addition, the change of these parameters was investigated in 79 keratoconic eyes that have consecutive topographic maps obtained within 26 months period. Paired t–test and Pearson correlation analysis was used.
Mean patient age was 32,4±15,2 years (range 15 to 59 years). One–hundred and 5 patients had bilateral keratoconus and 7, unilateral keratoconus. The mean radius of the apex was 1,19±0,70 mm, and the semimeridians were 232,17±37,82 degrees (right eyes) and 299,32±33,92 degrees (left eyes). The mean elevation of the apex was 0,064±0,051 mm. The mean tangential and mean spheric curvatures were 54,37±7,89 diopters (D) and 55,47±7,10 D, respectively. The mean pachymetry of the thinnest point was 367,33±61,75 µm. The correlations between apex elevation and apex mean spheric curvature and apex elevation and apex tangential curvature was 0.714 and 0.656, respectively (both p<0.0001). The correlation between apex elevation and thinnest point pachymetry and apex elevation and apex pachymetry was –0.369 (p<0.0001) and –0.221 (p=0.004), respectively. Apex elevation and SimK minimum values increased and thinnest point radius decreased significantly during 26 months follow–up (p<0.05). Other parameters did not change significantly.
Orbscan II provides detailed and accurate information about topographic characteristics and progression of keratoconic corneas. These parameters can be useful in the follow–up, contact lens fitting and corneal surgery of keratoconus patients.
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