| Summary: | OBJECTİVE: To compare the sensitivity and
specificity of elevation maps obtained from different topographical reference surfaces
used in the diagnosis of keratoconus.
MATERİALS
AND METHODS: In this study 40 eyes of 23 patients with keratoconus and 40 eyes of 25
refractive surgery candidates as a control group was measured with a
Scheimpflug camera (Sirius CSO-Italy). Using the receiver operator characteristic
curves (ROC), a comparison was made of the ability to differentiate keratoconus
from a normal cornea with anterior elevation(AE) and posterior elevation(PE)
measurements obtained from the spherical, aspherical, asphero-toric reference surfaces.
RESULTS: The ROC curve analysis showed
that posterior elevation measured from the aspherical and asphero-toric surfaces
had a significantly higher area under the ROC curves (0.987, 0.973
respectively) thanthevalueobtainedfromthesphericalreferencesurfaces. According to the data obtained from the ROC curve
analysis, the posterior elevation maps obtained from the aspherical and
asphero-toric reference surfaces had the highest sensitivity (97.5% for both)
and the posterior elevation map obtained from the aspherical reference surface
had the highest specificity (90%).
CONCLUSION: The highest sensitivity and
specificity values were obtained from the aspherical and asphero-toric
reference surfaces rather than from the spherical reference surface. When
compared to the anterior elevation values, the posterior elevation values were
found to be more sensitive and specific. Therefore, aspherical and asphero-toric
reference surfaces and a posterior elevation map would seem to be more accurate
in the differentiation of keratoconus and normal cornea.
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