Correlation of corneal elevation with severity of keratoconus by means of anterior and posterior topographic analysis.
OBJECTIVE
To investigate the severity of keratoconus in terms of corneal elevation differences with 2 different reference surfaces using topographic analysis.


METHODS
Eighty-six eyes of 50 patients with keratoconus of various clinical stages (61 male and 25 female eyes) with mean age of 37.3 ± 11.6 years were evaluated. Anterior and posterior corneal elevations were measured using topographic analysis (using a rotating Scheimpflug camera), and the imaging data were analyzed to estimate elevation differences as differential values from conventional best-fit-sphere and enhanced best-fit-sphere (exclusion of a 4-mm-diameter area from the most thinned cornea). The data correlated with the keratoconus severity index and Amsler-Krumeich classification of keratoconus.


RESULTS
There was a significant positive correlation between elevation differences and keratoconus severity index in both anterior and posterior surfaces (Pearson correlation coefficient, r = 0.66; P < 0.001; r = 0.74; P < 0.001). Cases of larger elevation differences in the anterior and posterior corneal surfaces were staged higher in Amsler-Krumeich classification (1-way analysis of variance, P = 0.040; P < 0.001). Cases of lower staging in the Amsler-Krumeich classification had a larger area under the receiver operating characteristic curve in the posterior elevation differences than in the anterior elevation differences, suggesting a greater diagnostic value of the posterior elevation measurement.


CONCLUSIONS
Anterior and posterior corneal surface height data obtained by elevation-based tomography provide useful information in improving keratoconus diagnostic accuracy and in grading the severity of keratoconus.
Department of Ophthalmology, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan. rishii-sin@umin.ac.jp
Rie
R
Ishii
Kazutaka
K
Kamiya
Akihito
A
Igarashi
Kimiya
K
Shimizu
Yoshikazu
Y
Utsumi
Takashi
T
Kumanomido
D000328:Adult; D019540:Area Under Curve; D019781:Corneal Topography / Q000379:methods*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index