Anterior chamber characteristics of keratoconus assessed by rotating Scheimpflug imaging.

PURPOSE: To compare anterior chamber parameters in normal eyes and eyes with mild to moderate keratoconus corneas using rotating Scheimpflug imaging and evaluate trends in corneal protrusion progression.

SETTING

Department of Ophthalmology, Semmelweis University, Budapest, Hungary.

METHODS

The anterior chamber depth (ACD) at the corneal center, thinnest point of the cornea, and 1.0 mm, 2.0 mm, and 3.0 mm paracentrally; central pachymetry; and posterior elevation were measured by Scheimpflug imaging (Pentacam) in eyes with keratoconus and eyes of refractive surgery candidates. A generalized estimating equation (GEE) was used to identify predictors of keratoconus. Correlations between posterior elevation and ACD at minimum pachymetry were analyzed by linear and piecewise linear regression.

RESULTS

The keratoconus group comprised 41 eyes (24 patients) and the control group, 70 eyes (41 patients). The ACD was significantly deeper in the keratoconus group than in the control group (P<.05) and was significantly correlated with posterior elevation. In the multivariable GEE model, posterior elevation (odds ratio [OR], 1.46; P<.001) and ACD at minimum pachymetry (OR, 7.54; 95% confidence interval, 1.35-42.05) were significant predictors of keratoconus. Segmented analysis of the correlation between posterior elevation and central ACD showed a better fit to data than linear regression and identified a 40 mum threshold level for posterior elevation. The GEE determined 450 mum as a similar threshold for central corneal thickness.

CONCLUSION

There was a threshold level of posterior corneal elevation and corneal thickness values beyond which the level of corneal protrusion in keratoconus accelerated.

FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.