An Early Finding of Keratoconus: Increase in Corneal Densitometry.

PURPOSE: To investigate the corneal densitometry in subclinical keratoconus with normal elevation and pachymetric parameters.

METHODS: Patients with clinical keratoconus in one eye and subclinical keratoconus in the fellow eye were identified. The study group was selected from patients with subclinical keratoconus who showed normal results from topographic and Belin-Ambrósio Enhanced Ectasia Display III (BAD) analysis (Kmean <47.2 diopters, inferior-superior asymmetry <1.4 diopters, and KISA% <60%, elevation <5 μm, PPIaverage <1.06, PPImaximum <1.44, ARTaverage <414 μm, ARTmaximum <339 μm, and final D <1.6). The control group was selected from candidates for refractive surgery. The densitometric analyses were performed through the Pentacam HR (Oculus, Germany).

RESULTS: The medical records of 3474 patients with keratoconus were examined, and 116 (3.3%) subclinical keratoconus cases were detected. Normal BAD analysis results were obtained from 38 patients (1.1%). The control group also consisted of 38 patients. There were no significant differences between the eyes with subclinical keratoconus and those of the control in corrected distance visual acuity and topographic, topometric, and tomographic parameters (P > 0.05). In all layers of the 0- to 2-mm zone and in the anterior and central layers of the 0- to 6-mm zone, corneal densitometry was significantly higher in the subclinical keratoconus than the control (P < 0.001). In discriminating eyes with subclinical keratoconus from normal, the anterior layer in the 0- to 2-mm zone showed the highest area under the curve (0.883; cutoff: 19.7; sensitivity: 75%; specificity: 90%) in a receiver operating characteristic analysis.

CONCLUSIONS: The increase in densitometry in the central zone could be useful in detecting subclinical keratoconus.