Scheimpflug tomographic changes across the keratoconus spectrum based on the modified Rabinowitz-McDonnell classification.

PURPOSE: To characterize spectrum-dependent changes in Scheimpflug tomographic parameters across normal, keratoconus suspect, and eyes with keratoconus classified using the modified Rabinowitz-McDonnell index.

METHODS

This retrospective comparative study included 115 eyes of 115 patients evaluated at a tertiary ophthalmology clinic. Based on the modified Rabinowitz-McDonnell index, eyes were categorized into control (n = 37), keratoconus suspect (n = 51), and keratoconus (n = 27) groups. All eyes underwent Scheimpflug tomography. Anterior and posterior keratometry values, corneal thickness parameters, corneal volume, anterior chamber depth, and pupil diameter were analyzed.

RESULTS

Anterior and posterior corneal curvature parameters increased progressively from control group to keratoconus suspect group and were highest in eyes with keratoconus (all p < 0.001). While anterior keratometric parameters and posterior corneal curvature differed significantly between control and keratoconus suspect groups, pachymetric measurements remained comparable, with significant thinning observed only in the keratoconus group (all p < 0.001). Corneal volume was higher in keratoconus suspect group compared with both control and keratoconus groups (p = 0.001). Anterior chamber depth was greater in keratoconus group, while pupil diameter was smaller in keratoconus suspect group (both p < 0.01).

CONCLUSION

When keratoconus is classified using central keratometry, Scheimpflug tomography demonstrates a clear, stage-dependent pattern of corneal change. Curvature-related alterations precede measurable thinning, highlighting that curvature-based classification remains clinically relevant and that tomographic parameters can enhance disease characterization across the keratoconus spectrum.