Purpose:
To describe the RIGITEST, a possible new method to estimate corneal hysteresis. To compare the corneal hysteresis between controls and keratoconus patients.
Methods:
Based on intraocular pressure (IOP) measurements by applanation (GAT) and Dynamic contour tonometry (DCT), the rigitest was calculated as [GAT/DCT-1.5]. 57 eyes of 57 patients (30 emmetropes, 27 keratoconus patients) were prospectively enrolled for this study. GAT measurements were taken 10 minutes before DCT, both were performed in sitting position. Keratoconus was determined using corneal topography and keratometry. The mean value of 2 measurements from the right eye of each patient was calculated and compared using t-Test. P values < 0.05 were considered statistical significant.
Results:
Keratoconus patients had thinner corneal thickness [mean ± SD][485.7 ± 49.0 vs 566.0 ± 40.2 µ; p <0.001], lower GAT [12.2 ± 3.3 vs 17.2 ± 3.8 mmHg; p<0.001], lower DCT [14.3 ± 1.9 vs 17.3 ± 3.2 mmHg; p< 0.001] and lower rigitest [0.9 ± 0.2 vs 1.1 ± 0.1; p<0.001] compared to normal subjects.
Conclusions:
Keratoconus eyes demonstrated thinner corneas and lower IOP measurements on GAT and DCT compared to normal eyes. In concordance with the pathophysiology of Keratoconus, these eyes demonstrated a decreased corneal hysteresis calculated by RIGITEST.
Keywords: keratoconus • refractive surgery