The Characteristics of Quick Contrast Sensitivity Function in Keratoconus and Its Correlation with Corneal Topography

Introduction To characterize quick contrast sensitivity function (qCSF) in keratoconus and its correlation with corneal topographic parameters. Methods Patients with keratoconus (n = 120) who visited the Fudan Eye and ENT Hospital between April and June 2021 were enrolled in our study. A total of 215 eyes were subdivided into three groups according to maximum keratometry (K-max): Group 1 (K-max <= 48 D, 74 eyes), Group 2 (48 D < K-max <= 55 D, 64 eyes), and Group 3 (K-max > 55 D, 77 eyes). Manifest refraction, best corrected distance visual acuity (BCVA), corneal topography, and the qCSF test were examined. Intergroup comparisons and correlations among various corneal topographic parameters and qCSF were analyzed. Results Significant differences in the area under the log CSF (AULCSF) and CSF Acuity among the three groups were found, which decreased with an increase in K-max. Contrast sensitivity (CS) between spatial frequencies of 3.0 to 18.0 cpd was significantly different (all P < 0.05) between Groups 1 and 2. The CS at all spatial frequencies was significantly different (all P < 0.05) between Group 3 and other two groups. At 3.0-18.0 cpd, CS decreased significantly (all P < 0.05) in Groups 1-3. Manifest refraction and topographic indices correlated significantly with qCSF parameters (all P < 0.05). Multivariable linear regression analysis showed that cylindrical refraction, logMAR BCVA, and index of surface variance had good predictive values for AULCSF and CSF Acuity. Conclusions The use of qCSF test can serve as a feasible tool to evaluate visual quality and severity of keratoconus, since changes in CS significantly correlated with keratoconus severity.