Impact of Keratoconus on Contrast Sensitivity

Abstract

Objective: Keratoconus (KC) disrupts corneal shape, leading to irregular astigmatism and increased higher-order aberrations (HOA), ultimately affecting visual quality. While visual acuity (VA) remains the standard, its limitations in early KC diagnosis are recognized. This study aimed to evaluate the impact of KC on contrast sensitivity function (CSF), a potentially more sensitive measure of visual performance.Material and Methods: A case-control design compared CSF in KC patients (n=7) to healthy controls (n=16). All subjects achieved the best-corrected visual acuity (BCVA) of 6/9 or better (logMAR ≤0.10). Corneal topography was measured using Tomey TMS-5 to confirm KC diagnosis. CSF was assessed with the Functional Acuity Contrast Test (FACT).Results: KC eyes exhibited significantly reduced CSF across all spatial frequencies compared to controls (p-value<0.05). Row A of the FACT chart (representing the lowest spatial frequency, 1.5 cpd) demonstrated the most prominent difference (t (21)=-3.073, p-value=0.003).Conclusion: Our findings reveal that KC patients, despite achieving good BCVA, demonstrate measurable deficits in CSF. This suggests CSF measurement with FACT may be a valuable tool for the early diagnosis and monitoring of KC, potentially offering a more sensitive and comprehensive assessment of visual function compared to BCVA alone.