Nourhan Elkady, Marwa Metwally Salama, Malak I Elshazly, Riad Shalash
RGP lens application was associated with different changes in inner and outer retinal layer thickness in keratoconus and healthy control eyes, whereas no significant between-group differences were found for the remaining OCT parameters. Keratoconus severity did not significantly influence these changes. The findings suggest that RGP lenses may affect selected OCT measurements through optical or image-acquisition influences rather than producing consistent short-term anatomical changes across the retina.
PURPOSE: To evaluate the effect of rigid gas-permeable (RGP) contact lens correction on macular optical coherence tomography (OCT) measurements in patients with keratoconus and determine whether retinal thickness differences persist after correction of corneal irregularity.
METHODS: This observational case-control study included 100 eyes from 100 participants, comprising 50 keratoconus eyes and 50 age-matched healthy control eyes, with one eye included from each participant. All participants underwent a comprehensive ophthalmic examination, including slit-lamp examination, manifest refraction, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), intraocular pressure measurement, dilated fundus examination, and corneal tomography. We diagnosed keratoconus using clinical and tomographic findings and classified it according to the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) criteria. Macular OCT measurements were obtained using the Early Treatment Diabetic Retinopathy Study (ETDRS) grid before and immediately after RGP lens application. For each eye, the change in every OCT parameter was calculated by subtracting the measurement obtained before RGP application from the measurement obtained afterward. We then compared these changes between the keratoconus and control groups. We applied Holm correction to account for multiple comparisons across 11 OCT parameters.
RESULTS: Changes in inner and outer retinal layer thickness differed significantly between the keratoconus and control groups after Holm correction. Inner retinal layer thickness showed a greater increase in keratoconus eyes than in control eyes (rank-biserial r = 0.37; 95% CI, 0.15-0.56; adjusted p = 0.015), whereas outer retinal layer thickness increased less in keratoconus eyes than in control eyes (rank-biserial r = -0.40; 95% CI, -0.60 to -0.19; adjusted p = 0.006). Central foveal thickness differed before correction, but this finding was no longer statistically significant after Holm correction (adjusted p = 0.059). We found no significant differences between the two groups for the remaining OCT parameters. Keratoconus eyes were classified as mild (n = 11), moderate (n = 26), or severe (n = 13) based on recorded K2 values. Disease severity did not significantly influence the changes in any OCT parameter after correction for multiple comparisons.
CONCLUSION: RGP lens application was associated with different changes in inner and outer retinal layer thickness in keratoconus and healthy control eyes, whereas no significant between-group differences were found for the remaining OCT parameters. Keratoconus severity did not significantly influence these changes. The findings suggest that RGP lenses may affect selected OCT measurements through optical or image-acquisition influences rather than producing consistent short-term anatomical changes across the retina.