Effect of apical clearance rigid corneal contact lens fitting on keratoconus progression: a controlled longitudinal...

To evaluate the impact of apical clearance rigid corneal contact lens (RCCL) fitting on keratoconus (KC) progression compared to untreated KC patients over a 12-month period.

This retrospective, controlled longitudinal study included 237 eyes with KC from two centers between 2018 and 2023. Following propensity score matching for baseline age and maximum keratometry (K_max), 31 eyes each were assigned to untreated and RCCL groups. RCCLs were fitted using the apical clearance method. Assessments at baseline, 3, 6, and 12 months included best-corrected visual acuity (BCVA), Scheimpflug corneal tomography and higher-order aberrations (HOAs). KC progression was defined by any of the following: an increase in K_max or anterior steep keratometry (K2) of >1.0 D, a decrease in thinnest corneal thickness (TCT) of > 10 μm, or a loss of >1 line of BCVA. Longitudinal changes were analyzed using generalized estimating equations (GEE).

No significant differences in BCVA, tomographic indices, or HOAs were observed between the untreated and RCCL groups at baseline or during follow-up at 3 and 12 months (all p > 0.05). KC progression rates were comparable between the groups, occurring in 12.9 % of untreated eyes and 19.35 % of RCCL treated eyes by 12 months (p = 0.731). GEE analysis revealed a significant reduction in K2 at 3 months within the RCCL group (p = 0.003); however, no other significant longitudinal differences were detected within or between groups at any follow-up period.

Apical clearance RCCL fitting did not significantly affect overall KC progression compared with no treatment over 12 months. However, the significant reduction in K2 at 3 months in the RCCL group suggests that one week of contact lens discontinuation may not be sufficient for the cornea to fully return to its natural state.