Fluid Reservoir Thickness and Corneal Edema during Open-eye Scleral Lens Wear

SIGNIFICANCE: There is debate concerning corneal oxygenation during scleral lens wear due to the potential additive hypoxic effect of a lens plus a fluid reservoir. This study investigated the agreement between theoretical models and empirical measurements of scleral lens-induced corneal edema with respect to central fluid reservoir thickness. PURPOSE: The purpose of this study was to examine the effect of altering the fluid reservoir thickness on central corneal edema during short-term open-eye scleral lens wear and to compare these empirical measurements with predictive theoretical models. METHODS: Ten participants (age, 30 +/- 4 years) with normal corneas wore highly oxygen-permeable scleral lenses (141 Dk x10(-11) cm(3) O-2 (cm)/[(s) (cm(2)) (mmHg)]) on separate days with either a low (mean, 144; 95% confidence interval [CI], 127 to 160 mu m), medium(mean, 487; 95% CI, 443 to 532 mu m), or high (mean, 726; 95% CI, 687 to 766 mu m) initial fluid reservoir thickness. Epithelial, stromal, and total corneal edema were measured using high-resolution optical coherence tomography after 90minutes of wear, before lens removal. Data were calculated or extracted from published theoretical models of scleral lens-induced corneal edema for comparison. RESULTS: Scleral lens-induced central corneal edema was stromal in nature and increased with increasing fluid reservoir thickness; mean total corneal edema was 0.69% (95% CI, 0.34 to 1.04%), 1.81% (95% CI, 1.22 to 2.40%), and 2.11% (95% CI, 1.58 to 2.65%) for the low, medium, and high thickness groups, respectively. No significant difference in corneal edema was observed between the medium and high fluid reservoir thickness groups (P = .37). Resistance in series oxygen modeling overestimated the corneal edema observed for fluid reservoir thickness values greater than 400 mu m. CONCLUSIONS: Scleral lens-induced central corneal edema increases with increasing reservoir thickness, but plateaus at a thickness of around 600 mu m, in agreement with recent theoretical modeling that incorporates factors related to corneal metabolism.