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 ×10 cm O2 (cm)/[(s) (cm) (mmHg)]) on separate days with either a low (mean, 144; 95% confidence interval [CI], 127 to 160 μm), medium (mean, 487; 95% CI, 443 to 532 μm), or high (mean, 726; 95% CI, 687 to 766 μm) initial fluid reservoir thickness. Epithelial, stromal, and total corneal edema were measured using high-resolution optical coherence tomography after 90 minutes 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 μm.

CONCLUSIONS

Scleral lens-induced central corneal edema increases with increasing reservoir thickness, but plateaus at a thickness of around 600 μm, in agreement with recent theoretical modeling that incorporates factors related to corneal metabolism.