Fluid reservoir thickness and corneal oedema during closed eye scleral lens wear

Purpose: To examine the relationship between central post-lens fluid reservoir thickness and central corneal oedema during short-term closed eye scleral lens wear, and to compare these empirical oedema measurements with open eye lens wear data and current theoretical modelling for overnight scleral lens wear. Methods: Ten participants (mean +/- standard error 30 +/- 1 years) with normal corneas wore scleral lenses (Dk 141 x 10(-11) cm(3) O-2 (cm)/[(sec.)(cm(2))(mmHg)) under closed eye conditions on separate days with an initial central post-lens fluid reservoir thickness considered to be low (160 +/- 7 mu m), medium (494 +/- 17 mu m), or high (716 +/- 16 mu m). Epithelial, stromal, and total corneal oedema were measured using high-resolution optical coherence tomography immediately after lens application and following 90 min of wear, prior to lens removal. Data were compared to open eye scleral lens induced corneal oedema and a theoretical model of overnight closed eye scleral lens wear (Kim et al., 2018). Results: Central corneal oedema was primarily stromal in nature and increased with increasing fluid reservoir thickness; the mean total corneal oedema was 3.86 +/- 0.50%, 4.71 +/- 0.28% and 5.04 +/- 0.42% for the low, medium, and high thickness conditions, respectively. A significant difference in stromal and total corneal oedema was observed between the low and high fluid reservoir thickness conditions only (both p <= 0.01). Theoretical modelling overestimated the magnitude of central corneal oedema and the influence of fluid reservoir thickness upon corneal oedema during closed eye conditions. Conclusion: Scleral lens induced central corneal oedema during closed eye lens wear increases with increasing fluid reservoir thickness, but at a decreased rate compared to theoretical modelling.