How Big Is Your Vault? Comparison Between Vault and Corneal Edema.

Background: Scleral lenses are used to provide optimal vision for patients who have corneal pathology. Current practitioners are looking towards scleral lenses to fit healthy corneas for the comfort and vision they provide. Material Dk and lens thickness are adjusted when considering oxygen permeability, however, with the rigid nature of scleral lenses, post-settle vault thickness must also be observed. To determine how vault thickness relates to corneal edema, this study examines corneal pachymetry values before and after an eight hour day of wear. Four different vaults were assessed to determine if a pattern exists.
Methods: Participants in this study were optimally fit in a 15.8 mm diameter scleral lens that provided limbal clearance. The lens thickness (400 microns) and material Dk (100) remained the same for each pair. The limbal clearance zone was adjusted to provide post-settling vaults of 100, 300, 500, and 700 microns. Change in average corneal thickness before and after lens wear for each subject was assessed.
Results: There appears to be a direct relationship between vault depth and corneal swelling. As vault increased corneal swelling increases. Corneal swelling was less than clinically significant. Average corneal swelling ranged from 0.62-1.70%. Conclusion: For practitioners fitting scleral lenses on healthy corneas, there appears to be a range of vaults that induce less that significant corneal swelling. Clinically significant corneal edema of 6% was not reached when fit with a lens providing 600-799 microns of vault. Subjects measured higher visual acuity when wearing lenses that provided a post-settl
vault in the 0-199 micron range. Further research is needed to better understand the effects of wearing scleral lenses for longer than eight hours.