Key Factor Influencing Corneal Edema with Scleral Lens Wear; Healthy Versus Unhealthy Corneas

ABSTRACT Scleral lenses are an important treatment option for irregular corneas, but improper fitting can cause hypoxia and edema. This review elucidates key factors influencing corneal edema with ScL wear in healthy and compromised corneas. ScL parameters like oxygen permeability, thickness, post-lens tear film thickness, limbal clearance, and alignment impact edema. Studies show high oxygen permeability (DK 100+) lenses under 300 μm thickness typically limit edema to under 2% in healthy eyes. Theoretical modeling and many studies advise post lens tear film thickness <200 μm. Compromised corneas are more susceptible to edema from hypoxia and mechanical stress. Shorter wearing times and close monitoring of corneal health are advised for compromised corneas. There are gaps regarding long-term safety, regional edema response, and the optimal lens parameters for compromised corneas. Further large studies controlling confounding factors and standardizing measurements would strengthen our understanding of the relationship between scleral lenses and corneal edema.