title: Scleral lens induced corneal swelling: what is the effect of varying Dk and lens thickness?
abstract: OBJECTIVE
  Scleral lenses remain an option for visual rehabilitation under some circumstances or when there are specific therapeutic indications. Wearing is often limited with polymethylmethacrylate lenses, but rigid gas permeable (RGP) scleral lenses offer a physiological improvement as measured with central corneal swelling. This study aimed to determine central corneal swelling with lenses of different oxygen transmissibilities and thicknesses.
  
  
  RESULTS
  Central corneal swelling was measured in four normal subjects wearing sealed RGP scleral contact lenses for 3 hours. The lenses used were of Dk 32, 59, and 115 with thicknesses of 0.15, 0.30, 0.60, and 1.20 mm. A reduction in central corneal swelling was associated with an increase in Dk and a reduction in lens thickness (P < 0.05). This relationship was found to be non-linear for higher transmissibilities.
  
  
  CONCLUSIONS
  The physiological improvement as measured by central corneal swelling was reduced with thin high Dk lenses, suggesting diminishing returns for further increases in Dk. For usual scleral lens thicknesses of 0.6 mm in a material with a Dk of 115, the mean central corneal swelling induced was less than 3%.
authors.affiliation: Optometry Department, Moorfields Eye Hospital, London, England.
authors.forename: K W
authors.initials: KW
authors.lastname: Pullum
authors.forename: F J
authors.initials: FJ
authors.lastname: Stapleton
mesh_terms: D000328:Adult; D003261:Contact Lenses / Q000009:adverse effects*; D003316:Corneal Diseases / Q000534:rehabilitation; D015715:Corneal Edema / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D012590:Sclera