Abstract
Purpose :
Scleral contact lenses have the potential to markedly reduce oxygen transmissibility (Dk/t) which is a concern for post-penetrating keratoplasty (PK) corneas that have a reduced endothelial cell density (ECD). This cross-sectional study determined the relationship between Dk/t of the scleral-tear lens system and corneal swelling in post-PK corneas as a function of ECD.
Methods :
Participants that had a PK at least 5 years prior for indications other than pseudophakic/aphakic corneal edema and wearing scleral lenses were recruited. Corneal thickness was measured with the Pentacam corneal topographer at 2 hours after waking but prior to their habitual lens insertion and repeated 6-8 hours after lens wear. ECD was measured with the Konan Specular microscope. Contact lens center thickness and oxygen permeability (Dk) were recorded and tear film thickness between the lens and cornea was measured with optical coherence tomography.
Results :
11 eyes of 9 participants were assessed. The mean {SD} ECD was 786 +-380 cells/mm2 with a range of 588-1890 cells/mm2. Average corneal clearance of the scleral lens was 119 microns. The mean Dk/t {SD} of the scleral-tear lens systems was 20.0 +-5.41. The mean {SD} morning central corneal thickness was 564.7 +-57.75 microns. All corneas showed some degree of swelling within the graft ranging from 39 to 174 microns at the thickest point. Eyes wearing lenses with Dk/t < 20 were found to have a higher average swelling (23.6%) at the thickest point when compared to eyes wearing lenses with Dk/t > 20 (13.2%, p<0.05). ECD was not significantly associated with corneal swelling.
Conclusions :
Lower Dk/t of the scleral-lens tear film combination was associated with increased corneal swelling in post-PK corneas that had low ECD. Most lenses were fitted with low central corneal clearance, and ECD was not predictive of increased corneal swelling in this range. Further investigation is needed to better understand the relationship between oxygen transmissibility, corneal swelling, and endothelial cell density in eyes fit with scleral lenses especially if fit with greater corneal clearance than in this study cohort.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.