Scleral lens–induced corneal edema in patients who have undergone radial keratotomy (RK) is worse at greater distances from the corneal center, and at the approximate location of corneal incisions, according to a case series published in Eye & Contact Lens.
The research assessed the magnitude and regional variation with regard to corneal edema produced by scleral lenses in post-RK eyes. The study participants had a median central corneal edema of 2.19% (P =.02) and an increase in magnitude and variability from 1.30% in the central 0 mm to 0.5 mm to 3.12% in the 2.5 mm to 3.0 mm midperiphery (P =.02).
Investigators included 9 eyes (4 right and 5 left) from 5 participants (median age 64 years). They used Scheimpflug imaging to measure corneal thickness across the central 6 mm before and after scleral lens wear, with changes in corneal edema assessed as a function of distance from the corneal center (six 0.5 mm annuli), as well as from 0° to 360°.
The researchers explain that there is a large magnitude of variation between both eyes of the same patient, with a range of 0.03% to 6.80% across all eyes, which is in line with previous research.
Vascularization forming along RK incisions after low Dk soft contact lens wear indicates that the midperipheral and peripheral cornea is more prone to edema compared with the central treatment zone, according to previous reports. These findings are also supported by results of the current research.
This increased susceptibility to edema in the midperipheral cornea may also derive from epithelial-barrier dysfunction at the level of the incisions, thus leading to increased epithelial permeability. Increases in the midperipheral fluid reservoir thickness may play a role in corneal edema changes.
“Practitioners should aim to minimize the fluid reservoir thickness to optimize oxygen delivery in post-RK eyes taking care to maintain corneal clearance to avoid mechanical contact with the anterior corneal surface,” according to the report.
Arnold TP, Vincent SJ. Scleral lens–induced corneal edema after radial keratotomy. Eye Contact Lens. Published online October 1, 2021. doi:10.1097/ICL.0000000000000835