Different sections of the tear layer have unique reactions to scleral lens wear, a study in Eye & Contact Lens reports. After wearing scleral lenses, patients’ tear layers were thickest in the temporal region and thinnest in the nasal region, according to researchers from Australia. They attributed this finding to regional differences in underlying scleral elevation, eyelid forces and lens centration.
The study enrolled 15 healthy adults who were approximately 23 years old and had normal corneas. The patients were fitted with a 16.5mm rotationally symmetric scleral lens in one eye. Using OCT, the researchers measured the post-lens tear layer thickness across the central 5mm at baseline and then again after 15, 30, 45, 60, 90, 120, 240 and 480 minutes. The investigators divided the post-lens tear layer into eight equal 45° segments for their analysis.
They observed a tilted optic zone immediately after lens insertion, with the greatest post-lens tear layer asymmetry between the nasal and temporal regions (156 ± 22μm more clearance temporally) and superior nasal and inferotemporal regions (124 ± 12μm more clearance inferotemporally). The study noted the magnitude of lens settling in each region was associated with the initial post-lens tear layer. Also of note: the superior nasal post-lens tear layer furthest from the pupil center stabilized after 90 minutes compared with the other regions, which stabilized after four hours. On average, after eight hours of lens wear, the post-lens tear layer decreased by 29%, and post-lens tear layer asymmetries between opposing regions decreased by 30%.
Post-lens tear layer asymmetries “diminished with lens wear, and stabilization occurred more rapidly in regions with less corneal clearance immediately after lens insertion,” the researchers wrote in their paper.
|Vincent SJ, Alonso-Caneiro D, Collins MJ. Regional variations in postlens tear layer thickness during scleral lens wear. Eye Contact Lens. November 8, 2019. [Epub, ahead of print].|