Corneal Endothelial Blebs Induced in Scleral Lens Wearers

In the bleb phenomenon, some endothelial cells transiently lose their specular reflection. This has been reported during contact lens wear and goggle-induced hypoxia or hypercapnia.

The purposes of this study were to determine whether blebs appear after scleral lens wear and if their appearance is influenced by lens clearance and to compare bleb and cell sizes.

Twenty-one subjects were fitted with two similar scleral lenses with different targeted clearances of 200 and 400 μm (the SL200 and SL400, respectively). Each lens was worn unilaterally for 25 minutes, whereas the other eye served as a control. Before and after lens wear, the endothelium was photographed using specular microscopy. The number of blebs and measurements of the areas of cells and blebs were analyzed. Paired t tests compared differences in the areas of cells and blebs. Differences in median bleb number were evaluated using the Wilcoxon test.

After wearing the SL200 and SL400 lenses, respectively, 9 and 14 subjects had at least one bleb. The median bleb number after wearing lenses was significantly different (SL200, 0.00; SL400, 1.00; P = .02). Bleb and cell areas were significantly different (blebs, 293 ± 28; cells, 370 ± 32 μm; P < .0001).

After 25 minutes of wearing scleral lenses with each of the two targeted clearances, SL400 induced significantly more blebs than did SL200, suggesting evidence of reduced oxygen and/or increased carbon dioxide levels under scleral lenses fitted with excessive clearance. Blebs may occur more in smaller cells.