How much does the shape of the white of the eye vary among people being considered for scleral contact lenses?

Details

The study aimed to examine conjunctival/scleral shape using a novel wide-field elevation topography device and software, and to propose a new classification system for scleral shape.

The Scleral Shape Study Group (SSSG) collaborated on this observational mapping and classification study. Data were collected from 152 eyes of prospective scleral lens patients using a new topography device and software specifically designed to measure and map the sclera out to as much as 22 mm. For each eye, the researchers generated circumferential scleral plots of sagittal height versus meridian at diameters of 14, 15 and 16 mm centered on the corneal center. They reviewed scleral shape patterns in all cases and classified them according to recurring characteristics.

Twelve eyes were excluded from the analysis because their data were incomplete. Among the remaining 140 eyes, 8 (5.7%) had primarily spherical plots and were classified as Group 1. Another 40 eyes (28.6%) were primarily regularly toric, largely following a toric (Sin2) curve with approximately 180° periodicity—the interval from one elevation to the next, or one depression to the next—and were classified as Group 2.

Fifty-seven cases (40.7%) had asymmetric depressions (or steep areas) or asymmetric elevations (or flat areas), forming Group 3. The remaining 35 cases (26%, as reported in the abstract) had a recognizable toric pattern with elevations and depressions, but these were irregularly spaced or did not have the customary 180° periodicity; these formed Group 4.

The researchers presented this new classification of conjunctival/scleral shape based on data made available through wide-field elevation topography. They concluded that it could help with scleral lens fitting and potentially soft lens fitting, because the landing zones of these lenses extend beyond the corneal borders.