Clinical evaluation of the decentration in different designs of scleral lenses

To validate a simple and highly repeatable method of measuring the displacement of scleral lenses from the pupillary center and to quantify scleral lens decentration of two different designs of scleral lens landing zones: spheric (SLZ) and toric (TLZ), with the validated method.

A prospective crossover study has been performed. Twenty patients (26.90 ± 3.03) with regular corneas participated voluntarily in the study and SLZ and TLZ landing zone Onefit™ MED scleral lenses were fitted. This study was divided into 2 phases. In the first phase, the validation of a new technique, using an image processing tool through the Matlab_R2017b software, to measure decentration was performed, compared with a subjective method consisting of a millimetric grid located in one of the slit lamp eyepieces. Intersession and interobserver repeatability were evaluated in the vertical and horizontal measurements of decentration with both methods. Once the best and higher repeatable method to assess decentration was found, phase 2 started and decentration of two different landing zone designs of scleral lenses were evaluated.

In the first phase, Matlab methodology for decentration analysis showed high repeatability for both horizontal and vertical axes (ICC ≥ 0.9), whereas the slit lamp method demonstrated lower repeatability (ICC < 0.5). Second phase showed a significant reduction in decentration after two hours of wear with TLZ design (p < 0.001), unlike the SLZ design, which had no significant changes.

The measurement of contact lens decentration by image processing using the Matlab software showed a high intersubject and intersession repeatability. SLZ tends to decenter inferiorly and temporarily. A toric landing zone design allows better centration but does not completely reduce the problem of decentration in either the vertical or horizontal axis.