This article was originally published in a sponsored newsletter.

Scleral lenses are fitted to the scleral bulbar conjunctiva and settle into the ocular surface tissue after lens application. A study evaluated the mean settling rates for three scleral lens designs.¹ Lens settling was measured immediately after lens application and then every 15 minutes until one hour. It was subsequently measured at two-hour increments until eight hours. Lens settling rates were highest after lens application. With the three lens designs, the amount of lens settling varied significantly. After eight hours, the three types of lenses settled from 88.1μm to 133.7μm.¹ According to nonlinear regression analyses, lens settling was calculated from 80% to 99% after eight hours.¹

In another study, a prospective, observational clinical study design was used to evaluate attributes of scleral lens settling.² A total of 42 eyes of 21 healthy Chinese adults (mean age 27.2 ± 4.1 years; three males and 18 females) who had refractive error (–5.50D ± 2.92D) were enrolled in the study.

Patients were fit with scleral lenses that had a diameter of 15.6mm. These lenses consist of four zones with peripheral back surface toricity. They are made of Boston XO material with a Dk of 100 and a center lens thickness of 300μm.

In the study, patients were evaluated on the day that scleral lenses were dispensed and again after wearing scleral lenses for three months. Participants wore scleral lenses for at least five days each week for eight hours each day. Visual acuity, ocular health, and lens fitting were evaluated at each visit. The post-lens tear thickness (PoLTT) at the pupil center was measured at each visit.

At the dispensing visit, PoLTT was quantified immediately after lens application and then 30, 60, 120, and 240 minutes after lens application. At the three-month visit, PoLTT was quantified immediately after lens application and again at 240 minutes. Statistical analysis was performed using repeated measures analysis of variance and paired-t test.

After 240 minutes of lens wear at the dispensing visit and after three months, lens settling was 126μm ± 33μm and 98μm ± 55μm, respectively. Immediately after lens application, there were no major differences between the dispense visit and three-month visit (t = –0.25, p = 0.81). At 240 minutes after lens application, there was a significant difference (t = –6.57, p < 0.001). The quantity of settling was greater at the dispensing visit compared to the three-month visit (average difference = 28μm ± 63μm, t = 2.73, p = 0.01).

In this study of 15.6mm scleral lenses in Chinese adults with refractive error, the PoLTT decreased over time after lens application. The quantity of scleral lens settling differed among patients (range: 71μm to 204μm). After three months, the settling amount did not increase, noting the long-term fitting stability of scleral lenses. In this study, the PoLTT can be estimated by utilizing the prediction model based after 30 minutes of scleral lens wear.

Reference(s):

1. Kauffman MJ, Gilmartin CA, Bennett ES, Bassi CJ. A comparison of the short-term settling of three scleral lens designs. Optom Vis Sci. 2014 Dec;91:1462-1466.
2. Deng R, Chen B, Wang F, et al. Settling characteristics of scleral lenses in Chinese adults with refractive error. Cont Lens Anterior Eye. 2024 Jan 2:102108.

Melissa Barnett, OD, FAAO, FSLS is the Director of Optometry at the University of California, Davis, specializing in anterior segment disease and specialty contact lenses. She is the past president of the Scleral Lens Education Society and is past chair of American Optometric Association Contact Lens and Cornea Section. She is an advisor to and/or has received honoraria or travel expenses from AccuLens, Alcon, Allergan, Bausch + Lomb, Bruder, Contamac, CooperVision, Johnson & Johnson Vision, Ocusoft, ScienceBased Health, Tarsus, and Visus Therapeutics.