Settling characteristics of scleral lenses in Chinese adults with refractive error.

Purpose: To investigate the settling characteristics of a scleral lens in Chinese adults with refractive error and to provide guidance for its clinical application.

Methods: A total of 21 healthy Chinese adults (27.2 ± 4.1 years) with refractive error were enrolled in this study. The average spherical equivalent was -5.50 ± 2.92 D. Subjects were fitted with 15.6 mm diameter scleral lenses. The central post-lens tear thickness (PoLTT) was measured immediately after lens placement, 30, 60, 120, and 240 min after lens insertion at the dispensing visit and immediately after lens placement and 240 min after three months through optical coherence tomography. Statistical analyses were conducted using repeated measures analysis of variance and paired-t test.

Results: At the dispensing visit, the amount of settling after 240 min of lens wear was 126 ± 33 μm. After three months, the amount of settling was 98 ± 55 μm after 240 min. No significant difference was detected in the PoLTT immediately after lens placement between the dispensing visit and after three months (t = -0.246, p = 0.807), while a significant difference was noted at 240 min after lens insertion (t = -6.575, p < 0.001). The amount of settling was higher at the dispensing visit than that after three months (average difference = 28 ± 63 μm, t = 2.733, p = 0.01). The prediction model of PoLTT over time was y = 26.263-0.690 × t + 0.001 × t + 0.926 × y (R = 0.939), where y denotes the predicted PoLTT at t min after lens insertion, y denotes the PoLTT at 30 min after lens insertion.

Conclusion: For the investigated small-diameter scleral lens (material: Boston XO, diameter: 15.6 mm, four-zone and periphery toric design), the PoLTT decreased over time after lens insertion in Chinese adults with refractive error, and the amount of settling varied among individuals (range: 71-204 μm). The amount of settling did not increase further after three months, indicating the long-term fitting stability of the scleral lens. Practitioners could estimate the PoLTT using the prediction model based on the PoLTT at 30 min after wearing lenses.