The Effect of Scleral Contact Lens Wear on Intraocular Pressure and Ocular Morphology

Abstract

Significance. Intra-ocular pressure (IOP) has been shown to increase after 2 to 8 hours of wearing a scleral contact lens (SL). However, cumulative impact of SL on IOP and ocular morphology remains unclear. We hypothesize sustained IOP increase will occur during longer-term SL wear, due to continued biomechanical changes (sub-atmospheric suction) induced by the SL on anterior segment structures. This may have ocular health implications, as elevated IOP over extended duration may potentially lead to glaucomatous damage in susceptible individuals. This study investigated the cumulative impact of one week of conventional daily wearing of SLs on IOP and ocular structures. Methods. 27 healthy adults (average age 26.3 ± 3.8 years) having normal corneas participated in this prospective within-subjects study. One eye of each subject was randomly selected for a 16.5 mm diameter best-fit SL. The fellow eye was fitted with a 14.0 mm diameter soft contact lens (SCL) which served as a control. Participants wore both lenses for 8 hours daily for 1 week. Measurements of IOP using a rebound tonometer (iCare), anterior segment structures using automated Scheimpflug tomography(Oculus Pentacam HR) and neuro neuro-retinal structures using optical coherence tomography angiography (OCTA) imaging (Optovue AngioVue) were assessed at morning (AM) and after 8 hours (PM) in three-day visits: the baseline measurement day, initial contact lens wear day, and 1week lens wear day. On the baseline day, no lenses were worn. Measures were taken pre-lens wear, pre-lens removal, and after lens removal in the first and last days of 1 week of lens wear. Paired two-tailed t-tests and repeated measure analysis of variance ANOVA were used for statistical analysis. Results. The study found that wearing SL for 8 hours resulted in an average IOP increase of (4.16 mmHg; p < 0.001) in 93% of participants on the first day. After a week of daily wear, 85% experienced an average IOP increase of (3.99; p < 0.001) mmHg. Anterior chamber volume (ACV) increased significantly by 11.48 mm³ on the first day and 11.44 mm³ after a week, (p < 0.001). Anterior chamber depth (ACD) increased by 0.09 mm initially and 0.06 mm after a week, (p < 0.001). Nasal angle (NA) II decreased by 3.37º and 3.18º on the two examination days (p < 0.001), while temporal angle (TA) increased by 1.71º and 1.58º, (p < 0.05). Optic disc rim area reduced by (0.03 mm2; p < 0.001) mm and (0.02 mm2; p < 0.04) mm², and retinal nerve fiber layer (RNFL) thickness decreased by (3.26μm; p <.001) and (3.00μm; p <.001) μm after 8 hours of wear on the two examination days. SCLs did not cause significant changes in most measurements. Ocular changes were of similar magnitude regardless if it was after one day or one week of daily SL wear. Conclusion. SL wear resulted in an increase in IOP in young healthy participants, as well as iridocorneal angle changes, anterior chamber expansion, and neuro-retinal reduction. All these changes were found to be reversible upon removal of the scleral lenses.