The Impact of a Scleral Lens on the Eye

Purpose: There are several gaps in understanding ocular effects of a scleral lens (SL), particularly in the composition of the fluid reservoir (FR) that bathes the cornea and the impact of the landing zone radius (LZR) on the eye. The purpose of this dissertation is to (1) identify and compare molecules in the FR to basal tears, (2) determine the composition of the FR in midday fogging (MDF), and (3) determine if conjunctival compression from the LZR changes the intraocular pressure (IOP) and optic nerve head minimum rim width (MRW). Methods: (1) In normal subjects (n=15) wearing SL for 8-hour, basal and FR tear samples were collected, and immunomodulatory molecules were quantitated using Luminex multiplex immunoassay and compared between tear sample types. (2) In normal subjects (n=13) wearing SL, optical coherence tomography (OCT) was used to quantitate MDF, which was then correlated to relative lipid and protein abundances (mass spectrometry), SL parameters, and ocular surface health outcomes. (3) In normal subjects (n=26) wearing a SL on one (test) eye, MRW and IOP were measured using OCT imaging and iCare tonometry, respectively, at baseline, 2- and 6-hours SL wear and compared to the untreated (control) eye. Results: (1) Matrix metalloproteinase (MMP)-9 and MMP-10 were significantly greater in the FR, reaching 62.7 and 25.8 ng/ml, respectively, after 8-hours SL wear. (2) MDF samples were positively correlated to levels of wax esters (r = +0.76, P = 0.01) and hydrophobic lipids, negatively correlated to conjunctival compression (r = -0.59, P = 0.048), and not correlated to negative ocular surface health outcomes. (3) MRW thinning was not different in the test eyes after 6-hours of SL wear (-8 μm) vs control (-6 μm) eyes (P = 0.09). Mean IOP increased 2 mmHg post-SL removal (P = 0.02). Conclusions: In normal SL wearers, the FR is distinct from the basal tears and may retain inflammatory molecules. Hydrophobic lipids are primarily correlated to MDF, supporting the need for development of a lipophilic solution in the SL bowl to reduce the risk of MDF. Despite a modest increase in IOP post-SL removal, MRW is not significantly impacted during SL wear.