Comparison of the Cellular Response to Overnight Contact Lens Wear on the Sclera and Cornea

Abstract

Purpose: To investigate the overnight inflammatory response to a hydrogel carrier material designed for a 24-hour intraocular pressure (IOP) monitoring device mounted on the superior, scleral bulbar conjunctiva, and compare it to overnight lens wear on the cornea.

Methods: Eight participants were recruited to a sleep lab for 3 non-consecutive visits. The 1st visit consisted of overnight sleep (8 hrs) with no contact lens in place (baseline); the 2nd visit consisted of overnight sleep with a hydrogel contact lens fitted bilaterally to the cornea; and the 3rd visit consisted of overnight sleep with a hydrogel contact lens placed bilaterally on the superior, scleral bulbar conjunctiva, beneath the upper lid. Immediately upon awakening, participants had the lenses removed and their eyes washed using a non-contact irrigation system. The expression of the C3a receptor (C3aR), CD95 (Fas, cell death inducing receptor), CD54 (ICAM-1), CD66b (degranulation marker), and CD45 (Pan leukocyte marker) on polymorphonuclear leukocytes (PMN) was evaluated by flow cytometry for each visit and is reported as arbitrary fluorescent units (AFU).

Results: Flow cytometric analysis of PMN revealed a significant decrease in the expression of C3aR after overnight contact lens wear on the cornea (13 ± 7 AFU, p < 0.01) as compared to overnight lens wear over the sclera (42 ± 23 AFU) and no lens wear (35 ± 11 AFU). A reduction in CD54 expression was observed for overnight lens wear over the sclera and the cornea (25 ±6 AFU,p ≤ 0.03; 26 ±8 AFU, p > 0.05) when compared to baseline (37 ±12 AFU). For all visits, CD95 remained at background levels and there was no significant difference in CD66b expression.

Conclusions: These results suggest that overnight lens wear on the cornea alters the expression of C3aR, a receptor important in the regulation of the leukocyte inflammatory response mediated by complement activation. PMN response to overnight contact lens wear on the superior, scleral bulbar conjunctiva was similar to the control condition with no contact lens. Silicone hydrogel contact lenses, approved for overnight wear on the cornea, may be safely mounted on the scleral bulbar conjunctiva and presents a promising carrier material for a 24-hour IOP monitoring device.

Keywords: 568 intraocular pressure • 557 inflammation • 480 cornea: basic science