THE EFFECT OF EYE CLOSURE ON PROTEIN AND COMPLEMENT DEPOSITION ON GROUP-IV HYDROGEL CONTACT-LENSES - RELATIONSHIP TO TEAR FLOW DYNAMICS

Purpose. This study was designed to determine the effect of overnight eye closure on the rate and composition of protein deposition on high water content ionic matrix soft contact lenses !Group IV SCLs) and to extrapolate from this data information on the probable change in the r ate of reflex-type tear secretion associated with eye closure. Methods . Group IV SCLs were temporally sampled after equivalent periods of we ar under closed eye (C) or open eye (O) conditions. Lenses were rinsed in saline and the majority of the tightly bound protein extracted at 90 degrees C in 40% urea, containing 1% SDS, 1 mM DTT, 100 mM Tris-HCl (pH 8.00). Residual protein was determined by Coomassie staining of t he extracted lenses and densitometric analysis, Extracted protein was quantitated and separated by SDS-PAGE. Gels were either stained with C oomassie blue or reversibly stained with imidazole-zinc and blotted. B lots were PAS stained, or lectin and antibody probed for glycoproteins , secretary IgA (sIgA), IgG, lysozyme and complement C3, Laboratory si mulated deposition studies were carried out on unworn lenses exposed t o HPLC purified lysozyme. Results. The protein in the saline rinse, to a large degree mirrored the composition of tear fluid in which the le ns had been residing (O or C). This would suggest that the saline wash consists of residual tear fluid and loosely adherent protein, In cont rast, the urea extracts were highly homogeneous consisting primarily o f lysozyme and to a lesser extent lysozyme dimer. This supports the co ntention that the Group IV SCL functions in the eye much as cationic e xchange resin selectively absorbing lysozyme. C extracts also proved r elatively enriched in trace amounts of sIgA, IgG and complement C3 and its breakdown products. High levels of C3 and C3 breakdown products w ere specifically recovered only in the C worn lens extracts from a sub ject experiencing unilateral contact lens associated corneal infiltrat es from the affected eye. In all subjects, markedly less protein (lyso zyme) was recovered in urea extracts of lenses exposed to 7-8 h of clo sed eye as compared to open eye wear (0.20 +/- .08 versus 0.79 +/- .15 mg/lens (n = 6)). Temporal studies further revealed that deposition w as linearly related to duration of wear during the initial phase of co nditioning film formation giving rise to rate constants for lysozyme d eposition of 2.2 +/- 0.29 (n = 5) and 0.20 +/- 0.06 mu g/min (n = 4) u nder open and closed eye conditions respectively. With further wear, d eposition eventually reached a steady state, Under laboratory conditio ns, lysozyme was much rapidly and quantitatively removed from solution in a manner following a hyperbolic plot. This suggests that during th e initial phase of deposition the rare of deposition is limited by the capacity of the tear fluid to deliver lysozyme to the lens surface un der these two extremes of conditions. Conclusions. Eye closure profoun dly affects the rate of lysozyme deposition on Group IV hydrogels and the composition of minor biofilm constituents in a manner that could a ffect biocompatibility, Finding support the contention that eye closur e results in a >90% reduction in the rate of reflex-type tear secretio n.