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P. Situ, T. L. Simpson, L. W. Jones, D. Fonn; Changes in Corneal and Conjunctival Sensitivity With Silicone Hydrogel Lens Wear. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6347.
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To examine changes in ocular surface sensitivity to tactile, pneumatic mechanical and chemical stimulation following a short period without lens wear and after refitting with silicone hydrogel lenses and the effects of lens-solution interactions on sensitivity.
48 asymptomatic contact lens wearers were enrolled. Phase 1 included no lens wear (≥ 4 days) and then balafilcon A lenses (PureVision; PV) with a hydrogen peroxide-based regimen for 2 weeks. Phase 2 included wear of PV lenses with multipurpose solution preserved with either POLYQUAD®& ALDOX® (OPTI-FREE RepleniSH) or PHMB (ReNu MultiPlus) (each for 1 week) with a 2-week washout period between solutions. Cochet-Bonnet or computer-controlled Belmonte esthesiometers delivered tactile (nylon thread), or pneumatic mechanical (air at 50°C) and chemical (air mixed with CO2) stimulae respectively, to the cornea and conjunctiva to determine thresholds. Sensitivity and corneal fluorescein staining were assessed at baseline, after 2 and 8 hours of lens wear on day 1 and at the end of each wearing cycle (at 2-hours).
In phase 1, corneal tactile and corneal and conjunctival mechanical thresholds changed between visits (ANOVA all p<0.05). Tactile thresholds increased at the 1-day 8-hour and the 2-week visits from no-lens wear baseline (Tukey HSD both p<0.05). Corneal mechanical thresholds were lower on Day 1 (2 and 8 hours of lens wear) than with habitual lens wear (Tukey HSD, both p<0.05), while the conjunctival thresholds decreased at Day 1 (2-hours of lens wear) and Week 2 compared to no lens wear (Tukey HSD, both p<0.05). In phase 2, there were significant differences in chemical threshold and staining scores between solutions (ANOVA both p<0.05). At Day 1 and Week 1 (2 hours of lens wear), the chemical thresholds were lower with PHMB-preserved solution compared to the solution preserved with POLYQUAD®& ALDOX® (Tukey HSD both p<0.05). Staining was inversely correlated to conjunctival chemical thresholds (all p<0.05).
Ocular surface sensitivity changed in adapted lens wearers after lenses were refit following an interval without lens wear, and during lens wear with different care regimens. Corneal staining occurring with certain lens-solution combinations is accompanied by sensory alteration of the ocular surface, i.e., higher levels of staining are correlated with increased conjunctival chemical sensitivity.
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