Abstract
Purpose: :
The purpose of this study was to evaluate the osmolarity values and symptomatic changes in a normal population throughout their initial month of contact lens wear
Methods: :
Asymptomatic first-time lens wearers with a baseline tear osmolarity less than 308 mOsm/L were selected for inclusion in the study (N=11, age=19-23 years). Extended wear hydrophilic silicone hydrogel contact lenses (Biofinity® Comfilcon A) were worn for 8 hours per day, 6 days per week throughout the month. Tear film osmolarity values were measured in the lateral meniscus using the TearLab Osmolarity System according to the following schedule: 30 minutes prior to insertion of the contact lens, 2 hours and 8 hours after the insertion of the lens (with the lens in the eye), and 1 hour after removal of the lens. Dryness and discomfort symptoms were measured using the visual analog scale (VAS; 0-10) according to the same timetable as the osmolarity measurements, while the McMonnies symptom questionnaire was tested at each visit. Osmolarity and symptom measurements were taken on day 1, week 1 and week 4 of the study.
Results: :
No significant changes were seen in osmolarity between baseline (297.7±10.4mOsm/L), 2 hours (296.6±11.7mOsm/L), or 8 hours after insertion of the contact lens (296.9±11.7mOsm/L). Tear osmolarity was slightly lower than baseline 1 hour after removal (293.1±12.3mOsm/L), but the difference was not statistically significant. No significant increases in osmolarity were seen throughout the month, however three subjects showed brief excursions between 316 and 323 mOsm/L following lens use. Neither the VAS values for dryness (range 0.6±0.5 to 2.5±2.8), discomfort (range 0.7±0.6 to 2.7±1.9) nor the scores obtained with the McMonnies questionnaire (mean = 7.1±3.9) demonstrated a symptomatic impact of the silicone hydrogel lens
Conclusions: :
Osmolarity measurements remain stable along the study, as lens wears showed little deviation in subjects with baseline osmolarities below 308 mOsms/L. The measured sensations presented values that suggest a minimal dryness and discomfort along the study and the McMonnies scores also showed no dry eye symptoms. Normal, first-time contact lens wearers were shown to tolerate Comfilcon A lenses well, and exhibited no significant increases in tear film osmolarity or symptoms throughout a month of extended wear.
Keywords: contact lens • cornea: tears/tear film/dry eye • contact lens