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Piyush Patel, Fiona Soong, Jalaiah Varikooty, Nancy Keir, Lyndon Jones; Ocular Signs and Symptoms in Contact Lens Wearers in a Controlled Low Humidity Environmental Exposure Chamber (LH-EEC), A Natural Provocation Research Model. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5473.
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To evaluate the effects of contact lens (CL) wear on the ocular surface under controlled conditions of low humidity and airflow, to assess the validity of a natural provocation research model for the study of dry eye and contact lenses.
The LH-EEC is validated to maintain uniform low relative humidity (10±3%) and comfortable room temperatures which mimic natural arid outdoor/indoor environs. Ten symptomatic CL wearers discontinued CL wear and used Refresh PLUS® tears t.i.d for 48hrs prior to LH-EEC Visit. Upon return to the clinic, subjects were randomly fit with 1-day Acuvue® Moist® (etafilcon A): CLA in one eye and 1-Day Acuvue® TruEye™ (narafilcon A): CLB in the contralateral eye. They were then exposed to LH-EEC for 180 mins with visual tasking throughout. Total Ocular Symptom Scores (TOSS) (dryness+grittiness+burning/stinging+itchiness) were rated 0-4 (maximum score of 16) at entry and at set intervals within the EEC. Tear Break Up Time (TBUT), fluorescein corneal staining and lissamine green conjunctival staining were collected pre and post LH-EEC using Efron scale (0-4) on the NEI grid for the cornea and nasal & temporal conjunctival zones.
After 180 mins in LH-EEC, mean increase from baseline was CLA=+1.4±1.2 and CLB=+1.0±0.7 for corneal staining and CLA=+1.30±0.78 and CLB=+1.20±0.72 for conjunctival staining. The mean reduction in TBUT (secs) was CLA=-0.3±0.2 and CLB=-0.8±0.7. Symptoms escalated throughout the exposure period with TOSS increasing from baseline for both lenses (CLA=+2.4±1.7 and CLB of +3.30±1.16), with the mean change for CLB being significant (p=0.02). Similarly, the dryness symptom score showed a trend to increase for CLA (+1.1±0.5) and a significant increase (p=0.001) for CLB (+1.40±0.31).
The LH-EEC Contact Lens Dry Eye model exacerbates ocular symptoms and signs while controlling all environmental variables. After only 180 mins of exposure, signs indicative of ocular surface desiccation and a parallel increase in dry eye symptoms were measurable. The LH-EEC model provides a valuable clinical research option for the study of CL and dry eye which provides rapid symptoms and signs typically found in longer periods of in-eye wear outside the LH-EEC.
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