From Tear Film Instability to Symptoms: an Experimental Model

Title From Tear Film Instability to Symptoms: an Experimental Model
Author, Co-Author Jun Zhang, Carolyn Begley, Arthur Bradley, Larry Thibos, Ping Situ, Trefford Simpson, Ziwei Wu
Program Number
Four Seasons Ballroom
Indiana University School of Optometry
Abstract Purpose: We hypothesis that tear film stability (TFI) over the pupil decreases optical quality, visual acuity (VA) and stresses the ocular surface, leading to visual disturbance and ocular irritation. In this TFI model, visual disturbance and ocular irritation were measured with and without a contact lens (CL).

Methods: 10 subjects had 2 visits, with and without a CL. A 3-channel optical system was used to monitor TFI by retroillumination (RI), VA and residual aberration-RMS fit error (RMSFE) (Liu et al, 2010). Subjects kept one eye open for up to 30 sec. Discomfort and blurry vision during and after trial were rated by visual analogue scales (VAS) and the current symptom questionnaire(CSQ) was used to rate dry eye-like symptoms before and after testing.

Results: TFI occurred in 72% of all trials, including 86% with and 58% without CLs. The decrease in logMAR VA ranged from 0.026 to 1.209 (mean 0.586±0.272) with CLs, and from 0.062 to 1.049 (mean 0.437±0.231) without CL. The increase of RMSFE ranged from 343.6 to 4514.5 (mean 1911.5±984.3) with CL, and from 176.8 to 3112.7 (mean 582.6±387.8) without CL. The larger increase in pre-CL tear film optical aberrations was statistically significant (paired t-test, p<0.05). The VAS symptom of discomfort (0- 10) increased from 1.29±1.56 to 5.62±2.49 with CL, and from 0.67±0.57 to 4.67±1.53 without CL, while blurry vision increased from 0.90±0.99 to 6.51±2.22 with CL and from 0.40±0.40 to 2.50±1.31 without CL. The median CSQ sum score (0-50) was 11 with CLs and 5 without CLs before testing and showed a significant increase to 41 and 44, respectively (Wilcoxon Signed-Rank Test, p<0.03).

Conclusion: Our model of TFI leads to decreased VA and optical quality and increased discomfort without a CL. Similarly, TFI while wearing a CL appears to induce visual disturbance, but alters the acute sensory response to TFI. Both conditions lead to sustained ocular irritation under different mechanism. Although the experimental model controlled the level of tear film exposure, it produced highly variable optical, visual and symptomatic consequences.
Affiliation of Co-Authors Indiana University, School of Optometry, Indiana University, School of Optometry, Indiana University, School of Optometry, Indiana University, School of Optometry, University of Waterloo, Optometry and Vision Science, Indiana University, School of Optometry