Comparison of two artificial tear formulations for dry eye through high-resolution optical coherence tomography

Purpose: The aim was to determine the efficacy of two artificial eye-drop formulations by analysing the lower tear film meniscus volume through a commercial high-resolution spectral-domain optical coherence tomographer. Methods: Twenty dry eye patients (12 men, eight women, aged 57.5 +/- 8.4-years) with refractive errors from -2.50 to +0.75-D (mean -1.34 +/- 1.02-D) and cylinders lower than 1.00-D were examined. Tear meniscus volume was measured before, immediately after and 10, 30 and 60-minutes after instillation using the Copernicus high-resolution spectral-domain optical coherence tomographer (Optopol Tech SA, Zawiercie, Poland). Volume was calculated from the local area obtained from tomograms considering a regular distribution of the tear meniscus across the eyelid. Ten subjects were randomly assigned to first receive either polyethylene glycol (Blink Intensive, Abbot Medical Optics Inc, CA, USA) or hypromellose (Artific, Farma-Lepori SA, Barcelona, Spain) three times daily in both eyes for one month. Measures were then repeated and after a one-week wash-out period they were switched to the other eye-drop for another month. Results: Mean baseline volume was 0.38 +/- 0.10 mu L, while mean baseline volume after the wash-out period was slightly higher, 0.39 +/- 0.10 mu L (p = 0.638). Analysis of variance showed significant differences in meniscus volume with time after instillation with both formulations (p < 0.001), mean volume decreasing with time. At 30 and 60 minutes following instillation, values decreased to almost baseline (average difference 0.02 +/- 0.03 mu L at t(30), p = 0.016 and 0.01 +/- 0.01 mu L at t(60), p = 0.098). Conclusion: An increase in tear film meniscus volume in dry eyes from the use of eye-drops has been shown. High resolution imaging of lower tear film meniscus with clinical optical coherence tomography systems provides useful measures of tear volume. Both formulations assessed in the present study are efficient in increasing tear meniscus volume and reducing dry eye signs and symptoms, although results in terms of increase in meniscus volume were higher with the polyethylene glycol formulation.