Epithelial Irregularity Index (EIF) as an Objective Measure of Dry Eye: A Pilot Study

Abstract

Purpose: : Utilizing ultra-high resolution optical coherence tomographer (UHT-OCT), corneal surface damage or "irregularity" due to desiccation, tear film instability and/or evaporation can be objectively quantified as an Epithelial Irregularity Factor (EIF). The purpose of this study was to characterize both EIF as well as other signs and symptoms in dry eye subjects before and after treatment.

Methods: : 19 subjects recruited from the BPRI Dry Eye Clinic (15 women/4 men; mean age 53±17 years) completed this study. Subjects qualified if one positive baseline symptom or sign (one eye) of dry eye was met: (a) a single symptom score of ≥3 on the Shihpai questionnaire; (b) NEI graded NaFl corneal staining of >1; (c) TFBUT < 10 sec or (d) Schirmer I test < 5mm. EIF was measured using a custom-built spectral domain anterior segment UHT-OCT. Imaging was performed prior to any other test to avoid potential alterations of the ocular surface. 32 radial frame images were captured in 2.7 seconds after which vertical and horizontal frames were extracted and analyzed using custom-built software. The thickness profile of the central 3mm of corneal epithelium was used to calculate the EIF, which represents the standard deviation of epithelial thickness in this area. Scores range between 0 and ≈4microns and preliminary work suggests scores over 1.3 are indicative of dry eye. Following baseline measurements, subjects were instructed to use Systane® Gel Drops QID for ≈ 6 weeks (range 3-15). All clinical measurements were repeated at the end of treatment. This study was registered on Clintrials.gov; NCT01483989.

Results: : The mean EIF at baseline was 2.0±0.6 and corresponded to mean clinical data as follows: Shihpai symptom score 15±5; osmolarity 309±22 mOsm; TFBUT 3.0±2.0 sec; Schirmer I 5.7±7.8 mm; NaFl staining 5.4±4.0. Improvements in all clinical dry eye measures were seen following treatment with Systane® Gel Drops, with significance reached with TFBUT (4.9±3.8 sec; p = 0.009); Schirmer I (9.6±9.5 mm; p = 0.013) and EIF (1.6±0.5; p = 0.001).

Conclusions: : Data from this pilot study demonstrate the potential utility of EIF as an objective measure of corneal abnormalities associated with dry eye as well as the microscopic resolution of these abnormalities after effective treatment such as with Systane® Gel Drops.

Clinical Trial: : http://www.clinicaltrials.gov NCT01483989

Keywords: cornea: epithelium • cornea: tears/tear film/dry eye