A novel OCT technique to measure in vivo the corneal adhesiveness for sodium carboxymethylcellulose in humans and its validity in the diagnosis of dry eye

Purpose. The purpose of this work was to gather preliminary data on tear film stability, and the adhesive properties of the corneal surface in dry eye patients and control group subjects, using a new, minimally invasive optical coherence tomography (OCT) imaging method. Methods. We screened 85 human subjects for dry eye and classified them in two groups, as dry eye or normal patients. Sodium carboxymethylcellulose (NaCMC) adhesiveness over the central cornea was measured using Fourier domain anterior segment OCT. The corneal adhesiveness for NaCMC was compared between the two groups, correlated with classical tests, and analyzed for diagnostic validity and repeatability. Results. The corneal adhesiveness for NaCMC median and mode values was fair (between 1 and 3 minutes) for dry eye subjects (n 1/4 36) and borderline (between 3 and 5 minutes) for control group subjects (n 1/4 49), and was significantly different between the two groups (P < 0.001). Significant correlations were observed between the corneal adhesiveness measures and dry eye patients' symptoms (P < 0.001), Schirmer I test (P < 0.001), ocular surface staining (P < 0.001), and, particularly, fluorescein break-up time (P < 0.001). The area under the receiver operating characteristic curve was 0.94 (P < 0.001), suggesting reliable sensitivity and specificity of OCT imaging. A statistically significant intraclass correlation (ICC) value of 0.99 was found for measurements of corneal adhesiveness on two subsequent days at the same time (P < 0.001). Conclusions. This minimally invasive, novel technique of OCT imaging of the corneal surface following NaCMC drop instillation provides a measure of corneal adhesiveness. This technique may improve the clinician's ability in the understanding and diagnosis of the dry eye syndrome