Preliminary investigation on tear film alterations in latent herpes stromal keratitis

Abstract

To investigate tear film alterations in patients with latent herpes stromal keratitis (HSK). Prospective comparative case series study. Twenty-four patients with latent HSK in one eye and 28 age and gender matched healthy individuals were recruited. All subjects were evaluated by subjective symptoms of dry eye, tear film break-up time (BUT) and Schirmer I test (SIT). Laser in vivo confocal microscopic investigation was performed in 12 patients with severe tear film instability (BUT ≤ 5 s). Data distribution and homogeneity of variance was analyzed. Statistical comparisons of the mean values between different groups were performed using Kruskal-Wallis test, Mann-Whitney test or student t-test. Most of latent HSK patients (n = 22/24, 91.7%) had symptoms as dryness, burning sensation, redness and foreign body sensation. Both eyes of patients with latent HSK had hyposecretion (SIT, control eyes (16.2 ± 3.2) mm/5 min; affected eyes (10.4 ± 7.8) mm/5 min; lateral eyes (11.2 ± 8.8) mm/5 min; control and affected, U = 135.0, P < 0.001; control and lateral, U = 155.0, P = 0.001) and decreased tear film stability [BUT, control eyes (12.1 ± 0.7) s, affected eyes (4.3 ± 3.3) s, lateral eyes (9.2 ± 4.4) s; control and affected, U = 28.0, P < 0.001; control and lateral, U = 114.0, P < 0.001] as compared to control group (Kruskal-Wallis nonparametric test). The value of BUT showed significant difference between affected eyes and healthy eyes (U = 90.0, P < 0.001), whereas no difference of the value of SIT was found (U = 273.0, P = 0.757). Abnormal SIT (≤ 10 mm/min) and BUT (≤ 10 s) was presented in 14 (58.3%) and 23 (95.8%) affected eyes, as well as in 14 (58.3%) and 17 (70.8%) lateral eyes, respectively. Laser in vivo confocal microscopy investigation in 12 affected corneas with abnormal tear film showed morphological alterations as corneal epithelial metaplasia with polymorphism and enlarged cells, reflective nuclei, and decreased nucleus/cytoplasm ratio; decreased nerve density in subepithelial plexus and obvious branching and beading, which is similar to those changes caused by dry eye. Most of latent HSK patients had abnormal tear film. Dry eye related alterations could be found in affected corneas with abnormal tear film by in vivo confocal microscopy.