Abstract
Purpose :
Ocular pain is responsible for significant morbidity in dry eye disease. This study aims to establish the association between severity of dry eye symptoms, corneal dendritic cell density (DCD), corneal sub-basal nerve plexus (SBNP) features, tear cytokine profile and serum vitamin D.
Methods :
52 patients (23 males, 29 females) and 43 healthy volunteers were included in the study with informed written consent and approval of the Institutional Ethics Board. Ocular discomfort was graded using ocular surface disease index (OSDI) questionnaire. Patients with OSDI scores indicating symptoms of dry eye, normal Schirmer’s values and low TBUT were categorized as EDE. Healthy volunteers with Schirmer’s values > 10 mm, TBUT > 5 seconds without dry eye were controls. The SBNP from central cornea was assessed by confocal imaging (Heidelberg Engineering GmbH) using a 400x400 microns2 frame followed by quantitation (CCMetrics, UK). Dendritic cell density(DCD) was estimated using Cell CountR (Heidelberg). Total serum vitamin D was also measured. Schirmer's test strips from each subject was used to extract tear proteins followed by cytometric bead array to determine relative cytokine profile.
Results :
A significant increase in OSDI scores was observed in EDE(median 20.8) and controls (median 4.2) (P<0.001). An increase in DCD was also observed between EDE (5.6 cells/mm2) patients and controls (48.1 cells/mm2) (P<0.001). A significant decrease in nerve fiber density and branching was observed in EDE patients with OSDI score >23 (P<0.05). A positive correlation was observed between DCD and OSDI discomfort subscale (r = 0.348; P<0.0003), and SBNP features. An inverse correlation was observed between vitamin D and OSDI scores (r = –0.332; P=0.0095), and mature DCD (r = –0.322; P=0.0122). Significantly higher level of IL-17A/F, IFNγ, MCP1, IL-4, IL-10 and decreased IL-2 concentrations was observed in patients' tears compared (P<0.05).
Conclusions :
Our data suggest that ocular discomfort in EDE could be due to increased corneal DCD on SBNP features. Furthermore, low vitamin D level can result in severe symptoms by altering the tear inflammatory cytokine levels and influencing nociception or through lack of negative regulation on DC activation/migration.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.