Changes in ocular surface immune cell proportion are associated with dry eye disease (DED) type and severity, according to research findings published in The Ocular Surface

Researchers conducted a cross sectional, observational study to determine the proportions of immune cell subsets on the ocular surface in patients with DED. Participants included 22 eyes of 15 healthy participants as a control group and 96 eyes of 48 patients diagnosed with dry eye disease.

Investigators collected ocular surface cells from ocular surface wash samplesFlow cytometry-based immunophenotyping using immune cell type-specific fluorochrome-conjugated antibodies was used to determine the proportions of various immune cell subsets on participants’ ocular surfaces. 


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Between groups, clinical signs and symptoms of DED — tear break-up time, Schirmer’s test 1, and ocular surface discomfort score — were significantly different, with significantly lower tear break-up time in participants with evaporative DED (n=36) and aqueous deficient DED (n=60) compared with the control group. Schirmer’s test 1 was significantly lower in those with aqueous deficient DED compared with both controls and participants with evaporative DED, and ocular surface discomfort score was significantly higher in both DED groups. 

Patients with DED had higher proportions of leukocytes, neutrophils, macrophages, CD4 T cells, CD8 T cells, CD4/CD8 T cell ratio, CD4-CD8 double positive T cells, gamma delta T cells, and NKT cells compared with controls. Only proportions of leukocytes, neutrophils, CD4 T cells, CD8 T cells, and CD4/CD8 T cells ratio were significantly increased, however. 

Patients with aqueous deficient DED also demonstrated a significant increase in proportion of leukocytes compared with evaporative dry eye disease and controls, while both types of dry eye disease demonstrated a significant increase in percentages of total neutrophils and a marked but not statistically significant increase in activated neutrophil proportion was seen in aqueous deficient dry eye disease, but not evaporative dry eye disease or controls. 

Fluorescein staining was used to investigate corneal epithelial defects in the eyes. Corneal staining was seen in 28% of eyes with evaporative DED and 55% of eyes with aqueous deficient DED. Tear break-up time and Schirmer’s test 1 were significantly lower in those with corneal staining compared with those without in both DED subgroups. 

Investigators noted a higher percentage of leukocytes in both DED subsets with corneal staining compared with those without. The proportion of total and activated neutrophils were higher in aqueous deficient DED with corneal staining vs those without. 

Researchers also evaluated the ratio of neutrophils and NK cells in the study cohort. Compared with the participants in the control group, significantly higher CD66b+/CD56+ AND CD66b+/CD56Low ratios were seen in both DED subgroups; increasing trends were seen in the CD66b+/CD56High ratio. In patients with aqueous deficient DED with corneal staining, significantly higher ratios of CD66b+/CD56+, CD66B+/CD56Low, and CD66b+/CD56High were seen vs participants in the control group. These, and the presence of significantly higher CD66b+/CD56+ and CD66b+/CD56Low ratios in evaporative DED patients regardless of corneal staining “suggest a possible implication of neutrophils/NK cells ratio” in DED. 

OSDI scores were negatively correlated with tear break-up time and Schirmer’s test 1 values, while a positive correlation was noted between tear break-up time and Schirmer’s test 1 in the study cohort. A favorable association was also noted between NK cells and dry eye disease indices, and neutrophil/NK cell ratio demonstrated a positive relationship with OSDI scores. 

Study limitations include the potential that the ocular surface wash method may have only collected superficial and trafficking ocular surface immune cells. 

“This information from human eyes will enable effective development of targeted immune directed therapeutic options for the management of dry eye disease,” the researchers conclude. 

Reference

Nair AP, D’Souza S, Shetty R, et al. Altered ocular surface immune cell profile in patients with dry eye disease. Ocul Surf. Published online April 13, 2021. doi:10.1016/j.jtos.2021.04.002