Corneal epithelial dendritic cell density in a healthy population and its relationship with age and sex: A Meta-Analysis of in vivo confocal microscope data

Abstract

Purpose : There are multiple in-vivo confocal microscopic reports of corneal epithelial dendritic cell (CEDC) density in a healthy population. This study aimed to generalize CEDC density in a healthy population at both the central and peripheral cornea and associations with age and sex by conducting a meta-analysis.

Methods : A systematic literature review was conducted via Medline, Google Scholar, Scopus, PubMed, Embase and Cochrane library up to May 2018. Studies using the Heidelberg Retinal Tomography with a Rostock Corneal Module and reporting central and peripheral CEDC density in healthy subjects were included. The mean and standard deviation of CEDC in each study was calculated using a random effect model and heterogeneity (I²) was examined using Q-statistics. Meta-regression was carried out to estimate the effect of age and sex, and sub-group analyses were conducted by study population, methods, age and sex to examine heterogeneity.

Results : 42 studies were identified and 39 datasets were included, with a total number of 1203 participants, aged 18-81 years. The meta-analysis showed that average CEDC density in healthy central and peripheral cornea is 26.4 ± 13.6 and 74.9 ± 22.7 cells/mm², respectively. There was no association between age and central CEDC density (b= -0.0796, p=0.63) but the peripheral CEDC density decreased with increasing age (b= -1.66, p=0.02). CEDC density was not affected by sex at either central (b= -0.0144, p=0.90) or peripheral cornea (b= 25.99, p=0.48). There was a significant heterogeneity among studies reporting central (I²: 94.5%) and peripheral CEDC density (I²: 96.1%). The only sub-group analysis which significantly improved heterogeneity was by age (25-40 years) (I²:52.6%); further stratification by age was not possible due to large age ranges reported.

Conclusions : This study provides useful baseline data of central and peripheral CEDC density in a normal population. The effect of age and sex on CEDC density was inconclusive in literature, however, CEDC density seems to be affected by age but not by sex based on this analysis. There were limited studies in youth (<18 years), precluding more detailed analysis.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.