Abstract
Purpose :
Corneal nerves play an important role in maintaining ocular surface health. Abnormalities in the system can contribute to a variety of eye diseases. Several mediators support peripheral and central nerve function and an examination of their contribution to corneal nerve health is an important avenue of study. This study examines associations between two molecules: brain-derived neurotrophic factor (BDNF) and glutamate, with various corneal nerve metrics.
Methods :
Prospective study of individuals seen in the Miami Veterans Affairs eye clinic. Individuals completed ocular pain symptoms questionnaires and underwent comprehensive ocular surface assessment, including confocal microscopy. Individuals provided a blood sample which was analyzed for BDNF and glutamate. Free BDNF levels were measured using R&D Free BDNF Quantikine ELISA Kit (#DBD00). Glutamate was measured using Glutamate Assay Kit (Fluormetric, ab138883). Samples were run in duplicate following manufacture’s protocol. Our primary goal was to examine relationships between serum BDNF and glutamate levels and measures of corneal nerve structure and function.
Results :
134 individuals were included, with mean age of 55.8±4.7 (range 48-67 years); 89% (n=119) self-identified as male, 55% (n=74) as White, and 37% (n=49) as Hispanic. BDNF levels ranged from 14.0 ng/ml to 82.0 ng/ml (n=114), mean of 39.9 ng/ml (SD±12.1). Glutamate levels ranged from 0 ng/ml to 3.2 ng/ml (n=125), mean of 1.2 ng/ml (SD±0.6). BDNF and glutamate levels were not related to ocular pain metrics examined with a variety of dry eye and pain questionnaires. However, some relations were noted with respect to corneal nerve metrics, with BDNF associating with lower central nerve density (r=-0.22, p=0.04) and complexity (r=-0.25, p=0.03) and glutamate associating with a higher beading density (r=0.28, p=0.008). Glutamate levels were also related to corneal sensitivity with higher levels (1.5±0.5 ng/ml) in those with decreased sensation (n=21) and lower levels (0.9±0.5 ng/ml) in those with increased sensation (n=15), as compared to individuals who were qualitatively assessed to have normal sensation via the cotton tip test (1.2±0.6 ng/ml, n=89, p=0.01)
Conclusions :
BDNF and glutamate levels relate to various aspects of corneal nerve function and structure. Future studies are needed to understand how levels of these molecules impact ocular surface health.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.