Objective quantification of trabecular meshwork pigmentation and correlation to primary open-angle glaucoma disease severity

Purpose: In this study, we further evaluated a unique early biomarker that has been demonstrated to be correlated with primary open-angle glaucoma in a pilot study. This novel biomarker correlated an increased ratio of pigmentation in the inferior trabecular meshwork (TM) compared to the superior TM with a greater degree of visual field loss in a small subset of patients. We evaluated this association in a larger group of patients. Methods: This is a retrospective single-center analysis of Black and Afro-Latino patients that make up the local New York inner-city community of Advanced Eyecare of New York in Queens Village and Harlem, New York City with a diagnosis of primary open-angle glaucoma. We reviewed 335 consecutive glaucoma and glaucoma suspect patients with imaging of the TM via the GS-1 gonioscope. The degree of pigmentation was then quantified using ImageJ software to measure the ratio of pigmentation in the superior to inferior TM. We then created a ratio based on these superior to inferior TM measurements for each patient and compared this ratio to the patient's mean deviation of the visual field. Results: Results from 529 eyes in 335 patients demonstrated a positive correlation between the superior-inferior ratio (SIR) of pigmentation and visual field loss. The greater the degree of pigmentation asymmetry between the superior and inferior angle, the greater the extent of visual field deterioration. There was also a positive correlation between the SIR and age. Conclusion: In a larger cohort of patients with glaucoma or glaucoma suspects, on TM pigment assessment with Image J, there was a positive correlation between SIR and worsening visual field mean deviation. Further research is required to evaluate a greater number of normal patients, glaucoma suspects, and glaucoma patients. Further research is also necessary to produce automated TM images and to develop automated assessment of TM pigment density with artificial intelligence to compare with other clinical factors such as age, IOP, OCT, and retinal nerve fiber layer thickness. Since the TM is where damage initially occurs to cause glaucoma, this can potentially lead to earlier detection before IOP elevation and retinal ganglion cell loss.