Monitoring glaucoma is all about noticing change over time to the structure and the function of the eye. Thus, clinicians must first establish a baseline for both. New equipment, such as OCT angiography (OCT-A), now allows clinicians to gather the data needed for that baseline sooner and sooner, with the hope of earlier diagnosis and better outcomes.

With that in mind, researchers looked into the deep-layer microvasculature dropout of pre-perimetric primary open-angle glaucoma (POAG) patients. They looked at the records of 94 eyes with pre-perimetric POAG with β-zone parapapillary atrophy (βPPA) and categorized them according to the presence of deep-layer microvasculature dropout. The team measured the visual field mean deviation (MD), global and sectoral (6-sector) retinal nerve fiber layer (RNFL) thickness, as well as age, focal lamina cribrosa (LC) defect, width of βPPA with and without Bruch’s membrane (BM; βPPA+BM and βPPA-BM) and optic disc hemorrhage for both the dropout and non-dropout groups. They defined deep-layer microvasculature dropout as a complete loss of microvasculature within the choroid or scleral flange on OCT-A.

The study shows deep-layer microvasculature dropout in 35.1% of the pre-perimetric POAG eyes. The dropout eyes also had significantly thinner RNFL in all areas except the inferonasal sector. The dropout group also showed worse visual field MD, a higher prevalence of focal LC defect and larger βPPA-BM. The groups had no statistically sigificant difference in age, optic disc hemorrhage or βPPA+BM width. The investigators noted that worse visual field MD, thinner RNFL and higher prevalence of focal LC defect were significantly associated with dropout.

The researchers say their findings call for future studies that can help to reveal the pathogenic role of deep-layer microvasculature dropout in the glaucoma development.

Suh M, Na J, Zangwill L, Weinreb R. Deep-layer microvasculature dropout in preperimetric glaucoma patients. J Glaucoma. March 18, 2020. [Epub ahead of print].