Visits to the eye clinic typically include glaucoma screening such as patients’ peripheral vision and intraocular pressure (IOP) — although evidence is mounting that damage to the macula may occur in early glaucoma, as well. This damage may well be missed if glaucoma is thought to be only a peripheral disease.
“More stringent IOP control as well as structural and functional testing specific to the macula, may be necessary to prevent irreversible progressive loss in the central field due to glaucoma,” according to a study in the Journal of Glaucoma. Investigators at Columbia University Medical Center Harkness Eye Institute, New York, conducted the longitudinal analysis to evaluate macula-directed tests, such as 10-2 visual field (VF) patterns and spectral domain optical coherence tomography (SD-OCT) of macular regions (ClinicalTrials.gov Identifier: NCT02547740). Participants comprised 119 patients (191 eyes) with glaucomatous optic neuropathy, from 20 to 80 years of age — mean age 66.3 years — enrolled from October 2015 to September 2019.
Patients underwent standard automated perimetry (SAP) and SD-OCT assessments 4 to 6 months apart, for 4 visits or more. On follow-up IOPs were a mean 14.6±3.5 mm Hg. Using goodness-of-fit relationships, IOP changes were most closely linked to OCT parameters: global macula ganglion cell layer (GCL), inferior macula GCL, mean macular vulnerability zone (MaVZ) GCL, and mean less vulnerable zone (LVZ) macula GCL. The most closely-associated VF parameters were 10-2 pattern standard deviation and 10-2 mean deviation.
This study also compared glaucoma progression rates of patients (72 eyes) who reported a diagnosis of hypertension with those who did not have high blood pressure. VF and OCT data were analyzed to find progression rates, and there was no meaningful difference in rate of increase between the groups. However, association between glaucoma progression and hypertension were found in goodness-of-fit models for global macula GCL+, inferior macula GCL+, mean GCL+ of MaVZ, and mean macula GCL+ of LVZ, as well as VF tests including 10-2 pattern standard deviation and 10-2 mean deviation.
Perfusion to the optic nerve head is a factor affecting glaucoma advancement, and is subject to interactions of IOP, blood pressure, and local circulation. Lower blood pressure and higher IOP can potentially decrease perfusion to the optic nerve head, limiting its metabolic requirements. Also, individuals with chronic high blood pressure may acclimate to a higher pressure range for the autoregulation of retinal blood flow. This, in addition to vascular endothelium changes may result in normal or low blood pressure reducing perfusion to the optic nerve head.
Individuals with normal tension glaucoma (NTG) typically fare better with lower IOP values and are more predisposed to exhibit central retinal damage. Additional research demonstrates that patients with NTG and diurnal fluctuations in their diastolic blood pressure and IOP were at higher risk for glaucoma progression.
Limitations of this study included differences in follow-up intervals, and self-reporting of hypertension diagnosis, as well as no examination of the degree and management for BP elevation. Macular parameters showed a goodness-of-fit relationship to hypertension, but not statistically significant — perhaps due to these limitations. “Nevertheless, our findings suggest that systemic blood pressure may play a role in glaucomatous damage to the macula,” investigators report.
Chang AY, Tsamis E, Blumberg DM, et al. The role of intraocular pressure and systemic hypertension in the progression of glaucomatous damage to the macula. Journal of Glaucoma. Published online March 23, 2022. doi:10.1097/ IJG.0000000000002018