Low Blood Pressure Linked to Structural Progression in Medically Treated Normal-Tension Glaucoma Eyes

Systolic and diastolic blood pressure are among the most significant risk factors for progressive thinning of the peripapillary retinal fiber nerve layer (RFNL) and macular ganglion cell inner plexiform layer (GCIPL) in patients with medically treated normal-tension glaucoma (NTG), according to a retrospective cohort study from South Korea.

While intraocular pressure (IOP) is the most significant risk factor for NTG progression, several other factors also influence its development and progression, the investigators said. To determine which other risk factors impact progression, researchers reviewed the medical records of all patients who visited a South Korean glaucoma clinic between November 2012 and July 2019. All participants underwent complete ophthalmic examinations. Inclusion criteria for the study included a best-corrected visual acuity of 20/40 or better and an open angle on gonioscopy. Their NTG was diagnosed when their glaucomatous optic discs (neuroretinal rim thinning and excavation) and peripapillary RNFL defect (regardless of the presence or absence of glaucomatous VF defects) were observed and the maximum untreated IOP was less than 21 mm Hg on three repeated measurements collected during separate follow-up visits. Excluded from the study were those with secondary causes of glaucomatous optic neuropathy. They also excluded those with a history of glaucoma (including glaucoma filtration surgery) or refractive surgery, and neurologic or systemic diseases influencing optical coherence tomography (OCT) measurements. 

The study included 166 NTG patients with an average age of 56.5 years and an average mean deviation of -4.2 dB. The structural progression endpoint was determined by OCT. Significant thickness differences in the peripapillary RNFL or macular GCIPL that exceeded baseline test-retest variability were identified with event-based guided-progression analysis. IOP and systemic blood pressure were measured at each visit throughout the follow-up period and the risk for progression was evaluated with Cox regression. Myopic disc features and antihypertensives also were analyzed. A decision-tree analysis was used to determine cutoff values and influential risk factors.

Structural progression was identified in 62 eyes. The occurrence of disc hemorrhages, presence of diabetes, and lower minimum systolic blood pressure were associated with progression (hazard ratio [HR]: 2.116, P =.005; HR: 1.998, P =.031; HR: 0.968, P =.005; respectively). The cutoff value derived from the tree analysis of minimum systolic BP was 108 mm Hg. 

The team’s analysis found that systolic blood pressure may impact progressive peripapillary RNFL thinning more than diastolic blood pressure, while the opposite may be true for progressive macular GCIPL thinning. Researchers concluded that meeting the identified blood pressure target values may help prevent glaucoma progression. As such, hypotension should be evaluated for NTG patients during follow up.

This study was subject to several limitations. First, researchers only investigated structural progression, not functional progression, which excluded eyes with advanced glaucoma. Second, only daytime IOP and blood pressure were measured. Third, because of the limited number of patient records, antihypertensive medication data were only available for 34 eyes. Fourth, because of the retrospective design of the study, the sequential relationship between blood pressure/IOP variables and structural progression could not be demonstrated. Lastly, blood pressure was only measured in the upper right arm. 

Reference

Lee K, Yang H, Kim JY, et al. Risk factors associated with structural progression in normal-tension glaucoma: intraocular pressure, systemic blood pressure, and myopia. Invest Ophthalmol Vis Sci. 2020;61(8):35. doi: 10.1167/iovs.61.8.35