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Nocturnal blood pressure ‘overdippers’ have higher risk for ODH in normal-tension glaucoma
A “nonphysiologic” nocturnal blood pressure dip is a risk factor for the occurrence of optic disc hemorrhage in patients with normal-tension glaucoma, according to researchers.
Optic disc hemorrhage may be associated with IOP-independent risk factors and vascular mechanisms may play a role in the pathogenesis of optic disc hemorrhage in some normal-tension glaucoma eyes, the researchers wrote.
Researchers enrolled 698 eyes of 349 consecutive Korean patients with normal-tension glaucoma (NTG) who underwent 24-hour IOP and ambulatory blood pressure monitoring in the habitual position, were examined for optic disc hemorrhage (ODH) every 4 to 6 months with optic disc photography and had 5 reliable visual field tests with a minimum follow-up of 3 years.
Patients were classified as either “nonphysiologic” dippers, including nondippers and overdippers and “physiologic” dippers.
A reduction of nocturnal blood pressure in the range of 10% to 20% relative to daytime levels is typical for those considered normotensive subjects and in the majority of hypertensive patients, researchers said. A “physiologic” dip is blood pressure that exhibits an excessive (>20%) range and minimal dips (<10%) are termed “nonphysiologic” dippers.
A total of 118 patients were classified as physiologic dippers, 185 nondippers and 46 overdippers, with 87 patients having a hypertension diagnosis.
ODH was detected in 107 eyes, 15.3% and visual field progression in 60 eyes, 8.6% out of the total number of patients.
Overdippers showed a significantly greater frequency of ODH than nondippers or dippers, according to researchers. Being an overdipper was an independent risk factor for ODH occurrence during follow-up, which averaged 4.32 years.
“It is plausible ... that ‘nonphysiologic’ blood pressure dippers such as overdipper or nondipper NTG patients might be susceptible to the development of ODH owing to the common abnormal vascular entity,” the researchers wrote.
The researchers suggest that, “ODH detection during follow-up may be associated with abnormal nocturnal blood pressure dip in some NTG subjects, in which overdippers are at greater risk of ODH development compared with “physiologic” dippers,” they added.
A profound nocturnal blood pressure dip may have an important impact on the active disease process that can lead to repetitive ODHs in some NTG patients, researchers concluded. –by Abigail Sutton
Disclosure: The researchers reported no relevant financial interests.
Perspective
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The development of optic disc hemorrhages (ODH) has been positively linked to the presence or development of glaucoma. Normal-tension glaucoma (NTG) is thought to have a greater prevalence of ODH, which is theorized to be a result of altered ocular blood flow to the optic nerve head and linked to altered vascular flow or dysregulation.
The development of glaucoma is thought to occur by a combination of mechanical forces (increased IOP) and perfusion abnormalities. The development of ODH as an indication of “nonphysiological dips” in nighttime blood pressure would seem to support the premise that vascular perfusion abnormalities are a crucial component in glaucoma and, in particular, NTG.
The patients who had “above normal” dips in blood pressure during the night were not only more likely to develop ODH but also had more visual field progression. Additionally, the patients with ODH also demonstrated greater fluctuations in their systemic blood pressure throughout the day, strengthening the vascular relationship with ODH and NTG progression.