Education Committee Highlights WGC-2021 | part 9.1

Is this really a risk factor for glaucoma? The debate

This debate was introduced by Prof Henry Jampel. Two factors were considered in the debate: Sleep apnoea and blood pressure and its treatment as risk factors for glaucoma.

Is sleep apnoea really a risk factor for glaucoma?
The pro side of this debate was taken by Dr Samantha Lee and Dr. David McKay took the opposing viewpoint.

Dr Samantha Lee introduced her talk by highlighting that there are 3 types of sleep apnoea: central, mixed/complex and obstructive sleep apnoea (OSA) which is the commonest and makes up 90% of all sleep apneas. She mentioned that there were conflicting findings on the association between OSA and glaucoma. While some studies found significant associations between glaucoma and sleep apnoea, others did not. She noted that there may be regional differences in the association between OSA and glaucoma. Studies that had found a significant association between OSA and glaucoma included other populations apart from Caucasian populations.

She suggested that there may be regional or ethnic differential effects in the association between OSA and glaucoma. A possible explanation for this may be the prevalence of normal tension glaucoma (NTG) which is more common in Asian populations compared to Caucasian populations. Other possibilities could be genetic interactions although there are relatively few known OSA genes. She noted that studies have found thinner RNFL, worse visual field defects and higher IOP in patients with OSA which can be associated with the use of CPAP treatment which is known to elevate nocturnal IOP. She concluded that OSA is a risk factor of glaucoma, especially in non-Caucasian populations and control for OSA may help slow down glaucoma progression.

Dr David McKay discussed the opposing viewpoint that sleep apnoea is not a risk factor for glaucoma. He stated that it is possible that OSA itself leads to glaucoma or the treatment leads to glaucoma. He noted that better studies were needed to fully understand the association between sleep apnoea and glaucoma. He mentioned that although long-term continuous positive airway pressure (CPAP) therapy increases intraocular pressure (IOP) which can worsen glaucoma, on the other hand, it improves ocular perfusion pressure and this can benefit glaucoma. He concluded that there were not enough studies to concretely conclude that sleep apnoea causes glaucoma. However, patients with glaucoma should be asked if they have sleep apnoea and patients with sleep apnea should be asked to get their eyes examined for glaucoma.

Blood pressure and its treatment are risk factors for glaucoma
Regarding the second topic, Dr Fotis Topouzis took the viewpoint that blood pressure and its treatment are risk factors for glaucoma while Dr. Dale Heuer opposed the viewpoint.

Dr Topouzis noted that there were conflicting reports on the association between blood pressure and glaucoma. He noted that direct microvascular damage from systemic hypertension can impair blood flow to the optic nerve. A recent systematic review and meta-analysis reported that hypertension was positively associated with the risk of primary open-angle glaucoma (POAG). A higher incidence of progression has been reported in glaucoma patients with non-physiological nocturnal blood pressure (BP) dips compared to those with normal dipping patterns.

Therefore, he suggested that high systolic BP, low diastolic BP and extreme nocturnal dips are associated with glaucoma onset and progression.
He concluded that hypertension can lead to vascular damage and impaired autoregulation which eventually leads to optic nerve damage. Hypotension which could be primary or resulting from the use of antihypertensive can also result in impaired autoregulation and reduced blood flow which leads to the common pathway of optic nerve damage.

Dr Dale Heuer opposed the viewpoint that systemic hypertension is a risk factor for glaucoma. Several studies showed that there was no relationship between hypertension and glaucoma. He concluded that based on the findings of a meta-analysis that included 60 studies, blood pressure was positively associated with the risk of POAG although the association was significant only in cross-sectional studies and not in longitudinal studies or case-control studies. He concluded that lower BP recommendations by cardiologists can lead to potentially dangerously low ocular perfusion pressure which may lead to a higher risk of glaucoma.

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