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Presence of coronary artery calcification associated with higher IOP
Intraocular pressure is significantly associated with subclinical atherosclerosis, according to a study recently published in the British Journal of Ophthalmology.
Ye and colleagues conducted a cross-sectional study of 10,723 asymptomatic participants to evaluate the relationship between IOP and coronary artery calcification.
Researchers utilized a non-contact tonometer and automatic air puff control to measure IOP and cardiac CT to measure coronary artery calcium.
Results showed that, after adjusting for extraneous variables, increased prevalence of coronary artery calcium was significantly associated with increasing levels of IOP.
"It is presumed that the increased risk of coronary artery calcium status and distribution of higher IOP have a coexisting pathophysiology," the authors wrote. "There is a possibility that high blood pressure would play an important role in both increased IOP and coronary artery calcium.
“Elevated blood pressure, an established risk factor for cardiovascular disease, has been reported to be associated with elevated IOP levels,” the researchers continued. “In our study, systolic blood pressure, diastolic blood pressure and hypertension status were positively correlated with higher quartile distribution of IOP. It has been inferred that high blood pressure contributes to the elevation of ciliary artery pressure in the eye, increasing the ultrafiltration and production of aqueous humor. This mechanism has been postulated as the cause of elevated IOP."
They concluded: "This is the first study to evaluate the association between the risk of subclinical coronary atherosclerosis and IOP, demonstrating that the presence of coronary artery calcium is associated with higher IOP. The present study provides more insight into understanding the process of subclinical atherosclerosis in cardiovascular disease and the relationship with higher IOP as a common pathophysiology."
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Glaucoma is a complex set of disorders, with intraocular pressure being the most important of many risk factors. Cardiovascular diseases such as diabetes and hypertension are known to be associated with IOP, but until now no study has shown a direct association between the risk of cardiovascular disease and IOP.
Coronary artery calcium (CAC) detected by cardiac CT predicts future coronary artery disease. Ye and colleagues have completed an ambitious cross-sectional study to investigate the relationship between CAC and IOP and found that a higher IOP is significantly associated with the presence of CAC, regardless of conventional cardiovascular risk factors.
While interesting, this study raises more questions for the clinician than it answers. It is presumed that the increased risk of CAC and higher IOP have a related pathophysiology. Possible important role players include elevated blood pressure, obesity, metabolic conditions, sympathetic neural tone, blood glucose, corneal collagen cross-linking – the list goes on. While we should thank Ye and colleagues for making a contribution to our understanding of this poorly understood condition, we clinicians will not change our treatment approach until these associations are clarified and unique treatment options emerge.
Having said that, mounting evidence suggests that it might be advisable to weigh cardiovascular health a bit more heavily in treating glaucoma patients.