Is there a link between HTN and glaucoma?

By Liz Meszaros

Could the treatment of hypertension (HTN) be at cross-purposes with the treatment of glaucoma? queried Ruth D. Williams, MD. 

Dr. Williams, a glaucoma consultant and partner at the Wheaton Eye Clinic, Naperville, IL, explored the possible effects and correlations in concomitant treatment of these two chronic disease states. She began by outlining the similarities between the treatment of HTN and glaucoma:

Ruth Williams, MD, says that clinical trials have attempted to elucidate more on the association between blood pressure-both high and low––and glaucoma. (Photo by Stevan Nordstrom)

·      Both are chronic diseases that can be difficult to control.

·      Treatment of both can require multiple medications and fixed-combination drugs.

·      Treatment endpoints are poorly defined, and often difficult to achieve, even when defined.

·      Medication adherence challenges are common in both disease states.

Clinical trials have attempted to elucidate more on the association between blood pressure-both high and low––and glaucoma, continued Dr. Williams.

“It is important to note that even though much work has been done about the elevation of intraocular pressure (IOP) at night, and the systemic hypotension that frequently occurs at night, we have not discussed this very much in our clinical practices in the past 10 years,” Dr. Williams said.

Ocular perfusion pressure (OPP) is an important concept. Several formulas exist to calculate OPP, but fundamentally, OPP is the difference between the arterial blood pressure and eye pressure, and a low OPP is a significant risk factor for glaucoma progression.

She reviewed the results from one of the most recent of these studies, which was presented at the 2013 American Glaucoma Society annual meeting.

OPP risk factor

Researchers acknowledged the growing evidence that OPP is a glaucoma risk factor, and that this may be an especially significant factor when IOPs are relatively low, said Dr. Williams. Carlos G. de Moraes, MD, presented his study of 85 patients, all with normal tension glaucoma, and 32% who had both systemic HTN and normal-tension glaucoma.¹

Dr. Moraes and colleagues monitored ambulatory blood pressures every 30 minutes for 48 hours, at 6-month intervals. One-third of patients had systemic HTN, and two-thirds were being treated with medications.

Over a mean follow-up of 5 years, 24% of patients had progression by visual field. Low blood pressure during sleep was a strong predictor of visual field progression. Further, the longer and greater the dips in mean arterial pressure below the daytime average, the greater this risk for progression became compared with patients with normal systemic blood pressure (P = 0.020). Finally, patients with treated HTN who had nighttime dips had faster progression.

The authors suggested that glaucoma specialists work with cardiologists and internists to avoid nocturnal HTN in glaucoma patients on antihypertensive medications, noted Dr. Williams.

“My take-away message from this is: Ask your patients about blood pressure. If the blood pressure is low, call the cardiologist or internist,” concluded Dr. Williams. “It’s worth a phone call, because when I call cardiologists or internists, most of the time, they have never thought about low blood pressure and how it might affect the optic nerve. If the blood prssure is low, could it affect the end organ perfusion of other systems, such as brain function?”

REFERENCES

1.    De Moraes CG, Link AR, Wells MT, et al. Large and sustained blood pressure dips are associated with visual field progression in normal-tension glaucoma. Paper presented at the 23rd Annual AGS Meeting; March 1, 2013; San Francisco, CA.