Evidence suggests that ocular perfusion pressure is a strong risk factor for glaucoma. Ocular perfusion pressure is the relationship between the eye pressure and the blood pressure.
If the blood pressure is low, especially if the eye pressure is elevated, blood has difficulty getting into the eye to supply oxygen and important nutrients, and to remove waste products.
However, even in individuals with normal eye pressure, their blood pressure may be low enough naturally, or as a result of treatment for their high blood pressure, to deprive the eye of adequate blood flow.
Normally, our bodies adapt to changes in blood pressure, body position, or other changes in order to maintain constant circulation to important areas such as our brain or our eyes.
For some individuals, their bodies may lack the ability to adjust the circulation appropriately, so the tissue may not be properly nourished and may suffer damage over time.
Intraocular pressure (IOP) has been found to be associated with systemic blood pressure levels in population based studies. The relation appears to be reasonably consistent across the range of values of IOP and both systolic and diastolic blood pressures.
It has been postulated that treatment of hypertension may place the eye at relatively increased risk of visual field deficits because of an imbalance in the relation of blood pressure to IOP.
This thought has been given credence, in part, because of the clinical dictum that sudden lowering of blood pressure is associated with loss of visual field in some people.
Blood pressure increases with age in most populations, and medical intervention has been successful in lowering blood pressure and the subsequent risk of the systemic sequelae of high blood pressure.
During any given clinic day, we can expect to be asked a version of this question from one of our patients.
Whether patients return to follow-up confident that their intraocular pressure (IOP) is going to be elevated because their blood pressure has been high, or they were recently diagnosed with high blood pressure and are concerned about getting glaucoma, the underlying patient concern is the same.
Who can blame them? Both glaucoma and systemic hypertension have similar risk factors and patient demographics, so a large majority of our patients suffer from both. These patients go to many different physicians in various specialties who manage and control their “pressure.”
Naturally patients assume they’re related, and they want to know how. Ophthalmologists and glaucoma specialists have been asking this same question for years.
There are complex interactions between blood pressure and IOP, which can influence glaucoma development.
High blood pressure could potentially increase IOP by increased production of aqueous humor by means of elevated ciliary blood flow and capillary pressure and decrease of aqueous outflow as a result of increased episcleral venous pressure.
So how do you address this question that at best has a muddled answer? In general, we see this as a teaching moment, an opportunity to further discuss with patients the various aspects of their disease and our treatment plan.
We explain that although there is some thought that they are related, there is no consensus in clinical studies showing that elevated blood pressure causes elevated IOP.
We then use this time to go over how, in reality, low blood pressure has been more consistently shown to worsen glaucoma, especially in normal-tension glaucoma.
We stress that what is important is that patients work with their primary care clinicians and cardiologists to optimize their cardiovascular risk factors. We typically transition the conversation to the importance of compliance and follow-up for both chronic conditions.
Although there is no consensus for a direct correlation between them, both uncontrolled hypertension and uncontrolled glaucoma can lead to retinal vein occlusions, which in turn can lead to acute neovascular glaucoma.
We then review their blood pressure medications and discuss if they are taking them at night. If they are, we recommend conferring with their primary care physician or cardiologist regarding switching to a morning regimen to avoid nocturnal hypotension.
Lastly, we remind them that healthy diet and exercise can be beneficial for both diseases. We further explain that while exercise and especially aerobic exercise are good, we advise against the head-down positioning in some yoga poses that have been shown to elevate IOP.
In the end, although there is no consensus regarding a correlation between elevated blood pressure and elevated IOP, this scenario provides a great opportunity for clinicians to have a discussion with patients anout their health care.
By helping them better understand their disease and empowering them to be involved in their care, clinicians can help prevent permanent vision loss.