ELEVATED INTRAOCULAR PRESSURE

Dr. Carolina Valdivia answers a question from a 58 year-old man with glaucoma and elevated intraocular pressure that is not controlled well with medication.

I recently was diagnosed with glaucoma. I also am diabetic and have hypertension and high cholesterol. At the time of my diagnosis, my eye specialist informed me that my eye pressure was 50 and that some veins behind my eyes might be closed. After taking medicines and eye drops for 10 days, my pressure dropped down to 17. But as soon as my doctor stopped the medications, my pressure increased again to 34. This eye specialist now is advising that I should have glaucoma surgery.

Will I be cured of my glaucoma after the operation? How risky is glaucoma surgery? Please help me with your kind and valuable guidance.

In reading the description of your problem, two things particularly caught my attention. The first is that you have three chronic diseases in addition to glaucoma: high blood pressure (hypertension), high blood cholesterol (hypercholesterolemia) and diabetes. Each of these is associated with glaucoma. The second area of concern is that the initial measurement of the pressure inside your eye (intraocular pressure) was 50 mmHg.

Sudden intraocular pressures of this magnitude (50 mmHg) are due to angle-closure glaucoma, are accompanied by extreme pain, and constitute a medical emergency. However, in most patients intraocular pressure increases gradually, progressing from upper levels in the normal range to levels of 30-40 mmHg over a period of several months to several years. These individuals may experience some mild discomfort, but it is just as probable that the elevated intraocular pressures will be imperceptible.

The speed at which glaucoma progresses depends on the degree of elevated intraocular pressure. This usually means that people with intraocular pressures of 35 mmHg develop optic nerve fiber damage at a faster rate than persons with intraocular pressures of 23 mmHg. Your doctor had to act immediately to lower the intraocular pressure of 50 mmHg in your eyes. If left untreated, levels this high can cause rapid and catastrophic damage to the optic nerve.

I define a normal intraocular pressure as one that falls within the range of 10-20 mmHg. But, in fact, the more accurate definition of normal intraocular pressure is one that produces no damage to the optic nerve. For example, in normal tension glaucoma, pressures of 16-20 mmHg may cause damage.

Glaucoma surgery is indicated when medications prove ineffective, either because intraocular pressures remain high or if managing pressure within a normal range proves difficult.

Although you did not indicate the specific type of glaucoma that you have in your question, a diagnosis of neovascular glaucoma seems likely. Neovascular glaucoma is a secondary glaucoma. There are three factors that predispose a person to blockage of the central retinal vein (or some of its branches) or the central retinal artery - the major causative factors of neovascular glaucoma. These are high blood pressure, elevated cholesterol, and diabetes. You report having all three of these conditions, which places you at high risk. The treatment for neovascular glaucoma focuses on controlling the following three problems.

1. Lowering the elevated intraocular pressure.
2. Inhibiting the proliferation of new blood vessels (neovascularization) in the iris and anterior chamber angle in the front part of the eye.
3. Controlling diabetes, high blood pressure, and/or high cholesterol.

A number of studies have shown that a laser surgery treatment performed on the retina called panphotocoagulation is successful in reducing or eliminating neovascularization. While this lowers the probability of further damage to the optic nerve, damage that already has occurred remains. At this time, there is no cure for any type of glaucoma.

It is possible that despite having all three of the major risk factors for the central retinal vein or artery blockage that leads to neovascular glaucoma, you may have a primary glaucoma (no known cause external to the eye). There are two major types: primary open-angle glaucoma and primary angle-closure glaucoma. In cases of primary glaucoma where management of intraocular pressure is very difficult, glaucoma filtration surgery (trabeculectomy) is recommend. In this procedure, the surgeon creates a new pathway for drainage of fluid inside the front part of the eye called aqueous humor by removing a section of tissue in the drainage angle of the eye. This opening is covered partially with a flap of tissue from the sclera (white part of the eye) and conjunctiva (clear covering over the sclera). As aqueous humor flows through this channel, it causes the covering to swell slightly, producing a bubble called a bleb. Your ophthalmologist can monitor the bleb to ensure that aqueous humor is flowing freely.

Given the clinical situation you describe, completion of a surgical procedure would be the next recommended step. This would be glaucoma filtering surgery in the case of a primary glaucoma or panphotocoagulation laser surgery in the case of neovascular glaucoma. In the case of neovascular glaucoma, sometimes both surgeries are performed. However, performing the glaucoma filtering surgery before the panphotocoagulation laser procedure is not recommended. On the other hand, if the filtering surgery is performed after panphotocoagulation, success can be improved.

All surgeries carry some risk. In glaucoma surgery, inflammation caused by the procedure itself temporarily can cause elevated intraocular pressure. In your case, your intraocular pressure does not appear to be well controlled, despite your taking both oral medication and eye drops. In consultation with your ophthalmologist, you must weigh the risks and benefits of having glaucoma surgery against the potential risk of eventual blindness if you remain on your current treatment regimen. Your prognosis will depend on the degree of current damage to the optic nerves in your eyes.

Carolina Valdivia, MD

REFERENCE:

Salim S and Shields MB. Pretrabecular Mechanisms of Intraocular Pressure Elevation. In: Tombran-Tink J, Barnstable CJ, and Shields MB. Mechanisms of the Glaucomas: Disease Processes and Therapeutic Modalities. Totowa, New Jersey: Humana Press, 2008:83-98.

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