Glaucoma is a chronic, progressive deterioration of the optic nerve (the bundle of nerve fibers at the back of the eye that carry visual messages from the retina to the brain). It is usually caused by or worsened by pressure inside the eye (intraocular pressure, or IOP) that is too high for the continued health of the nerve. The only proven treatment of glaucoma is lowering of IOP in order to prevent or to slow down the damage to the optic nerve. Glaucoma treatment usually begins with medications or laser techniques, but when these have failed or are not tolerated, your ophthalmologist may suggest surgical procedures. The delicate, microscopic incisional methods include trabeculectomy with or without ExPRESS microshunt implantation, tube shunt (glaucoma drainage device) implantation, and cyclophotocoagulation. There are also newer procedures called MIGS, or minimally invasive glaucoma surgery. Each has its own special uses, advantages and disadvantages. In this article we will discuss the risks and benefits of glaucoma surgery.
The Benefits Outweigh the Risks
There are risks with any type of surgery, and the risks for glaucoma surgery are discussed in this article so that you can have an open dialogue with your ophthalmologist. It is important to note, however, that glaucoma surgery is very successful at substantially slowing the progression of glaucoma and achieving the intended eye pressure. Furthermore, if glaucoma is inadequately treated, it is almost certain that vision will be lost.
Although glaucoma surgery can prevent further vision loss and on rare occasions improves vision, damage that has already occurred as a result of glaucoma is considered permanent and not yet reversible.
It is important to understand that vision can be reduced or even, in very rare instances, totally lost as a result of any of these glaucoma operations; however, vision loss is not a common side effect. Therefore, it is more likely that surgery will benefit your vision in the long run.
With any of these operations, complications can occur even with the best surgical techniques. Uncommon or rare complications include bleeding inside the eye, infection, and fluid pockets behind the retina due to very low eye pressures. Bleeding inside the eye can be a very serious complication, so you should talk with your ophthalmologist if you are on blood thinners and follow his/her instructions about continuing or discontinuing the medication prior to surgery.
Eye doctors give antibiotics before, during, and after the surgery, as well as maintain meticulous sterile techniques to try and avoid any infection. However, on very rare occasions, infection inside the eye may occur, which can be very serious and may threaten vision. These infections can occur weeks, months, or even years after the surgery. Therefore, if you have early signs of infection such as redness, pain, or excessive tearing, you should see your ophthalmologist immediately in order to treat infection before it becomes serious.
Low Eye Pressure
Sometimes, the surgery can lead to eye pressures that are too low, also called hypotony. This is more common soon after the surgery. With hypotony, fluid may collect behind the retina (choroidal detachment), which can cause a shadow in your peripheral or side vision. Usually this is temporary as the pressure returns to the levels that were intended. Sometimes, however, hypotony persists and surgery must be performed in order to fix this problem.
More common than causing eye pressure that is too low, these glaucoma surgeries may fail over time due to the natural healing or scarring tendencies of the eye, resulting in eye pressures that are higher than intended. Sometimes, the scarring is so intense that the operation may fail to achieve a lowered pressure and you may need to restart your glaucoma medications or undergo repeat surgery.
Cataract formation most likely will be accelerated by glaucoma surgery, but luckily cataracts are fairly easy to fix surgically. Sometimes glaucoma surgeries are combined with cataract surgery if your ophthalmologist feels that the cataracts are having a moderate to significant impact on your vision.
While it is important to understand the risks discussed above, many of which are rare, it is also important to recognize that the vast majority of glaucoma surgeries are successful at slowing the progression of glaucoma and achieving the intended eye pressure.
Next month we will discuss the details of the various glaucoma surgeries.
Yvonne Ou, MD Assistant Clinical Professor of Ophthalmology Glaucoma and Cataract Surgery UCSF Department of Ophthalmology
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