by Krisha McCoy, MS
Anatomy and Physiology
The eye is like a camera. It has a pupil that allows light to enter, an iris to determine how much light to admit, a lens to focus the light, and a retina onto which an image is focused.
When you look at an object, light rays are reflected from the object through the cornea, pupil, and lens. The cornea and lens focus the rays onto the retina, which converts the light into electrical signals. These signals are then carried to the brain along the optic nerve.
Reasons for Procedure
The anterior chamber, or front compartment of the eye, is filled with a watery fluid called the aqueous humor that bathes and nourishes the cornea and lens. As the aqueous humor flows in from the posterior chamber, it continuously drains through the trabecular meshwork, which lies where the iris meets the cornea. Proper flow of the aqueous humor keeps the pressure inside the eye-or intraocular pressure-normally balanced.
If the aqueous humor drains out too slowly or is produced too quickly, it can cause a buildup of fluid, increasing the intraocular pressure. In glaucoma, the increased pressure compresses the optic nerve fibers in the back of the eye. Under the strain, these fibers become damaged and eventually die, which may result in permanent vision loss. In some rare cases of glaucoma, damage occurs to the optic nerve fibers even though the pressure in the eye is within a â€˜normalâ€˜ range.
In most cases of glaucoma, the damage to the optic nerve fibers slowly causes a decrease in peripheral, or side, vision. Without treatment, this can eventually lead to complete blindness.
Since glaucoma is best treated before symptoms develop, doctors use a number of tests to diagnose it as early as possible. These tests include: visual acuity, to measure how well you see at various distances, visual fields, to measure your peripheral vision, tonometry, to measure intraocular pressure, retinal examination after pupil dilation, to allow your doctor to view your retina and optic nerve.
The goal of treating glaucoma is to prevent or reduce loss of vision by keeping intraocular pressure under control. Treatment options include: eye drops or pills that decrease fluid production and/or increase drainage, trabeculoplasty, a laser procedure that increases fluid drainage from the trabecular meshwork, peripheral iridotomy, a laser procedure that opens a narrow or closed drainage angle, cyclophotocoagulation, a laser procedure that reduces production of the aqueous humor, and trabeculectomy, an incisional surgery that removes some of the trabecular meshwork in the eye.
While medications and surgical treatments may help prevent further vision loss, they cannot restore vision that is already lost due to glaucoma.
In the days leading up to your procedure: Arrange for a ride to and from the hospital or doctor's office. Continue to take your eye drops, unless your doctor tells you otherwise. If your surgery requires an incision, your doctor may advise you to avoid medication that can thin your blood, such as aspirin or ibuprofen, for several days prior to your procedure. If you regularly take other medications, herbs, or dietary supplements, your doctor may recommend temporarily discontinuing these as well. Do not start taking any new medications, herbs, or dietary supplements before consulting your doctor.
Glaucoma surgery generally takes 10-60 minutes, depending on the procedure. In preparation: If you are having a laser procedure, you will be seated facing the laser machine. Eye drops will be administered to numb your eye. A small device will be placed in your eyes to hold your eyelids open.
In a laser trabeculoplasty, your doctor will use a special contact lens held over the front of your eye to focus a beam of laser light onto the trabecular meshwork. If successful, this will allow more fluid to leave the eye, thus lowering the intraocular pressure.
A peripheral iridotomy is used to open up a closed, or narrowed, angle between the cornea and iris that is interfering with the drainage of fluid. In this procedure, your doctor will use the laser to make a small hole in your iris, allowing fluid to flow more freely within your eye.
In cyclophotocoagulation, your doctor will use a laser to destroy parts of the ciliary body, which produces the aqueous humor. If successful, this will reduce the production of fluid, decreasing the pressure in your eye.
In a trabeculectomy, your doctor will use small instruments to remove a tiny piece of tissue from the wall of the eye, leaving a small hole through which the aqueous humor can drain out and be reabsorbed into the bloodstream.
Risks and Benefits
Possible complications of glaucoma surgery include, but are not limited to: increased sensitivity to light, scratchiness in the eyes, eye inflammation, eye infection, bleeding, loss of vision, loss of eye, need for more surgery, and/or increased intraocular pressure.
Benefits of successful glaucoma surgery include: safe intraocular pressures, elimination or reduction of the need for glaucoma medications, and/or decreased risk of vision loss.
In glaucoma surgery, or any procedure, you and your doctor must carefully weigh the risks, benefits, and treatment alternatives to determine whether it is the most appropriate choice for you.
After the Procedure
After the procedure: You will usually be monitored for 1-2 hours before being released. You may be given an eye patch or bandage to wear temporarily. You will be prescribed eye drops and instructed on their use. Your doctor will likely advise you to keep your eye dry for a time by avoiding swimming or showering, and to temporarily refrain from driving, heavy lifting, or straining. Your doctor will give you instructions on when it is safe to resume exercise and other activities.
Once home, contact your doctor immediately if you experience: signs of infection, such as fever and chills, sudden change in vision, severe headache, pain in your eye, and/or redness, swelling, bleeding, or discharge in your eye.
- About glaucoma. The Glaucoma Foundation website. Available at: http://www.glaucomafoundation.org/education_content.php?I=14. Accessed October 25, 2004.
- American Academy of Ophthalmology. Available at: http://www.aao.org/. Accessed October 2004.
- Glaucoma: what you should know. National Eye Institute website. Available at: http://www.nei.nih.gov/health/glaucoma/glaucoma_facts.asp. Accessed October 25, 2004.
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