Glaucoma

The optic nerve is made up of many nerve fibers that carry images to the brain. It's like an electric cable containing numerous wires. When glaucoma damages the optic nerve fibers, blind spots develop. If the entire nerve is destroyed, blindness results.

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ome people are born with the iris (the colored part of the eye) too close to the drainage angle. In these eyes, which are often small and farsighted, the iris can be sucked into the drainage angle and block it completely. Since the fluid cannot exit the eye, pressure inside the eye builds rapidly and causes an acute closed-angle attack.

Chronic open-angle glaucoma is the most common form of glaucoma in the United States. Typically, open-angle glaucoma has no symptoms in its early stages, and vision remains normal. As the optic nerve becomes more damaged, blank spots begin to appear in your field of vision. You typically won't notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large. If all the optic nerve fibers die, blindness results. 

Symptoms of closed-angle glaucoma may include: Blurry vision; Severe eye pain; Headache; Rainbow-colored halos around lights; Nausea and vomiting This is a true eye emergency. If you have any of these symptoms, call your Eye M.D. immediately. Unless this type of glaucoma is treated quickly, blindness can result. Unfortunately, two-thirds of those with closed-angle glaucoma develop it slowly without any symptoms warning an acute attack might be coming.

 

Causes/Risk Factors

The most important risk factors for glaucoma include: Age (60 years and older); Elevated eye pressure; Family history of glaucoma; African or Spanish ancestry; Farsightedness or nearsightedness; Past eye injuries; Steroid use; Other health problems like diabetes or migraine headaches Your Eye M.D. will weigh all of these factors before deciding whether you need treatment. You may simply need to be monitored closely. This means your risk of developing glaucoma is higher than normal.

Make sure to have regular examinations to detect the early signs of damage to the optic nerve. Regular medical eye exams can help prevent unnecessary vision loss.

Tests/Diagnosis

Regular eye examinations by your Eye M.D. are the best way to detect glaucoma. Of the following four common tests for glaucoma, the first two are routine.

The tonometry test measures the inner pressure of the eye. Usually drops are used to numb the eye. Then the doctor or technician will use a special device that measures the eye's pressure. Ophthalmoscopy is used to examine the inside of the eye, especially the optic nerve. In a darkened room, the doctor will magnify your eye by using an ophthalmoscope (an instrument with a small light on the end).

The perimetry test is also called a visual field test. During this test, you will be asked to look straight ahead and then indicate when a moving light passes your peripheral (or side) vision. This helps draw a "map" of your vision.

Gonioscopy is a painless eye test that checks if the angle where the iris meets the cornea is open or closed, showing if either open angle or closed angle glaucoma is present. Some of these tests may not be necessary for everyone.

These tests may need to be repeated on a regular basis to keep track of any changes in your condition.

Treatment Options

Treatment can prevent vision loss, but as a rule
damage caused by glaucoma is irreversible.

Typically, medication is the first line of treatment for glaucoma. Medications in the form of eye drops or oral tablets are used to either limit the production of fluid and/or increase the drainage capabilities of the eye. Since these medications can have side effects, the goal is to use the smallest possible dose required to achieve the desired effect. While monitoring the effects of treatment, it is common for a doctor to change the amounts and types of medication used. Even though the medications may be somewhat unpleasant or inconvenient to use or even appear to produce no apparent improvement, dutiful compliance to the treatment schedule is essential for the control of internal eye pressure and preservation of the remaining vision.

Note: If medications are not taken as prescribed and eye pressure remains uncontrolled, blindness will result.

In some cases of Chronic Open Angle Glaucoma, medication does not produce a sufficient reduction in fluid pressure and surgery may be necessary. Surgery does not cure glaucoma nor does it improve vision, but it can help to control the eye's internal fluid pressure and preserve the remaining vision.

Note: The eye is always anesthetized before glaucoma surgery, making the experience relatively comfortable for the patient. 

Your surgeon may choose to perform one or more
of the following surgical treatments:

Filtering Drainage Treatment: Reducing internal eye pressure by draining excess aqueous humor

  • Laser Trabeculoplasty - A laser light is focused onto the Trabecular meshwork to open the channels and allow the aqueous humor to flow out of the eye and into the drainage canal more easily.

  • Trabeculotomy - A small instrument is inserted into the drainage canal to create an opening through the Trabecular meshwork into the front chamber of the eye. It is through this newly created opening that fluid can drain out more readily. Typically, this technique is used in the treatment of children with 
    uncontrolled glaucoma.

  • Trabeculectomy - A small flap is created in the sclera (the white wall of the eye) and an opening is made into the eye to form a new drainage canal that will allow fluid to drain more easily into the bloodstream. When the procedure is successful, the conjunctiva (clear membrane covering iner lids and outer eyeball, excluding the cornea) expands directly over the location where the tissue was opened. This bulge of conjunctiva, known as a filtering bleb, indicates fluid is draining out of the eye and into the bloodstream.

  • Viscocanalostomy - The viscocanalostomy, currently under clinical investigation, involves creating two flaps in the sclera - with a smaller inner scleral flap located underneath a larger outer scleral flap. The advantage of this procedure is that it does not penetrate the eye, which eliminates post-operative complications such as extremely low intraocular fluid pressures and hemorrhages that may occur after a trabeculectomy procedure. The long-term results of the viscocanalostomy procedure are under investigation.  

  • Seton Insertion - When all other glaucoma treatment options have been explored, the surgeon may elect to insert a small valve system, called a seton, into the wall of the eye. Like a trabeculectomy, this procedure involves creating a filtering bleb in order to allow the intraocular fluid to drain more easily. NOTE: Typically, the filtering bleb is located out of view, covered by the eyelid.

Most of these procedures can easily be combined with cataract surgery - requiring a minor alteration of the cataract incision. It is important to note, in many cases, the cataract procedure alone can help to reduce intraocular fluid pressure.

Non-filtering Drainage Treatment: Decreasing the amount of aqueous humor production

  • Endoscopic Cyclophotocoagulation (ECP) - This new procedure uses an infrared laser to cauterize the ciliary body. During this non-filtering treatment, a microprobe is inserted into the eye through a small incision; if performed at the time of a cataract procedure, the same incision may be used. This microprobe emits a focused beam of intense light energy to sear the ciliary tissues, resulting in reduced production of aqueous humor and a decrease in internal 
    eye pressure.

Recommended intervals for eye exams are:

Ages 20 to 29: Individuals of African descent or with a family history of glaucoma should have an eye examination every 3 to 5 years. Others should have an eye exam at least once during this period.

Ages 30 to 39: Individuals of African descent or with a family history of glaucoma should have an eye examination every 2 to 4 years. Others should have an eye exam at least twice during this period.

Ages 40 to 64: Every 2 to 4 years. Ages 65 or older: Every 1 to 2 years.