Glaucoma is a common eye disease, with an estimated 2 million Americans being affected. It is the second most common cause of legal blindness in this country, and the first among African Americans. To make the situation even worse, glaucoma usually offers no symptoms until it is very advanced. Vision lost from glaucoma cannot be regained.
The Diagnosis and Treatment of Glaucoma by Richmond Eye Associates
All of the physicians (M.D.'s) of Richmond Eye Associates diagnose and treat glaucoma. We use advanced technology testing devices to aid in the diagnosis and monitoring of glaucoma. For difficult to manage or advanced cases of glaucoma, consultation with a glaucoma specialist may be indicated for further treatment options, including laser treatment and surgery.
The next sections discuss the diagnosis and treatment of glaucoma in adults.
What is glaucoma?
Glaucoma is an eye disorder where optic nerve is damaged over time, usually related to the pressure of the eye. The optic nerve carries visual information from the retina to the brain. Usually, a high pressure inside of the eye leads to a gradual loss of nerve fibers contained within the optic nerve. This leads to a loss of vision, usually involving the peripheral vision first. The relationship between the pressure inside of the eye and the risk of glaucoma is complicated:
The normal eye pressure usually ranges between 10 and 21 mmHg, with an average of 16, when measured by an eye doctor. The eye pressure (or IOP, for intraocular pressure) can vary throughout the day, and is not affected by blood pressure, reading, sinus problems, or eye-strain.
Some people can have a high eye pressure (over 21) consistently, and yet never suffer any optic nerve damage from the pressure.
Most people with elevated eye pressure will eventually get damage to the optic nerve. If the pressure approaches 30 or higher, the damage may come faster and be more severe.
Some people can get optic nerve damage with even what is considered to be a NORMAL pressure (under 22). This type of glaucoma is termed "low tension glaucoma".
If the optic nerve becomes damaged by glaucoma, blind spots in the vision will occur. Usually this affects the peripheral vision first (the side vision). If it is untreated, the central vision can be lost from glaucoma as well. Usually both eyes are affected by glaucoma if it is present, but one eye may be affected more severely.
What are the different types of glaucoma?
There are many different types of glaucoma, but basically they fall into two categories: open-angle and closed-angle glaucoma. The "angle" of the eye is an area where fluid drains from the eye back into the blood circulation. The eye produces fluid on the inside in order to maintain its shape and for nourishing structures within the eye. This fluid is drained by an area located at the junction of the cornea and the iris inside of the eye.
In "open-angle" glaucoma, this drainage area appears to be unobstructed when viewed by the physician. This is the most common form of glaucoma, and it is not fully understood why the pressure within the eye becomes elevated. It is also known as "primary open-angle glaucoma" (POAG) or as "chronic open-angle glaucoma" (COAG).
In "closed-angle" glaucoma, the drainage angle is physically blocked, and is not visible to the physician.
Open-angle glaucoma is the most common form of glaucoma by far. It rarely offers any physical symptoms: there is no pain, no pressure sensation, no blurring of vision. The intraocular pressure is often only mildly elevated, and the optic nerve is gradually damaged over a period of months and years.
Other, less common types of open-angle glaucoma include:
- Pigmentary glaucoma: In this condition, pigment granules liberated by the iris and other structures within the eye are thought to clog the outflow channels. This variety tends to occur in younger individuals, and may be worsened by vigorous physical activity, which may disperse more pigment. This type of glaucoma can give symptoms because the pressure may spike to very high levels at times (over 40). This may cause eye discomfort, blurred vision, rainbows or halos around lights, or headache.
- Low tension glaucoma (or normal pressure glaucoma): This subcategory of open-angle glaucoma is characterized by optic nerve damage occurring at normal or even low intraocular pressures. This may be common in the very elderly (over 80). Other tests need to be done to diagnose this condition.
Closed-angle glaucoma is more rare, but also more severe in symptoms. During an attack of "angle-closure", the iris rotates toward the cornea and blocks the outflow channels suddenly and completely. Intraocular pressures over 60 are not uncommon, which can cause severe eye pain, nausea, vomiting, redness, blurred vision with rainbows around lights, and sudden loss of vision. This requires emergency treatment to cure, and usually requires a laser procedure to be done to break an attack or prevent future attacks. The other eye, if at risk of an attack, is typically treated prophylactically by laser.
Who is at risk for glaucoma, and how is it diagnosed?
Glaucoma can affect people of all races, background, and age, and can occur in people who are otherwise completely healthy. However, there are certain groups of people who are especially at risk for glaucoma. These include:
- People over 60 years old
- African Americans
- People with a family history of glaucoma
- People with vascular diseases such as diabetes
- People who are very nearsighted
It is recommended to have a complete eye examination for glaucoma:
- At age 35 and 40
- Every two to three years after age 40
- Every one to two years after age 60
- Every one to two years after age 35 if there are any special risk factors, as listed above
The diagnosis of glaucoma cannot be accomplished by a brief screening examination. While free pressure screenings done at health fairs can help to detect people with a high eye pressure, a normal pressure found does not rule out that glaucoma is present. This is because the pressure can fluctuate throughout the day, and because some people with glaucoma never have an elevated pressure.
The examination to determine whether or not glaucoma is present includes the following:
- A complete eye examination, including checking the vision, pupil reaction, biomicroscopic examination of the structures of the eye, the intraocular pressure (tonometry), and an examination of the optic nerve and retina.
- The eye pressure can be checked in different ways. The standard method is called applanation tonometry. In this method, anesthetic drops are placed in the eyes and a device using a blue light gently touches the eye.
- Special attention needs to be paid to the appearance of the iris, and of the drainage angle of the eye.
- The optic nerve needs to be evaluated closely for evidence of damage from glaucoma.
If there is suspicion for glaucoma, a visual field test can be done. This test is usually scheduled separately, and is run by a technician. This test usually lasts about 20 minutes, and the peripheral, or side, vision of each eye is tested for any blind spots. The ophthalmologist will then review the results of the test.
The "glaucoma suspect"
A person is considered a glaucoma suspect if there are risk factors present for glaucoma, but not any evidence of damage to the peripheral vision. Some cases of glaucoma suspect could include:
- A person with a high eye pressure, but normal nerve appearance and normal visual field testing. (Also known as ocular hypertension.)
- A person with glaucoma in the family, and a suspicious appearance to the optic nerve, but normal visual field testing.
- An African American with a borderline high eye pressure and a family history of glaucoma.
The diagnosis of glaucoma
A diagnosis of glaucoma can be made if there is suitable evidence for glaucoma based on the eye examination performed by an ophthalmologist. Usually to diagnose glaucoma, there are blind spots in the field of vision. Other situations where glaucoma may be diagnosed include:
- There is high eye pressure or evidence of angle-closure glaucoma.
- If there are repeatedly high eye pressures despite normal visual field testing. Damage may be imminent in these cases.
- If there is progressive worsening of the appearance of the optic nerve or worsening of blind spots on the visual field test.
Once glaucoma is diagnosed, the main goal of treatment is to lower the pressure within the eye to the point that damage will not continue. Usually, initial treatment is in the form of eye drop medications.
In some cases more than one eye drop, and even oral medications can be used to control the pressure. Repeated follow-up examinations are needed to determine the effectiveness of any medication used to lower the pressure.
Some important points about glaucoma medications include:
- Eye drops used for glaucoma are administered at different times depending on the medication. Some are only once a day, while some are used up to four times a day. It is important to fully understand the physician's instructions about how often to use the medication.
- If a medication is to be used more than once a day, it is important to spread out the dosages as much as possible. (Example: If an eye drop is to be used twice a day, and the first dosage is given at 7:00 AM, use the second dosage around 7:00 PM, not midnight.)
- Once the eye drop is administered, hold the eyes closed for a few minutes and apply pressure to the inside corner of the eye. This helps to prevent drainage of the eye drop immediately into the tear drainage system (and away from the eye).
- Since some of the eye drop will inevitably get into the tear drainage system, some of the medication could be absorbed into the general circulation. Glaucoma eye drops can cause physical symptoms in some people. Your physician will discuss this with you.
The optic nerve is periodically re-evaluated using automated visual field testing, fundus photography, and Optical Coherence Tomography (OCT). If damage still seems to be occurring, the eye pressure may have to be lowered further. Each individual eye has its own optimal pressure.
Surgical treatment of glaucoma
In cases where medication alone cannot control glaucoma, there are surgical options. Each carries its own potential risks and benefits.
- Laser surgery: Angle-close glaucoma can be cured by a procedure called laser peripheral iridotomy. In this procedure, a laser makes small hole in the iris to redirect fluid flow within the eye. Open-angle glaucoma can be treated by procedures called argon laser or selective trabeculoplasty (ALT or SLT). Here, the drainage angle of the eye is treated precisely by a laser to help open the drainage channels. With both procedures, recovery time is almost immediate.
- Filtering surgery: This is a micro-surgical procedure done in the operating room under local anesthesia. A new drainage channel is made for fluid to exit the eye and form a bubble (or "bleb") under the conjunctiva, which is a thin membrane lining the white part of the eye. Usually, this bleb is hidden by the upper eyelid.
There are other options for the treatment of glaucoma, and new medications and procedures are frequently made available.