Glaucoma: Overview, Risk, Causes, Diagnosis, Treatment, Prognosis: Glaucoma can be hereditary. Half of the estimated two and one half million Americans that have Glaucoma don’t know it. And it can strike at any age. Once diagnosed, however, it can usually be controlled. But it requires professional attention and persistent care. Don’t let Glaucoma dim the bright future you have ahead of you. Call for a screening today and let us tell you about Glaucoma: Overview, Risk, Causes, Diagnosis, Treatment, Prognosis
Glaucoma: Overview, Risk, Causes, Diagnosis, Treatment, Prognosis
Heterogeneous group of disorders
- Affects more than 67 million people
- Second leading cause of blindness worldwide; leading cause in blacks
- Permanent loss of vision due to death of retinal ganglion cells and their axons
- Treatment aimed at slowing or stopping progression of damage
Glaucoma is one of the leading causes of permanent blindness in the world. It affects two to three million Americans. Glaucoma takes away a victim’s sight slowly, but relentlessly, and in most cases, without any signs or symptoms. Visual damage from glaucoma is irreversible and permanent. Blindness from glaucoma, however, can be prevented with proper preventive eye care.
Who is at Risk for Glaucoma?
Glaucoma can strike people of any age, sex, and race.
Certain individuals, however, are at increased risk.
Those at increased risk include persons of African descent, those with a family history of glaucoma, persons with diabetes and possibly those with nearsightedness or high blood pressure. The risk of glaucoma also increases as one gets older. The risk of glaucoma increases markedly in people of African descent over the age of 35 years, and in people of Caucasian descent over the age of 50 years. Other risk factors for glaucoma include a history of trauma to the eye.
- Significant Diurnal fluctuation in intraocular pressure [IOP]
- Elevated intraocular pressure (IOP)
- Increased Cup/disc ratio of optic nerve
- Advanced age
- Race (Blacks 6-8 X Non-Blacks)
- Family history
- Concomitant conditions (e.g., diabetes, BP)
- Compromised ocular hemodynamics
- Abormal Drainage of Aqueous Humor
What is Glaucoma?
Glaucoma is a disease of the optic nerve, which is the nerve that connects your eye to your brain. This nerve transmits visual information from the eye to the brain, thereby allowing you to see. Typically the nerve damage is caused by elevated pressure due to abnormally poor drainage of fluid out of the eye through the trabecular meshwork.
In most cases, glaucoma damage progresses very slowly, over a period of several years. However, sometimes this damage can progress more rapidly. As the damage to the nerve progresses, a person begins to lose vision.
This loss of vision begins with the side, or peripheral, vision. This is vision that you may not be aware of, but is very important in everyday activities of mobility such as walking and driving. The loss of this peripheral vision progresses as long as the disease is not treated. If treatment is not given or not effective, then the visual loss can progress until it begins to involve the central, or vision used to read and write. It is at this point that a victim of glaucoma may begin to notice problems with vision.
If treatment is still not given, then all vision in the eye can be lost. Visual loss from glaucoma is irreversible. Because vision lost from glaucoma can never be restored, it is critical to detect glaucoma before significant damage has occurred to the nerve and initiate effective treatment. Even if vision loss has occurred, treatment for glaucoma can be provided to prevent further loss of vision.
Causes of Glaucoma
High pressure inside the eye is known to be one of the factors that cause glaucoma. The normal eye continuously produces and drains fluid (aqueous) internally in order to maintain the normal shape and pressure of the eye. This pressure balance and shape is necessary for you to see properly.
In glaucoma, there may be a blockage of fluid drainage or an excess of fluid production, which leads to high pressure inside the eye.
- A Major Risk Factor for Visual Field Damage
- Blockage of the eyes’ natural drainage system increases IOP
- IOP exceeding 21 mmHg falls above the normal range
- Goal of therapy is reducing IOP and preserving visual field
If you have high eye pressure, the increased pressure may damage your optic nerve due to compression or reduction of the normal blood flow to the critical structures of the optic nerve. Some people, however, are able to tolerate higher eye pressures without developing glaucoma damage to the optic nerve. The reason for this is unknown.
The target for success in many studies has been eye pressure below 21mm, whereas new clinical information reveals that vision is preserved to a much greater degree if pressures are maintained at 16mm or below.
Some people develop glaucoma even without evidence of increased pressure inside the eye. In fact, recent studies show that up to 50 percent of people with glaucoma may not have high eye pressure measurements.
Japanese descent are more prone to have glaucoma without elevated eye pressure,and normal-pressure glaucoma is more common in Japan than high-pressure glaucoma.
The two leading theories are that damage to the nerve is caused by poor circulation to the nerve, or that abnormally high concentrations of naturally occurring chemicals or hormones cause the damage.
Many of these people with normal pressure glaucoma also have other problems with their circulation, such as heart disease, poor circulation to their legs and feet, or hardening of the arteries.
Dr. Duplessie can detect glaucoma damage by the appearance of your optic nerve. A normal healthy nerve has a small depression in the center.
As damage from glaucoma progresses, this depression or hole in the center of the nerve becomes deeper, enlarges, and damages the healthy tissue of the nerve. Dr. Duplessie can detect progression of the disease by periodically examining the appearance of the nerve.
If you have glaucoma or are at high risk of having glaucoma [a glaucoma suspect], Dr. Duplessie will want to examine your optic nerve two or three times a year, to detect definite glaucoma damage as soon as it occurs. This will allow treatment to begin before the glaucoma has a significant effect on your vision.
Visual Field Loss – A test of your peripheral vision.
Another way to diagnose glaucoma is to determine if peripheral or side vision has been lost and if damage has occurred to record the current amount of peripheral loss. Glaucoma does not affect your central reading vision until the late stages of the disease. At this late stage, a glaucoma victim may already be partially blind. Therefore, it is important to measure the peripheral vision in the early stages of the disease so that proper treatment can be given to stabilize vision and prevent blindness. This is accomplished with visual field testing, which is an examination that measures the amount of peripheral and central vision lost.
To test the visual field, you place your head against a headrest and stare at a target light that is placed directly in front of the eye being tested.
The machine then flashes lights in your peripheral vision. Some of these lights are bright and easy to see. Others are so dim that they are impossible to see even if you have no visual damage. Most lights are somewhere in between. When you see the light, you press a button and the machine registers your response. The machine then prints out a map showing any areas where you cannot see properly.
Dr. Duplessie will repeat this measurement periodically to determine if the glaucoma treatment has been effective in stabilizing the damage.
The pressure within the eye or intraocular pressure has classically been thought of as the “key” measure for diagnosis of the disease. The eye pressure varies depending on the time of day that the measurement is obtained. Stability over time is important.
There are other types of specialized testing that may also be used including: conofocal scanning laser analysis (HRT II); scanning laser polarimetry (GDx); and short wavelength perimetry.
Major Types of Glaucoma
Normal (low) tension glaucoma
The most common type of glaucoma is open-angle glaucoma. Open-angle glaucoma means that there is no visible obstruction to the aqueous (fluid) drainage area inside the eye. It is thought that there may be an invisible obstruction (tissue) to fluid drainage in the trabecular meshwork, which is the structure in the eye that drains the fluid. This type of glaucoma typically causes no symptoms until the damage and visual loss is very advanced.
Another type of glaucoma is narrow-angle glaucoma. This type of glaucoma may cause symptoms of sudden pain, redness, blurred vision, and colored haloes around lights. This condition is called acute narrow-angle glaucoma, and must be treated immediately. Failure to treat this condition immediately can cause permanent loss of vision.
Sometimes narrow-angle glaucoma is a chronic condition that does not cause any symptoms, like open angle glaucoma.
Open-Angle Glaucoma Treatment
There are several ways to treat this disease. There is a growing sentiment among eye care professionals that a healthy lifestyle, cessation from smoking and exercise may be valuable in reducing eye pressure.
Glaucoma Treatment Options
Most commonly, treatment begins with eye drops that are designed to lower the pressure in the eye.
These drops are used from one to four times daily, depending on the medication. They are designed to decrease the amount of fluid produced in the eye, or to increase the amount of fluid drained from the eye. Like all medications, these eye drops can have side effects. There are also oral medications that are available to lower the eye pressure but often with greater side effects then the eye drops.
- Beta-adrenergic blockers
- Miotics (cholinergics)
- Hyperosmotic agents
- Carbonic anhydrase inhibitors
- Selective alpha2-adrenergic agonists
- Prostaglandin analogues
Laser treatment – Trabeculoplasty
Another method of treating glaucoma is with a laser. There are currently two different types of lasers used to increase the amount of fluid drained from the eye:
a thermal laser that creates micro-burns in the trabecular meshwork.
Selective Laser Trabeculoplasty-
a newer non-thermal laser that targets the pigment cells in the trabecular meshwork.
The applications can be repeated more than once.
Studies and trials with the Argon laser have shown pressure reduction in Caucasian patients to have a duration of two to three years with the lower pressures remaining a year or two longer in Black patients.
Both lasers may reduce the number of eye drops used to control the pressure but rarely does the laser treatment eliminate the need for the drops. The laser treatment is usually performed in the office, takes only a few minutes, and is normally painless.
The third way to treat glaucoma is with microsurgery. Studies have consistently revealed that the eye pressure is reduced to a greater degree through surgical intervention than the use of eye drops, laser or a combination of these treatments but with an increased risks of complications.
The surgical procedure that has been considered the “gold standard” for penetrating procedures is trabeculectomy. In this procedure, a small drainage hole is created in the eye, usually located in the upper portion of the eye. This allows fluid to drain out of the eye and into the circulation behind the eye in the eye socket. This procedure effectively drains fluid from the eye as long as the tissues do not scar sufficiently during the healing phase after the procedure.
Narrow-Angle Glaucoma Treatment
If you are at risk for or have narrow angle glaucoma, Dr. Duplessie will recommend a preventive laser treatment that creates a small opening in the iris or colored part of the eye. Sometimes narrow angle glaucoma is a chronic condition that is treated with the same medicines or microsurgery for open angle glaucoma.
Advanced Glaucoma Intervention Study (AGIS)
Mean IOP and Visual Field Loss
586 eyes followed over 6 or more years
- Positive correlation between IOP and visual field loss
- Patients who were below 18 mm Hg at 100% of visits had little or no progression over 6 years
- Patients with 25% of visits >18 mm Hg had greater risk of clinically significant visual field progression over 6 years.
- Sustained IOP reduction below 18 mmHg is correlated with stability of visual field