Types of Glaucoma
Following are the different types of glaucoma and their potential causes.
Primary Open-Angle Glaucoma (POAG)
is by far the most common type of glaucoma. Moreover, its frequency increases greatly with age and it is a chronic, not acute, disease. This increase occurs because the drainage mechanism gradually may become clogged secondary to aging, even though the drainage angle is open. As a consequence, the aqueous fluid does not drain from the eye properly. The pressure within the eye, therefore, builds up painlessly and without symptoms. Furthermore, as mentioned previously, since the resulting loss of vision starts on the side (peripherally), people are usually not aware of the problem until the loss encroaches near or into their central visual area. This type of glaucoma is said to be primary because its cause cannot be attributed to any discernable structural changes within the eye.
Normal-tension (pressure) glaucoma
or low tension glaucoma are variants of primary chronic open-angle glaucoma that are being recognized more frequently than in the past. This type of glaucoma is thought to be due to decreased blood flow to the optic nerve. This condition is characterized by progressive optic-nerve damage and loss of peripheral vision (visual field) despite intraocular pressures in the normal range or even below normal. This type of glaucoma can be diagnosed by repeated examinations by the eye doctor to detect the nerve damage or the visual field loss.
Congenital Glaucoma (Infantile Glaucoma)
is a relatively rare, inherited type of open-angle glaucoma. In this condition, the drainage area is not properly developed before birth. This results in increased pressure in the eye that can lead to the loss of vision from optic-nerve damage and also to an enlarged eye. The eye of a young child enlarges in response to increased intraocular pressure because it is more pliable than the eye of an adult. Early diagnosis and treatment with medication and/or surgery are critical in these infants and children to preserve their sight.
Secondary Open-Angle Glaucoma
is another type of open-angle glaucoma. It can result from an eye (ocular) injury, even one that occurred many years ago. Other causes of secondary glaucoma are inflammation in the iris of the eye (iritis), diabetes, cataracts, or in steroid- susceptible individuals, the use of topical (drops) or systemic (oral or injected) steroids (cortisone). It can also be associated with a retinal detachment or retinal vein occlusion or blockage. (The retina is the layer that lines the inside of the back of the eye.) The treatments for the secondary open-angle glaucomas vary, depending on the cause.
is a type of secondary glaucoma that is more common in younger men. In this condition, for reasons not yet understood, granules of pigment detach from the iris, which is the colored part of the eye. These granules then may block the trabecular meshwork, which, as noted above, is a key element in the drainage system of the eye. Finally, the blocked drainage system leads to elevated intraocular pressure, which results in damage to the optic nerve.
Exfoliative Glaucoma (Pseudoexfoliation or PXE)
is another type of glaucoma that can occur with either open or closed angles. This type of glaucoma is characterized by deposits of flaky material on the front surface of the lens (anterior capsule) and in the angle of the eye. The accumulation of this material in the angle is believed to block the drainage system of the eye and raise the eye pressure. While this type of glaucoma can occur in any population, it is more prevalent in older people and people of Scandinavian descent. It has recently been shown to often be associated with hearing loss in older people.
Angle-Closure Glaucoma (closed-angle glaucoma or narrow-angle glaucoma) is a less common form of glaucoma in the Western world but is extremely common in Asia. Angle-closure glaucoma may be acute or chronic. The common element in both is that a portion of or the entire drainage angle becomes anatomically closed, so that the aqueous fluid within the eye cannot reach all or part of the trabecular meshwork. In acute angle-closure glaucoma, the patient's intraocular pressure, which ordinarily is normal, can go up very suddenly (acutely).
This sudden pressure increase occurs because the drainage angle becomes closed and blocks off all the drainage channels. This type of glaucoma can occur when the pupil dilates (widens or enlarges). As a result, the peripheral edge of the iris can become bunched up against its corneal attachment, thereby causing the drainage angle to close. Thus, the problem in angle-closure glaucoma is the difficulty with access of the eye fluid to the drainage system (trabecular meshwork). In contrast, remember that the problem in open-angle glaucoma is clogging within the drainage system itself. In chronic open-angle glaucoma, portions of the drainage angle remain closed over a long period of time and damage the drainage system. As more and more areas become closed, the pressure within the eye rises, often over a period of months or years.
Glaucoma Sign and Symptoms
Glaucoma does not usually cause any symptoms to begin with.
It tends to develop slowly over many years and affects the edges of your vision (peripheral vision) first.
For this reason, many people do not realise they have glaucoma, and it's often only picked up during a routine eye test. If you do notice any symptoms, they might include blurred vision, or seeing rainbow-colored circles around bright lights.
Both eyes are usually affected, although it may be worse in 1 eye.
Patients with Primary Open-Angle Glaucoma and chronic Angle-Closure glaucoma in general have no symptoms early in the course of the disease. Visual field loss (side vision loss) is not a symptom until late in the course of the disease. Rarely patients with fluctuating levels of intraocular pressure may have haziness of vision and see haloes around lights, especially in the morning.
Symptoms of Primary Open-Angle Glaucoma
The most common form of glaucoma, primary open-angle glaucoma, develops slowly and usually without any symptoms. Many people are not aware they have the condition until they have significant vision loss. Initially, glaucoma affects peripheral or side vision, but it can advance to central vision loss. If left untreated, glaucoma can lead to significant vision loss in both eyes, and may even lead to blindness.
Symptoms of primary open-angle glaucoma are:
- Gradual loss of peripheral vision, usually in both eyes
- Tunnel vision in the advanced stages
Symptoms of Angle-Closure Glaucoma
(also called “closed-angle glaucoma” or “narrow-angle glaucoma”)
A less common type of glaucoma, acute angle-closure glaucoma, usually occurs abruptly due to a rapid increase of pressure in the eye. This type happens when someone’s iris is very close to the drainage angle in their eye. The iris can end up blocking the drainage angle. You can think of it like a piece of paper sliding over a sink drain. When the drainage angle gets completely blocked, eye pressure rises very quickly. This is called an acute attack. It is a true eye emergency, and you should call your ophthalmologist right away or you might go blind.
Here are the signs of an acute angle-closure glaucoma attack:
- Severe eye pain
- Nausea and vomiting (accompanying the severe eye pain)
- Sudden onset of visual disturbance, often in low light
- Headaches (on the same side as the affected eye)
- Blurry or foggy vision
- Rainbow colored rings or halos around lights
- Reddening of the eye
- Dilated pupil
Many people with angle-closure glaucoma develop it slowly.
This is called chronic angle-closure glaucoma.
This type of glaucoma progresses more slowly and can damage the optic nerve without symptoms, similar to open-angle glaucoma.
Similarly, people with normal-tension glaucoma will not experience any symptoms until they begin to lose peripheral vision.
Symptoms of Congenital Glaucoma in Infants
This usually shows up in newborns or during your baby’s first few years. Symptoms include:
- Tearing, sensitivity to light, and eyelid spasms
- A larger cornea and clouding of the normally transparent cornea
- Habitual rubbing of the eyes, squinting, or keeping the eyes closed much of the time
Symptoms of Secondary Glaucoma and Other Forms
Symptoms depend on what's causing your pressure to rise. Inflammation inside your eye (the doctor will call this uveitis) can cause you to see halos. Bright lights might bother your eyes (you’ll hear the doctor call this light sensitivity or photophobia).
If a cataract is the cause, your vision will have been worse for a while.
If you have had an injury to your eye, an advanced cataract, or inflammation in your eyes, your eye doctor will check often to make sure you don’t have glaucoma, too. Another common cause of secondary glaucoma is topical or systematic use of steroids.