Glaucoma: Types, Symptoms, Diagnosis And Treatment

Glaucoma refers to a group of related eye disorders that all cause damage to the optic nerve that carries information from the eye to the brain. Glaucoma usually has few or no initial symptoms.

In most cases, glaucoma is associated with higher-than-normal pressure inside the eye — a condition called ocular hypertension. But it also can occur when intraocular pressure (IOP) is normal. If untreated or uncontrolled, glaucoma first causes peripheral vision loss and eventually can lead to blindness.

Basic causes of peripheral vision loss include:

• Glaucoma.
• Retinitis pigmentosa.
• Eye strokes or occlusions.
• Detached retina.
• Brain damage from stroke, disease or injury.
• Neurological damage such as from optic neuritis.
• Compressed optic nerve head (papilledema)
• Concussions (head injuries)

On the basis of the available data, we estimate that there are approximately 11.2 million persons aged 40 years and older with glaucoma in India. Primary open angle glaucoma is estimated to affect 6.48 million persons. The estimated number with primary angle-closure glaucoma is 2.54 million. Those with any form of primary angle-closure disease could comprise 27.6 million persons. 

Types Of Glaucoma

The two major categories of glaucoma are open-angle glaucoma (OAG) and narrow angle glaucoma. The "angle" in both cases refers to the drainage angle inside the eye that controls the outflow of the watery fluid (aqueous) that is continually being produced inside the eye.

If the aqueous can access the drainage angle, the glaucoma is known as open angle glaucoma. If the drainage angle is blocked and the aqueous cannot reach it, the glaucoma is known as narrow angle glaucoma.

Variations of OAG include: 

• primary open angle glaucoma (POAG),
• normal-tension glaucoma (NTG), 
• pigmentary glaucoma, 
• pseudoexfoliation glaucoma, 
• secondary glaucoma 
• congenital glaucoma.

Variations of narrow angle glaucoma include include 

• acute angle closure glaucoma, 
• chronic angle closure glaucoma, 
• neovascular glaucoma.

Primary open-angle glaucoma.

This common type of glaucoma gradually reduces your peripheral vision without other symptoms. By the time you notice it, permanent damage already has occurred.

If your IOP remains high, the destruction caused by POAG can progress until tunnel vision develops, and you will be able to see only objects that are straight ahead. Ultimately, all vision can be lost, causing blindness.Acute angle-closure glaucoma. 
Produces sudden symptoms such as 

• eye pain, 
• headaches, 
• halos around lights, 
• dilated pupils, 
• vision loss,
• red eyes, 
• nausea 
• vomiting

Also, pain is unlikely and permanent damage to the eye's optic nerve may not be noticed until symptoms such as tunnel vision occur.

The cause of normal-tension glaucoma is not known. But many doctors believe it is related to poor blood flow to the optic nerve. Normal-tension glaucoma is more common in those who are Japanese, are female and/or have a history of vascular disease.

Four Key Facts About Glaucoma

1. Glaucoma is a leading cause of blindness

Glaucoma can cause blindness if it is left untreated. And unfortunately approximately 10% of people with glaucoma who receive proper treatment still experience loss of vision.

2. There is no cure (yet) for glaucoma

Glaucoma is not curable, and vision lost cannot be regained. With medication and/or surgery, it is possible to halt further loss of vision. Since open-angle glaucoma is a chronic condition, it must be monitored for life. Diagnosis is the first step to preserving your vision.

3. Everyone is at risk for glaucoma

Everyone is at risk for glaucoma from babies to senior citizens. Older people are at a higher risk for glaucoma but babies can be born with glaucoma. Young adults can get glaucoma, too.

4. There may be no symptoms to warn you

With open-angle glaucoma, the most common form, there are virtually no symptoms. Usually, no pain is associated with increased eye pressure. Vision loss begins with peripheral or side vision. You may compensate for this unconsciously by turning your head to the side, and may not notice anything until significant vision is lost. The best way to protect your sight from glaucoma is to get tested. If you have glaucoma, treatment can begin immediately.

Glaucoma Symptoms

Glaucoma often is called the "silent thief of sight," because most types typically cause no pain and produce no symptoms until noticeable vision loss occurs.

For this reason, glaucoma often progresses undetected until the optic nerve already has been irreversibly damaged, with varying degrees of permanent vision loss.

But with acute angle-closure glaucoma, symptoms that occur suddenly can include blurry vision, halos around lights, intense eye pain, nausea and vomiting. If you have these symptoms, make sure you see an eye care practitioner or visit the emergency room immediately so steps can be taken to prevent permanent vision loss.

Diagnosis, Screening And Tests For Glaucoma

During routine eye exams, a tonometer is used to measure your intraocular pressure, or IOP.

• In Goldmann applanation tonometry (GAT), numbing eye drops are applied and a lightweight probe gently touches the eye to measure eye pressure.
• In non-contact tonometry (NCT), a gentle puff of air flattens the center of the cornea briefly to measure eye pressure. No numbing eye drops are needed.

If your IOP is higher than 30 mmHg, your risk of vision loss from glaucoma is 40 times greater than someone with intraocular pressure of 15 mmHg or lower.  scanning laser polarimetry (SLP), optical coherence tomography (OCT) and confocal scanning laser ophthalmoscopy — to create baseline images and measurements of the eye's optic nerve and internal structures.

Then, at specified intervals, additional images and measurements are taken to make sure no changes have occurred over time that might indicate progressive glaucoma damage.

Visual field testing is a way for your eye doctor to determine if you are experiencing vision loss from glaucoma. 

Gonioscopy also may be performed to make sure the aqueous humor can drain freely from the eye. to measure drainage angle Ultrasound biomicroscopy is another technique that may be used to evaluate the drainage angle.

Glaucoma Treatments

Treatment can involve glaucoma surgery, lasers or medication, depending on the severity. Eye drops with medication aimed at lowering IOP usually are tried first to control glaucoma.

Because glaucoma often is painless, people may become careless about strict use of eye drops that can control eye pressure and help prevent permanent eye damage.

In fact, non-compliance with a program of prescribed glaucoma medication is a major reason for blindness caused by glaucoma.

If you find that the eye drops you are using for glaucoma are uncomfortable or inconvenient, never discontinue them without first consulting your eye doctor about a possible alternative therapy.

Glaucoma Prevention

Currently, regular eye exams are the best form of prevention against significant glaucoma damage.

Early detection and careful, lifelong treatment can maintain vision in most people. In general, a check for glaucoma should be done:

• before age 40, every two to four years
• from age 40 to age 54, every one to three years
• from age 55 to 64, every one to two years
• after age 65, every six to 12 months

Anyone with high risk factors should be tested every year or two after age 35. Those at higher risk include people of African descent, people with diabetes, and people with a family history of glaucoma. You are at increased risk if you have a parent or brother or sister with glaucoma.

Timely Diagnosis and Appropriate Treatment are Key to Glaucoma Prevention

Benefits of Exercise

A regular program of moderate exercise will benefit your overall health, and studies have shown that moderate exercise such as walking or jogging three or more times every week can have an IOP lowering effect.

Yoga can be beneficial, but it’s best to avoid inverted positions such as headstands and shoulder-stands, as these may increase IOP.

Protect Your Eyes

Wearing protective eyewear is important when engaged in sports activities or home improvement projects.

Eye injuries can result in traumatic glaucoma or secondary glaucoma, so protecting your eyes from injury is another way to prevent glaucoma

In addition to regular exercise and an active lifestyle, you also can reduce your risk for glaucoma by not smoking, maintaining a healthy weight, and eating a varied and healthy diet.