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Glaucoma


What is Glaucoma?

Glaucoma is a group of eye disorders that lead to progressive damage to the optic nerve. People with glaucoma can lose nerve tissue, resulting in vision loss. Not everyone with high eye pressure may develop Glaucoma, and any one with even normal eye pressure may develop Glaucoma.

It is the second leading cause of blindness in U.S. and mostly occurs to people above 40 years, although an infant (congenital) form of glaucoma exists.

What Causes Glaucoma?

There are many theories about the cause of glaucoma, like increased in fluid pressure in the eye, or lack of adequate blood supply to the nerve, but the exact cause is still unknown. Other risk factors include thinner corneas, chronic eye inflammation and taking medications that increase the pressure in the eyes.

Following are the different types of glaucoma and their potential causes:

1. Primary open-angle glaucoma:- This is the most common form of glaucoma. Damage to the optic nerve is slow and painless. Those affected can lose a large portion of vision before they notice any vision problems.

This is the most common form of glaucoma which develops slowly without any pain or symptoms. Many people having glaucoma are unaware of it until they have significant vision loss. Initially it affects peripheral or side vision, but can gradually affect central vision and if left untreated, it can also cause blindness in both eyes.

One of the reason of its development is that the eye's drainage system becomes inefficient over time, which causes increased amount of fluids and gradual buildup of pressure within the eye. The other reason for developing this type of glaucoma is poor blood flow (perfusion) to the optic nerve.

2. Angle-closure glaucoma:- This type of glaucoma usually occurs due to rapid increase of pressure in eye. It occurs to people who have a very narrow drainage angle (formed by the cornea and the iris). With age, when lense in eye become large, pushing the iris forward and narrowing the space between the iris and cornea, causing the fluid in eye getting blocked in the drainage system. Therefore the fluid builds up and eye pressure increases.

This type of glaucoma is less common, but is a medical emergency that can cause vision loss within a day of its onset. Although an acute attack often affects only one eye, the other eye may be at risk of an attack as well.

This type of glaucoma cannot be prevented currently, but if diagnosed early can be prevented. Its symptoms may include severe eye pain, nausea, redness in the eye, seeing halos or colored rings around lights and blurred vision.

3. Secondary glaucoma:- This type of glaucoma results from an injury or other eye disease. It may be caused by a variety of medical conditions, medications, physical injuries and eye abnormalities. Infrequently, eye surgery can lead to secondary glaucoma.

4. Normal-tension or low-tension glaucoma:- In this form of glaucoma, eye pressure remains within the "normal" range, but the optic nerve is damaged nevertheless. It is not known why this happens.

Possibly, people with low-tension glaucoma have an abnormally sensitive optic nerve. Or they may have a reduced blood supply to the optic nerve caused by a condition such as atherosclerosis, a hardening of the arteries. Under these circumstances even normal pressure on the optic nerve can cause damage.

Risk of forming Glaucoma

The following factors can increase risk of forming glaucoma:

People with family history or African American over age 40 & Hispanics above age 60 have higher risk of developing glaucoma than Caucasians and the risk increases with increasing age. African American are much more likely to suffer permanent vision loss. People of Asian descent and Native Alaskans are at higher risk of angle-closure glaucoma. People of Japanese descent are more likely to develop low-tension glaucoma.

Having medical conditions such as blood pressure, diabetes, heart disease, eye injury like being hit in eye which causes internal damages and trauma and any other factors that increases eye pressure can cause glaucoma.

Certain features of eye anatomy, namely thinner corneas and optic nerve sensitivity, indicate an increased risk for developing glaucoma. Conditions such as retinal detachment, eye tumors and eye inflammations may also trigger glaucoma. Some studies suggest that high amounts of nearsightedness may also be a risk factor for glaucoma. Using corticosteroids (including cortisone, hydrocortisone and prednisone) for prolonged periods of time appears to put some people at risk of getting secondary glaucoma.

How is Glaucoma Diagnosed?

It is diagnosed through comprehensive eye examination. Since it is a progressive diseas, which means it worsens over time. Some optic nerve may resemble with glaucoma, but patients may not have any other risk factor, such patients should have routine comprehensive exam to monitor changes.

Glaucoma testing includes:

  • Patient history to determine any symptoms the patient is experiencing and if there are any general health problems and family history that may be contributing to the problem.

  • Visual acuity measurements to determine if vision is being affected.

  • Tonometry to measure the pressure inside the eye to detect increased risk factors for glaucoma.

  • Pachymetry to measure corneal thickness. People with thinner corneas are at an increased risk of developing glaucoma.

  • Visual field testing, also called perimetry, to check if the field of vision has been affected by glaucoma. This test measures your side (peripheral) vision and central vision by either determining the dimmest amount of light that can be detected in various locations of vision, or by determining sensitivity to targets other than light.

  • Evaluation of the retina of the eye, which may include photographs or scans of the optic nerve, to monitor any changes over time.

  • Supplemental testing, which may include gonioscopy. This procedure offers a view of the angle anatomy, which is where eye fluid drainage occurs. Serial tonometry is another possible test. This procedure acquires several pressure measurements over time, looking for changes in the eye pressure throughout the day. In addition, devices can be used to measure nerve fiber thickness and to look for tissue loss on specific areas of the nerve fiber layer.

How is Glaucoma Treated?

There is no cure for glaucoma and patients suffering from it may require treatment for rest of their life. Keeping eye pressure under control may stop or slow down the damage caused to optic nerve and vision loss. Regular use of prescription eye drops are normally first and very common treatment.

  • Medications: A number of medications are currently available to treat glaucoma. Typically, medications reduce elevated pressure in the eye. A single medication or a combination of medications may be prescribed. The type of medication may change if it is not reducing pressure enough or if the patient is experiencing side effects.

  • Surgery: Procedures include laser treatment, making a drainage flap in the eye, inserting a drainage valve, or destroying the tissue that creates the fluid in the eye. All procedures aim to reduce the pressure inside the eye when medication is not sufficient. Surgery cannot reverse vision loss.
    • Laser surgery: Laser trabeculoplasty helps fluid drain out of the eye. A high-energy laser beam stimulates the structure that drains fluid from the eye (the trabecular meshwork) so that fluid drains more efficiently. The results may be somewhat temporary, and the procedure may need to be repeated in the future.
    • Conventional surgery: If eye drops and laser surgery aren't controlling eye pressure, you may need a trabeculectomy. This filtering microsurgery creates a drainage flap. Fluid can then percolate into the flap and later drain into the vascular system.
    • Drainage implants: Drainage valve implant surgery may be an option for adults with uncontrolled glaucoma or secondary glaucoma or for children with glaucoma. A small silicone tube is inserted in the eye to help drain fluid.

Treatment for acute angle-closure glaucoma
Acute angle closure glaucoma is a medical emergency and medications should be taken to reduce eye pressure as soon as possible. They will also likely undergo a laser procedure called laser peripheral iridotomy. In this procedure, a laser beam creates a small hole in the iris to allow fluid to flow more freely into the front chamber of the eye where it then can drain.