Glaucoma – The Silent thief of sight
Q. What is Glaucoma ?
A. Glaucoma is eye disease which result in loss of vision by permanently damaging the optic nerve, the nerve that transmits visual images to the brain. The leading cause of irreversibl blindness, glaucoma often produces no symptoms until it is too late and vision loss has begun.
An elevated eye pressure (the Intraocular pressure, or IOP) is generally, but not always, associated with the development of glaucoma, although additional factors also play a role in its development. The optic nerve fibers inside the eye are damaged, resulting in vision loss that begins in the peripheral fields of vision. Glaucoma usually affects both eyes, but one eye may be more severely affected than the other.
Q. What is the optic nerve?
A. The optic nerve is a bundle of more than 1 million nerve fibers. It connects the retina, the light-sensitive layer of tissue at the back of the eye, with the brain . A healthy optic nerve is necessary for good vision.
Q.What are different types of glaucoma?
A. Open-angle glaucoma, the most common form of glaucoma, is estimated to affect about 10 million. indians -half of whom don’t know they have it. It has no symptoms at first. But over the years it can steal your sight. With early treatment, you can often protect your eyes against serious vision loss and blindness.
In low-tension or normal-tension glaucoma, optic nerve damage unexpectedly in people with normal eye pressure. People with this form of the disease have the same types of treatment as open-angle glaucoma.
In closed-angle glaucoma, the fluid at the front of the eye cannot reach the angle and leave the eye because the angle gets blocked by part of the iris. People with this type of glaucoma have a sudden increase in pressure. Symptoms include severe pain and nausea as well as redness of the eye and blurred vision. This is a medical emergency. The patient needs immediate treatment to improve the flow of fluid. Without treatment, the eye can become blind in as little as one or two days. Usually, prompt laser procedure can clear the blockage and protect sight.
In congenital glaucoma (Picture below) children are born with defects in the angle of the eye that slow the normal drainage of fluid. Children with this problem usually have obvious symptoms such as cloudy eyes,sensitivity to light, and excessive tearing. Surgery is usually the suggested treatment, because medicines may have unknown effects in infants and be difficult to give to them. The surgery is safe and effective. If surgery is done promptly, these children usually have an excellent chance of having good vision.
Secondary glaucomas can develop as a complication of other medical conditions They are sometimes associated with eye surgery or advanced cataracts, eye injuries, certain eye tumors, or uveitis (eye inflammation). A severe form, called neovascular glaucoma, is linked to diabetes. Also, corticosteroid drugs used to treat eye inflammations and other diseases can trigger glaucoma in a few people. Treatment is with medicines, or conventional surgery.
Q. How does glaucoma damage the optic nerve?
A. In many people, increased pressure inside the eye causes glaucoma. In the front of the eye is a space called the anterior chamber. A clear fluid flows continuously in and out of this space and nourishes nearby tissues.
The fluid leaves the anterior chamber at the angle where the cornea and iris meet (see diagram). When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.
Open-angle glaucoma gets its name because the angle that allows fluid to drain out of the anterior chamber is open. However, for unknown reasons, the fluid passes too slowly through the meshwork drain. As the fluid builds up, the pressure inside the eye rise, it can damage the optic nerve and cause vision loss.
Q. Who is at risk?
A. Although anyone can get glaucoma, some people are at higher risk than others, They include:
- Age over 45 years
- Family history of glaucoma
- History of elevated intraocular pressure
- High myopia( Nearsightedness )
- Hyperopia ( Farsightedness ), Farsighted people may have narrow drainage angles, which predispose them to sudden attacks of angle-closure glaucoma.
- History of injury to the eye
- Use of steroids, either in the eye or systemically (orally or injected)
Q. How is glaucoma detected?
A. Most people think that they have glaucoma if the pressure in their eye is increased. This is not always true. High pressure puts you at risk for glaucoma. It may not mean that you have the disease.
Whether or not you get glaucoma depends on the level of pressure that your optic nerve can tolerate without being damaged. This level is different for each person. Although normal pressure is usually between 12-21 mm Hg, a person might have glaucoma even if the pressure is in this range. That is why an eye examination is very important.
To detect glaucoma, we will do the following tests:
Visual acuity: This eye chart test measures how well you see at various distances.
Tonometry: This standard test determines the fluid pressure inside the eye. There are many types of tonometry. We are equipped with latest Tonometers.
Q. What are the symptoms of glaucoma?
A. At first, open-angle glaucoma has. no symptoms. Vision stays normal, and there is no pain. As glaucoma remains untreated, people may notice that although they see things clearly in front of them, they miss objects to the side and out of the corner of their eye.
Without treatment, people with glaucoma may find that they suddenly have no side vision. It may seem as though they are looking through a tunnel. Over a period of time, the remaining forward vision may decrease to tunnel vision to blindness.
Ophthalmoscopy after Pupil dilation: This procedure is done to examine the optic nerve (seen as the optic disc) at the back of the eye. Damage to the optic nerve, called cupping of the disc, can be detected in this way. Cupping, which is an indentation of the optic disc, can be caused by increased intraocular pressure. Additionally, a pale color of the nerve can suggest damage to the nerve from poor blood flow or increased intraocular pressure.This examination provides a better view of the optic nerve to check for signs of damage.
Pachymetry determines the thickness of the cornea. Corneal thickness can affect the measurement of intraocular pressure. Thicker corneas may give falsely high eye pressure readings and thinner corneas may give falsely low pressure readings. Furthermore, thin corneas may be an additional risk factor for glaucoma.
Gonioscopy is done by numbing the eye with anesthetic drops and placing a special type of contact lens with mirrors inside the eye. The mirrors enables to view the interior of the eye from different directions. The purpose of this test is to examine the drainage angle and drainage area of the eye. In this procedure, we determine whether the angle is open or narrow and find any other abnormalities within the angle area. As indicated earlier, individuals with narrow angles have an increased risk for a sudden closure of the angle, which can cause an acute angle-closure glaucomatous attack.
Visual Field Analysis (VFA ) / Perimetry:
This test measures your side (peripheral) vision. It helps us to find out if you have lost side vision, a sign of glaucoma. Visual fields detect any early (or late) signs of glaucomatous damage to the optic nerve , measured by a computerized assessment. For this procedure, one eye is covered and the patient places his or her chin in a type of bowl. Then, when the patient sees lights of various intensities and at different locations, he or she pushes a button. This process produces a computerized map of the visual field, outlining the areas where the eye can or cannot see.
We have latest Humphrey Visual field Analyzer( VFA ) From Carl Zeiss Meditec USA
OCT( Ocular Coherence tomography) :
It is latest modality of investigation in glaucoma which gives 3D high definition of scans of various tissues of eye.
We have latest RTVue FD OCT( Ocular Coherence tomography) (Optovue, USA) which is an ultra-high speed, high resolution OCT and enable to visualize the retinal tissue and optic nerve with ultra-high clarity in a fraction of seconds
All of these tests need to be repeated at intervals to assess the progress of the disease and the effect of the treatment
Q. Can glaucoma be treated?
A. Yes. Although you will never be cured of glaucoma, treatment often can control it. This makes early diagnosis and treatment important to protect your sight.
We normaly use Eyedrops for newly diagnosed glaucoma and that is sufficient in most cases; however, in some advanced cases surgery may be required for adequate control.
Medicine: Medicines are the most common early treatment for glaucoma. They come in the form of eyedrops and tablets. Some cause the eye to make less fluid. But most lower pressure by helping fluid drain from the eye. Now latest eyedrops are very good and they control eye pressure by putting just once in the night. You may need to use more than one eye drops and/or tablets to control your eye pressure. Glaucoma often has no symptoms, people may be tempted to stop or may forget to take their medicine. So regular checkup is very important.
Laser iridotomy : involves making a hole in the colored part of the eye (iris) to allow fluid to drain normally in eyes with narrow or closed angles using laser energy, this is done as OPD procedure.
Conventional surgery ( Trabeculectomy ) : surgery is often done after medicine and laser have failed to control your eye pressure The purpose of surgery is to make a new opening for the fluid to leave the eye. In this surgery small piece of tissue from the white (sclera) of the eye is removed to creates a new channel for fluid to drain from the eye.In some patients, surgery is about 80 to 90 percent effective at lowering pressure. However, if the new drainage opening closes, a second operation may be needed.
Q. What can you do to protect your vision?
A. If you are being treated for glaucoma, be sure to take your glaucoma medicine every day and see your eye doctor regularly. You can also help protect the vision of family members and friends who may be at high risk for glaucoma especially those over 45 yrs of age. Encourage them to have an eye examination through dilated pupils every six months.
We want to protect your eyes
Dr Rajesh Kapoor