Glaucoma is a group of conditions, in which high pressure inside the eye (intraocular pressure) damages the optic nerve of the eye. Glaucoma usually affects both the eyes. It commonly occurs in adults above 40 years of age, but can even occur in newborn babies. The vision lost due to glaucoma is irreversible and hence it is very important to detect this disease as early as possible and treat early to preserve vision.
Our eyes contain a clear fluid called aqueous humour, which is continuously produced in the eye to bath and nourish the structures inside it. The fluid normally drains out of the eye through drainage canals in a fine meshwork located around the edge of the iris (the coloured part of the eye that surrounds the pupil). In people with glaucoma the fluid fails to drain due to some defect and thus increases the pressure inside the eyes called raised Intraocular Pressure (IOP) (or Tension) which damage the optic nerve of the eye. The optic nerve connects the eye to the brain and carries the visual signal. This damage to the optic nerve results in loss of peripheral visual fields initially and later on affects the central vision as well.
1. Open angle glaucoma
It happens when the eye's drainage canals of the eye become clogged over time. The inner eye pressure (also called intraocular pressure or IOP) rises because the correct amount of fluid cannot drain out of the eye. With open angle glaucoma, the entrances to the drainage canals are clear and open. The clogging problem occurs further inside the drainage canals, similar to a clogged pipe below the drain in a sink. Most people have no symptoms and no early warning signs. If open angle glaucoma is not diagnosed and treated, it can cause a gradual loss of vision. This type of glaucoma develops slowly and sometimes without noticeable sight loss for many years. It usually responds well to medication, especially if caught early and treated. This form of glaucoma is more common in Caucasians.
2. Closed angle glaucoma
This type of glaucoma is also known as acute glaucoma or narrow angle glaucoma. It is more common in Asians and is very different from open angle glaucoma in that the eye pressure usually rises very quickly.This happens when the entrance to the drainage canals are very narrow or covered over, like a sink with something covering the drain. Symptoms of angle closure glaucoma may include headaches, eye pain, nausea, rainbows around lights at night, and very blurred vision.
In most cases of glaucoma, the patient is not aware of the gradual loss of sight until vision is significantly impaired. However, if glaucoma progresses without adequate treatment, the following symptoms may occur in some individuals:
Anyone can develop glaucoma. Some people are at higher risk than others. They include:
The tonometry test measures the inner pressure of the eye. Usually drops are used to numb the eye. Then the doctor or technician will use a special device that measures the eye's pressure.
Ophthalmoscopy is used to examine the inside of the eye, especially the optic nerve. In a darkened room, the doctor will magnify your eye by using an ophthalmoscope (an instrument with a small light on the end). This helps the doctor look at the shape and color of the optic nerve.
Perimetry is a procedure where the patient wears a patch over one eye and looks straight ahead at a bowl-shaped white area. At the same time, the computer presents lights in fixed locations around the bowl. The patient indicates each time he or she sees a light, which is why perimetry is able to provide a map of the visual fields. The type of vision loss associated with glaucoma is relatively specific, and perimetry can detect the typical visual-field defects of glaucoma disorder.The perimetry test is also called a visual field test.
4. Retinal Nerve Fibre Analysis/OCT
Retinal Nerve Fibre Analysis/OCT Nerve fibre analysis is a newer method of glaucoma testing in which the thickness of the nerve fibre layer is measured. Thinner areas may indicate damage caused by glaucoma. This test is especially good for patients who may be considered to be a glaucoma suspect and also to indicate if a person's glaucoma is progressively becoming worse. The OCT instrument utilizes a technique called optical coherence tomography which creates images by use of special beams of light. The OCT machine can create a contour map of the optic nerve, optic cup and measure the retinal nerve fiber thickness. Over time this machine can detect loss of optic nerve fibers.
Glaucoma is a chronic (long lasting) progressive condition. Any vision loss that has occurred, before glaucoma was diagnosed, cannot be reversed. Glaucoma treatments include medicines, laser trabeculoplasty, conventional surgery, or a combination of any of these. While these treatments may save remaining vision, they do not improve sight already lost from glaucoma.
Medicines. Medicines, in the form of eyedrops or pills, are the most common early treatment for glaucoma. Some medicines cause the eye to make less fluid. Others lower pressure by helping fluid drain from the eye. These medicines are generally to be used lifelong, and it is very important to use the medicines regularly at prescribed timings and not to stop the medicines without consulting the doctor.
Laser trabeculoplasty. Laser trabeculoplasty helps fluid drain out of the eye. Your doctor may suggest this step at any time. In many cases, you need to keep taking glaucoma drugs after this procedure. Laser trabeculoplasty is performed in your doctor's office or eye clinic. Before the surgery, numbing drops will be applied to your eye. As you sit facing the laser machine, your doctor will hold a special lens to your eye. A high-intensity beam of light is aimed at the lens and reflected onto the meshwork inside your eye. You may see flashes of bright green or red light. The laser makes several evenly spaced burns that stretch the drainage holes in the meshwork. This allows the fluid to drain better.
Glaucoma Filtering surgery. Conventional surgery makes a new opening for the fluid to leave the eye. Your doctor may suggest this treatment at any time. Conventional surgery often is done after medicines and laser surgery have failed to control pressure.
As with laser surgery, conventional surgery is performed on one eye at a time. Usually the operations are four to six weeks apart. Conventional surgery is about 60 to 80 percent effective at lowering eye pressure.