Glaucoma is a condition in which the pressure within the eye is elevated. The elevated pressure damages the optic nerve. Because such nerve damage can lead to blindness, the pressure must be lowered by medication, laser therapy or surgery.
Open-angle glaucoma, the most common form of the disease, has no symptoms at first. It is a progressive disease characterized by optic nerve damage. High eye pressure is the most significant recognized risk factor for the development and progression of the disease. The pressure in the eye builds up gradually. At some point, side vision (peripheral vision) is lost and without treatment, total blindness will occur.Risk factors for open-angle glaucoma include:
Closed-angle glaucoma may be acute or chronic. Acute closed-angle glaucoma results when the normal flow of eye fluid (aqueous humor) between the iris and the lens becomes suddenly blocked. Symptoms may include severe pain, nausea, vomiting, blurred vision, and seeing a rainbow halo around lights. Acute closed-angle glaucoma is a medical emergency and must be treated immediately or blindness could result in one or two days. Chronic closed-angle glaucoma progresses more slowly and can produce damage without symptoms, similar to open-angle glaucoma.
Congenital glaucoma is a condition where babies are born with defects that prevent the normal drainage of fluid from the eye. Juvenile glaucoma has been used to describe open-angle glaucoma in children, adolescents and young adults.
Secondary glaucoma occurs as the result of some other recognizable medical condition in the eye or the body, and can be of the open-angle or closed-angle variety
Neovascular glaucoma results from abnormal blood vessel growth that blocks the fluid drainage channels of the eye, resulting in increased eye pressure. Low blood supply to the eye as a result of diabetes, insufficient flow of blood to the head due to blocked arteries in the neck, or blockage of blood vessels in the back of the eye can cause the abnormal blood vessel growth.
Currently, there is no “cure” for glaucoma; however, early diagnosis and treatment can control glaucoma before vision loss or blindness occurs. Several tests can help your eye doctor detect glaucoma. Individuals at high risk for glaucoma should have a dilated pupil eye examination every year. Tests involved in the diagnosis of glaucoma include:
Ophthalmoscopy allows the eye doctor to examine the interior of the eye by looking through the pupil with a special instrument. It is helpful in detecting damage to the optic nerve that is due to the effects of glaucoma.
Gonioscopy allows the doctor to view the front part of the eye (anterior chamber) to determine if the iris is closer to the back of the cornea than usual. This test can help diagnose closed-angle glaucoma.
Tonometry measures the pressure inside the eye. The following are examples of tonometers: One is the air puff, or noncontact tonometer, that emits a puff of air. The eye’s resistance to the air indicates the eye pressure. Another is the applanation tonometer which actually touches the eye’s surface after your doctor has placed drops in both your eyes to numb them. The applanation tonometer measures the amount of pressure necessary to flatten the cornea. The applanation tonometer is the most sensitive. But, the patient must have a clear, regularly-shaped, cornea in order for the applanation tonometer to function properly.
Visual field testing measures the entire area that can be seen when the eye is looking forward. This documents straight-ahead (central) and/or side (peripheral) vision. This test measures the dimmest light that can be seen at each spot tested. The test requires the patient to respond to the appearance of light by pressing a button every time a flash of light is perceived.
Pachymetry involves using an ultrasonic wave instrument to help determine the thickness of the cornea. This test can help your doctor better evaluate your eye pressure readings.
Optic nerve imaging helps the eye doctor document how the optic nerve changes over time. Scanning laser polarimetry (GDx), confocal scanning laser ophthalmoscopy (Heidelberg Retinal Tomograph or HRT II), and optical coherence tomography (OCT) are all examples of optic nerve imaging techniques. All three imaging techniques are painless and non-invasive.
Early treatment for open-angle glaucoma will usually begin with medications (eye drops, for example) that either help the eye to drain fluid more effectively or cause it to produce less fluid. Several forms of laser surgery can also help fluid drain from the eye. Incisional surgery to create a new opening for fluid to drain is usually performed after the other treatment options have failed.