What is Glaucoma?
Most people know glaucoma is related to pressure within the eye. More specifically, it is a disease of the optic nerve and an elevated eye pressure can increase the risk of damage.
The optic nerve carries the images from the eye to the brain. In glaucoma, blind spots develop because of gradual injury to the optic nerve. Considerable damage to the nerve fibers can be done before visual loss is even noticed by the patient. Early detection and diagnosis through regular periodic examinations is important in the prevention of visual loss and even blindness.
Types of glaucoma
Within the eye, a liquid called aqueous humor is produced continuously just behind the iris. This fluid fills the space in the front of the eye and drains via porous openings in front of the iris, called the trabecular meshwork. With glaucoma, drainage can be reduced in several different ways.
Open angle glaucoma is the most common. In this type, the drainage pores in the trabecular meshwork tissue in the angle of the front chamber of the eye becomes abnormal over time, reducing outflow of fluid from the eye. This causes the eye pressure to increase.
Narrow angle glaucoma is much less common. In this type, the angle of the front chamber of the eye is too narrow, and fluid cannot escape as quickly as it is produced, causing eye pressure to rise. Occasionally when the angle is extremely narrow, it can close completely creating a sudden and dangerously high pressure, with redness and severe pain in the eye. This is called acute angle closure glaucoma and requires immediate medical attention to prevent blindness.
Normal tension glaucoma was once thought to be rare, but now is thought to be more common. In this form of the disease, the fluid drainage structures are working well, but the optic nerve is fragile and becomes damaged by eye pressures considered to be normal. Some of these patients are thought to have poor blood circulation to the optic nerve.
Congenital or juvenile glaucoma are usually hereditary and occur in infants and children.
Secondary glaucoma refers to various types of the disease that are due to other causes, such as severe eye injuries, medications (i.e. prolonged steroid use), inflammatory eye diseases, and following some eye surgeries.
How is glaucoma diagnosed?
Since glaucoma usually has no symptoms in the early stages, regular periodic eye examination is required for detection before vision loss occurs. This examination should include a thorough history, and a comprehensive eye examination, which involve eye pressure measurement, evaluation of the optic nerve and a peripheral vision test.
How is glaucoma treated?
The most common treatment for glaucoma is eye drops. These lower the eye pressure by decreasing production of aqueous humor fluid or by improving its drainage. Sometimes when drops alone are not effective, oral medications are used as well. Other treatments include the use of various laser treatments to reduce eye pressure or improve the function of the eye's drainage areas. Finally, surgery may be considered to create a new channel for fluid drainage, when medical therapy and lasers cannot adequately control the pressure.
Who is at risk for glaucoma?
Glaucoma can occur at any age, but persons at risk for glaucoma include those with:
- Age of 45 years or older
- Family history of glaucoma
- High intraocular pressure
- African descent
- Long term steroid/cortisone use
- Previous eye injury