Glaucoma
Definition
Glaucoma is a disease of the optic nerve. In a normal eye, light images
are focused on the retina, or film in the back of the eye. The retina is
actually made up of in part, over one million individual nerves that
pass along the back of the eye and come together as the optic nerve.
This bundle of nerves carries important visual information to the brain
for processing.
Through an unclear mechanism, typically associated with an elevated
pressure in the eye, individual retinal nerve fibers are lost, and the
optic nerve hollows out. Viewed head on, this loss of tissue gives the
nerve a more “cupped out” appearance. Clinically, a patient with
glaucoma will develop a decrease in peripheral vision, or blind spots,
as individual nerve fibers are lost. Eventually central vision is
affected. Like most nerve damage, glaucomatous visual loss is
irreversible.
Types of Glaucoma
Typically, glaucoma can be subdivided into open angle or narrow angle
glaucoma. Narrow angle glaucoma implies that the drainage system, or
angle between the iris and cornea, is narrow or closed, and the fluid
within the eye (aqueous humor) cannot escape. Often a rapid increase in
pressure occurs with a painful, red and hazy eye. Medical and laser
treatment is indicated to break a narrow angle glaucoma attack. Eyes at
risk for narrow angle attacks can be discovered on an eye exam and prophylacticaly treated with a laser to prevent future glaucoma.
While open angle glaucoma can occur from various causes, it usually
occurs by itself with no known reason. Unlike narrow angle glaucoma,
open angle glaucoma is painless and slowly progressive. A patient may
not know that he or she is affected until it is too late. This slow
build up of pressure damages the optic nerve over months to years.
Treatment is usually with eye drops, although lasers or surgery can be
employed.
Who is at risk?
Narrow angle glaucoma usually affects people who are
hyperopic (far
sighted) and older. Previous eye trauma, diabetes or other eye pathology
are also risk factors. Open angle glaucoma can occur in anybody, but
certain demographic subpopulations are more prone. Older people, people
of African American decent, myopes (near sighted people), diabetics, and
folks with a family history of glaucoma are more at risk. However,
glaucoma can affect anyone, even children and people with otherwise
healthy eyes.
Screening and Detection
While it is sometimes obvious, frequently glaucoma is a difficult
diagnosis to make in its early stages. Ophthalmologists exam the eye for
pressure, optic nerve abnormalities and visual field defects. Other
tests such as nerve fiber layer and corneal thickness evaluations are
also reviewed. Early diagnosis is essential since prompt treatment is
readily available and can prevent irreversible vision loss.
Treatment and Prognosis
As mentioned early, treatment of narrow angle glaucoma is usually
definitive and future attacks are unlikely. Usually a painless laser is
used to create a small hole in the iris to allow better drainage.
Sometimes eye drops or oral medications can be given to temporarily or
permanently reduce the eye pressure or open the angle.
Open angle glaucoma requires a life long commitment to eye drops
although lasers and surgery can be used. Typically, with the ease of use
and minimal side effects, eye drops are employed first. Often more than
one type of drop is needed. Lasers or surgery to increase drainage are
reserved for advanced glaucoma or in patients unable to tolerate the
drops. Glaucoma treatment can be highly successful in a patient who
takes his or her drops properly and returns for routine monitoring. A
long life of normal vision is the goal of glaucoma treatment and is
often achieved with minimal side effects.
But getting checked is the first step.
~ Peter S. Schwartz, MD
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