Glaucoma: A group of disorders characterized by
abnormally high IOP (Intraocular pressure). Glaucoma is an increase
in IOP causing changes in the optic disk (nerve). It occurs in three
primary forms: 1.) chronic open-angle (primary), 2.) acute closed-angle,
3.) congenital. It may also be secondary to other causes. In the
united States approximately 12% over the age of 40 accounts for new
cases of blindness. Prognosis is good with early treatment.
Cause: Chronic open -angle glaucoma results from over production
of aqueous humor or obstruction of its outflow through the trabecular meshwork
or the canal of Schlemm. Most common glaucoma affecting 90% of all
patients.
Acute closed -angle glaucoma, also called narrow-angle glaucoma, results
from obstruction to the outflow of aqueous humor from anatomically narrow
angles between the anterior iris and the posterior corneal surface.
It also results from shallow anterior chambers, a thickened iris that causes
angle closure on pupil dilation, or a bulging iris that presses on the
trabeculae, closing the angle – peripheral anterior synechiae
Congenital glaucoma is inherited as an autosomal recessive trait.
Secondary glaucoma can result from uveitis, trauma, or drugs such as corticosteroids.
Vein occlusion or diabetes can cause neovascularization in the angle.
Symptoms:
Mild aching in the eyes
Gradual loss of peripheral vision
Seeing halos around lights
Reduced visual acuity (especially at night, that is not correctable
with glasses)
The onset of acute closed-angel glaucoma is typically rapid, constituting
an ophthalmic emergency. If not treated promptly, this glaucoma produces
blindness in the affected eye in 3 to 5 days. Symptoms may include:
Unilateral inflammation and pain
Pressure over the eye
Moderate pupil dilation that’s nonreactive to light
Cloudy cornea
Blurring and decreased visual acuity
Photophobia
Seeing halos around lights
Nausea and or Vomiting
Treatment:
For chronic open-angle glaucoma: to decrease IOP through administration
of beta-blockers, such as timolol or betaxolol, epinephrine, or diuretics,
such as acetazolamide.
Drug treatment may also include: miotic eyedrops – to facilitate
outflow of aqueous humor
Argon laser trabeculoplasty or surgical filtering procedure called trabeculectomy
– which creates an opening for aqueous outflow. (This may be done
if drug therapy does not work)
For treating acute closed-angle glaucoma as an emergency, drug therapy
may lower IOP. If pressure does not decrease, laser iridotomy or
surgical peripheral iridectomy must be performed immediately to save the
patient’s vision.
Iridectomy relieves pressure by excising part of the iris to reestablish
aqueous humor outflow. A prophylactic iridectomy is performed a few
days later on the normal eye.
Narcotic analgesics may be needed for pain.