ASTIGMATISM. Though the cornea has no BLOODves-
sels it has numerous NERVEendings that make it
highly sensitive. Because it is the outermost por-
tion of the eye, the cornea is also highly vulnera-
ble to injury.
For further discussion of the cornea within the
context of ophthalmologic structure and function
please see the overview section “The Eyes.”
See also CORNEAL INJURY; CORNEAL TRANSPLANTA-
TION; LENS; REFRACTIVE ERRORS.
corneal injury Lacerations, punctures, and blunt
trauma to the CORNEA. Because of its position,
somewhat protruding at the front of the EYE, the
cornea is at risk for damage that can jeopardize
vision.
Corneal injuries require immediate
medical attention. Any puncture or
penetrating wound to the eye is a med-
ical emergency. Loosely patch botheyes
to minimize eye movement.Dust, dirt, pollen, and other particulates in the
air can scratch the surface of the cornea. Particles
that adhere to the inside of the upper eyelid or
objects that slash across the cornea before the eye-
lid reflexively closes may cause lacerations (cuts)
to the cornea. Though the cornea has no blood
vessels and thus cannot bleed, it has numerous
nerve endings that unmistakably sound the alert
when injury occurs. Injury to the cornea also can
diminish VISUAL ACUITY. Puncture or penetrating
injuries can destroy the cornea and expose the
inner eye to traumatic damage as well as
INFECTION. Even minor ABRASIONSand lacerations
can cause temporary vision impairment as well as
present the risk for infection. Loss of the eye is
possible when a significant penetrating wound
allows the inner contents of the eye to escape.
Symptoms of corneal injury include
- discomfort ranging from a scratchy sensation to
frank PAIN - PHOTOPHOBIA(sensitivity to light)
- excessive tearing
- inability to keep the eye open
- blurred or distorted vision
The ophthalmologist can identify a corneal
injury with FLUORESCEIN STAINING, a simple and pain-
less procedure. Any areas of injury on the cornea
absorb the fluorescein dye, causing them to glow
green under blue light. Serious injuries to the
cornea, or embedded foreign objects, may require
immediate surgery to minimize loss of vision.
Treatment for injuries that affect only the surface of
the cornea may include ophthalmic ANTIBIOTIC MED-
ICATIONS(drops or ointment) and patching of the
affected eye. Protective eyewear, worn whenever
there is the potential for particles or objects to strike
the eye, helps prevent corneal injuries.
See also CORNEAL TRANSPLANTATION; TRAUMA TO
THE EYE.corneal transplantation The replacement of a
diseased CORNEAwith a healthy donor cornea. In
the United States, ophthalmologists perform more
than 45,000 corneal transplantations each year;
up to 90 percent of people who receive trans-
planted corneas experience restored vision; suc-
cess depends on the reason for the transplant.
Ophthalmologists may recommend corneal trans-
plantation to treat:- BULLOUS KERATOPATHY
- KERATOCONUS
- KERATITIS
- significant CORNEAL INJURY
Donor corneas are harvested within a few
hours of death and can be preserved for up to 14
days. Current practice does not employ blood type
or tissue type matching for corneal transplanta-
tion, though some studies suggest matching the
blood type of donor and recipient reduces the risk
for rejection.CORNEA DONATION
Nearly anyone can donate his or her corneas
after death. There is no cost to the donor. An eye
bank coordinates the harvesting, testing, storage,
and dispensing of donated corneas. Many states
incorporate organ donor authorization with dri-
ver’s licenses. People should tell family members
that they wish to donate their corneas.corneal transplantation 81