Encyclopedia of Health and Medicine

108 The Eyes
• INFECTION, such as BLEPHARITIS, CONJUNCTIVITIS, IRI-
TIS, HORDEOLUM, KERATITIS, UVEITIS
• CHALAZION
• ENTROPION
• Dirty contact lenses or contact lenses worn too
long
Photophobia that occurs with FEVER
may indicate MENINGITIS and requires
emergency medical attention.
The diagnostic path typically includes SLIT LAMP
EXAMINATION with FLUORESCEIN STAINING to determine
whether there is corneal injury and OPHTHAL-
MOSCOPY to evaluate the structures of the inner
eye. These examinations often require anesthetizing
drops in the eye to numb the discomfort the
lighted instruments cause. Treatment targets the
underlying cause, which, when resolved, generally
ends the photophobia. ANTIBIOTIC MEDICATIONS,
usually ophthalmic solutions or ointment placed
in the affected eye, are necessary to treat bacterial
infections. Wearing sunglasses to restrict the
amount of light that can enter the eye helps
reduce the sensitivity response. Some people are
naturally photophobic without underlying eye
conditions and should wear sunglasses for
improved comfort in bright-light settings.
See also BACTERIA; TRAUMA TO THE EYE.
phototherapeutic keratectomy (PTK) Treatment
with an excimer (cool) laser to smooth irregularities
and dissipate cloudiness in the CORNEA. PTK is
an AMBULATORY SURGERY procedure, with local anesthetic
to numb the surface of the EYE and a mild
sedative for comfort. The procedure takes 20 to 45
minutes, depending on the extent of corneal
sculpting needed. The ophthalmologist may prescribe
ophthalmic ANTIBIOTIC MEDICATIONS and antiinflammatory
medications after the procedure.
Changes in VISUAL ACUITY are generally complete in
one to two months.
CONDITIONS PTK CAN TREAT
ASTIGMATISM
corneal clouding
corneal degeneration
corneal dystrophy
corneal scarring
recurrent corneal erosion
recurrent KERATITIS
REFRACTIVE ERRORS
The risks and potential complications of PTK
include
• INFECTION
• worsened visual acuity
• RECURRENCE of the original problem
Most people experience improved visual acuity
or relief from corneal PAIN following PTK.
See also CORNEAL TRANSPLANTATION; SURGERY BENE-
FIT AND RISK ASSESSMENT.
pinguecula A thickened area of the conjunctival
tissue on the EYE, usually forming on the inner
(NOSE) side of the eye. A pinguecula may be clear,
yellow, or gray in color, and develops slowly. It
presents no threat to vision or the eye, and is
more common in people over age 50. Many people
do not notice that they have pingueculae or
consider them normal features of their eyes,
though some people experience irritation and a
sensation of grittiness in the affected eye. People
who spend a lot of time in the sun or have other
long-term ultraviolet light exposure are more
likely to develop a pinguecula. Ophthalmologists
recommend wearing sunglasses or protective eyewear
that filters ultraviolet light. There is no reason
to treat a pinguecula unless it puts pressure on
the CORNEA or otherwise interferes with vision.
See also CONJUNCTIVITIS; PTERYGIUM; SCLERITIS.
presbyopia A progressive change in the eyes
that occurs with aging, in which it becomes
increasingly difficult to focus on near objects.
Presbyopia occurs because the LENS loses
FLEXIBILITY, limiting its ability to adjust between
near and far focus. The lens becomes unable to
contract to thicken in the center as near focus
requires, resulting in the inability to see objects
that are close, such as when reading. Most people
begin to notice presbyopia when they reach their
mid-40s in age. People who have MYOPIA (nearsightedness)
may also find that their distant vision
improves as presbyopia advances. The EYE changes
responsible for presbyopia reach their end point
by about the mid-50s, after which the stiffening of
the lens stabilizes. Eyeglasses, contact lenses, and
surgery offer options for correcting presbyopia.