P

papilledema Swelling of the optic disk, the point
at which the OPTIC NERVEenters the RETINA, that
results from increased pressure within the skull.
Papilledema typically signals serious neurologic
damage such as STROKEor TRAUMATIC BRAIN INJURY
(TBI) that causes bleeding (HEMORRHAGE), brain
tumor, extreme HYPERTENSION, or inflammatory
INFECTION such as ENCEPHALITIS and MENINGITIS.
Though papilledema is not a disorder of the EYE,
untreated it will result in complete loss of vision
because the swelling interrupts the flow of blood
to the optic NERVE.
Doctors check for any signs of papilledema dur-
ing a routine OPHTHALMIC EXAMINATION, as often
papilledema is an early sign of a neurologic prob-
lem. The need for intervention to relieve the
intracranial pressure is urgent, not only to pre-
serve vision but also often as a lifesaving measure.
The nature of the intervention depends on the
underlying cause. Extremely elevated blood pres-
sure points to hypertension as the cause; other
causes require NEUROLOGIC EXAMINATIONfor further
evaluation and diagnosis. With prompt treatment
to reduce the intracranial pressure, papilledema
typically resolves in about six to eight weeks and
vision, if affected, returns to its previous level.
Swelling around the optic disk may occur for
various reasons that are not the result of increased
intracranial pressure. These are usually ophthal-
mologic in nature, such as GLAUCOMAand ISCHEMIC
OPTIC NEUROPATHY. The conditions threaten vision,
but they are not life-threatening.
See also OPTIC NERVE ATROPHY; RETROBULBAR OPTIC
NEURITIS; TOXIC OPTIC NEUROPATHY.

papillitis INFLAMMATIONof the optic disk, the por-
tion of the OPTIC NERVEthat enters the RETINA(also
called the “blind spot”). Papillitis typically results

from, and may be an early diagnostic indicator of,

systemic inflammatory conditions such as MULTIPLE

SCLEROSISand temporal arteritis. The inflammation

also may follow viral or bacterial INFECTIONsuch as

SINUSITIS, especially in children, and occurs rarely

as a complication following stings from wasps and

bees. Papillitis often affects only one EYEthough

can involve both eyes. Within hours of its onset

the inflammation can cause complete loss of

vision in the affected eye. Rapid treatment to

reduce the inflammation, or to treat the underly-

ing condition causing the inflammation, can sal-

vage vision. However, loss of vision is often the

reason people seek medical attention, by which

time there may already be permanent damage to

the optic disk. Occasionally the inflammation

develops over the course of several weeks, pro-

ducing progressive loss of vision as well as loss of

color perception.

See also BACTERIA; PAPILLEDEMA; RETROBULBAR

OPTIC NEURITIS; TOXIC OPTIC NEUROPATHY; VIRUS.

photophobia Heightened sensitivity to bright

light, usually the result of INFLAMMATIONor irrita-

tion to structures of the EYE or with MYDRIASIS

(extended dilation of the pupil). Photophobia

causes discomfort in the eye ranging from a burn-

ing sensation to outright PAIN. Often there is exces-

sive tearing and the eye becomes reddened in

response to the irritation. In severe photophobia it

may be impossible to keep the eye open. Photo-

phobia is common in the HEALINGperiod following

CATARACT EXTRACTION AND LENS REPLACEMENT and

CORNEAL TRANSPLANTATION. Photophobia may be a

symptom of numerous conditions affecting the

eye, including

• CORNEAL INJURY, such as ABRASIONSand burns

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