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Red Eye
The most common change in appearance is a red eye. Redness is usually due to dilation of blood vessels in the eye, usually in the thin membrane that covers the insides of the eyelids (conjunctiva), but sometimes in other eye structures such as the white of the eye (sclera), the connective tissue layer between the sclera and the conjunctiva (episclera), or the circular, colored area of the eye (iris) and nearby structures (uveal tract). Dilation is the result of inflammation, which can have many causes.
Many conditions dilate the blood vessels in the conjunctiva, including fatigue, allergies, infections, abrasions or ulcers of the cornea, and foreign bodies in the eye.
Conditions that inflame the sclera, episclera, and uveal tract include episcleritis, scleritis, and acute closed-angle glaucoma. These conditions usually also cause eye pain.
Sometimes redness is caused by bleeding of vessels in the conjunctiva. A forceful cough or a direct blow can cause a blood vessel in the conjunctiva to burst, resulting in a solid, bright red patch of blood on the sclera. Sometimes the bleeding turns the whole sclera bright red. With an allergy or a bacterial infection, the eyelids and other tissue around the eye may also become red, swollen, or both.
An eye examination usually reveals the cause of red eye, particularly if a slit-lamp examination is done. The cause is treated. Doctors do not usually recommend using eye drops, such as tetrahydrozoline, that simply shrink the dilated blood vessels.
Dark Spots
Dark (pigmented) spots can appear on the iris or conjunctiva. Some are present at birth, and others may appear with age. Although often insignificant, any dark spot that grows should be evaluated by an ophthalmologist to ensure that it is not cancer.
Pupil Size
Normally, both pupils (the black area in the middle of the iris) are the same size. Pupils become large (dilate) in the dark and become small (constrict) in bright light. Although some people have much larger pupils than others, large or small pupils by themselves do not necessarily indicate a problem or abnormality. The pupils tend to become smaller with age. Constricted or dilated pupils may be caused by certain drugs used to treat eye diseases. Pupil constriction may be caused by opioid drugs, such as morphine. Pupil dilation may be caused by amphetamines, antihistamines, cocaine, and marijuana. Small, irregularly shaped pupils may be caused by syphilis.
Unequal pupils (one large and one small) may be caused by conditions that affect one eye differently than the other. Such conditions may include injury or inflammation of the eye, injury of the nerves that control the pupil, head injury, brain tumors, and using eye drops in only one eye. Rarely, a person is born with pupils of different sizes.
During a complete eye examination, doctors shine light into each pupil, which causes them to constrict. No treatment is needed to modify pupil size.
Inflammation Around the Eye
The eyelids and tissues around the eyes may become swollen, red, or both as a result of allergy, infection, or other inflammation. Disorders can involve the eyelids (as in a chalazion, stye, or blepharitis), tear ducts (as in dacryocystitis), or sinuses. The roots of the eyelashes may become infected, sometimes resulting in the eyelashes falling out. Allergies or infections may also lead to abnormal secretions from the eyes, which may harden (crusting) and cause difficulty in opening the eyes when waking.
An eye examination, including a slit-lamp examination, is usually done. If infection is suspected, a culture (the process of growing a sample of the eye cells in a laboratory) may be needed. Doctors sometimes need to determine whether the sinuses are infected, which may require imaging studies such as a computed tomography (CT) scan. The cause is treated.
Other Changes
The sclera become yellow, as does the skin, in people who have jaundice (see Manifestations of Liver Disease: Jaundice). The eyelids may droop (ptosis). Ptosis may occur in people who have myasthenia gravis (see Peripheral Nerve Disorders: Myasthenia Gravis) and disorders that cause nerve damage. Sometimes the eyes are unusually wide open and prominent, usually because they are being pushed forward (exophthalmos). Exophthalmos can occur in people who have Graves' disease (see Thyroid Gland Disorders: Causes).
People with these symptoms require an eye examination and a general medical evaluation. Treatment is directed at the cause.
Last full review/revision December 2006 by Kathryn Colby, MD, PhD
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