Merck Manual

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Other Eye Symptoms


Christopher J. Brady

, MD, Wilmer Eye Institute, Retina Division, Johns Hopkins University School of Medicine

Last full review/revision May 2021| Content last modified May 2021
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Dry eyes

The disorder is most often idiopathic or associated with older age but can also be caused by connective tissue diseases (eg, Sjögren syndrome, rheumatoid arthritis, systemic lupus erythematosus). See Keratoconjunctivitis Sicca for a discussion of dry eyes.

Eye discharge

Discharge is often accompanied by a red eye and commonly is caused by allergic or infectious conjunctivitis, blepharitis, and, in infants, ophthalmia neonatorum (neonatal conjunctivitis). Infectious discharge may be purulent in bacterial infection, such as staphylococcal conjunctivitis or gonorrhea. Less common causes include dacryocystitis and canaliculitis.

Diagnosis is usually made clinically. Allergic conjunctivitis can often be distinguished from infectious by predominance of itching, clear discharge, and presence of other allergic symptoms (eg, runny nose, sneezing). Clinical differentiation between viral and bacterial conjunctivitis is difficult. Cultures are not usually done, but are indicated for patients with the following:

  • Clinically suspected gonococcal or chlamydial conjunctivitis

  • Severe symptoms

  • Immunocompromise

  • A vulnerable eye (eg, after a corneal transplant, in exophthalmos due to Graves disease)

  • Ineffective initial therapy


Halos around light may result from cataracts; conditions that result in corneal edema, such as acute angle-closure glaucoma or disorders that cause bullous keratopathy; corneal haziness; mucus on the cornea; or drugs, such as digoxin or chloroquine.

Blue hues

Certain conditions may cause a blue tint to the visual field (cyanopsia), such as cataract removal or use of sildenafil. Cyanopsia may occur for a few days after cataract removal or as an adverse effect of sildenafil and possibly other phosphodiesterase-5 (PDE5) inhibitors.


Scotomata are visual field deficits and are divided into

  • Negative scotomata (blind spots)

  • Positive scotomata (light spots or scintillating flashes)

Negative scotomata may not be noticed by patients unless they involve central vision and interfere significantly with visual acuity; the complaint is most often decreased visual acuity. Negative scotomata have multiple causes that can sometimes be distinguished by the specific type of field deficit as identified by use of a tangent screen, Goldmann perimeter, or computerized automated perimetry (in which the visual field is mapped out in detail based on patient response to a series of flashing lights in different locations controlled by a standardized computer program).

Positive scotomata represent a response to abnormal stimulation of some portion of the visual system, as occurs in migraines.

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