Red Eye

We commonly think of “Red Eye” as a main symptom, whereas we’ d be less likely to miss serious eye disease if we thought instead of “Painful Eye” vs. Red Eye without real pain.

To skim through the clinician’s thought-process, scroll through first the non-serious causes, looking for clues like types of discharge, etc. Then we’ll discuss the serious causes. For more in-depth discussion & explanations, see Red Eye — Full Text. See also Diagrams — Eye Anatomy.

Causes of Red Eye(s)

xxxxxxxxNo Eye Pain  xxxxxxxxPainful  !!!  
โ€ข Viral Conjunctivitis (“pink-eye”)
โ€ข Bacterial Conjunctivitis
โ€ข Herpes Conjunctivitis
โ€ข Allergies (Airborne & Contact allergies)
โ€ข STD Causes (Gonorrhea, Chlamydia)
โ€ข Foreign Body on Conjunctiva
โ€ข Episcleritis
โ€ข Pterygium (inflamed)
โ€ข Subconjunctival Hemorrhage
โ€ข Corneal Abrasion / Foreign Body
Corneal Ulcer / Keratitis
โ€ข Scleritis
โ€ข Iritis / Uveitis
โ€ข Optic Neuritis (eye often not red)
โ€ข Acute Closed-Angle Glaucoma
โ€ข Corneal Abrasion (recurrent)
โ€ข Contact Lens Wearer

xxxxxxSee also Diagrams — Eye Anatomy

Painful Red Eye  =  Very Serious !!!

  • True Eye Pain!ย  Worse than a scratchy, gritty, itchy, irritating sensation like “something-stuck-in-eye”
  • Except for the Corneal Abrasion, we send all other truly painful red eyes to an ER which has an ophthalmologist on-call, or to an ophthalmologist if same-day appointment available

New Vision Changes (measured formally) โ†’ urgent ophthalmology evaluation

  • Be sure apparent vision deficit is real, by Pinholing


Thin, Watery Discharge:  Most likely Viral or Allergic Conjunctivitis

1.  Symptoms present under 3 weeks, No other diagnosis below likely

            >>  Viral Conjunctivitis

2.  Both Eyes Red, PLUS any of following:

  • Other Hay Fever symptoms (runny nose, sneezing); OR
  • Symptoms present over 3 weeks; OR
  • Frequent recurrent bouts

            >> Allergic Conjunctivitis

3.  History of recent eye-drop use; OR Lots of eye cosmetics

            >> Contact Allergy

4.  Follicles inside lining of lower lid; Symptoms present several wks (esp. if recent genital STD)

            >> Chlamydia Conjunctivitis [picture in link]

5.  Groups of blisters on an eyelid.  Only one eye involved.

            >> Herpes simplex Conjunctivitis

6.  One-sided red eye, and Foreign Body noted (may need to look under upper lid)

            >> Foreign Body on Conjunctiva

6a. If symptom of Foreign Body began where people were cutting or hammering steel

            >> refer to an Ophthalmologist (see link Foreign Body)

7.ย  Local Redness, only the eye, & NOT the inside lining of lower lid.ย  Often NO tearing or discharge

            >> Episcleritis  [picture in link]

Thick Discharge

1.  Profuse discharge, wipe it away & more recurs within minutes (white / yellow / green):

            >> Bacterial Conjunctivitis

2.  Discharge horrible, covers the entire eye (esp. if genital STD symptoms)’; Swelling of conjunctiva

            >> maybe Gonorrhea [picture in link].  Send to ER (may need IV antibiotics)

No Discharge

1.  Localized Redness in just one part of eye, with NO redness inside lining of lower eyelid

2.  Conjunctiva Red, both over eye(s) & also lining of the eyelid(s)

  • Usually an itchy sensation
  • Symptoms less than 3 weeks, and no other diagnosis above likely

            >> Viral Conjunctivitis


1. Vomiting, Severe Eye Pain, Cloudy Cornea

            >> Acute Closed-Angle Glaucoma:  send straight to ER for surgery

2. Spot on Cornea (might only see by staining)

            >> Keratitis:   send right to ophthalmologist, via ER if specialist available

3. Severe pain, worse with eye movement

  • Bluish hue to sclera
  • Tender eyeball (by gently wiggling it through the closed eyelid)

            >> Scleritis:  send right to ophthalmologist, via ER if specialist available

4. Non-reactive pupil (usually tiny) &/Or Pain in red eye when light shined in other eye

            >> Iritis:  Call ophthalmologist

5. Abnormal pupils by Swinging Flashlight Test (see Afferent Pupillary Defect)

  • Pain maybe worse with eye movement.
  • Eye may not look red.

            >> Optic Neuritis:  Call ophthalmologist

6. Contact Lens Wearer with new eye pain โ†’  Beware early Corneal Ulcer

  • If lens has been out for a day, & still painful, send right to ophthalmologist, via ER if specialist available
  • If lens recently out, and pain getting worse, won’t let up, send right to ophthalmologist, via ER if specialist available
  • If spot noted on cornea, send right to ophthalmologist, via ER if specialist available
  • If lens still in, question sanity. Remove lens ASAP !!!

7. Same-day trauma, and fluorescein staining shows a Corneal Abrasion

  • If pain in eye when light shined in other (non-painful) eye: send right to ophthalmologist, via ER if ophthalmologist available
  • If a topical anesthetic didnโ€™t relieve the pain for a few minutes, the injury is also deeper than the cornea:  send right to ophthalmologist, via ER if specialist available there
  • If neither of above (temporary pain relief obtained by topical anesthetic):
    • No Eye Patch (studies show it delays healing)
    • Pain medicine (even narcotics) for 1 day
    • If not all better in 24 hours, send right to ophthalmologist (this is rare)

See also Red Eye โ€” Full Text for more in-depth explanations and discussions.

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