Red Eye - Evaluation / DDx

Differential Diagnosis:

· Conjunctivitis (allergic, bacterial, viral, etc.): most common cause of a red eye.   
o   Allergic presents with watery discharge and itching, diffuse conjunctival redness in both eyes and atopic symptoms. 
o   Viral is usually preceeded by URI (usually progresses to both eyes). Herpes Zoster opthalmicus is an ophthalmologic emergency, leading to permanent blindness: associated headache with vesicular skin eruption in the distribution of the opthalmic branch of the trigeminal nerve—start antiviral therapy and immediate referral to optho.
o   Bacterial is usually unilateral, mucopurulent discharge, associated with crusting of the eyelashes in the morning.  Gonococcal conjunctivitis in sexually active young adults with copious purulent discharge can be blinding--requires culture, systemic abx and immediate optho eval.

· Subconjunctival Hematoma:  can result from coughing or straining, painless and spontaneously resolve over 2 weeks.  History is critical to rule out trauma or foreign body.

· Scleritis: severe, constant boring ocular pain, worse with eye movement, photophobia and raised hyerperemic lesion, which obscures the underlying vasculature (may be localized or diffuse).  Often associated with collagen vascular or autoimmune disease.  Can progress to orbiral rupture--urgent referral to optho.

· Episcleritis: red, flat more superficial lesion, which allows visualization of the underlying vasculature and sclera, can be mildly painful (generally self-limited)

· Uveitis: Uvea is derived from the Latin word for grape (ie. the eyeball); the anterior uvea includes the iris and ciliary body (which also makes the aqueous humor), the posterior uvea includes the choroid and retina.  Uveitis is associated with autoimmune diseases and some systemic infections (in the US, most common cause is ankylosing spondyltitis, followed by sarcoidosis). Refer to ophthalmology.
o   Anterior uveitis includes iritis or iridocyclitis (ciliary body inflammation).
o   Intermediate uveitis is inflammation of the vitreous humor
o   Posterior uveitis includes inflammation of the choroid and retina
o   Panuveitismeans that all portions of the uveal tract are inflamed.
o   Signs and symptoms depend on which portion of the uveal tract is involved:
§  Anterior uveitis presents as redness, pain, photophobia, ciliary injection and an irregular pupil (visual loss is variable, only if there is macular edema). 
§  Intermediate uveitis can present with "floaters" due to the inflammation in the vitreous fluid
§  Posterior uveitis does not often present with pain or redness, but visual loss is determined by degree of inflammation
Good photo of anterior uveitis, demonstrating an irregular pupil:  http://www.kellogg.umich.edu/theeyeshaveit/red-eye/anterior-uveitis.html

· Endopthalmitis: intraocular infection; can be postoperative (usually occurs within 6 weeks of surgery), or can occur as a rsuly of trauma/globe penetration, or from hematogenous (ie. candidemia) or local spread of infection (ie. sinusitis).  Symptoms include decreased viual acuity, red painful eye, corneal edema, hypopyon (pus in the anterior chamber).  Emergency referral to optho.

· Acute angle-closure glaucoma: acute onset of severe pain, red eye, blurred vision, frontal headache, halos around lights, increased intraocular pressure, mildly dilated, sluggish pupil. Emergency referral to optho.

· Corneal conditions: prominent “foreign body” sensation, blinking, tearing; flourescein stain is helpful in diagnosis.  Ddx includes keratitis (viral, bacterial, non-infectious), ulceration, abrasions.  Often need referral to ophthalmology to rule out foreign body, HSV, or ulcer.

· Other: blepharitis, chemical injury, trauma, orbital cellulitis (see below)

(Victoria Kelly MD, 5/24/11)