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1. What is the difference between iritis and conjunctivitis?

Uveitis is inflammation of one or all parts of the uveal tract, including the iris, the ciliary body, and the choroid.  So iritis is a Uveitis, but confined to the iris.  To distinguish iritis from conjunctivitis, notice where the conjunctiva is most red.  In iritis, the conjunctiva is most red at the border of the iris (peri-limbis), compared to conjunctivitis, where the conjunctiva is most red everywhere else but the limbis. (1)

Additionally, consensual photophobia (pain in the affected eye occurs when light is shown into the unaffected eye) occurs in iritis and not in conjunctivitis.

On slit lamp exam, if the patient has iritis, you may notice floaters in the anterior chamber (which represent WBC floating in the fluid).  Some describe this as ‘dust in a sunlit room,’ and this is called flair.

On slit lamp exam you may also notice precipitates (WBC) on the endothelium, which is a hallmark of iritis.

In 50% of cases, the cause of the iritis is unknown (1).  Other causes include trauma, inflammatory diseases (inflammatory bowel disease, reactive arthritis, ankylosing spondylitis) or infectious (herpes, toxoplasmosis, Lyme disease). (1)

The treatment is very different for these, that is why it’s important to distinguish them.

Conjunctivitis is usually treated with topical antibiotics (if bacterial or possibly bacterial), but patients with iritis need an ophthalmologist referral.    Complications from iritis include increased intraocular pressure (with subsequent damage to the optic nerve if not treated) from posterior synechiae.  (1).

Most cases of conjunctivitis are self-limiting, but if the patient is immunocompromised, the condition could progress to sight-threatening conditions.

A few things to remember about conjunctivitis:

1. In the neonate, consider Neisseria gonorrhoeae.  This type of infection can be invasive and can lead to rapid corneal perforation.  (2, 3)  This is much less common in the US with topical antibiotic treatment at birth.  It usually occurs on days 3-5 after birth.
2. Chlamydial conjunctivitis can also occur in neonates. It can also be associated with pneumonia (even up to 6 months after their conjunctivitis).  (3)  Again, this is not common in the US.  The incubation period for Chlamydial conjunctivitis is 5-14 days.
3. Neonatal Herpes conjunctivitis usually occurs in the first 2 weeks after birth. (3)
4. Trachoma infection is a chronic insidious Chlamydia Trachomatis infection.  It actually is the leading cause of blindness in the world, blinding 10% of those infected.  (2)

You need to ask about contacts.  Corneal abrasions are common when a patient sleeps with contact lens in, and college kids are likely to do this when they are either too tired from studying or partying to bother to take the contacts out.  The reason this is important is that if the corneal abrasion is related to a contact lens, the organism is more likely Pseudomonas.

The other question to ask is whether the visual acuity was taken with her glasses on.  Visual acuity testing in the ED is designed to determine if there is a new decrease in the ability of the patient to see.  To test visual acuity in a patient with poor vision, without their glasses on, is challenging to interpret. I usually test the vision with the glasses on (I want to know if the vision has acutely decreased).  If the photophobia is causing too much pain, I try checking visual acuity after applying a topical anesthetic.  If the patient doesn’t have their glasses with them, you can try using a pin hole.  Either way, it’s important to look for an acute decrease in vision, not if the patient has bad vision at baseline (i.e. find out if the baseline vision has gotten worse, not if the patient just needs glasses).

3. What is the difference between corneal abrasion and cornea ulcer?

Both can cause pain, red eye, and photophobia.  And both will appear as a red eye with significant limbic flush (due to irritation of the cornea).

A corneal abrasion is a very superficial defect in the cornea. A corneal ulcer is a much deeper injury and infection. Sometimes you may see the corneal ulcer even before staining.  The infection can be from a bacterial source or viral (herpes—which usually causes dendritic staining (see pictures).

Bacterial Ulcer.   Note the limbic flush.

Viral Ulcer (Herpes). Note the dendritic staining pattern.

In corneal ulcers, you may also see a hypopyon (a layering of WBC in the anterior chamber).

Herpes simplex virus is the most common cause of corneal ulcer in the US. (4)   Bacterial causes in the US include staphylococcal infection, Pseudomonas Aeruginosa, Streptococcus pneumonia, and Moraxella.  (4)  Pseudomonas Aeruginosa infections may have a bluish or green mucopurulent discharge.

Treatment for a corneal ulcer involves consultation with an ophthalmologist and antibiotics.  Treatment for a corneal abrasion involves topical antibiotics.  Topical non-steroidal anti-inflammatory drugs have been shown in Meta analysis to be effective pain medications to administer.  (5).   Eye patches have not been shown to improve outcome and are not recommended. (5).  For patients with corneal abrasions related to contact lens wear, consideration for possible pseudomonas infection and treatment with antibiotics to treat this infection should be used (ciprofloxacin, gentamicin, tobramycin, ect.). (5)  Its important to remind the patient NOT to wear the contact lens until they have been re-evaluated by the ophthalmologist.