Corneal Abrasions - Eye emergencies

Cornea

The cornea is a transparent layer over the anterior part of the eye that serves as a  protective coat, aids refraction, and filtration of some UV light. Cornea has no blood vessels and receives nutrients through tears as well as from the aqueous humor. It is innervated primarily by the ophthalmic division of the trigeminal nerve and the oculomotor nerve.

https://www.allaboutvision.com/resources/cornea.htm

Corneal Abrasion

Corneal abrasion is the most common form of eye trauma presenting to the emergency department. Abrasions may result from contact lens wear, foreign objects blown into eyes or other trivial trauma. Patients present with a feeling of foreign body sensation, photophobia, and tearing. It is important to enquire about the work circumstances and the mechanism of injury because injuries with the use of high-speed machine are associated with corneal laceration and globe perforation. 

Examination (Evert the eyelids to look for a foreign body)

• Exam reveals conjunctival injection, tearing, and lid swelling. 
• Blepharospasm may accompany due to severe pain (may require a topical anesthetic to do the examination). Relief of pain with topical anesthesia is virtually diagnostic of corneal abrasion. 
• Photophobia 
• Decreased visual acuity (if the abrasion is in the central visual axis or if there is an associated iritis)
• Use Seidel's test to check for open globe injury 

The corneal abrasion is often visible to the naked eye as an irregular area of light reflection off the cornea

• Slit lamp examination: Shows a flare and cells from iritis if the abrasion is large and >24 hours old. It is crucial to check the entire thickness of the cornea for a full-thickness laceration, and the Seidel test should be negative. The abrasion usually appears as a superficial, irregular corneal defect appearing bright green under the cobalt blue light after instillation of fluorescein.

A series of small, fine-lined vertical/linear corneal abrasions seen with fluorescein staining suggests the presence of a foreign body embedded in the tarsal conjunctiva of the upper lid

Treatment

Majority of corneal abrasions heal spontaneously and thus treatment is aimed at relieving pain and preventing infection. 

Cycloplegics - Believed to relax the ciliary body and relieve pain from spasm (However, no good evidence exists in the literature to support the common practice of using cycloplegics/mydriatics for the treatment of routine corneal abrasions)

Pain Relief: Traditionally, these agents have never been prescribed for home use, because they may cause a secondary keratitis, compromise epithelial wound healing, and block effective corneal protective reflexes and sensation. Topical NSAIDs provide pain relief and do not impair healing in patients with corneal abrasions. 

Antibiotics
Topical antibiotics ointment are usually prescribed

• Non-contact lens wearers: erythromycin ointment.
• Contact lens wearers: cover for Pseudomonas species (ophthalmic ciprofloxacin, ofloxacin, etc.)

Antibiotic drops are more comfortable than ointments but must be administered every 2-3 hours. Ointments that retain their antibacterial effect longer can be used less often (every 4-6 h) but are more uncomfortable due to visual blurring.

Patching no longer recommended for abrasions involving < 50% of the cornea. A meta-analysis of 7 trials in patients with corneal abrasion showed similar healing rates between patching and no patching. Patching the eye does not promote healing. Abrasions from fingernails, vegetable matter, or a contact lens should not be patched, as they are at higher risk of infection.

Tetanus prophylaxis

Consult Ophthalmology in ED for:

• Large abrasions (involving > 50% of the cornea)
• Findings suggestive of corneal ulceration.
• Inability to remove retained FB.
• Hypopion

Smaller abrasions should be checked in 48 to 72 hours. 

Further Reading:

• Flynn CA, D'Amico F, Smith G. Should we patch corneal abrasions? A meta-analysis. J Fam Pract. 1998 Oct. 47(4):264-70.
• http://rebelem.com/topical-pain-control-for-corneal-abrasions/
• https://anatomyforemergencymedicine.wordpress.com/2015/05/03/031-eye-anatomy-part-2/

Posted by:

              

     Lakshay Chanana

     

     ST4 Trainee

     Royal Infirmary of Edinburgh

     Department of Emergency Medicine

     Edinburgh

     Scotland

     @EMDidactic