Intern Diagnostics: Corneal Pathology

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Ophthalmologic complaints encompass 1.5% of total emergency department visits, with diseases of the cornea accounting for some of the most common. In this post, we will review four of the most common corneal pathologies as well as their acute management from the emergency department perspective.

The Cornea

The cornea is the most anterior structure of the eye. It performs the initial refraction of light onto the lens, and it acts a barrier between the internal structures of the eye and the outside world. The cornea is innervated by the ophthalmic branch of the trigeminal ganglion, and has 300-600 times the nociception of skin.

The cornea is divided into five distinct layers:

  • Epithelium

  • Bowman’s membrane

  • Stroma

  • Descemet’s membrane

  • Endothelium 

Keratitis

Bacterial keratitis with hypopyon - courtesy of Matthew Burton - CC BY-NC 2.0 - Original At https://www.flickr.com/photos/communityeyehealth/32271352440

This refers to inflammation of the cornea from any source. Keratitis is associated with corneal edema, the migration of inflammatory cells, and congestion. There are numerous causes of keratitis, which can be divided into infectious and non-infectious etiologies.

  • Infectious: Most commonly bacterial (Staphylococcus, Streptococcus, Pseudomonas), but can also be viral (HSV, VZV), fungal (Aspergillus, candida), or protozoal (acanthamoeba)

  • Non-Infectious: UV keratitis, peripheral ulcerative keratitis, xeropthalmia, neurotrophic corneal ulcers

Abrasions and ulcers are rwo pathologies that involve damage to the corneal epithelium are corneal abrasions and corneal ulcers, which together make up 13% of ophthalmologic emergencies.

Corneal Abrasion

Corneal abrasions are defects that are more superficial, only involving the epithelial layer of the cornea. Abrasions are typically the result of superficial trauma, such as from fingernails, debris, or contact lenses, but can also occur spontaneous particularly in patients with diseases causing dry eye. Corneal abrasions should be treated with topical antibiotics, typically erythromycin or ciprofloxacin for contact lens wearers to cover for pseudomonas.

corneal abrasion with fluoroscein uptake - Courtesy of Dr. James Heilman - CC by SA 4.0 - original at https://commons.wikimedia.org/wiki/File:Corneal_Abrasion_with_Fluorescein_Staining.jpg

DefinitionHistoryTreatmentOphtho Consult?
AbrasionEpitheliumAcute, traumaTopical erythromycinNo
UlcerStroma + infiltrateInsidious onsetStronger topical abx/antiviralsYes

Corneal Ulcer

Corneal ulcers also involve the epithelium, however they also extend through Bowman’s membrane into the stroma. Corneal ulcers typically begin as keratitis, and a break in the epithelium allows for microbial entry. The most common pathogens are consequently the same pathogens that cause keratitis, detailed above. As corneal ulcers are typically from an infectious source, corneal scraping for culture and sensitivities is an important part of the workup performed by ophthalmology. Corneal ulcers are typically treated with topical antibiotics or antivirals depending on anticipated etiology. In the emergency department, it is important to look at previous culture data for patients with recurrent ulcers. Certain etiologies such as gonococcus may require admission for IV antibiotics. Topical steroids have mixed utility, and decisions regarding the timing of their addition are typically left to ophthalmology and are dependent on sterility.

Endophthalmitis

Endophthalmitis denotes a purulent inflammation of the intraocular fluids, both aqueous and vitreous. Endophthalmitis most commonly occurs post-operatively, especially after cataract surgery, but also can occur after trauma or from endogenous spread. The vast majority of cases are due to gram positive bacteria, with the most frequent isolate being staph epidermidis. The hallmark physical exam finding of endophthalmitis is a hypopyon, which is a collection of white blood cells in the anterior chamber of the eye. Endophthalmitis can also be associated with more systemic symptoms, so blood cultures can be valuable. Treatment involves intravitreal injections of antibiotics and possible vitrectomy.

Corneal Foreign Body

Corneal foreign body with rust ring - Courtesy of Margreet Hogeweg - CC BY-NC 2.0 - original at https://www.flickr.com/photos/communityeyehealth/8408519738

Foreign bodies can lodge in any layer of the cornea. Specific considerations should be taken to address the nature of the foreign body itself. For example, organic material is associated with a higher risk of infection, metallic foreign bodies and leave a rust ring on the cornea, and the presence or absence of contact lenses can necessitate broader antibiotic coverage. Fluorescein exams are useful for detecting superficial foreign bodies and associated abrasions, whereas orbital CT scans may be useful for more deeply embedded objects or suspected penetrating objects. A notable physical exam finding is hyphema, or a collection of red blood cells in the anterior chamber, which indicates globe perforation. Globe perforation can also be detected on fluorescein exam with a positive Seidel sign. If there is concern for globe perforation, an ophthalmologist should be consulted immediately.

All foreign bodies should receive a thorough slit lamp exam, including examination of the entire eye, lash line, and upper eyelid. Multiple removal techniques can be utilized including irrigation, a damp cotton swam, a 25-30 gauge bevel of a needle, or a corneal burr. After extraction, patients should receive prophylactic topical antibiotics, a Tdap vaccination, and lubricating eyedrops.

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Cite As: Carroll K., LaFollette R. Intern Diagnostics: Corneal Pathologies. TamingtheSRU. www.tamingthesru.com/blog/diagnostics/corneal-pathology

Post by Katie Carroll, MD

Dr. Carroll is a PGY-1 in Emergency Medicine at the University of CIncinnati

Peer Editing and Post by Ryan LaFollette, MD

Dr. LaFollette is an Assistant Program Director and co-editor of TamingtheSRU.com