Bacterial Corneal Ulcer
Name: Paul D Chamberlain, 4th year medical student, Baylor College of Medicine; Dr. Amy Lin, Associate Professor, University of Utah Moran Eye Center.
Topic: Bacterial Corneal Ulcer
The cornea is the “window” of the eye and consists of five layers (from anterior to posterior): the epithelium, anterior limiting lamina (i.e. Bowman’s layer), stroma, endothelial basement membrane (Descemet’s membrane), and endothelium (image 1). Like ulcers elsewhere in the body, a corneal ulcer is a complete disruption of the epithelial cell layer with an inflammatory response. Unlike other areas of the body, the cornea is dehydrate and avascular which both contribute to its impressive clarity and transparency. The avascular nature of the cornea, however, poses a challenge for the body to fight off infections due to an impaired ability for the immune system to access the infection. For this reason, corneal infections require topical antibiotics and urgent attention.
Corneal ulcers are generally due to bacterial infection, and occur most frequently in patients wearing contact lenses, especially if worn through the night. Bacterial corneal ulcers may also develop secondary to corneal abrasions, blepharitis, or ocular trauma and can be fungal, parasitic, viral or sterile (auto-immune) in addition to bacterial. Patients typically complain of decreased vision, severe pain, redness, or light sensitivity. On physical exam the patient will have injected conjunctiva with a dense collection of inflammatory cells in the cornea called an “infiltrate” (image 2). Marginal corneal ulcers are more commonly multiple and in the periphery of the cornea (where it meets the sclera). These may be due to an immune reaction to staphyloccal toxins from chronic blepharitis (eyelid infection). In severe corneal ulcers, there can be a hypopyon, or dense collection of white blood cells in the anterior chamber (image 4).
Critical to the management of corneal ulcers is assessing the depth of involvement of the cornea and assessing for potential perforation (image 3). This is accomplished with the seidel test. In the seidel test, a small amount of fluorescein dye is placed on the area of ulceration. Using a UV light (either in a slit lamp or with a wood’s lamp) the examiner looks to see if the dye begins to drain down from the ulcer and becomes less bright, indicating that it is being diluted by fluid leaking from the eye. If there is leakage, this is considered “seidel positive.”
Corneal ulcers are an ocular emergency and patients should be referred to an ophthalmologist immediately, as a delay in treatment may result in corneal perforation, endophthalmitis (infection of the entire eye), and/or permanent corneal scarring and subsequent visual impairment. Central corneal ulcers are generally more serious than marginal corneal ulcers. Patients should not be given topical analgesics such as proparacaine for pain relief as continued use horrifically damaging to the eye. To help with pain control, the patient should be prescribed topical parasympatholytics such as atropine or cyclopentolate to reduce ciliary muscle spasm. Culturing the infection on presentation prior to starting treatments also helps guide management in complex or unusual cases.
Leitman MW. (2017). Manual for Eye examination and Diagnosis 9th Ed. Hoboken, NJ: John Wiley & Sons, Inc.