A corneal ulcer forms when the surface of the cornea is damaged or compromised. Ulcers may be sterile (no infecting organisms) or infectious. The term infiltrate is also commonly used along with ulcer. Infiltrate refers to an immune response causing an accumulation of cells or fluid in an area of the body where they don't normally belong.
Whether or not an ulcer is infectious is an important distinction for the physician to make and determines the course of treatment. Bacterial ulcers tend to be extremely painful and are typically associated with a break in the epithelium, the superficial layer of the cornea. In some cases, the inflammatory response involves the anterior chamber along with the cornea. Certain types of bacteria, such as Pseudomonas, are extremely aggressive and can cause severe damage and even blindness within 24-48 hours if left untreated.
Sterile infiltrates on the other hand, cause little if any pain. They are often found near the peripheral edge of the cornea and are not necessarily accompanied by a break in the epithelial layer of the cornea.
There are many causes of corneal ulcers. Contact lens wearers (especially soft) have an increased risk of ulcers if they do not adhere to strict regimens for the cleaning, handling, and disinfection of their lenses and cases. Soft contact lenses are designed to have very high water content and can easily absorb bacteria and infecting organisms if not cared for properly. Pseudomonas is a common cause of corneal ulcer seen in those who wear contact lenses.
Bacterial ulcers may be associated with diseases that compromise the corneal surface, creating a window of opportunity for organisms to infect the cornea. Patients with severely dry eyes, difficulty blinking, or who are unable to care for themselves, are also at risk. Other causes of ulcers include: herpes simplex viral infections, inflammatory diseases, corneal abrasions or injuries, and other systemic diseases.
Signs and Symptoms
The symptoms associated with corneal ulcers depend on whether they are infectious or sterile, as well as the aggressiveness of the infecting organism.
Severe pain (not in all cases)
White spot on the cornea, that depending on the severity of the ulcer, may not be visible with the naked eye
Detection and Diagnosis
Corneal ulcers are diagnosed with a careful examination using a slit lamp microscope. Special types of eye drops containing dye such as fluorescein may be instilled to highlight the ulcer, making it easier to detect.
If an infectious organism is suspected, the eye care practitioner may order a culture. After numbing the eye with topical anaesthetic eye drops, cells are gently scraped from the corneal surface and tested to determine the infecting organism.
The course of treatment depends on whether the ulcer is sterile or infectious. Bacterial ulcers require aggressive treatment. In some cases, antibacterial eye drops are used every 15 minutes. Steroid medications are avoided in cases of infectious ulcers. Some patients with severe ulcers may require hospitalization for IV antibiotics and around-the-clock therapy. Sterile ulcers are typically treated by reducing the eye's inflammatory response with steroid drops, anti-inflammatory drops, and antibiotics.
Illustrations by Mark Erickson
With acknowledgement to St. Lukes Eye Hospital.