INTRODUCTION	Section 2 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

Background: Because of its potential to permanently impair vision or perforate the eye, a corneal ulcer is considered an ophthalmologic emergency. While corneal ulcers occasionally may be sterile, most are infectious in etiology. Ulcers due to viral infection occur on a previously intact corneal epithelium. Bacterial corneal ulcers generally follow a traumatic break in the corneal epithelium, thereby providing an entry for bacteria. The traumatic episode may be minor, such as a minute abrasion from a small foreign body, or it may result from such causes as tear insufficiency, malnutrition, or contact lens use. Increased use of soft contact lenses in recent years has led to a dramatic rise in the occurrence of corneal ulcer, particularly due to Pseudomonas aeruginosa. In addition, with the introduction of topical corticosteroid drugs in the treatment of eye disease, fungal corneal ulcers have become more common.

Peripheral ulcerative keratitis (PUK) is a complication of rheumatoid arthritis (RA) that can lead to rapid corneal destruction (corneal melt) and perforation with loss of vision.

Mooren ulcer is a rapidly progressive, painful, ulcerative keratitis, which initially affects the peripheral cornea and may spread circumferentially and then centrally. Mooren ulcer can only be diagnosed in the absence of an infectious or systemic cause.

Pathophysiology: Klebsiella pneumoniae mucoid phenotype and its ability to form biofilm may be important in producing a corneal ulceration. Agents, such as N-acetylcysteine, may have a role in treatment because they inhibit biofilm formation.

Mooren ulcer is an idiopathic ulceration of the peripheral cornea, which may be due to an autoimmune reaction or it may be associated with the hepatitis C virus.

Frequency:

• Internationally: A study from the United Kingdom reports factors associated with an increased risk of a corneal invasive event: wearing extended-wear hydrogel lenses, male gender, smoking, and the late winter months (March > July).

  Authors from the United Kingdom also report an 8 times higher incidence of corneal invasive event in contact lens wearers who sleep in contact lenses compared with wearers who use lenses only during the waking hours.

Mortality/Morbidity: Corneal scarring and vision loss are possible.

Sex: Studies from the United Kingdom suggest that males who wear extended-wear contact lenses are at increased risk of forming a corneal ulcer.

Age: Corneal injury or infection can affect people of all ages.

However, young adults (aged 21-30 y) have been found to have a high incidence of corneal ulcer. This association is probably due to the fact that young adults are likely to use extended-wear contact lenses.

	CLINICAL	Section 3 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

History: Important information includes contact lens use, recent trauma, previous ocular surgery or injury, and presence of systemic or ocular disease. Question the patient regarding use of ocular medications such as topical steroids.

• Erythema of eyelid and conjunctiva

• Mucopurulent discharge

• Foreign body sensation

• Blurred vision

• Light sensitivity

• Pain

• Contact lens profile - Extended wear, daily wear, worn during sleep, lens cleaning system

• Collagen vascular disease (rheumatoid arthritis)

• Smoking history

• Diabetes mellitus

• Exposure to sulphur mustard

• Inquiring about the dietary habits of a patient with a corneal ulcer is important because vitamin A deficiency is associated with corneal ulcer formation.
  • Inadequate vitamin A can occur in a patient with an intentional diet deprivation or unintentional deprivation found in young children and pregnant women from Africa and Southeast Asia.

  • Secondary vitamin A deficiency may be found in a patient with celiac disease, sprue, cystic fibrosis, pancreatic disease, duodenal bypass, congenital partial obstruction of the jejunum, obstruction of the bile ducts, giardiasis, and cirrhosis.

Physical:

• Visual function is affected variably, depending on the location of the ulcer and whether associated corneal and uveal inflammation is present. Obtain visual acuities on all patients with ocular complaints.

• Examination of the lids and the conjunctiva may reveal associated inflammation in these locations.

• The eye is typically erythematous, and ciliary injection is often present. Pupillary constriction is usually present secondary to ciliary spasm and iritis.

• Purulent exudate may be seen in the conjunctival sac and on the surface of the ulcer, and infiltration of the stroma may result in a creamy opacity of the cornea. The ulcer often is round or oval, and the border generally is demarcated sharply, with the base appearing ragged and gray.

• Slit-lamp examination may reveal findings of iritis, and hypopyon may be present. Hypopyon is an accumulation of inflammatory cells in the anterior chamber that produces a layered meniscus in the inferior anterior chamber.

• Fluorescein staining may reveal the characteristic dendritic ulcer of herpes simplex virus (HSV) infection.

• A Wood lamp may be useful, since the ulcer associated with P aeruginosa fluoresces in ultraviolet light.

Causes:

• Herpes simplex virus infection
  • HSV is the most common cause of corneal ulcer in the US. Although not always present, the classic finding in HSV infection is a branching dendritic ulcer.

  • Infection with HSV may interfere with corneal sensation, resulting in corneal anesthesia.

• Traumatic corneal injury

• Contact lenses, particularly soft lenses

• Chronic topical steroid use

• Varicella-zoster virus (VZV) infection
  • VZV can cause a corneal ulcer. Although corneal involvement can occur in varicella (chickenpox), it is uncommon and typically benign. The form of zoster (shingles) involving the ophthalmic branch of the trigeminal nerve is a more common corneal infection caused by VZV.

  • When herpetic eruption occurs along the nose, the nasociliary branch of the ophthalmic nerve is involved, indicating that corneal involvement is likely. This is known as the Hutchinson sign.

  • The dendritic pattern seen in HSV infection is not seen with zoster infection, although pseudodendrites, which only vaguely resemble true dendrites, may be present. Loss of corneal sensation is a prominent feature of zoster infection.

  • In contrast to the usual benign course in varicella and HSV, corneal complications in ophthalmic zoster can be severe and blinding.

• Bacterial infections
  • Numerous bacteria have been reported to cause corneal ulcer, although staphylococcal species, P aeruginosa, Streptococcus pneumoniae, and Moraxella species are reportedly the most common causes in the US.

  • Clinical characteristics of corneal ulcers caused by various bacteria are not sufficiently distinct to determine the causal bacterial agent, although a corneal ulcer having a bluish or green mucopurulent discharge is almost pathognomonic for P aeruginosa.

  • Most corneal ulcers are centered, but some occur at the periphery of the cornea (ie, marginal ulcers).

  • Although the location of the ulcer does not correlate well with the causative organism, a marginal ulcer is more likely to occur as a result of staphylococcal blepharoconjunctivitis. This ulcer is not due to direct bacterial infection but rather is an inflammatory reaction to staphylococcal bacterial antigens and toxins. The ulcer usually is self-limited and lasts from 7-10 days, but it is likely to recur unless the underlying blepharoconjunctivitis is treated.

• Fungal infections: Fungal ulcers are caused by Candida, Fusarium, Aspergillus, Penicillium, Cephalosporium, and mycosis fungoides species.

• Sulphur mustard