Corneal Abrasions, Erosion, and Ulcers

Overview

Anatomy

The cornea is a transparent, avascular part of the eye that covers the iris, anterior chamber, and pupil.

The corneal layers include: 

• Epithelium
• Bowman’s membrane
• Stroma
• Descemet membrane
• Stroma

Definition

Corneal epithelial defects are conditions that disturb the structural integrity of the cornea.

Corneal abrasions, erosions, and ulcers are defects in the corneal epithelium and are classified by the depth of involvement of corneal layers:

• Corneal abrasions are defined as a defect in the corneal surface epithelium. 
• Corneal erosions involve the corneal epithelium and epithelial basement membrane.
• Corneal ulcers (also known as ulcerative or bacterial keratitis) are a defect in the surface epithelium that involves the underlying stroma.

Epidemiology

• Corneal epithelial defects make up about 8%–13% of all emergency cases related to the eyes.
• More common in women 
• Corneal ulcers are much more common in those who wear contact lenses or wear contact lenses for extended periods of time. 
• Fungal corneal ulcers are more common in young men who are outdoor workers. 
• In tropical environments, fungal corneal ulcers make up about 50% of all cases of corneal epithelial defects.

Etiology

• Corneal abrasions: 
  • Traumatic corneal abrasions: 
    • By fingernails, paper, branches, paws, contact lenses
    • Foreign bodies in the eye
    • Contact lens–related abrasions
  • Spontaneous abrasions: 
    • May occur with no immediate injury
    • An underlying defect in the corneal epithelium (e.g., epithelial basement membrane dystrophy) may cause this problem.
• Corneal erosions:
  • Due to recurrent insult to the cornea and trauma
  • In cases of no obvious history of trauma, corneal epithelial, stromal, and endothelial dystrophies should be suspected.
• Corneal ulcers: 
  • Autoimmune:
    • Rheumatoid arthritis
    • Systemic lupus erythematosus
    • Connective tissue disorders
    • Vasculitis
  • Idiopathic: 
    • Referred to as Mooren’s ulcers
    • Noninfectious ulcerations
  • Bacterial:
    • Staphylococcus aureus
    • Pseudomonas aeruginosa
    • Streptococcus pneumoniae
    • Escherichia coli
  • Viral:
    • Herpes simplex 
    • Varicella zoster
    • Cytomegalovirus
  • Fungal:
    • Warmer climatic conditions after exposure of the corneal wound to plant/vegetative material or in individuals with prolonged use of steroids. 
    • Aspergillus, Fusarium, Candida albicans, and other Candida species are the most common fungal pathogens. 
  • Protozoa: Acanthamoeba is found in freshwater and in soil and can cause keratitis and corneal ulcers primarily in contact lens wearers.

Pathophysiology

• Corneal abrasions, erosion, and ulcers have similar pathophysiology. 
• These conditions are caused by insult or injury to the corneal epithelium and are due to various causes. 
• Abrasions occur when the wound includes only the surface epithelium. 
• Corneal erosions are a result of recurrent insult by abrasions or ulcers. 
• Together, these abrasions and erosions cause changes in the composition of the corneal layers and may cause a decrease in visual acuity. 
• Corneal ulcers occur in 4 stages when the wound includes the stroma and cellular infiltration:
  1. Progressive infiltration: characterized by the infiltration of lymphocytes into the epithelium
  2. Active ulceration: Active ulceration results from necrosis and sloughing of the epithelium, Bowman’s membrane, and the involved stroma.
  3. Regression: induced by the natural host defense mechanisms, and a line of demarcation develops around the ulcer
  4. Cicatrization: Healing continues by progressive epithelialization, which forms a permanent covering and scar.

Clinical Presentation

Individuals usually have a history of trauma to the globe, either by foreign body or finger.

• Corneal abrasions:
  • Severe pain
  • Photophobia
  • Reluctance to open the eye
  • Foreign-body sensation
• Corneal ulcers: 
  • Pain
  • Erythema of eyelid and conjunctiva
  • Discharge from the eye
  • Foreign-body sensation
  • ↓ Vision
• Corneal erosion:
  • Pain
  • Photophobia
  • Erythema
  • Tearing

Diagnosis

Physical examination

• Proper history taking and ophthalmic examination: 
  • History taking points toward the etiology of the condition and may provide a direction for further management.
  • A careful physical examination of the eye must be done to determine the extent of injury and to rule out any perforations or immediate loss of visual acuity. 
• Slit-lamp examination is the gold standard to detect corneal defects by examining: 
  • Corneal foreign bodies
  • Corneal epithelium
  • Corneal stroma, including ulceration, perforation, and infiltrates, and edema
  • Corneal endothelium
  • Signs of corneal dystrophies
  • Anterior chamber for depth and the presence of inflammation, including cell and flare, hypopyon, hyphema
    • Hypopyon, or pus in the anterior chamber, might be present in cases of infective corneal ulcer.
    • Hyphema, or blood in the anterior chamber, might be present in cases of penetrating injuries.
• Extraocular movements should be tested to rule out any pain with movement of the eye or double vision.
• Fluorescein dye examination must be done to confirm corneal abrasion. 
  • The dye stains the basement membrane brightly, which is exposed in the area of the injury.  
  • Defects light up green with a Wood’s lamp.
• Evert the eyelid to check for retained foreign body.

Management and Complications

Management

• Corneal abrasions:
  • Removal of foreign body, if present
  • Topical antibiotic therapy
  • Analgesia provided by cycloplegia
  • Pressure patch: 
    • Contraindicated in individuals with abrasions caused by contact lens wear or in cases in which foreign body is still present. 
    • Applied for  < 24 hours 
    • Promotes epithelial proliferation and migration, as the lid is kept stationary over the epithelial defect.
• Topical steroids must not be used in any case.

• Corneal erosions:
  • Recurrent (or spontaneous) corneal erosions are treated in the same way as traumatic abrasions. 
  • Lubricants are the 1st line of therapy
  • Analgesics
  • Topical antibiotics
  • Individuals unresponsive to lubrication or who have large erosions can be treated with an extended-wear bandage soft contact lens. 
  • In cases in which no improvement occurs, minor surgical procedures can be done:
    • Anterior stromal micropuncture: 
      • In cases of erosion outside the visual axis
      • Not a preferred method of treatment, as it causes scarring, glare, and blurred vision and has a high failure rate.
    • Epithelial debridement is done for lesions in the visual axis. 
    • Phototherapeutic keratectomy is done in individuals for whom all other treatment methods have failed: 
      • Mechanical debridement of the overlying corneal epithelium.
      • A laser is used to ablate part of Bowman’s layer 
• Corneal ulcers:
  • Bacterial corneal ulcers: 
    • Topical antibiotics
    • Systemic antibiotics might be necessary in cases of severe infections
    • Cycloplegic drugs are used to reduce pain caused by ciliary spasm. 
    • Systemic analgesics 
  • Viral corneal ulcers:
    • Systemic antivirals
    • Cycloplegic and analgesic drugs
  • Fungal corneal ulcers:
    • Topical antifungals should be used for 6–8 weeks.
    • Systemic antifungal drugs may be required in severe cases.
    • Nonspecific treatment includes cycloplegics and analgesics.
    • Steroids are contraindicated.
  • Acanthamoeba corneal ulcers: 
    • 12–16 weeks of anti-amoebic therapy
    • Mechanical debridement.

Complications

• Corneal scarring
• Infective corneal ulcers
• Perforation
• Corneal opacities
• Irregular astigmatism
• Vision loss

Differential Diagnosis

• Hyphema: condition in which blood collects in the anterior chamber. Hyphema is most commonly caused by trauma. Partial or complete loss of visual acuity is the 1st sign of hyphema. Management includes analgesics, cycloplegics, topical steroids, and patching.
• Hypopyon: condition in which inflammatory cells and exudates collect in the anterior chamber. Hypopyon is a result of an underlying infection and is often seen in bacterial and fungal corneal ulcers. The main symptoms are pain and partial or complete loss of visual acuity. The condition is treated by topical and systemic antibacterial or antifungal agents given along with analgesics. 
• Iritis: inflammation of the anterior or posterior chamber and iris. The main symptoms of iritis include pain, photophobia, and pain associated with ocular movements. Management includes topical cycloplegics and topical steroids.
• Chemical burns: ocular emergency. Chemical burns are a result of exposure of the eye to various chemicals. Alkali injuries are the most common. Chemical burns produce extensive damage to the ocular surface epithelium, cornea, and anterior segment, resulting in permanent unilateral or bilateral visual impairment. These injuries should be managed as an emergency condition, and rehabilitation plays a major role in restoring vision.
• Foreign body: can be partially or completely lodged in the cornea and can be mistaken for a corneal ulcer. A foreign body might itself cause a corneal ulcer. A foreign body causes damage to the epithelium and hence provides entry for various pathogens. Management includes removal of the foreign body and use of topical antibiotics, topical cycloplegics, and systemic analgesics. 
• Herpes simplex virus epithelial keratitis: usually found in individuals with compromised immunity and is caused by herpes simplex virus. The presence of multiple small branching epithelial dendrites on the surface of the cornea is the hallmark sign for this condition. Symptoms are pain, erythema, decreased visual acuity, and excessive tearing. Management is antiviral therapy or lamellar keratoplasty.