Description

• Corneal injuries via: a foreign body (most commonly abrasion), ultraviolet (UV) burns, or chemical contact burns.
  • Corneal abrasions: result from any single or repetitive violation by cutting or scratching the thin, protective, clear coat of the exposed corneal epithelium.
  • Corneal stromal ulceration: any violation of the epithelial layer of the cornea leading to direct exposure of the underlying corneal stromal layer, may result (especially with delay in diagnosis/treatment) in infectious keratitis which may lead to an infected corneal ulcer.
  • Superficial ulcers, limited to loss of the corneal epithelium, are the most common form of ulceration.
  • Peripheral ulcerative keratitis (PUK) is noninfectious, complicating many autoimmune diseases with corneal ulceration.
• UV burns of the cornea (photokeratitis) occur when exposed to intense sunlight, tanning booth light, halogen lamp, welding torch, or close lightening flash with unprotected or inadequate UV eye protection.
  • Strictly involve a 6- to 12-hour latency of acute, intense pain in a photophobic red eye
• Chemicals directly on the cornea may cause serious, extensive damage to the epithelial or deeper layers.
• Corneal abrasion and keratitis/ulceration can each cause scarring which may lead to impaired vision or permanent vision loss.

Epidemiology

All unprotected eyes are vulnerable to corneal injuries.

Incidence

• Corneal abrasions:
  • Eight percent of total ER visits are eye trauma-related; 64% of these eye complaints are abrasions via direct minor trauma.
  • Twelve percent of corneal abrasions relate to contact lenses, particularly in young people.
  • Only conjunctivitis and subconjunctival hemorrhage surpass corneal abrasion as a cause of red eye complaints.
• Worldwide, infectious keratitis and ulceration is 5th leading cause of blindness.
• Chemical ocular injuries: 67% occur in men at work, aged 20 to 30 years old; 33% occur by assault incidents in United Kingdom.
• In United States, 1 million ER and clinic visits per year result in a keratitis diagnosis.

Etiology and Pathophysiology

• Corneal abrasions: usually caused by mechanical scratching, from various foreign bodies or chemical and flash (UV) burns
• Recurring: Acute corneal injuries or spontaneous defects can cause corneal scarring and permanent vision loss.
• Corneal ulcers: The injury precedes keratitis and infectious corneal ulceration.
  • Contact lenses use, impaired immunity (HIV), corneal trauma or abrasion, and ocular surface disease can promote keratitis or cause corneal ulceration. Ischemia of the cornea induces edema which plays a significant role in epithelial dysfunction. Trauma, ischemia, and increased intraocular pressure can result from edema which then itself can promote further edema.
• Pathogens causing ulcerations include the following:
  • Gram-positive bacteria ~20–69%; Staphylococcus aureus and coagulase-negative Streptococcus are common.
  • Gram-negative bacteria ~21–35%; Pseudomonas sp. most common, especially contact lenses users
  • Herpes simplex (most common viral cause) with or without bacterial superinfection; herpes zoster
  • Fungal: Fusarium, Aspergillus, Curvularia, and Candida; rank order varies geographically.
  • Parasites: Acanthamoeba is very, very rare in United States, but 85% are in contact lenses users
• Autoimmune disorders: Sjögren, PUK, rheumatoid arthritis, inflammatory bowel disease
• Corneal ulceration is more common in immunocompromised: cancer, HIV, and diabetes mellitus (DM).
• Ocular surface diseases: Chronic blepharitis, entropion, Graves eye disease, and dry eyes/corneal dystrophy/bullous keratopathy/mucous membrane pemphigoid promote ulceration.

Risk Factors

• Acute eye trauma: direct contact trauma, chemical burn, UV overexposure
• Contact lenses use:
  • The most common contributing factor for bacterial keratitis in United States
  • Risky handling of contact lenses (poor hand and lenses hygiene)
  • Extended wear lenses, excessive wear times
• Perioperative time: sedation and general anesthesia
• Lack of proper eye protection
• Males, age 20 to 34 years old
• Manufacturing, construction, agricultural work (equatorial especially)

General Prevention

• Strong, face/periorbital, skin contact-fitting eyewear during:
  • Work (auto mechanics, metalworkers, miners, etc.) or anywhere hammering, grinding, sawing
  • Contact sports
• Occupational Safety and Health Administration mandates safety standards for at risk employees; see https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.102.

Commonly Associated Conditions

• Xerophthalmia (common) or exophthalmos (occasional); allergic eye disease (common)
• Severe vitamin A deficiency (associated with corneal keratitis—rare)
• Neuropathy of cranial nerve V1, the ophthalmic branch (rare)
• DM (occasional), immunocompromise (e.g., HIV), connective tissue disease: bacterial (occasional) or fungal (rare) ulcers
• Critically ill or patients under anesthesia with impaired blink reflex or lagophthalmos and those on intermittent positive pressure ventilation (occasional)