Corneal disorders

The cornea is the external, transparent layer of the eye covering the iris and pupil. The cornea is highly sensitive, and corneal disorders (e.g., abrasions, infection, erosion, ulcers, foreign bodies) are often painful and associated with reduced visual acuity. Diagnosis is most commonly clinical, based on slit lamp examination with fluorescein staining. Treatment includes supportive care (including analgesics) and foreign body removal, if present. Topical antibiotics may be used, e.g., in corneal abrasions and corneal ulcers. Therapeutic contact lenses are used in keratoconus. Keratoplasty (corneal transplantation) is generally a last resort for patients with significant visual impairment or failed treatment for infection.

For inflammatory disorders of the cornea, see “Conjunctivitis” and “Keratitis.”

Also see “Cornea” in “Eye and orbit.”

Definition ^[1]

A defect in the epithelial surface of the cornea caused by trauma

Etiology ^[2]

• Direct injury (e.g., scratch from fingernail or makeup brush)
• Foreign body under the eyelid
• Prolonged contact lens wear or improperly fitted lenses
• Entropion
• Trachoma

Clinical features ^[1][2]

• Foreign body sensation in the eye
• Eye pain
• Epiphora
• Photophobia
• Blurred vision
• Conjunctival injection

Diagnostics ^[1][2]

• Corneal abrasion is a clinical diagnosis.
• Perform a thorough eye examination, including slit lamp examination with fluorescein staining.
• Characteristic findings on slit lamp examination include:
  • Traumatic injury: linear or geographic shapes
  • Contact lens-related: round, central defect composed of punctate lesions
  • Foreign body under eyelid: multiple vertical lines

Resolution of pain with local anesthetic in the setting of superficial eye injury suggests corneal abrasion. ^[2]

Exclude open globe injury and corneal foreign bodies in all patients with corneal abrasion.

Management ^[1][2]

• Remove foreign body from the cornea and/or eyelid if present.
• Provide analgesia for corneal pain. ^[3][4]
  • Oral NSAIDs: mild to moderate pain
  • Topical NSAIDs, e.g., ketorolac (off-label) ^[1]
  • Systemic opioid analgesics: severe pain ^[1][2]
• Consider prophylactic topical antibiotics for:
  • Deep or potentially contaminated abrasions (e.g., erythromycin ) ^[1][2]
  • Contact lens wearers or immunocompromise: antibiotics with antipseudomonal activity, e.g., ciprofloxacin (off-label) ^[1][2]
• Avoid eye patches and use caution with topical anesthetics. ^[3][5]

Limit use of topical NSAIDs to 2–3 days due to risk of corneal toxicity. ^[1]

Disposition ^[1][2]

• Consult ophthalmology urgently for:
  • Signs of active infection (e.g., corneal infiltrate)
  • Corneal ulcer
  • Evidence of open globe injury
  • Hypopyon or hyphema
  • Retained foreign body
  • Chemical burns
• Arrange follow-up in 24 hours if corneal abrasion is > 4 mm, contact lens-related, or accompanied by a decrease in visual acuity.
• Refer to ophthalmology if symptoms have not improved at follow-up.

Complications ^[1][2]

• Infection (e.g., bacterial keratitis)
• Corneal ulcer
• Traumatic iritis
• Recurrent corneal erosion

For full-thickness lacerations, see “Open globe injury.” ^[2][6]

• Definition: traumatic corneal defect caused by a sharp object
• Diagnostics: slit lamp examination to exclude full-thickness defects and foreign bodies ^[2]
• Management
  • Consult ophthalmology urgently.
  • Conservative management of small, superficial lesions is similar to that of corneal abrasions.
  • Deeper or more extensive lesions may require surgical repair.

Etiology ^[1][2]

• Most commonly results from dust or debris blown into the eye during:
  • High-risk activities without adequate protective eyewear, e.g., grinding, drilling, sawing, welding, mowing
  • Exposure to high winds

Clinical features ^[1][2]

• History of sudden onset and persistent discomfort following trauma
• Signs of ocular inflammation: copious tearing, redness, foreign body sensation, difficulty keeping the eye open, photophobia, and blurred vision

Diagnostics ^[1][2]

• Perform a thorough eye examination, including slit lamp examination, evaluation for open globe injury, and eversion of the upper eyelid.
• Characteristic findings on examination include:
  • Visible foreign body
  • Rust rings
  • Corneal defect without visible foreign body
• If no foreign body is seen but suspicion of penetrating injury is high, obtain imaging (e.g., orbital CT scan or ultrasound). ^[7]

Corneal foreign bodies that penetrate the full thickness of the cornea should be considered as open globe injuries that require urgent ophthalmology consultation. ^[2]

MRI is contraindicated for the evaluation of suspected metallic foreign bodies.

Management ^[2][7]

Corneal foreign body removal

Utilize a stepwise approach from the least to most invasive technique.

• Administer a topical anesthetic (e.g. tetracaine )
• Irrigate the affected eye copiously with saline.
• Sweep a moist cotton swab over the object and cornea.
• Attempt removal with a 25–27 gauge needle, corneal spud, or burr drill.
  • Ask the patient to look at a distant object to stabilize the eye.
  • Visualize the foreign body using magnification (e.g., loupes, slit lamp).
  • Hold the instrument tangential to the cornea.
  • If using a needle or corneal spud: Scoop or pick up the foreign body with the instrument.
  • If using a burr drill: Hold the burr against the foreign body until removed.
• Residual rust rings may be removed during initial presentation or after 24–48 hours.

Do not attempt to remove the foreign body if an open globe injury is suspected.

Supportive treatment ^[1][2][7]

• Tetanus prophylaxis
  • Indicated for penetrating eye injury
  • Consider for potentially contaminated foreign bodies, concomitant chemical burns, or tissue necrosis
• Analgesia and antibiotic prophylaxis: See “Corneal abrasion” for indications and recommendations.

Disposition ^[1][2]

• Consult ophthalmology urgently for:
  • Suspected open globe injury
  • Inability to remove a foreign body
  • Large or deep foreign bodies
  • Foreign bodies affecting the central field of vision
• See also “Corneal abrasion.”

Complications ^[1][2][7]

Complications from a corneal foreign body are rare but may include:

• Corneal abrasion
• Open globe injury
• Secondary iritis ^[8]
• Rust rings may delay corneal healing and/or impair visual acuity (if centrally located).

• Definition ^[9]
  • Detachment of the corneal epithelium from the tissue layers below, including the basement membrane and Bowman membrane
  • Recurrent corneal erosion: chronic relapsing corneal erosion
• Etiology ^[10][11]
  • Spontaneous due to lack of regenerative capacity of the cornea, associated with the following risk factors:
    • Corneal dystrophy
    • Corneal ulcers (e.g., from herpes simplex keratitis )
    • Contact lens use, especially if poorly fitted
    • Diabetes mellitus
    • Dry eye disease
  • Secondary to injury of the cornea (e.g., corneal abrasion, entropion)
• Clinical findings: sudden-onset symptoms similar to those of corneal abrasion, typically upon waking or without obvious signs of ocular trauma.
• Diagnostics: See “Corneal abrasion.”
• Treatment ^[1][12]
  • Acute (within 24 hours of symptom onset)
    • As with corneal abrasion
    • Artificial tears and nightly lubricant eye drops
  • Recurrent corneal erosion or symptoms > 24 hours
    • Specialized ophthalmological treatment may include the following ^[13]
      • Therapeutic contact lenses
      • Stromal micropuncture
      • Corneal epithelial debridement and/or phototherapeutic keratectomy
• Prognosis
  • Excellent, provided diagnosis and treatment are initiated promptly
  • Complete healing of recurrent corneal erosion may take years.

Definition ^[2]

• Corneal ulcer: (ulcerative keratitis): a defect of the corneal epithelium and underlying stroma that occurs secondary to infection or inflammation
• Infectious keratitis: an infection of the cornea (also called “infectious corneal ulcer”) ^[14]
• Peripheral ulcerative keratitis: inflammation at the margin of the corneal stroma caused by autoimmune disease (also called “peripheral corneal ulceration”) ^[15]

Etiology

Corneal ulcers most frequently occur as a complication of keratitis. ^[2][16]

• Bacterial keratitis
  • Common organisms: Staphylococcus, Streptococcus, Mycobacterium, and Pseudomonas
  • Risk factors:
    • Contact lens wearing
    • Corticosteroid use
    • Eye trauma
    • Prior ocular surgery
• Viral keratitis
  • Herpes simplex keratitis
  • Herpes zoster keratitis
• Fungal keratitis: most common in agricultural workers and patients using corticosteroids
• Noninfectious keratitis ^[15][17]
  • Autoimmune disease, e.g., rheumatoid arthritis, systemic lupus erythematosus
  • Keratoconjunctivitis sicca

Clinical features ^[2][16]

• Eye pain and/or foreign body sensation
• Epiphora
• Conjunctival injection
• Photophobia
• Blurry/decreased vision
• Discharge from eye

Diagnostics ^[2][16]

Corneal ulcer is a clinical diagnosis based on slit lamp examination with fluorescein staining. Bacterial and viral cultures can help direct definitive treatment.

• Characteristic findings on slit lamp examination
  • Corneal epithelial defect
  • Stromal edema or infiltration
  • Anterior chamber cells and flare (∼ 25% of patients) ^[18]
• Findings indicating viral corneal ulcer
  • Herpes simplex keratitis
    • Herpetic lesions on conjunctiva or lids
    • Slit lamp examination: dendritic lesions or amoeba-shaped ulcer
  • Herpes zoster keratitis
    • Dermatomal vesicular rash
    • Possible signs of uveitis, iritis, or choroiditis
    • Slit lamp examination: similar to HSV keratitis
  • See also: “Viral keratitis”

Management ^[2][16]

• All patients
  • Consult ophthalmology urgently.
  • Provide analgesia for corneal pain.
• Corneal ulcer secondary to bacterial keratitis ^[19]
  • Initiate broad-spectrum topical antibiotics (e.g., ciprofloxacin ).
  • Consider topical corticosteroids and/or systemic antibiotics in consultation with ophthalmology.
• Corneal ulcer secondary to herpes simplex keratitis ^[19][20]
  • Initiate topical or systemic antiviral therapy.
    • Topical: e.g., trifluridine ^[20]
    • Systemic: e.g., famciclovir (off-label) ^[20]
  • Topical corticosteroids may be administered in consultation with ophthalmology for keratitis affecting the stroma or endothelium.
• Corneal ulcer secondary to herpes zoster keratitis
  • Initiate antiviral therapy for herpes zoster.
  • See also “Herpes zoster ophthalmicus.”

Disposition ^[2][16]

• All patients should be seen by ophthalmology within 24 hours.
• Admit patients with:
  • Herpes zoster ophthalmicus and immunocompromise or retinal involvement
  • Severe symptoms
  • No access to urgent ophthalmologic follow-up care

Complications ^[1][2]

• Vision loss
• Corneal scarring and/or perforation
• Endophthalmitis
  

Corneal ulcers are an ophthalmological emergency and can result in permanent corneal scarring and vision loss.

Corneal degeneration

• Definition: changes of the cornea that cause corneal deterioration and, potentially, dysfunction
• Etiology
  • Normal aging
  • Secondary to various pathological processes (e.g., calcium salt deposits in band keratopathy associated with hypercalcemia in the setting of sarcoidosis)

Band keratopathy ^[21]

• Definition: a type of corneal degeneration that involves the appearance of a band-shaped area of calcification across the central cornea ^[9]
• Etiology
  • Idiopathic
  • Risk factors
    • Hypercalcemia (e.g., hyperparathyroidism, sarcoidosis), hyperphosphatemia (e.g., chronic renal failure)
    • Chronic, inflammatory eye disease (e.g., uveitis, keratitis)
    • Exposure to harmful chemicals (e.g., mercury vapors)
    • Family history of band keratopathy
• Pathophysiology: increased serum calcium, serum phosphate, and/or corneal surface pH (caused by chronically inflamed eyes) → change in solubility of calcium and phosphate → calcium phosphate precipitation out of tears, aqueous humor, and corneal tissue → calcium phosphate deposition as salts in the Bowman layer and superficial stroma of the cornea
• Clinical findings
  • Decreased visual acuity
  • Foreign body sensation
  • Photophobia
• Diagnostics
  • Slit lamp examination showing band-like, horizontal, opaque white areas on the cornea
  • Followup includes investigation of underlying causes and may include:
    • Serum calcium and phosphate measurement
    • Parathyroid hormone level measurement
    • Renal function tests
    • Sarcoidosis workup (e.g., serum ACE, chest x-ray)
• Treatment
  • Treatment of the underlying cause (e.g., uveitis, hypercalcemia)
  • Superficial debridement and lamellar keratectomy
• Prognosis: Visual deficits caused by band keratopathy can typically be treated successfully but will recur if the underlying condition is not addressed.

Corneal dystrophy ^[22]

• Definition: A group of inherited noninflammatory disorders that cause the buildup of various substances in the cornea and result in morphological changes.
• Classification: There are many different types of corneal dystrophy. The most common are:
  • Fuchs corneal dystrophy (see below for details)
  • Lattice corneal dystrophy
  • Map-dot-fingerprint corneal dystrophy
• Etiology: inherited condition
• Clinical findings: Because corneal dystrophies are a heterogeneous group of diseases, they can affect the eye in different ways. Symptoms may include:
  • Progressive visual impairment
  • Corneal erosion (see “Symptoms” in corneal erosion, above)
• Diagnostics: visible structural changes and/or deposits on slit lamp examination.
• Treatment
  • See “Treatment” in corneal erosion, above.
  • Keratoplasty in severe cases or when other treatment modalities have not been successful

Fuchs dystrophy ^[23]

• Definition: inherited disease that predisposes to progressive loss of corneal endothelial cells
• Pathophysiology: corneal endothelial cells are responsible for maintaining the transparency of the cornea by balancing water and electrolyte flow into and out of the corneal layers; deterioration of corneal endothelial cells → decreased outflow of water from the corneal stroma → corneal edema, opacification, and bullous epithelial detachment ^[24]
• Clinical findings
  • Reduced visual acuity
  • Blurred vision, glare, and halos, often improving over the course of the day ^[25]
  • Eye pain or foreign body sensation in the eye
• Diagnostics
  • Early Fuchs dystrophy is asymptomatic, but cornea guttata (droplet-shaped structures in the Descemet membrane consisting of collagen and thought to have been secreted by stressed corneal endothelial cells) can be seen on slit lamp examination. ^[26]
  • Advanced disease: Slit lamp examination shows corneal thickening, edema, bullae, and fibrotic scarring.
• Treatment ^[27]
  • Asymptomatic patients do not require treatment.
  • Symptomatic treatment
    • Medical treatment to dehydrate the cornea: hyperosmolar eye drops, warm dry air (e.g., hair dryer held at arm's length)
    • For pain or foreign body sensation in the eye: NSAIDs, bandage contact lenses
  • Keratoplasty: indicated in advanced disease with marked loss of vision that does not improve over the course of the day and if pain cannot be alleviated by symptomatic treatment

Corneal deposits

A variety of substances can accumulate in the cornea to create deposits. Two of the more well-known causes of corneal deposits are presented below.

Arcus senilis (corneal arcus)

• Definition: a condition associated with normal aging, in which annular deposits of lipids appear around the corneal margin ^[28]
• Epidemiology: Incidence increases with age. ^[29]
  • 60% in those 50–60 years
  • Almost 100% in those > 80 years
• Clinical findings: asymptomatic
• Diagnostics: slit lamp examination
• Treatment
  • In older patients: no treatment necessary
  • Occurrence before 50 years of age: rule out lipid disorders

Kayser-Fleischer ring

• Definition: green-brown, copper deposits are a diagnostic sign of Wilson disease (See “Clinical features” in Wilson disease.)

Keratoconus

• Definition: a noninflammatory corneal condition in which the cornea becomes thinner than normal and develops a conic shape, bulging outward at the center ^[30]
• Etiology: unknown; frequently associated with other conditions
  • Neurodermatitis
  • Allergic asthma
  • Hay fever
  • Marfan syndrome
  • Ehlers-Danlos syndrome
  • Down syndrome
  • A positive family history of keratoconus has been found in a minority of cases (10%)
• Clinical findings: symptoms are often initially unilateral; however, they always become bilateral in the further course of disease ^[22]
  • Progressive decrease in visual acuity
  • Myopia
  • Astigmatism
  • Photophobia
• Diagnostics
  • Slit lamp examination showing protrusion and thinning of the cornea
  • Ultrasound pachymetry (measurement of corneal thickness via ultrasound)
  • Computerized corneal topography
• Treatment ^[31]
  • Correcting astigmatism and myopia: glasses or rigid gas permeable contact lenses ^[31]
  • In progressive keratoconus: crosslinking with UV-A light (corneal crosslinking)
  • If conservative treatment options fail: keratoplasty
• Complications
  • Corneal hydrops (corneal rupture): tearing of the Descemet membrane and endothelium → penetration of intraocular fluid into the stromal tissue of the cornea → acute pain and deterioration in vision caused by corneal opacification

Keratoglobus ^[31]

• Definition: noninflammatory corneal condition, in which the cornea becomes thinner than normal and develops a more globular shape, bulging outward at the center
• Etiology: unknown; associated with disorders of collagen synthesis (Marfan syndrome, Ehlers-Danlos syndrome)
• Clinical findings, diagnostics, and treatment: similar to those of keratoconus

Astigmatism

• See astigmatism

• See “Keratitis” and “Conjunctivitis.”

Keratoplasty (corneal transplantation) ^[32]

• Indications
  • Significant visual impairment as a result of pathological changes in the cornea, e.g., opacification, irregular curvature
  • Keratitis that cannot be controlled by conservative treatment
• Procedure: replacement of diseased cornea with cornea harvested from a recently deceased donor
  • Perforating keratoplasty (replacement of the complete cornea): indicated when both anterior and posterior corneal layers are damaged
  • Lamellar keratoplasty (replacement of only the anterior or posterior corneal layers): indicated when only anterior or posterior corneal layers are damaged
• Follow-up care
  • Graft rejection prevention: corticosteroid eye drops
  • Monitoring and treatment for graft rejection