The eye. Certain corneal conditions, such as infection, injury, abnormal curvature, and opacification, can cause restricted vision. Because the cornea is well innervated by the , it is very sensitive and corneal disorders are often painful. Diagnosis of corneal disorders is made via and, in some cases (e.g., corneal abrasion or erosion), fluorescein staining. Treatment typically involves local measures, such as antibiotic eye drops, ointments, and therapeutic contact lenses. Corneal transplantation is generally only performed as a last resort in patients with significant visual impairment or failed treatment for infection.is the transparent, outermost layer of the
Anatomy of the cornea
Also seein .
Corneal abrasion and erosion
- Definition: scrape or scratch injury on the corneal epithelium
- Epidemiology: most common eye injury
- Injury from an object (e.g., tree branch, fingernail, ball, mascara brushes) hitting, flying into, or poking the eye
- Foreign matter stuck under the eyelid
- Prolonged contact lens wear or improperly fitted lenses
- UV light (i.e., UV keratitis)
- Thermal burns (e.g., cigarettes, matches)
- Dry eyes (e.g., Sjogren syndrome)
- Clinical findings 
- Diagnostics: examination of the eye using fluorescein staining 
- Removal of any retained foreign object
- NSAIDs (e.g., , ), or narcotics, depending on pain severity  : oral , topical
- Infection prophylaxis 
- Consider eye patching
- Small, uncomplicated corneal abrasions: rapid healing of the epithelium expected within approx. 24–48 hours; no followup necessary
corneal abrasion. Therefore, daily followup until healing has been confirmed is recommended in the following cases:
can occur as a complication of
- Young children
- Association with decreased vision
- Abrasions from contact lenses
- Larger abrasions
Retained foreign bodies in the eye that cannot be removed warrant urgent referral to an ophthalmologist!
Corneal erosion 
- Etiology 
- Clinical findings: sudden-onset symptoms similar to those of corneal abrasion (see above), typically upon waking or without obvious signs of ocular trauma.
- Diagnostics: See above.
- Acute (within 24 hours of symptom onset)
- As with , above
- Artificial tears and nightly lubricant eye drops
- Recurrent corneal erosion or symptoms > 24 hours
- Acute (within 24 hours of symptom onset)
- Excellent, provided diagnosis and treatment are initiated promptly
- Complete healing of recurrent corneal erosion may take years.
Corneal denegeration, dystrophy, and deposits
- Definition: changes of the cornea that cause corneal deterioration and, potentially, dysfunction
- Normal aging
- Secondary to various pathological processes (e.g., calcium salt deposits in associated with in the setting of )
Band keratopathy 
- Definition: a type of corneal degeneration that involves the appearance of a band-shaped area of calcification across the central cornea 
- 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
- Prognosis: Visual deficits caused by band keratopathy can typically be treated successfully but will recur if the underlying condition is not addressed.
Corneal dystrophy 
- 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:
- 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 , above)
- Diagnostics: visible structural changes and/or deposits on slit lamp examination.
Fuchs dystrophy 
- 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 
- Clinical findings
- 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. 
- Advanced disease: Slit lamp examination shows corneal thickening, edema, bullae, and fibrotic scarring.
- Asymptomatic patients do not require treatment.
- Symptomatic treatment
- 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
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 
Epidemiology: Incidence increases with age. 
- 60% in those 50–60 years
- Almost 100% in those > 80 years
- Clinical findings: asymptomatic
- Diagnostics: slit lamp examination
- In older patients: no treatment necessary
- Occurrence before 50 years of age: rule out
- Definition: green-brown, copper deposits are a diagnostic sign of (See “Clinical features” in Wilson disease.)
Curvature anomalies of the cornea
- Definition: a noninflammatory corneal condition in which the cornea becomes thinner than normal and develops a conic shape, bulging outward at the center 
- Etiology: unknown; frequently associated with other conditions
- Clinical findings: symptoms are often initially unilateral; however, they always become bilateral in the further course of disease 
- Treatment 
- 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
Inflammatory conditions of the cornea
- See the following articles:
Keratoplasty (corneal transplantation)
Keratoplasty (corneal transplantation) 
- Procedure: replacement of diseased cornea with cornea harvested from a recently deceased donor
- Follow-up care