What is the Cornea?
The cornea is the eye’s outermost layer. It is the clear, dome-shaped surface that covers the front of the eye.
Although the cornea is clear and seems to lack substance, it is actually a highly organized group of cells and proteins. Unlike most tissues in the body, the cornea contains, under normal circumstances, no blood vessels to nourish or protect it against infections. Instead, the cornea receives its nourishment from the tears and aqueous humor that fills the chamber behind it. The cornea must remain transparent to refract light properly, and the presence of even the tiniest blood vessels can interfere with this process. To see well, all layers of the cornea must be free of any cloudy or opaque areas.
Cornea and Anterior Structures Diagnoses
The Cornea and Refractive Surgery Service provides comprehensive care to patients with corneal and anterior segment disease, and provides refractive surgery for vision correction. Our specialists are in the best position to evaluate, and often treat, common eye disorders in their early stages. If the disease progresses, however, a specialist in corneal medicine and surgery is better able to manage all aspects of the problem.
Common disorders of the cornea and anterior chamber (front of the eye) that may be evaluated initially in the Comprehensive Ophthalmology Service or in the Cornea Service:
- Allergic conditions, which can cause redness, itching, blurry vision and swollen eyelids
- Blepharitis, an inflammation of the eye lid
- Cataract, a cloudiness of the normally clear lens of the eye
- Conjunctivitis, or inflammation of the covering of the eye and inner eye lid
- Dry eye, in which the quality or amount of tears is compromised, and the eye is unable to keep its surface well lubricated and comfortable
- Disorders associated with refractive clarity. These disorders may be corrected with a variety of approaches including eyeglasses, contact lenses, surgery and refractive surgery. They include:
- astigmatism, an uneven curvature of the corneas
- hyperopia, or farsightedness
- keratoconus, uneven curvature in the center of the cornea
- myopia, or nearsightedness
Less common disorders of the cornea and anterior chamber may require the attention of a cornea specialist for diagnosis and care. Some of these include:
- Cornea dystrophies, including Fuchs’ endothelial, Lattice and MDF dystrophies
- Infections (bacterial, viral and fungal), including herpes zoster (shingles), ocular herpes simplex, and others. These infections can reduce visual clarity, produce corneal discharges, and perhaps erode the cornea. Severe corneal infections can lead to corneal scarring, which can impair vision and may require a corneal transplant.
- Inflammatory disorders with significant eye implications (episcleritis, uveitis)
- Iridocorneal endothelial syndrome (ICE), in which disorders of the iris and the cornea occur in conjunction with glaucoma
- Stevens-Johnson Syndrome, a skin disorder that can affect the eyes
- Pseudophakic Bullous Keratopathy (PBK), a rare complication of cataract surgery
- Pterygium, a type of growth on the cornea
The cornea can be damaged after a foreign object has penetrated the tissue, such as from a poke in the eye. At other times, bacteria or fungi from a contaminated contact lens can pass into the cornea. Situations like these can cause painful inflammation and corneal infections called keratitis.