Definition and Overview

The cornea is the transparent covering found in front of the eye. It is composed of cells and proteins and plays crucial roles including refracting light. Once the light is refracted, it can already get inside the lens, which then sharpens the light’s focus before it proceeds to the retina, which transmits the light into signals that can be interpreted by the brain. As the outer covering, it also acts as the eye’s protection against germs and irritants that may cause eye infection. On the other hand, it maintains its healthy condition by being nourished by the tear ducts.

Corneas have the ability to repair themselves in cases of minor injuries. However, they remain susceptible to other conditions including degeneration and infection. These can have a negative impact on vision, which may then limit a person’s movement and reduce the quality of life.

Causes of Condition

Here are some of the common causes of corneal problems:

  • Allergens – The body is designed to pay attention and eliminate threats such as bacteria or viruses. It may also consider common allergens like pollen to be a threat. When the immune system is activated by the body to respond to these threats, a chemical known as histamine is released. Histamine, therefore, is a natural product of the body’s defense. However, when the immune system goes into overdrive, the amount of histamine in the body is also higher, which may then cause adverse reactions including watery or red eyes.

  • Pathogens – Many of the corneal infections are caused by pathogens, particularly bacteria and viruses. These include those that cause shingles, conjunctivitis, and keratitis. The bacteria or virus can get into the body when there’s a tear in the cornea or when a person wears contaminated contact lens. Depending on the source of infection, the condition may be transmitted from person to person.

  • Hereditary – Corneal problems is ruled out as hereditary if no other cause can be determined and if the problem equally affects both eyes. A classic case is dystrophy, in which the epithelium cells, which are the outermost layer of the cornea, start to erode or when there’s a buildup of a cloudy layer on the cornea, both of which can significantly reduce vision.

  • Refractive errors – Sometimes the shape of the cornea, which is a dome, isn’t perfect. This leads to refractive errors, which can distort vision, preventing a person from seeing far (myopia) or near (hyperopia) objects. It may also lead to astigmatism.

Key Symptoms

  • Inability to focus clearly on an object
  • Pain in the eyes
  • Blurry vision
  • Discharges of the eyes
  • Constant tearing of the eyes
  • Feeling as if something is stuck in the eye
  • Changes in vision
  • Redness
  • Unusual light sensitivity

Who to See and Treatments Available

There are two types of professionals that you can consult in regards to eye problems. If the problem is related to refractive errors, an optometrist can help as the problem can be usually corrected by wearing the right contact lens or glasses.

If the problem is more complex or deals with the specific parts of the cornea, an ophthalmologist is the one to seek.

The treatment for corneal problems depends on the causes:

  • If it’s a refractive error, the patient is recommended to wear glasses or contact lenses, which now come in different forms, to help correct vision.

  • If the problem is an infection, medications like anti-viral or anti-fungal drops are recommended. If it’s transmittable, the patient is recommended to avoid having close contact with others until the disease is cleared. As a form of prevention, people are advised not to use or share their belongings with others. They are also directed to wash hands regularly.

  • If the problem is hereditary, the ophthalmologist will closely monitor the progression of the disease. Normally, they take years before the symptoms appear, and in some cases, they are asymptomatic. For the at-risk group, they are advised to visit their doctor at least once a year for monitoring.

  • If the corneal issue has already progressed, the objective of the treatment is to retain as much vision as possible. In the case of keratoconus, wearing a soft contact lens is often helpful in the early stages, but a corneal transplant may be considered if the damage is significant.

  • If the cause is an underlying disease, management of the disease will usually resolve corneal problems

  • Yanoff M, Cameron D. Diseases of the visual system. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 431.

  • Groos Jr. EB, Chang BH. Complications of Contact Lenses. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:vol 4; chap 27.

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