Cornea & Corneal Disease

Cornea & Corneal Disease
The cornea protects the eye from germs and dust, and shields it from UV radiation. It is also an outer lens that directs and focuses light so we can focus better. This thin structure is divided into five layers: epithelium, bowman’s layer, stroma, Descemet’s membrane, and endothelium.


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Frequently Asked Questions

These include astigmatism, nearsightedness and farsightedness. During this process, light is bent by the cornea and lens to focus the light on the retina. After light hits the retina directly, it is converted into signals and sent to the brain. In people with refractive errors, the light does not bend or hit the retina in the right place, which results in imperfect vision for the patient.

  • Corneal infection (keratitis): Corneal infections are rare, but they can be treated with antimicrobial eye drops. Severe infections may persist longer and may require stronger antibiotic, antifungal, or antiviral treatments. If left untreated, it can erode the cornea causing serious damage, and a corneal transplant may be the only option.
  • Dry eye: Dry eye is characterized by decreased tear quality and production, causing patients to experience a lack of moisture and discomfort in their eyes. The main symptom of dry eye is a scratchy or sandy sensation within the eyes. Other symptoms include excess tearing, periods of dryness, stringy discharge, pain, and redness of the eye. This condition is common in dry environments, with the use of specific medications, or with certain conditions such as menopause or rheumatoid arthritis. 
    • Recommended treatments for dry eye include artificial tears and ointments to add moisture to the eye, and wearing wrap-around glasses while outside to prevent dryness. In severe cases of dry eye, temporary blocking of the eyelid puncta with punctal plugs is an effective treatment option, as well as topical cyclosporine therapy, which is used to enhance tear production. See our page on Dry eye syndrome
  • Corneal dystrophies: Corneal dystrophy is a condition that can affect the clarity of multiple parts of the cornea. The condition causes loss of normal vision due to a cloudy buildup of the cornea. There are numerous corneal dystrophies, but these are a few of the more common conditions:
    • Fuch’s Dystrophy: The endothelium cells begin to deteriorate and are no longer able to pump water out of the cornea, which causes the cornea to swell. Symptoms begin with temporary blurred vision, and as it worsens, blurred vision will become constant. It can eventually lead to severe pain and vision issues.
    • Keratoconus: Develops when the cornea begins to thin and eventually bulges out, forming a cone shape. Initially, vision issues can be controlled with eyeglasses. As the condition worsens and scarring develops, special contact lenses are recommended to continue vision improvement. Corneal collagen crosslinking can stop the development of keratoconus, and transplants can be done in severe cases.
    • Map-Dot-Fingerprint Dystrophy/Epithelial Basement Membrane Dystrophy: The deepest layer of the epithelium is not completely developed, making the epithelial cells unable to stick to it easily. This leads to erosion, causing the nerve endings to be exposed, which leads to severe pain. Patients may also experience tearing and light sensitivity.
  • Pterygium: This is a pinkish growth on the cornea that is common among adults aged 20 to 40. Usually, patients will request surgical removal since it is easily noticeable. 
  • Shingles: This is also known as herpes zoster, caused by the varicella-zoster virus, which is also responsible for chickenpox. Once a person recuperates from chickenpox, the varicella-zoster remains in their body in an inactive form. Unfortunately, the virus may become active again in some people, having the ability to infect any part of the body, including the eye. These infections cause rashes and painful inflammations.
  • Ocular herpes: This occurs due to the herpes simplex virus, causing painful sores on the eyelid. Ocular herpes also leads to the inflammation of the cornea. Even though this problem could be treated with antiviral medications, there is a high likelihood of recurrence.

Descemet’s Stripping Endothelial Keratoplasty (DSEK):
This procedure is also known as the sutureless corneal transplant. The doctor performs a partial corneal transplant of just the inner layers of the cornea. This procedure is preferred because of faster recovery times and a low risk of transplant rejection. It also eliminates the adverse effects of stitches. It is usually preferred for dystrophies that cause corneal swelling.

Phototherapeutic Keratectomy (PTK):
PTK uses an excimer laser to remove the damaged outer layers of the cornea, making tissue healing and growth possible. PTK also corrects and reshapes the stroma lens for better refraction of light. The biggest advantage of PTK is faster recovery compared to a corneal transplant.

Epithelium: The epithelium is an important barrier for foreign material, while at the same time allowing nutrients to enter the cornea. It is also connected to nerve endings, making it sensitive to pain.

Bowman’s layer: Directly beneath the epithelium, it is made up of a strong layer of fibrous tissue known as collagen.

Stroma: If your cornea were to be injured, this layer would protect it and form a scar as it heals. It is the thickest layer and is also made up of collagen and water. It not only provides protection, but also allows light to pass through its unique shape. LASIK and PRK procedures target this layer for vision correction.

Descemet’s membrane: Under the stroma is a membrane made of collagen that holds the stroma and endothelium together.

Endothelium: A thin layer that is constantly pumping fluid out of the stroma to keep the cornea clear and to prevent it from getting hazy. The cornea can recover from minor injuries because there are so many protective layers. However, if the endothelium is damaged, then a corneal transplant is required.

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