What is the Cornea?

The cornea is the clear, front part of the eye and is often referred to as the “window” of the eye. The cornea is surrounded by the sclera, which is the white part of the eye. It lies in front of the pupil and colored iris and allows light from images we see to enter the eye and to be focused. For this reason, the cornea is a very important part of the eye to maintain.

Layers of the Cornea


1. The corneal epithelium is the outer layer of the cornea and is constantly being sloughed off and replenished like the outer layer of skin on our body.

2. The second layer of the cornea is called Bowman’s Layer. The main purpose of the Bowman’s Layer is to help hold the outer layer of the cornea to the third layer. It’s like glue between two sheets of paper.

3. The corneal stroma is the third, middle layer of the cornea and is the thickest layer. It makes up about 90% of the cornea so it is important that it remains clear.

4. Descemet’s membrane is the fourth layer of the cornea and separates the stroma from the innermost layer of the cornea. Descemet’s membrane is very thin when we are young, and gradually thickens as we age.

5. The final, innermost layer of the cornea is called the endothelium. This layer is only one cell thick. It is like a honeycomb, with each hexagon-shaped cell pieced together to form the inner lining of the cornea. On one side of the corneal endothelium is Descemet’s membrane, and on the other is the fluid that fills the space between the cornea, iris, and pupil. This innermost layer controls the amount of fluid that can pass into the cornea which prevents haziness, ensuring you have a clear view through the front of your eye.




Dry Eye Syndrome / Ocular Surface Disease

With each blink of our eyes, tears gently spread across the cornea to keep the surface of our eyes lubricated. Our tears help to reduce the risk of infection and keep the surface of the eye smooth and clear.

  • Ocular surface disease/dry eye syndrome includes conditions of the eyelids, tear ducts, tear quality, and eye surface that lead to dry eye. The severity of ocular surface disease can range from mild to very severe and the condition is usually chronic. For this reason, ocular surface disease requires regular, ongoing treatment by your eye doctor. There are several factors that can cause ocular surface disease: The lacrimal gland that produces the watery part of tear film can be dysfunctional.
  • The tears that your eyes produce could be of poor quality due to problems with oil glands of the eyelids. This problem leads to dryness and inflammation due to rapid tear evaporation.
  • Bacterial overgrowth on the eyelids and lashes can contribute to symptoms.

Symptoms include:

  • Irritated, gritty, or sandy sensation in the eye
  • Burning sensation in the eye
  • Blurred vision
  • Excessive watering of the eye
  • The feeling of having something in your eye

Factors that cause or worsen dry eyes:

  • Age
  • Certain medications
  • Certain medical conditions like diabetes and inflammatory diseases
  • Hormonal changes
  • Long-term use of contact lenses


  • Artificial tear eye drops can be used to help supplement your own natural tears
  • Conserving tears by having a doctor place small silicone plugs in the tear ducts to
    slow the natural drainage of tears
  • Consuming omega 3 fatty acids improve the quality and quantity of tear film oil
  • Warm compresses and gentle eyelid massage
  • Treating inflammation on the surface of the eye or eyelid
  • Antibiotics if bacterial overgrowth is present

What is going on in the eye

Dry Eye

Fuch’s Dystrophy

Fuch’s (pronounced Fook’s) dystrophy is a common condition in adults and can have a big impact on vision. When a patient has Fuch’s dystrophy the inner most layer of the cornea, the endothelium, is affected. Since this layer of the cornea regulates the level of fluid within the cornea, if it stops working extra fluid will cause swelling of the cornea and will cloud vision. Even before swelling occurs vision can be affected by bumps called guttata that form on Descemet’s membrane around the endothelium.

Symptoms include:

  • Sensitivity to light
  • Foggy or blurred vision
  • Eye pain
  • Difficulty seeing at night, or halos around lights
  • Poor vision when you first wake up that gets better throughout your day
  • Feeling like something is in your eye


At Orion Eye, we offer the newest innovation in corneal transplant surgery (DMEK) that only replaces Descemet’s membrane and the endothelium. Leading to the best visual outcomes and fastest recovery compared with other corneal transplant options. There are many factors that are considered when determining which treatment would be best for each patient. If a patient is not a candidate for the DMEK procedure, then a nano-thin Descemet’s stripping endothelial keratoplasty (DSEK) can be offered. In this technique, the donor tissue includes endothelium, Descemet’s membrane, and a thin layer of corneal stroma. The results of nano-thin DSEK more closely approach the results of DMEK then other forms of DSEK.


A pterygium (tuh-RIJ-ee-uhm) is a wedged-shaped growth from the conjunctiva, the membranous covering of the eye, that invades the cornea, the clear portion of the eye covering the iris and pupil. Most people with a mild pterygium experience no symptoms and don’t require surgery. However, if the pterygium continues to grow and threatens vision or changes the shape of the eye, surgery to remove the pterygium may be recommended.

It is not entirely clear what causes a pterygium to develop but prolonged exposure to the sun’s ultraviolet rays, as well as dry or dusty environments, are believed to play a role. A pterygium most often affects people who spend a lot of time outdoors in sunny, windy climates.

Symptoms include:

  • The appearance of a raised pink, white, or red lesion on the eye, usually on the side closest to the nose.
  • Redness and irritation of the eye.
  • A foreign body sensation, or the feeling that you have something in your eye.
  • Decreased or blurry vision.

Ocular surface squamous neoplasia (OSSN)

OSSN represents a spectrum of diseases that are much like common skin cancers but
located on the surface of the eye. Risks of developing these ocular surface tumors include
ultraviolet exposure, strains of human papilloma virus, and immunosuppression. When
suspected, these tumors are removed with a special technique to reduce the risk of
recurrence. The tissue is then evaluated by an ocular pathologist to confirm the diagnosis.
Once OSSN is confirmed, further treatment after surgery with topical medications is often

Our Cornea Specialist

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General Eye information

Eye Safety

How to Insert Eye Drops

How Often to Have Eye Exams

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