Corneal Disorders
Corneal Disorders
The cornea is a clear, dome-shaped window of the front of your eye which focuses light into your eye.
The cornea has five layers:
- Epithelium: the outermost, protective layer of the cornea.
- Bowman’s Membrane: this second protective layer is strong.
- Stroma: the thickest layer of the cornea. It is made up of water, collagen fibres and other connective tissue. This strengthens the cornea and makes it flexible and clear.
- Descemet’s Membrane: a thin, strong inner layer that is also protective.
- Endothelium: the innermost layer made up of cells that pump excess water out of the cornea.
Corneal Dystrophies
Corneal dystrophies are a group of rare genetic eye disorders. With corneal dystrophies, abnormal material builds up in the cornea. Most corneal dystrophies affect both eyes. They progress slowly and run in families.
There are more than 20 different types of corneal dystrophies. They are generally grouped into three categories:
- Anterior or superficial corneal dystrophies. These affect the outermost layers of the cornea: the epithelium and Bowman’s membrane/
- Stromal corneal dystrophies affect the stroma, which is the middle and thickest layer of the cornea.
- Posterior corneal dystrophies affect the innermost parts of the cornea: the endothelium and the Descemet membrane. The most common posterior corneal dystrophy is Fuch’s dystrophy.
The symptoms of corneal dystrophy depend upon the type of corneal dystrophy. Some people experience no symptoms. In others, the build-up of material in the cornea causes it to be opaque (not clear). This leads to blurred vision or vision loss.
Many people also experience corneal erosion. This happens when the layer of cells on the surface of the cornea (the epithelium) loosens from the layer underneath (Bowman’s membrane). Corneal erosion causes:
- mild to severe pain in the eye.
- light sensitivity.
- feeling like something is in the eye.
Because most corneal dystrophies are genetic, family history of the disease increases your risk. Corneal dystrophies can appear at any age. Men and women are equally affected by most corneal dystrophies, except for Fuch’s dystrophy. Fuch’s dystrophy affects women more frequently than men.
Credit: American Academy of Ophthalmology
Written By: Kierstan Boyd
Reviewed By: William Barry Lee MD
Sep. 06, 2019
Keratoconus
Keratoconus is when the cornea thins out and bulges like a cone. Changing the shape of the cornea brings light rays out of focus. As a result, your vision is blurry and distorted, making daily tasks like reading or driving difficult.
Doctors do not know for sure why people have keratoconus. In some cases, it appears to be genetic (passed down in families). About 1 out of 10 people with keratoconus have a parent who has it too. Keratonconus is also associated with eye allergies and excessive eye rubbing. Keratoconus often starts when people are in their late teens to early 20s. The vision symptoms slowly get worse over a period of about 10 to 20 years.
Keratoconus usually takes years to go from early- to late-stage. For some people, though, keratoconus can get worse quickly. The cornea can swell suddenly and start to scar. When the cornea has scar tissue, it loses its smoothness and becomes less clear. As a result, vision grows even more distorted and blurry.
Keratoconus treatment depends on your symptoms. When your symptoms are mild, your vision can be corrected with eyeglasses. Later you may need to wear special hard contact lenses to help keep vision in proper focus.
Here are other ways that your ophthalmologist might treat keratoconus:
- Intacs. This is a small curved device that your ophthalmologist surgically puts in your cornea. Intacs help flatten the curve of your cornea to improve your vision.
- Collagen cross-linking. Your ophthalmologist uses a special UV light and eye drops to strengthen the cornea. Doing this helps to flatten or stiffen your cornea, keeping it from bulging further.
- Corneal transplant. When symptoms are severe, your opthalmologist may suggest a corneal transplant. Your ophthalmologist replaces all or part of your diseased cornea with healthy donor cornea tissue.
Credit: American Academy of Ophthalmology
Written By: Kierstan Boyd
Reviewed By: Elena M Jimenez MD
Mar. 21, 2019