What is the Cornea?
The cornea is the transparent front part of the eye that covers the iris and pupil. People often think the colored part of their eye, or the iris, is part of the cornea, but it’s not. If you think of a watch, the iris and pupil are akin to the watch face, while your cornea is likened to the crystal that covers the watch face.
Light waves are carried into the interior of the eye by the surface of the cornea and its purpose is to gather and focus visual images.The cornea is always subject to damage from grit or particles that inevitably find their way into the eye.If the cornea's smooth surface becomes scratched or if it becomes swollen, the clarity of the cornea is disturbed and vision becomes blurry and foggy.
Keratoconus occurs in about one out of every 1,000 individuals. It is one of the more obscure and less widely known eye diseases making it difficult to diagnose. The disease results in thinning and weakening of the cornea, the clear lens that is the front of your eye. As a result, the cornea bulges out of its smooth, dome-like structure, and adopts a more conical and irregular configuration. Because of this change in shape, the cornea loses its ability to form a clear image in the eye and the patient's vision can decrease drastically.
Why does Keratoconus develop?
In the keratoconic cornea, light is not completely focused because of the corneal distortion. This causes scattering of light rays and the formation of"visual static", much like the static that you may find on a TV. This distortion, and consequent visual static, can increase over time, with decrease in vision. Biologically and structurally, the cornea is made up of layers of collagen protein which are fixed together by natural biologic sugars. Both the collagen and microstructure of the cornea are abnormal in keratoconus, causing a weakness of the corneal structure which then leads to optical problems. It is a progressive condition which, aside from distorting the cornea's natural optics, can also lead to scarring and other problems. The appearance and impact of keratoconus can vary widely from person to person. In its earliest stages, keratoconus often give the impression of astigmatism or nearsightedness, two of the more common eye conditions.
What causes Keratoconus?
The direct cause of keratoconus is uncertain. It may have a genetic, inheritable component. However, in many patients there are no family members with the disease. Similarly, most children of Keratoconus patients do not develop the disease, but they should be checked in early adolescence for signs.
Keratoconus is characterized by corneal thinning and vision instability. This may be caused by abnormalities in the normal collagen structure of the cornea. Collagen is the main structural component of the cornea. Collagen is a molecule that typically is very strong. In addition, the cells of the cornea (keratocytes), may not be normal, and contribute to the thinning and instability of the keratoconic cornea. The linkages of the collagen molecules and lamellae to one another may also be weak in keratoconus. This may allow the collagen pancakes to slide on one another and exacerbate KC progression. Because of this, it is important that the keratoconus patient does not rub his/her eyes in order to avoid mechanical shearing of the collagen pancakes. Finally, Inflammation may also play a role in keratoconus. Reactive oxygen species, or oxygen free radicals, may damage the corneal cells and collagen structure, and lead to keratoconus progression. Because of this, avoiding and treating eye inflammation (for instance, eye allergies) also may be important for the patient.
A corneal abrasion is a painful scrape or scratch of the surface of the clear part of the eye. This clear tissue of the eye that covers the iris or colored portion of the eye is called the cornea. The cornea has many nerve endings just under the surface, so that any abrasion of the surface may be painful. You should suspect a corneal abrasion if you have sustained an injury to your eye. Some symptoms you may experience:
- A feeling that there is something in your eye that you cannot get out.
- Blurred vision
- Eye pain in bright light
- Muscle spasms causing you to squint
The first and vital step after any eye injury is to have a full eye examination.
Although small abrasions may require no specific treatment, larger abrasions may require a topical antibiotic to prevent infection and to reduce pain and improve comfort. Eye pads may improve comfort and promote healing by preventing repeated eyelid blinking that may cause further physical disruption to the cornea. Contact lenses, mainly silicon hydrogels, can be used as"bandage contact lenses" as they provide more oxygen to the cornea and can be fitted tightly to improve healing. Serious or recurring abrasions may need to be treated with a laser surgery procedure called phototherapeutic keratectomy.
Pterygium most often refers to a benign growth of the conjunctiva, a delicate mucous membrane that covers the internal part of the eyelid and is attached to the cornea.
A pterygium is thought to be caused by exposure to sunlight, low humidity, and dust. As it is a benign growth, pterygium usually does not require surgery unless it grows to such an extent that it covers the pupil, obstructing vision or presents with acute symptoms.
Some of the irritating symptoms can be addressed with artificial tears and definitive treatment is achieved only by surgical removal. Long-term follow up is required as pterygium may recur.
A pinguecula is a yellowish, slightly raised abrasion that forms on the surface of the white part of your eye close to the edge of the cornea, a common type of degeneration of the conjunctiva, the delicate mucous membrane that covers the internal part of the eyelid and is attached to the cornea.
In most people, pingueculae cause few symptoms, however a pinguecula might create a feeling that something is in the eye.
In some cases, pingueculae become swollen and inflamed, a condition called pingueculitis. Irritation and eye redness from pingueculitis usually result from exposure to sun, wind, dust or extremely dry conditions.
Lubricating eye drops are usually prescribed for mild cases and surgical removal may be considered in severe cases when it interferes with vision, contact lens wear or blinking.
Fuchs' dystrophy is a slowly progressing corneal disease that usually affects both eyes, occurring more often in women than in men. Although doctors can often see early signs of Fuchs' dystrophy in people in their 30s and 40s, the disease rarely affects vision until people reach their 50s and 60s.
The early sign of this condition will be blurred vision on awakening that will gradually clear during the day. As the cornea retains fluids while we sleep it is normally thicker in the morning causing blurred vision. These fluids evaporate once we are awake. As the disease worsens, this swelling will remain constant and blurred vision will continue without clearing.
Treatment can include:
- Eye drops or ointments to reduce the amount of fluid in your cornea
- Use of a warm hair dryer at arm's length two or three times a day to evaporate excess fluid in the cornea
- Wearing soft contact lenses to improve vision and reduce discomfort
- Receiving a corneal transplant
If you suspect you have symptoms of Fuch's dystrophy, schedule an eye examination immediately.
What is a Corneal Transplant?
The Cornea of your eye is the color part of the eye ball. If the cornea is damaged, light that enters the eye can become distorting causing the image you see, to be blurry. Injury, infection, disease or previous eye surgery are ways a cornea can become damaged. It is possible to have mild damage to the cornea, only requiring repair rather than transplant.
Unfortunately, a transplant becomes necessary when the cornea becomes damaged beyond repair. The damaged area is replaces with healthy donor organ/ tissue. Corneal transplantation is done on a worldwide basis and is in fact, the most successful procedure performed worldwide. That statistic is due to the fact that corneal tissue does not have to be"matched" between donor and recipient making it much easier than most transplants. Any healthy cornea can be paired with another eye. If successful healing occurs without problems, this procedure can restore a person's vision.
Descemet's Stripping with Endothelial Keratoplasty (DSEK) is an exciting new technique ophthalmologists are now using. This is used to treat patients with cloudy corneas. Descemet's stripping allows the cornea to heal much faster, compared to traditional full thickness transplant. This is due to not having a requirement for stitches. The only part of the cornea replaced is the damaged inner layer resulting in rapid recovery of the patient's vision. People with Fuch's Dystrophy and Pseudophalic Bullous Keratopathy are all candidates for DSEK.
30 minutes to 2 hours is the typical amount of time a corneal transplant will take. This procedure will require you to take a pre-operative sedative and a local anesthetic. Technically you will be awake during the operation but very comfortable and not able to feel the procedure taking place. Your surgeon will use a high-powered microscope to complete the task. He or she will remove the damaged portion of the cornea and replace it immediately. To complete that part of the task your surgeon will use a very thin nylon thread. The stitches you receive may be slightly visible to others, but very mild in pain and should not interfere with your vision during the healing process.