Corneal Disease

The cornea is a .5 mm thick membrane consisting of five layers that constitute the front surface of the eye. This structure is disc shaped and is approximately 12 mm in diameter.

In order to provide good clear vision, the cornea must be transparent. This tough connective tissue is the most important refractive surface of the eye and does more to focus the entering rays of light than any other structure. For this reason, any defect or opacity in the cornea will have a profound effect on vision. In addition, the cornea has many nerve endings and even the slightest scratch can be extremely painful. The cornea maintains its integrity through different means, one of which is the constant flow of tears, which spreads over the eye through eyelid movement. Any condition that decreases the amount of tears or decreases the lid action will cause drying, discomfort and clouding of the cornea. Approximately 6 percent of blindness in the United States is caused by injury of diseases involving the cornea.

The most common symptoms of cornea disease include the following:

• Blurring of vision with a diffuse cloudy appearance.
• Multiple images seen when only one eye is open.
• Burning and irritation of the eye.
• A foreign body sensation as if a small piece of sand or other particle is felt underneath the eyelid.

One of the advantages in examining and treating the cornea is its accessibility for examination. It is easily examined with a slit lamp biomicroscope. There are also additional instruments used in examining the cornea, such as a keratometer, which measures the curvature of the anterior surface of the cornea, and a specular microscope.  This instrument is designed to see the endothelial cells lining the posterior surface of the cornea.

There are various types of corneal diseases and corneal conditions with many modalities of therapy. Treatment can involve the use of teardrops, antibiotics, steroid drugs, antiviral drops, soft contact lenses and surgery. When the cornea is significantly scarred, the only treatment that leaves any permanent visual result is a cornea transplant.

Corneal Transplant

The corneal transplant is the most successful of all transplant operations. In this procedure, a clear, healthy cornea is taken from a person who has arranged to donate his or her eyes prior to their death. It must be removed from the donor within a very short period of time following death and preserved.

The corneal transplant will only help patients whose cornea is scarred but the rest of the eye is good. Therefore, the ophthalmologist must examine the eye carefully to decide if the eye is stable and if the cornea transplant will be of help. It is frequently necessary to examine the eye with an ultrasound machine. This allows us to see behind the scarred cornea and evaluate the status of the posterior segment of the eye.

Because of the requirement for freshly donated eye tissue, it is sometimes difficult to give an exact date for surgery, but you will usually be given an approximate time and your name will be placed on the list of patients awaiting cornea transplants. When the cornea becomes available, you will be notified. The surgery is done on an outpatient basis under local anesthesia.  The operation is done under microsurgical conditions and the cornea is sutured in place with fine nylon sutures, which are thinner than a strand of your hair. There is minimal pain after the operation. You will feel some mild discomfort and sticking and a sensation of something being in your eye, which will be the stitches. The eye will water and "matter" for the first week or so. Vision will improve slowly and gradually over a period of several months to a year. The eye is bandaged only a day, and a metal eye shield is worn at night in order to prevent you from accidentally injuring the eye. Normal glasses can be used during waking hours and activities are limited for only a short period of time. The opposite eye is not bandaged. The operated eye is protected carefully during the healing period because nerves do not grow in the new cornea for many months and it is subject to drying if wind, dust, water or other irritants, such as shampoo, get into it. For this reason, you are asked not to wash your hair for the first week. After surgery, you will be given medication in drop form to use to treat the eye.

Post-operative visits will vary according to your condition but will usually be more frequent the first couple of weeks post-operatively and then decrease in frequency as the eye stabilizes. The stitches used in the surgery are small and "buried" so they offer very little irritation. The sutures can be removed anywhere from a few months up to a year, depending upon the technique and type of sutures used. There are also techniques that allow the sutures to remain in place permanently.

Spectacles and contact lenses are usually fitted after a year, and it is frequently necessary to wear contact lenses as opposed to spectacles to get the best vision. This is due to residual astigmatism.

The most important factor in determining the success of the transplant surgery is the disease that required it in the first place and the quality of the tissue used. For this reason, eye banks with strict quality control mechanisms have been established and corneal tissue is always of high quality.

In spite of all these efforts, not all cornea transplants are successful. Conditions such as keratoconus have a success rate of well over 90 percent. In some badly scarred and vascularized corneas, the success rate may be less than 50 percent. One of the reasons for failure can be rejection of the donor cornea. Graft rejection can occur in 15 percent of the cases and can frequently be caught in time and treated vigorously and sometimes reversed. For this reason, it is important you report any sudden change in your condition. Even if the cornea is rejected, a repeat graft can be done several times.

Other complications may include drying or breakdown of the corneal surface, which may require special soft therapeutic lenses and increased lubrication of the eye. Glaucoma can develop, which may be transient or permanent, but usually it can be controlled by medication. Occasionally, additional surgical procedures are required.  This may occur when sutures become loose or other problems develop. Rarely, serious complications, such as hemorrhage or infection, can occur. As with all conditions, you should take specific instructions from your doctor, so he can tailor your treatment to your eye condition and fully explain all risks, complications and alternatives. Fear of cornea transplants has been replaced by hope given through new advanced microsurgical techniques and the improvements in eye banking methods.