What is the Cornea?
The cornea is the transparent structure on the front of the eye through which we see. It is the tissue that is reshaped during laser vision correction. It begins the process of seeing by focusing onto the retina the light that it receives. There are five layers to the cornea, each with a distinct function: epithelium, Bowman’s membrane, stroma, Descemet’s membrane and endothelium.
Why Choose Us?
Our Cornea and External Diseases staff specializes in diseases of the eye’s external surface and cornea (such as inflammatory, infectious and degenerative diseases of the cornea, conjunctiva and lens) and contact lens-related problems. Our surgeons perform more than 1,700 cataract surgeries each year, with excellent outcomes and low complication rates.
Our corneal transplant surgeons also perform state-of-the-art procedures for numerous conditions that distort or cloud the cornea, including Descemet’s stripping automated endothelial keratoplasty (DSAEK), deep anterior lamellar keratoplasty (DALK) and other highly specialized transplants for very uncommon sight-threatening corneal conditions.
What We Treat
- Cataracts and Intraocular Lens Implantation
- Cataract Surgery
- Corneal Abrasion
- Corneal Conditions
- Corneal Dystrophies
- Corneal Infections
- Fuch’s Dystrophy
- Herpes Zoster (Shingles)
- Lattice Dystrophy
- Night Blindness
- Night Blindness (Low Vision)
- Ocular Herpes (herpes of the eye)
Intraocular Lens Implantation
What is an intraocular lens?
The eye contains a lens that focuses light so we can see. Sometimes the natural lens of the eye turns cloudy (which is called a cataract), and the only way to let light into the eye is to remove the whole lens. The natural lens is almost always replaced with an implantable medical device called an intraocular lens.
Why do people need intraocular lenses?
When natural lenses are removed from the eyes in cataract surgery, the eyes are left like cameras with no lenses. Even though light can get through, it will not make a clear image - just a fuzzy blur. The eyes need some kind of replacement lenses to be able to focus again.
Are there any alternatives to intraocular lenses?
Before intraocular lenses were invented, doctors could only prescribe eyeglasses or contact lenses after cataract surgery. Usually, the eyeglasses had to be very thick (“Coke-bottle” glasses) in order to match the strength of the eye's natural lens. But vision is not very good when eyeglass lenses are so thick, and thick contact lenses are not a much better option. Intraocular lenses were invented to solve these problems.
About 2 million people per year in the United States have cataract surgery, and almost all of them receive an intraocular lens. There are many different kinds of intraocular lenses. Your doctor can decide which lens is right for you only after a careful examination of your eye.
Intraocular lenses can be divided into two main groups: non-foldable and foldable. Intraocular lenses were originally made from a hard plastic material, but materials were later invented to make soft lenses that could be folded in half. This type of intraocular lens can be inserted through a smaller opening in the eye, which can be better for the patient because smaller incisions usually heal faster than larger ones.
What happens in the operation to implant intraocular lenses ?
Intraocular lenses are usually implanted during cataract surgery, which is usually performed with local anesthesia. That is, the patient is awake but does not feel the procedure. In a few cases, the surgeon will use general anesthesia (the patient is “asleep”).
The surgeon will make a very small opening in the front of the eye so the cloudy lens can be removed. There are two ways to remove the lens. One way is to remove it whole and the other is to use a special instrument to break the lens into pieces, then remove those pieces through a small incision.
Most cataract surgery is done with an instrument that breaks up lenses with ultrasound: sound waves that are too high in frequency for humans to hear. The energy from these ultrasound waves breaks up the lens in a process called phacoemulsification.
After the natural lenses have been removed, the intraocular lenses are placed into the eye. Usually, the intraocular lens goes where the natural lens had been. This area of the eye is called the posterior chamber. Sometimes, however, that might not be the best place for the intraocular lens so some lenses are designed to be placed in the anterior chamber, the area in front of the colored iris of the eye. Both types of lenses work well at putting the eye back into focus. Depending on which method of lens removal is used, the opening in the eye might not even need stitches. The patient is usually ready to go home about an hour after surgery.
Cataract surgery is sometimes performed without implanting intraocular lenses. It is usually possible to implant an intraocular lens at a later time. Surgeons often recommend the anterior chamber type of lens for those patients.
How successful are intraocular lenses?
More than 90% of the people who have cataracts removed see better after surgery than they did before. An important part of successful cataract surgery with an intraocular lens implant is following your doctor's instructions after surgery. Eye drops are prescribed after surgery to help the eye heal better and to prevent infection. Your doctor will have to examine your eye after surgery to make sure it is healing properly and to check your vision. It is important to keep these appointments with your doctor.
Does anyone need to wear eyeglasses or contact lenses after receiving an intraocular lens?
Most intraocular lenses are chosen to focus at what doctors call “distance” vision. By “distance,” they mean anything farther than 2 or 3 feet away from the eye. If the lenses are focusing at distance, eyeglasses will be needed to see clearly close-up. Many people who have cataract surgery are already used to wearing bifocals, so they are familiar with this type of vision.
What is corneal transplantation?
The cornea is the central part of the front of the eye through which we see. Normally, the cornea is smooth and clear. However, injury, disease or certain medical conditions can make it cloudy or difficult to see through. Sometimes this problem can be fixed by removing some or all of the cornea and replacing it with corneal tissue from an organ donor. This operation is called corneal transplantation.
About 46,000 corneal transplantations are performed in the United States every year, according to the Eye Bank Association of America. Information about becoming a corneal donor is available on the association's Website: www.restoresight.org.
Is it safe to receive donated corneal tissue?
Yes. The medical history of every organ donor is reviewed carefully, and blood tests are performed to check for infections prior to corneal transplantation. If there is any doubt about the safety of corneal transplantation, the donated tissues are used for medical research instead of being transplanted into a patient's eye.
Why do people need a corneal transplantation?
A doctor can recommend corneal transplantation only after a careful examination of the eye. The most common reasons for performing the operation are:
- Injury to the eye — Sometimes an injury will damage the cornea so severely that it will not heal correctly. The cornea plays an important role in vision, so even a small injury to it can greatly reduce vision. The doctor might recommend a corneal transplant to improve vision or, in more serious injuries, a transplant might be the only way to close the wound in the eye.
- Medical conditions — Some infections of the eye can cause damage to the cornea that will not heal. There are also certain medical conditions that make the cornea very thin or cloudy, or cause other problems that can only be treated by replacing the cornea.
- Pseudophakic bullous keratopathy — Some people experience corneal swelling and clouding after cataract surgery. This is known as pseudophakic bullous keratopathy and is a common reason for corneal transplantation.
- Keratoconus — Sometimes the cornea is thin and weak, and the normal pressure inside the eye makes the cornea bulge outward in a cone shape. This is called keratoconus, and it causes severe vision problems. If these problems are very troublesome, the doctor might recommend a corneal transplant. More information is available in the Keratoconus fact sheet available from the Cole Eye Institute.
What happens in a corneal transplantation operation?
Corneal transplantation can be done under general anesthesia; that is, with the patient “asleep.” Local anesthetic, in which the patient is awake but does not feel the procedure, also can be used.
A portion of the cornea is removed using scissors and a special instrument called a trephine, which works something like a tiny circular cookie-cutter. This leaves an opening in the patient's cornea.
A similarly sized trephine is used to cut a section from the donor cornea. This section of corneal tissue is placed into the opening in the patient's cornea and fastened with very small stitches. Many patients qualify for a partial-thickness corneal transplant procedure called DSAEK (Descemet's stripping with automated endothelial keratoplasty) tailored to particular corneal disorders. This procedure can provide faster recovery with less visual distortion.
After surgery, it is important not to put any pressure on the eye. It is best not even to touch or rub anywhere near the eye, so the doctor might put a shield over it. Wearing glasses or sunglasses will also help protect the eye.
Your doctor will prescribe eye drops to help the eye heal and prevent infection. It is necessary to keep using some of these medications for several months after a corneal transplant. Without these medications, the eye is much more likely to have problems with the new corneal tissue.
How successful is corneal transplantation?
The majority of the corneal transplantations done in patients with keratoconus, corneal scars and most types of corneal disease are successful. The operation is less successful in eyes with a corneal infection or severe injury such as a chemical burn. In a small number of cases, the new corneal tissue is rejected by the body even though the operation was successful and all medications were taken correctly.
The best way to avoid problems after corneal transplantation is to follow all of your doctor's advice, including using all medications as recommended and keeping all follow-up appointments. At these appointments, the doctor will check your vision in the eye with the transplant. It is not unusual for that eye to have vision that is very different from the other eye. This difference can be very disturbing, but eyeglasses or contact lenses can improve the situation. Vision can change rapidly after corneal transplantation, so it is necessary to visit the eye doctor more often than usual.