More than 47 000 cornea transplant surgeries are performed every year in the United States. Since 1961, more than 1 million people have had their eyesight restored with corneal transplants. The goal of this type of surgery is to replace the diseased cornea with healthy corneal tissue from an organ donor.
Corneal eye disease is the fourth most common cause of blindness (after cataracts, glaucoma and age-related macular degeneration) and affects more than 10 million people worldwide. The vision should improve gradually a few weeks after a corneal transplant. However, it can take anywhere from a couple of months to a year to have stable vision in the eye with the new cornea. It’s almost impossible to exactly match the curve of the new corneal tissue to the natural cornea. In all likelihood, there will be a certain degree of myopia and astigmatism. In fact, post-surgery refraction is unpredictable and large amounts of astigmatism will be challenging to correct with soft lenses or eyeglasses. This is due to the suturing and healing process that every transplanted cornea needs to go through with the natural eye. Mild amounts of myopia and astigmatism after a corneal transplant can be corrected with glasses but many times, the vision is unacceptable and rigid gas permeable contact lenses or hybrid lenses are necessary. In our specialty practice, most of these patients are wearing scleral lenses. The main reason we use these lenses are the following:
1. New corneas always have a risk of failure. Any contact lens that comes into contact with the donor cornea can cause irritation by putting mechanical stress on it. This may eventually lead to infection and then graft failure. Scleral lenses vault over the cornea because they are only supported by the white part of the eye. In addition, there is a constant reservoir of fluid (saline solution) between the lens and the cornea to ensure that it remains hydrated. This, in addition to correcting the vision, will protect the cornea from possible failure.
2. Outstanding vision correction. As previously mentioned, following a corneal transplant, there are often significant levels of myopia and irregular astigmatism. These types of refractive error can cause light sensitivity, visual distortion and headaches. A scleral lens is the only technology that can substitute the irregular transplanted cornea as an optical surface. The scleral lens and the layer of liquid behind it provide clear and comfortable vision to the majority of these patients.