Cornea Research Program
The Cornea Research Program within the Department of Ophthalmology-Research investigates diseases and treatments related to the cornea, including:
- Cornea transplantation
- Fuchs' dystrophy
- Laboratory cornea research
- Laser vision correction
- Optical function
Cornea transplantation is a commonly performed transplant of human tissue and has a high rate of success. Transplantation of specific layers, that is, the diseased layers of the cornea (lamellar corneal graft) is possible as an alternative to traditional full-thickness transplants (penetrating graft).
The potential advantages and disadvantages of the lamellar grafting technique are being studied in patients with corneal swelling from diseases such as Fuchs' dystrophy or bullous keratopathy. As part of routine postoperative visits, the corneal testing facility helps evaluate the structure and function of the healing cornea. This research could help the ophthalmology community decide the ongoing debate about which of these two procedures is best indicated for each patient.
Fuchs' dystrophy is a common inherited disease that affects the inner lining of the cornea (corneal endothelium). This thin and fragile layer is responsible for maintaining the cornea's clarity.
Diseases of the corneal endothelium can make the cornea swollen and cloudy, which leads to worsening vision. In Fuchs' dystrophy, corneal endothelial cells are gradually lost during a patient's lifetime and replaced by thickened, irregular bumps (guttae). Even though this is a common disease, the underlying cause is uncertain.
Investigators in the Department of Ophthalmology-Research are attempting to identify genes that might be responsible for Fuchs' dystrophy. Discovery of a genetic cause would assist in early identification of affected patients and could ultimately lead to gene therapy and alter the course of this progressive condition.
Laboratory cornea research
Researchers are also conducting laboratory studies aimed at developing a useful method for corneal cryopreservation, which would then allow permanent storage and true eye banking.
Donor corneas from donors who have consented to donate their eyes after death currently can be preserved for about only one week in U.S. eye banks. Permanent corneal storage could be obtained by cryopreservation at very low temperatures, but to date this method has not proved satisfactory for clinical use.
Donor corneas need a sufficient number of endothelial cells, which are responsible for corneal clarity, to qualify for successful transplantation. Many donor corneas can't be transplanted because they don't meet this criterion. These cells are needed because they do not normally divide, and so their numbers can't be replaced after transplantation.
In laboratory studies, Mayo Clinic researchers are developing methods to stimulate these cells to divide during donor corneal storage in order to increase their numbers, which would enable more corneas to qualify for transplantation, increasing donor supply.
An experimental model of corneal transplantation allows researchers to test the effectiveness of new methods of corneal storage before they are used in people. Researchers can also test new techniques for transplantation, such as the use of lasers, which improves the safety of transplantation techniques.
Laser vision correction
Refractive surgery, also called laser vision correction, is a common elective corneal surgery. People with refractive errors, such as myopia or astigmatism, may be candidates for laser vision correction, enabling them to see better without spectacles or contact lenses.
Refractive surgery has been performed with great success, but potential longer term consequences are still being investigated.
Mayo Clinic researchers have been studying a small group of patients who had the most common types of refractive surgery — laser-assisted in-situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) — in 1998, when the procedures were first introduced. The longevity of these studies and the detailed prospective evaluation of the cellular effects of laser corneal surgery are unique to Mayo Clinic.
Another research study compares PRK to its variant procedure known as laser-assisted subepithelial keratomileusis keratectomy (LASEK).
PRK and LASEK are both refractive surgery procedures that don't involve the creation of a flap, as LASIK does. Instead, the cells from the corneal surface (epithelium) are removed and laser treatment is applied to the underlying corneal stroma. PRK and LASEK only vary by the method of removal of the surface cells.
Studying the cellular response to the different methods of surface cell removal in the corneal-testing facility can help answer frequently debated questions in the refractive surgery community and provide new long-term data for these procedures.
The Cornea and External Eye Disease Service of the Department of Ophthalmology-Research at Mayo Clinic in Rochester, Minnesota, is evaluating the optical function of the cornea in response to various corneal surgeries, including corneal transplantation and laser vision correction of refractive errors, such as nearsightedness (myopia) and astigmatism.
The ability to see is the result of complex interactions involving all layers of the eye and the brain. Typically, vision (visual acuity) is measured by using an eye chart, but a true evaluation of visual function is much more difficult to assess.
The eye disease service explores how the cornea contributes to overall visual function. This is done using instruments that measure the cornea's curvature, clarity and thickness, and with the microscopic analysis of the cellular layers of this clear tissue. These measurements are correlated to a patient's visual function as measured by the ability to see fine detail and contrast.
These analyses require an array of testing devices and microscopes that result in some of the most detailed studies of human corneal function performed in the United States. The eye disease service occasionally recruits study participants with normal, abnormal or post-surgical corneas to obtain baseline or preliminary data with these various testing methods.