The cornea is the clear covering of the front of the eye which bends, or refracts, light rays as they enter the eye. For clear vision to occur, the cornea must have the correct shape and clarity to focus incoming light rays precisely on the retina at the back of the eye. When the cornea becomes cloudy or misshapen from injury, infection or disease, transplantation may be recommended to replace it.
There are several different corneal transplant procedures available to help restore vision in patients with corneal problems. The traditional corneal transplant procedure involves replacing the entire damaged cornea with a healthy one from a human donor, which is obtained from an eye bank. However, technological advances have allowed for the development of specialized procedures that replace only the damaged part of the cornea, while leaving the healthy parts intact.
There are diseases that only affect the innermost layer of the cornea, called the endothelium. The endothelial cells function like a pump and keep the cornea from swelling. Fuchs’ Dystrophy, an inherited eye disease that causes the endothelial cells to degenerate, results in corneal swelling and poor vision. As this condition progresses, vision will continue to worsen as damaged cells cannot grow back. Muro-128 drops or ointment can help reduce cornea swelling with mild-moderate Fuchs, but if the disease progresses it is not
In the past, a patient with a disease that only affected their endothelium needed to have their entire cornea replaced with a donor cornea (penetrating keratoplasty). This required ~ 16 sutures, a long visual rehabilitation, and other risks including rejection and wound dehiscence. Now there are advanced surgical techniques where partial thickness cornea transplants can be performed, and only the diseased part of the cornea is replaced. These newer techniques are safer and provide a faster, better visual recovery than traditional penetrating keratoplasty.
Endothelial keratoplasty (EK) is the generic term for partial thickness cornea transplants that replace the innermost layers of the cornea. Descemet stripping automated endothelial keratoplasty (DSAEK) was the first widely utilized endothelial keratoplasty techinque. Descemet membrane endothelial keratoplasty (DMEK) is the latest iteration of EK and provides, in general, a faster, better visual recovery with less risk of rejection than DSAEK.
Short for Descemet membrane endothelial keratoplasty, DMEK is a partial thickness cornea transplant where the innermost layers of the cornea (Descemet membrane, endothelium) are replaced with donor Descemet membrane and endothelium. This provides an exact anatomic replacement.
The surgery takes roughly 45 minutes and is typically done without the need for general anesthesia. A gas bubble is placed in the eye at the end of the case to help the transplant stay in place, and the patient is then allowed to go home. It is important that patients lie flat for 24 hours to maximize contact of the air bubble with the graft. For the next 48 hours, patients will lay flat 50% of the time (alternating 2 hours up, 2 hours down). Steroid and antibiotic drops will be used as the eye heals. Vision will be blurry initially but typically starts clearing up around day 3-4 (when the gas bubble clears the pupil) and it will improve over the next several weeks.
Short for Descemet stripping automated endothelial keratoplasty (DSAEK), DSAEK is also a partial thickness cornea transplant where diseased Descemet membrane and endothelium are replaced with donor Descemet membrane, endothelium, and posterior stroma (middle layer of the eye).
DSAEK surgery also takes roughly 45 minutes. The type of anesthesia utilized will be discussed with each patient individually. A gas bubble is placed in the eye at the end of the case to help the transplant stay in place, and the patient is then allowed to go home. It is important that patients lie flat for 24 hours to maximize contact of the air bubble with the graft. Steroid and antibiotic drops will be used as the eye heals.
RISKS OF EK SURGERY
While the EK (DMEK, DSAEK) procedures are considered safe for most patients, there are certain risks involved with any type of surgical procedure including infection, bleeding and more. Although rare, there is a risk of transplant rejection, which may result in redness, sensitivity to light and blurred vision. If you are experiencing these or any other symptoms after DMEK or DSAEK, you should contact your doctor to prevent any damage from occurring.
To learn more about the DMEK or DSAEK corneal transplant procedure, and to find out whether or not one of these procedures is right for you, please call us today to schedule a consultation.
There are certain eye conditions where the anterior layers of the cornea are diseased but the posterior layers remain healthy. One example is keratoconus, a condition where the normally round cornea begins to thin and bulge in a cone-like shape. Patients with keratoconus often need a rigid gas permeable contact lens or scleral lens to see to their full potential. In some patients, keratoconus progresses to the point where they can no longer see adequately with glasses or contact lenses. When the disease reaches this stage, a cornea transplant is needed to improve vision. A deep anterior lamellar keratoplasty (DALK) is a type of cornea transplant where the anterior layers of the cornea are replaced with donor tissue, but the posterior layers are left intact. There are multiple advantages to leaving the posterior layers intact, including decreased risk of graft rejection and failure, decreased risk of intraocular infection, and fewer postoperative complications.
Keratoconus is a progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape. The cornea is the clear, central part of the surface of the eye. In patients with keratoconus, the cone-shaped cornea deflects light and causes distorted vision.
Signs and Symptoms of Keratoconus
Keratoconus often begins to develop in the teen years to the early 20s, although it can develop at any age. Changes in the shape of the cornea occur gradually, usually over several years. In most patients with keratoconus, both eyes eventually become affected.
Keratoconus can be difficult to detect because it usually develops very slowly. Signs of keratoconus may include:
- Distorted and blurred vision
- Myopia (nearsightedness)
- Double vision
- Headaches due to eye strain
- Light sensitivity
Corneal Collagen Cross-Linking was FDA approved in the United States in the fall of 2016 and is a great procedure to reduce the risk of keratoconus continuing to progress. This procedure uses ultraviolet light and riboflavin (photosensitizer) to strengthen the chemical bonds in the cornea, with the goal of stopping corneal ectasia (bulging). This procedure is designed to stop the keratoconus from progressing, but it won’t significantly reduce changes that have already occurred. This makes screening in high risk patients, like those with a family history, important because cross-linking can be performed in them before significant changes in their cornea have occurred. Call our office for an appointment or for more details.
In patients who have pathology that affects the entire cornea, like a scar from trauma, a full-thickness cornea transplant (penetrating keratoplasty, or PKP) is required to improve vision.
Pterygium is a growth on the cornea (the clear front window of the eye) and the conjunctiva – the thin, filmy membrane that covers the white part of your eye (sclera). These growths are believed to be caused by dry eye, exposure to wind and dust and UV (ultra-violet) exposure.
In many cases no treatment is needed. Sometimes eyedrops and ointments may be used to reduce inflammation (swelling). If the growth threatens sight or causes persistent discomfort, it can be surgically removed.