In order to maintain good vision, the cornea (see section on Refractive Error and Ocular Anatomy) must remain crystal clear. Because it is under pressure, the fluid within the eye is constantly being forced into the cornea, which absorbs it like a sponge. A special layer of cells lines the inside of the cornea, serving to pump the fluid back into the eye, maintaining the cornea’s clarity. These cells are known as the corneal endothelium.
With age, or sometimes due to injury or other cause, these endothelial pump cells start to die. During an ocular examination, an eye doctor may notice guttae, small areas of abnormal material where the endothelial cells have been lost. It is common to see a few guttae in middle-aged and older individuals- up to 70% of people over 40 have them.
In some cases, however, the presence of more numerous guttae may signify the onset of a disease known as Fuchs’ Dystrophy. This disorder is probably hereditary, though the genetics are not well understood presently. Women tend to be affected more frequently and severely than men. With time, more and more endothelial cells die, leading to more visible guttae. As the endothelial pump function is lost, the cornea is unable to keep out fluid and it begins to swell, a condition known as corneal edema. This edema leads to blurred vision, which becomes worse as the disease progresses. At times the corneal surface can swell and form bullae, or blisters, leading to significant discomfort and foreign-body sensation. Ultimately, scarring of the corneal surface may develop, leading to significant vision loss.
Treatment of Fuchs’ Dystrophy depends upon the severity of disease. Symptoms are rare before age 50. For many, there are no symptoms at all and no specific treatment is required. For some, vision is blurred in the morning due to corneal swelling which develops overnight while the eyes are closed. Use of hypertonic saline ointment, such as Muro 128®, in the evenings can help alleviate this morning blurring. Hypertonic saline drops can be continued during the day if needed to help limit the degree of corneal swelling, improving both vision and comfort.
In more advanced cases, where the cornea becomes too swollen and hazy to treat medically, surgery may be necessary. Traditionally, full thickness corneal transplantation has been the standard procedure performed, and in much of the U.S. and the world remains the procedure of choice. A newer surgery, however, is performed by our physicians in many cases. Known as Deep Lamellar Keratoplasty (DLEK), this procedure involves replacement of only the inner layers of the cornea, including the diseased endothelial cells, while leaving the outer layers of the patient’s cornea intact. The benefits of this procedure over standard corneal transplantation include faster recovery, better uncorrected vision, and a structurally stronger eye with less susceptibility to injury. In most cases, the prospects for long term surgical success and good vision are excellent.