The last thing most teenagers expect is vision loss. Yet the teen years are the most common age of onset for a condition that causes progressive deterioration of eyesight. Although it does not result in total blindness, at least one in 10 people who have keratoconus (KC) eventually require a corneal transplant to maintain adequate vision for daily tasks.
KC is an inherited condition in which the cornea, the clear part of the eye that refracts light, thins and bulges outward. The misshapen cornea does not function properly, causing blurry vision that worsens over time.
“At first, we can correct the vision with glasses or contact lenses. As the condition progresses, the patient typically needs a hard, gas-permeable contact lens,” says Dr. Stephen Wexler, an ophthalmologist at Eye Care Associates of St. Louis. “The hard contact lens basically creates a new surface for the cornea, but even that may not be a permanent solution. Some patients become contact lens-intolerant, and then we need to look at more involved treatments.”
Before turning to corneal transplantation, a highly successful yet complicated surgery, some patients benefit from Intacs corneal implants. The implants are thin, plastic, semi-circular rings that surgeons insert into the cornea. “This is an intermediate step,” explains Dr. Anjali Pathak, medical director of the Washington University Refractive Surgery Center. “The rigid implants are placed in the periphery of the cornea, and as they flatten the cornea peripherally, it flattens centrally so that we can fit the patient with a contact lens.” Thus, the implants postpone or prevent corneal transplantation.
While corneas are considered one of the most successful organ transplants available, Pathak says that taking steps to avoid such significant eye surgery makes sense in most cases. “During a transplant, we remove the patient’s cornea and replace it with a donor cornea, so there is some risk of rejection,” she says. “Also, when we transplant a cornea we use 16 sutures, and each one can induce astigmatism,” she continues. “These patients still need corrective lenses, and they can still be hard to fit with contacts. There are also risks of infection, bleeding and even vision loss.”
The U.S. Food and Drug Administration initially approved Intacs in 1999 to treat mild myopia (nearsightedness), says Dr. Sean Mulqueeny of Mulqueeny Eye Centers. In 2004, the FDA granted Intacs a Humanitarian Device Exemption (HDE) for the treatment of keratoconus. Medical devices are classed as HDEs when they are used in the treatment of fewer than 4,000 patients per year with rare medical conditions.
“This approval is based on the excellent safety record of the Intacs inserts in patients with keratoconus and myopia, the relatively low number of U.S. patients affected by keratoconus, and the fact that no other treatment options exist for patients with progressive keratoconus other than an invasive corneal transplant,” explains Mulqueeny’s colleague Dr. Senthil Krishnasamy.
Various studies have shown that the procedure halts the progression of corneal thinning and improves vision in 75 to 88 percent of patients, he adds.
Certified Intacs surgeons like Krishnasamy insert the implants into semicircular corneal channels created by a mechanical device or a specialized laser during an outpatient procedure. Vision improvement is noticed shortly after the procedure, he says, and corrective lenses are fitted within a few weeks. Krishnasamy advises anyone who has keratoconus and can no longer wear hard contacts to find an experienced Intacs surgeon for assessment.