Evaluation of Safety of Ciliary Neurotrophic Factor Implants in the Eye

This study will evaluate the safety of a ciliary neurotrophic factor (CNTF) implant placed in the eye to allow the release of CNTF directly on the retina. The results of this study may lead to a larger investigation of CNTF implants to treat retinitis pigmentosa (RP), a progressive degenerative eye disease that begins with loss of peripheral vision and night blindness and often leads to blindness in later life.

Currently, there are no effective treatments for RP. Researchers have found, however, that certain proteins, called ciliary neurotrophic factor (CNTF), can partially protect cells in the eye if given directly inside the eye. A major challenge in treating RP is to deliver medicine directly into the eye. One way to ensure that CNTF gets into the eye is to surgically place an implant inside the eye to release the protein.

Patients 18 years of age and older with retinitis pigmentosa whose visual acuity is 20/100 or worse may be eligible for this study. Candidates will be screened with a medical history, physical examination, eye examinations, and eye photographs. The eye examination includes measurement of visual acuity and eye pressure, examination of the pupils and eye movements, and examination of the lens and back of the eye. In addition, patients will have the following tests:

• Visual field test: Patients look at a central spot on a white screen and tell the examiner whenever they see a small light appear at other places on the screen.
• Electroretinogram (ERG): Electrodes are taped to the patient's forehead. Special contact lenses are placed on the eyes, similar to normal contact lenses, after the eye has been numbed with drops. The contact lenses sense small electrical signals generated by the retina. The ERG measures the electrical activity of the retina when it is stimulated by light. For the ERG recording, the patient looks inside a large, hollow, dark sphere, and sees flashes of light, first in the dark, and then with a light turned on in the sphere.
• Optical coherence tomography: This test, done with the machine used to examine the eye, measures retinal thickness by producing cross-sectional pictures of the retina.

Participants undergo surgery at the NIH Clinical Center in a 30-minute operation to place the implant in one eye. The surgery is done under local anesthetic. Before the procedure, patients are given a steroid injection along side the eye to minimize inflammation after surgery. Following the procedure, patients return for follow-up visits once a month for 6 months. At these visits, several of the exams described above are repeated to evaluate treatment effects and check for adverse side effects. After 6 months, the implant is surgically removed. Post-surgical care for both implant and explant surgeries include examinations the day and week after surgery to examine the wound, a high dose of steroid immediately after surgery, oral antibiotics for 7 days, and eye drops for 1 week to prevent infection and inflammation.