DHA and X-Linked Retinitis Pigmentosa
This study is currently recruiting patients. For more information Click Here
Retinitis pigmentosa (RP) is characterized by progressive loss of visual function due to specific genetic mutations. This
trial is focused on patients with one of the most severe forms of the disease, X-linked inherited RP (XLRP). This disease
is characterized by early onset (typically loss of night vision as a child) followed by loss of peripheral vision as a teenager
and young adult. There is no male-to-male transmission of the disease in the family. There is no cure for RP and treatment
options are limited. Two clinical trials have not found a benefit from nutritional supplementation with the long-chain polyunsaturated
fatty acid, docosahexaenoic acid (DHA), at low daily doses although there is evidence that it slows disease progression in
certain instances. In this clinical trial, we propose that a high dose nutritional DHA supplement will slow the loss of visual
function and preserve usable vision in patients with XLRP.
This study is a 4-year placebo-controlled randomized clinical trial meaning that patients have a 50-50 chance of receiving
placebo or experimental treatment. A total of 60 patients will be enrolled; 30 will receive placebo and 30 will receive the
treatment. Entry criteria include diagnosis of XLRP by an ophthalmologist, age 8 to 32 years, male, sufficient visual function
such that disease progression can be followed for the entire duration of the trial, and a willingness to visit the testing
site (Dallas, TX) once a year.
Annual visual function testing includes ETDRS visual acuity, full-field and multifocal electroretinography (ERG), static
peripheral visual fields, and fundus photography. Cone ERG function is the primary outcome measure. All testing is free of
charge to study participants, expenses for travel and accommodations in Dallas (for example, Holiday Inn) are covered as well
as a $200 incentive for each completed visit.
Natural History and Genetic Studies of Usher Syndrome
This study is currently recruiting patients. For more information click here
This study will explore clinical and genetic aspects of Usher syndrome, an inherited disease causing deafness or impaired
hearing, visual problems, and, in some cases, unsteadiness or balance problems. Patients with type 1 Usher syndrome usually
are deaf from birth and have speech and balance problems. Patients with type 2 disease generally are hearing impaired but
have no balance problems. Patients with type 3 disease have progressive hearing loss and balance problems. All patients develop
retinitis pigmentosa, an eye disease that causes poor night vision and eventually, blindness.
Patients of any age with Usher syndrome may be eligible for this study. Patients who have had eye and hearing evaluations
are asked to send their medical records to the research team at the National Eye Institute (NEI) for review. They are also
asked to have a blood sample drawn by a medical professional and sent to NEI for genetic analysis. Finally, they are interviewed
about their family histories, particularly about other relative with eye disease. Patients who have not been evaluated previously
have the following tests and procedures at NIH:
-Family medical history, especially regarding eye disease. A family tree is drawn.
-Blood draw for genetic studies of Usher syndrome.
-Eye examination to assess visual acuity and eye pressure, and to examine pupils, lens, retina, and eye movements.
-Electroretinogram (ERG) to test the function of visual cells. Wearing eye patches, the patient sits in a dark room for
30 minutes. Electrodes are taped to the forehead and the eye patches are removed. The surface of the eye is numbed with eye
drops and contact lenses are placed on the eyes. The patient looks inside a hollow, dark globe and sees a series of light
flashes. Then a light is turned on inside the globe and more flashes appear. The contact lenses sense small electrical signals
generated by the retina when the light flashes.
-Fluorescein angiography to evaluate the eye's blood vessels. A yellow dye is injected into an arm vein and travels to
the blood vessels in the eyes. Pictures of the retina are taken using a camera that flashes a blue light into the eye. The
pictures show if any dye has leaked from the vessels into the retina, indicating possible blood vessel abnormality.
-Hearing tests to help determine the patient's type of Usher syndrome. Tests to evaluate hearing include examination of
both ears with an otoscope, evaluation of the middle ear and inner ear, and hearing tests using earphones that deliver tones
and words the subject listens and responds to.
-Vestibular testing for balance function. Balance testing involves three procedures:
Videonystagmography: This test records eye movements with little cameras. First the patient follows the movements of some
small lights. Next, while wearing goggles, the patient lies on an exam table and turns to the right and left. Lastly, a soft
stream of air is blown into the patient's ears four times, once in each ear with cool air and once in each ear with warm air.
Rotary chair test: With electrodes placed on the forehead, the patient sits in a rotary chair in a dark room. Several
red lights appear on the wall of the room and the patient follows the lights as they move back and forth. Then the chair turns
at several speeds, all slower than a merry-go-round.
Vestibular evoked potential: Electrodes are placed behind the patient's ear and at the base of the neck. Seated in a reclining
chair and wearing earphones, the patient hears a brief series of loud clicking sounds. When the sounds are on, the patient
is asked to lift his or her head up a few inches from the chair. The electrodes record information from the muscles in the
neck as the sounds enter the ear.