Dr. Dennis Hoffman, along with colleagues at the Retina Foundation and Texas Retina Associates, is conducting a Phase II Clinical Trial to better understand the potential for DHA supplemenatation to slow vision loss in patients in the early stages of one of the most severe forms of retinitis pigmentosa (RP), namely X-linked RP. It is thought that dietary supplementation with high doses of DHA may slow the progress of the disease as well as other forms of retinal degenerations, including age-related macular degeneration.

DHA, or docosahexaenoic acid, is an omega-3 fatty acid that is found in its highest concentration in humans in the brain and retina. It is currently considered a conditionally essential nutrient for optimal eye and brain health. Although our bodies can make small amounts of DHA, we must get the rest that we need from our food or from supplements. DHA is found in cold water fatty fish such as salmon, tuna, mackerel and sardines. Dietary DHA supplements are made from either fish oil or algae.

Researchers have found that patients with some forms of RP have reduced blood levels of DHA. It remains a puzzle as to why systemic levels of DHA would be reduced in a disease only affecting the eye. Nevertheless, this finding led to the question of whether or not DHA supplementation might slow the progression of vision loss.

There have been two previous clinical trials of DHA supplementation whose results were encouraging but not conclusive. Dr. Hoffman thinks that a higher dose of DHA than was used in the other trials may be needed to slow vision loss associated with RP. In this 4-year trial, 64 persons with X-linked RP receive either a high-dose DHA supplement or a placebo. Participants in the study come from across the U.S. and Canada, and sometimes include siblings.

“The benefits of DHA nutritional supplementation have not been defined as a treatment for RP, yet many patients with RP will self-medicate with DHA or fish oil, which contains DHA,” said Dr. Hoffman. “Thus, the goal of this trial is to definitively establish if DHA supplementation is giving false hope to patients with RP or is actually beneficial in slowing the loss of vision in patients with this blinding eye disease.”

Retinitis Pigmentosa (RP) is the most common inherited eye disease, affecting approximately 100,000 people in the U.S. People with RP have difficulty seeing in the dark or in dim lighting due to loss of rod photreceptors. As the disease progresses, they lose cone photoreceptors, causing a loss of peripheral vision that ends in tunnel vision. As patients grow older, the disease often leads to legal blindness.

X-linked RP is one of the most severe forms of RP and affects mainly males. It typically is detected as early as 4 or 5 years of age and leads to legal blindness by the third to fourth decade of life. Many patients with X-linked RP will never drive a car.

At present over 100 mutations in different genes have been identified that lead to RP. The severity of the disease and the time frame over which it occurs vary greatly depending on the affected gene. At present there is no known cure for this most common genetic eye disease.

Aaron (17) and Adam (20) DeLong are enrolled in the Retina Foundation's Phase II Clinical Trial for DHA Supplementation.

Aaron thinks they are participating in a worthwhile cause. "My RP isn't as severe as my brothers. So far, my eyes have not gotten worse. Only my night vision is affected so it hasn't been much of a problem. I am still driving and have my own car. Hopefully, the results from the trial will be good."

Adam and Aaron grew up Toledo, Ohio with their parents, Anne and John DeLong, two older brothers, Nick (27) and Nathan (22), and four dogs. Nathan is the only one of the brothers who does not have X-linked RP.

Anne DeLong remembers that "life was pretty normal around our house except that we left a lot of lights on." All of the boys learned to handle not being able to see in the dark. As the eldest, Nick was the pioneer. He was the first one, for example, to go to dances. Once he learned how to adjust to the dim lighting, he went to every dance and danced with all the girls. He joined the glee club and had one of the leads in the school play. "The boys constantly amaze us with the things they can do," say the Delongs.

Anne and John encouraged all of their sons to get an education. They explained that "we knew our boys were very smart and decided early on to let them show us what they could do." Today, Aaron is a high school junior and a potential national merit scholar. He is interested in the sciences, in designing more efficient cars and in helping the environment. Adam is majoring in clinical psychology at Bowling Green State University. Nathan is going to radiology school to be an X-ray technician. And Nick now lives in Austin, Texas, where he is an electrical engineer at Freescale Semiconductor.

As Nick and Adam got older, their RP got worse and they were no longer able to drive a car. Fortunately their brother Nathan was there to help with driving. "He has always taken very good care of his brothers," says Anne.

According to the DeLongs, the most difficult thing about raising children with a blinding eye disease - and they have talked with other parents about this - is that when you have a child with RP, things can compound so quickly. Anything that goes wrong can make life so much more difficult. That is why having a family that works together is important.

The DeLongs are also proud of the way Adam and Aaron have stuck with the study at the Retina Foundation. Four years is a long time to be involved in a clinical trial and to have to keep taking the pills and coming back to Dallas for testing.

Researchers at the Retina Foundation greatly appreciate the participation of the DeLong brothers and of all the other patients who are involved in this Phase II clinical trial.