The Retina is a Proving Ground for a Broad Range of Neurological Therapies

Many of the benefits of eye research are obvious. Good eye health, and saving and restoring vision from disease and injury, are critical to helping us live independently and perform the many activities that are part of our daily lives such as seeing the faces of friends and family, reading, and driving.

What’s good for the eye is good for the brain

However, research efforts for the eye, especially the development of therapies for the retina, are having a major impact on the advancement of treatments for the brain and neurological diseases and conditions. The retina is also an extension of the brain; its neurons are much like the neurons in the brain and nervous system. The retina, a thin piece of tissue which lines the back of the eye, is comprised of sensory neural cells that enable us to see.

That means that a treatment that might save or restore retinal neurons — some of these are referred to as neuroprotective therapies — might also help people with neurological conditions such as Alzheimer’s disease, Parkinson’s disease, or multiple sclerosis. In fact, the disease processes that occur in the retina are in some cases similar to those that affect the brain. For example, the harmful beta-amyloid proteins found in the brains of those with Alzheimer's disease also accumulate in the retinas of people with age-related macular degeneration, a retinal disease that’s the leading cause of blindness in people 50 years of age and older.

What makes the retina special?

For scientists, the retina is a particularly attractive target to initiate studies of therapeutic drugs and molecules that might ultimately have broad application to the brain and nervous system. The reasons are numerous:

• The retina is a small, clear, accessible target.
• Only a small dose of a therapy is needed. By contrast, it is much more difficult to dose for the brain. Also, less therapy needs to be manufactured for a trial.
• Scientists have technologies to noninvasively measure changes at the retina’s cellular level.
• Clinicians have the tools to easily measure changes in vision.
• Because patients have two eyes, the effect of an emerging therapy in the treated eye can be compared to the untreated eye in a clinical trial.
• A variety of emerging therapeutic approaches for the retina — e.g., gene therapies, stem cells, and drugs — may also be effective for neurological conditions.

A success story

In December 2017, a treatment known as LUXTURNA ™ became the first FDA-approved gene therapy for the eye or any inherited condition. Developed by Spark Therapeutics with preclinical support from the Foundation Fighting Blindness, the treatment has restored vision for children and young adults who were virtually blind from a genetic retinal disease called Leber congenital amaurosis. Thanks in part to the clinical success of LUXTURNA and other emerging retinal gene therapies, the number of gene therapy programs for all diseases has grown dramatically — from about 200 programs in 2014 to more than 700 in 2018 (source Pharma Intelligence Informa).