Inherited Retinal Disease and Gene Therapy

Five years ago, ophthalmologists might have been able to offer nothing more specific than a clinical suspicion that a patient had an inherited retinal disease. With treatment theoretical at best, genetic testing cost-prohibitive, both doctors and patients found their interactions demoralizing.

Since then, researchers have developed free and readily accessible genetic panels to help diagnose an inherited retinal disease. Instead of settling for a generic diagnosis based only on clinical criteria, doctors can name a disease based on specific mutations. By screening multiple family members, they can better understand inheritance patterns and the probabilities of transmitting the disease to future generations. Meanwhile, treatment prospects have improved.

Inherited retinal disease and gene therapy

What Is Retinitis Pigmentosa?

Peripheral pigmented bone spicules

Fig. 1: Peripheral pigmented “bone spicules, as seen in these fundus photographs, are a common finding of retinitis pigmentosa.

Retinitis pigmentosa is a group of rare eye diseases that affect the light-sensitive layer of tissue in the back of the eye. They stem from congenital defects in a person’s DNA and they’re progressive. They make cells in the retina break down slowly over time, causing patients to lose side vision and eventually central vision. Macular dystrophies, as the name suggests, affect the central part of the retina, the part responsible for reading and picking up details.

Symptoms usually start in childhood; parents may find that children have trouble adjusting to darkness or moving around in dim light. They may be unusually sensitive to bright light and lose some of their color vision. Over time, the field of vision narrows to create tunnel vision.

Unfortunately, patients with retinitis pigmentosa are also prone to other eye diseases, such as cataracts, refractive errors and edemas, the small pockets of fluid that cause swelling. Regular eye exams remain crucial in detecting these other conditions before they worsen.

How Can Gene Therapy Help?

Conventional treatments have targeted the inflammatory nature of these diseases, but not the underlying genetic issue. Our medical field has now entered the world of gene therapy with some patients able to receive the healthy, functioning version of their mutated gene.

The first breakthrough came five years ago, when the FDA approved Luxturna (voretigene), an implant created by Spark Therapeutics. Patients with bi-allelic RPE65 mutations, most of them young people, were treated with subretinal injections of this healthy gene in a viral vector. Visual gains have been modest but uplifting.

Variations Even Within a Family

Remarkably, there can be a fairly wide range of phenotypes within one family. This may be due to differences in sex or many other modifying factors in our genetic makeup. If either parent has a dominant gene for retinitis pigmentosa, they have a 1 in 2 chance of passing it down to a child. If both parents carry the recessive gene for it, they have a 1 in 4 chance of giving it to their offspring.

Researchers continue to analyze the various types of retinitis pigmentosa, in hopes of finding gene therapies that will address them all. With concrete genetic information, doctors can more confidently outline a patient’s visual prognosis.

To schedule a consultation with one of the retina specialists at Horizon Eye Care, call 704-365-0555 Monday-Thursday, 8 a.m. to 5 p.m., or Friday, 8 a.m. to 3 p.m. The optical department closes on Fridays at 2:30 p.m.