Genetic & Inherited Retinal Diseases
Although most retinal diseases are caused by factors such as age or underlying medical conditions, some are caused by genetic mutations that are passed down from parent to offspring. These conditions are known collectively as inherited retinal diseases. Many of these conditions can cause significant or total vision loss.
Retinitis pigmentosa is characterized by progressive deterioration of the retina’s light-sensitive cells, known as rods and cones. Although it’s considered to be a rare condition in terms of general health, retinitis pigmentosa is one of the most common inherited retinal diseases.
Retinitis pigmentosa is caused by genetic mutations in the genes that control the function and structure of rods and cones. Rods and cones are the photoreceptive cells that facilitate vision by absorbing light that enters the eye and converting it into electrical signals. These signals are sent to the brain in the form of neurological impulses, which the brain processes to form an image. Rods are primarily located along the retina’s peripheral edges and are responsible for perceiving brightness, darkness, shape, size, and movement. Cones are mostly concentrated in the macula, which is the central portion of the retina, and are responsible for visual acuity and color perception.
In the early stages of retinitis pigmentosa, which often first appear during childhood or adolescence, rods begin to deteriorate at an accelerated rate, leading to loss of peripheral vision and night vision. Because their field of vision is becoming increasingly restricted, patients with retinitis pigmentosa often stumble over things or have difficulties navigating through dark areas. As the disease progresses, the cones start to deteriorate as well, leading to decreased visual acuity, tunnel vision, and central vision loss.
Stargardt disease is a type of macular degeneration that is caused by a genetic mutation in a gene that is responsible for the production of specific proteins in the retina’s photoreceptors.
In most cases, Stargardt disease occurs when the retina is unable to produce a protein that filters toxic byproducts away from the retina’s cells. Because the protein is not there to do its job, the byproducts end up accumulating in the retina, forming a substance known as lipofuscin. As the disease progresses, lipofuscin continues to accumulate and damage the photoreceptor cells, eventually leading to cell death and ultimately causing progressive vision loss.
Leber Congenital Amaurosis
Leber congenital amaurosis is a condition that is caused by genetic mutations occurring in some of the genes that govern the development and function of the retina, typically resulting in severe vision impairment starting in infancy. In addition to vision loss, other vision issues that are commonly associated with Leber congenital amaurosis include:
- Photophobia (heightened sensitivity to light)
- Strabismus (crossed eyes)
- Hyperopia (extreme farsightedness)
- Nystagmus (rapid involuntary eye movements)
- Cataracts (clouded lenses)
- Irregular pupil reactions to light
- Irregular retinal pigmentation
Choroideremia is a rare retinal condition that is caused by mutations in a specific gene known as the CHM gene, which plays an important role in cell development and intracellular trafficking. When mutations occur in the CHM gene, certain cellular processes are disrupted, which leads to premature cell death. In the retina, this causes progressive vision loss.
Choroideremia predominantly affects males. Females with choroideremia are typically asymptomatic and act as carriers of the disorder. The condition often first manifests in childhood, causing atrophy of the retina, choroid, and pigmented retinal epithelium. Patients with choroideremia usually lose their peripheral vision but retain central vision, which can last for many decades. Central vision may deteriorate later in life.
How Inherited Retinal Diseases Are Diagnosed & Treated
The study of genetics and inheritable conditions is a constantly evolving field. There are many things that we are only starting to understand and many more that we have yet to discover. When it comes to inherited retinal diseases, the diagnostic process begins with a dilated eye exam, retinal photography, and other tests to assess the patient’s symptoms. At Retina Consultants of Minnesota, we also employ genetic testing to help us determine the presence of inherited retinal disease.
At this current time, most inherited retinal diseases do not have a cure or a standard established treatment. In some cases, symptoms may be managed using low vision aids. That being said, there are many research initiatives and clinical trials that involve gene therapy for inherited retinal diseases, many of which show great promise.
For genetic retinal diagnostics in Minnesota, contact Retina Consultants of Minnesota.