Rare genetic diseases can lead to inherited eye conditions that may impact your vision. Genetic testing is a key way to diagnose these eye issues in order to find support, treatment options, and even gene therapy.

Some visual disorders are the result of genetic mutations. Known as “inherited retinal diseases” (IRDs), these eye conditions have historically been difficult to diagnose and nearly impossible to treat. However, modern advances in genetic testing and gene therapy now offer hope to the 2 million people affected worldwide.

This article will discuss IRDs, possible symptoms you may experience, and who’s most at risk of genetically associated blindness. We’ll also explain how gene testing and gene therapy that can be used to diagnose and treat this inherited form of vision loss.

Research shows more than 260 genes have been identified that may lead to impaired vision and blindness when they contain a mutation.

The only way to know for sure is to go through genetic testing in order to receive a formal diagnosis.

Genetic testing is a multi-step process that may take weeks or months to complete. The process is often as follows:

  • collection of both your and your family’s health history
  • a detailed clinical exam that can include dilation, visual acuity testing, a slit lamp eye exam, imaging, a visual field test, or electroretinography
  • one or more specific IRD and related genes are identified for further investigation based on all the information gathered
  • a blood or saliva sample for analysis of your genome

Along the way, you may work with a genetic counselor to understand and manage the process. The genetic counselor can help you and your family anticipate and manage the emotional impact testing can have.

Additionally, the genetic counselor may help you understand which tests are most likely to be useful and which treatment options are most relevant.

With a combination of information and emotional support, the genetic counselor can help you make decisions about your care. These decisions can include how far to pursue genetic testing.

The most common IRDs are:

  • Retinitis pigmentosa (RP): This is a a genetic condition that causes the light-sensing cells in the retina to die off. The person affected is usually born with RP, but symptoms may not appear until later in childhood and become more noticeable with age.
  • Choroideremia: This disease is brought about by gene mutations that cause the retina and choroid to lose cells. This retinal disease, found primarily in males, causes progressive vision loss usually starting with night blindness.
  • Stargardt disease: This disease is also called “Stargardt macular dystrophy” or “juvenile macular degeneration.” It causes damage to the macula but rarely results in complete loss of vision.
  • Cone-rod Dystrophy (CRD): CRD is a rare group of eye diseases that cause light-sensitive cells (cones and rods) to deteriorate over time. Usually beginning in childhood, CRD affects light sensitivity in the retina and causes blurred vision.
  • Leber congenital amaurosis (LCA): LCA is a rare genetic disorder that can cause blindness in infants, sometimes at birth. LCA is linked to light sensitivity (photophobia), uncontrollable eye movements (nystagmus), extreme farsightedness, slow-reacting pupils, misshapen corneas, and crossed eyes (strabismus).

While some hereditary diseases (like glaucoma and cataracts) can put sight at risk, they’re distinct from other health conditions that have genetic links and may eventually lead to impaired vision or blindness.

An example of such a condition includes diabetes, which raises the risk of vision problems such as glaucoma or macular edema and diabetic retinopathy. However, just because diabetes has genetic links doesn’t mean vision issues are hereditary or guaranteed.

Another example may include sickle cell disease, a genetic condition that’s present at birth. Sickle cell disease is inherited when a child receives two variant genes (one from each parent) that code for abnormal red blood cell hemoglobin and can lead to impaired vision or even blindness over time.

After a diagnosis is made through genetic testing, doctors can then monitor your eyesight and help you find treatment and support as needed. An eye care team will also track your vision with regular exams and can help you find enabling supports and adaptations.

These are possible ways to prevent vision loss if you’re living with an inherited eye disease:

  • Wearing ultraviolet (UV) protective eyewear is often where to start. UV protection reduces exposure to potentially damaging or irritating UV light waves.
  • Lifestyle practices that support good overall health can be helpful in supporting eye health. If you don’t already, consider eating nutritious food, exercising regularly, and not smoking.
  • Assistive tools and technologies are becoming more widely available to people whose eyesight has been affected:
    • Screen readers and voice-recognition software make it easier to navigate computers and other kinds of screens.
    • Mobility aids, such as voice-enhanced GPS and auditory signals at crosswalks, make moving through the streets safer.
  • Specialized lenses or glasses can help correct vision.
  • Adjustable lighting can provide the proper level of brightness, reduce glare, and improve contrast, making it easier to see. Items and tools made to be high contrast, such as computer keyboards and control panels, can be easier to read.

Gene replacement therapy introduces a new gene into the cell to replace the mutated version and restore the cell’s function. For people with IRDs, this means injecting a working copy of the defective gene into the eye.

However, gene therapies to address IRDs are in the early phases and more research is needed. Gene replacement therapy has proven effective in addressing at least one inherited eye disease: LCA.

Researchers are investigating gene replacement therapies that will address other IRDs, and the overall outlook for people living with IRDs is hopeful.

Several clinical trials to investigate specific IRDs are underway and actively recruiting participants. These efforts may offer people affected by IRDs hope for a path forward that will preserve and possibly even improve their eyesight.

So far, the Food and Drug Administration (FDA) has only approved a single gene replacement therapy called “Luxturna.” While this therapy isn’t a cure, it restores sight for people with LCA caused by a mutation in the RPE65 gene.

The approval of Luxturna in 2017 represented a watershed moment in the treatment of IRDs. The approval exemplified that gene replacement therapy can be effective. In response, increased emphasis has been put on developing more gene-based therapeutics and continuing research.

Stem cell therapy may also be possible to restore the retinal pigment epithelium, which is a component of the retina that’s vital for visual functions. Microchip implants are also being tested to help affected eyes regain useful vision.

As always, it’s best to discuss any potential options with an eye care team.

Our understanding of sight loss and blindness caused by gene mutations has improved with the arrival of genetic testing. Vision researchers are discovering multiple new treatment strategies to help restore vision to those affected by IRDs.

These advances, along with the development of gene-based therapeutics like Luxturna, may offer the hope of sight-saving treatments for people living with IRDs.