Inherited retinal dystrophies (IRD) are a set of rare eye diseases. They affect your retina, or the part of your eye that detects light.
If you have IRD, you may find it hard to read or see in low light. Over time, you may lose part or all of your vision. There isn’t a cure, but an early and accurate diagnosis is key to helping you and your family plan for the future.
You’ll need specialized tests to find out if you have IRD. Your eye doctor may order some or all of the following.
These tests give your eye doctor a closer look at the health of your retina. You may get some painless eyedrops to widen, or dilate, your pupil beforehand.
Retinal imaging may include:
Optical coherence tomography (OCT). You’ll look into a machine for 5 or 10 minutes. Light waves will scan your eye. Your doctor will get highly detailed images of the layers and thickness of your retina.
Color fundus photography. A special camera takes pictures of your fundus, or the inner lining of your eye. These images show problems with blood vessels and other structures in your retina.
Autofluorescence (FAF). This exam shines blue light on your retina. That makes certain cells light up. This “glow” is called fluorescence. Certain patterns of it are linked to eye diseases.
Fluorescein angiography. Your doctor will put a special dye in a vein in your arm. The same camera used for fundus photography will record the blood flow in your eyes. These images can show if you have problems with the blood vessels in your retina.
Visual Field Testing
Your doctor can use visual field tests to check all areas of your eyesight. That includes what you see straight in front or to the side. That’s your central and peripheral vision.
It usually takes about an hour to test your visual field, but your part is pretty simple. You’ll need to:
- Look inside a bowl-shaped device.
- Stare at the center.
- Press a button every time you see a light flash.
The sparks of light start wide and get closer to the center of your vision. A computer makes a note of when you do or don’t see the light. This makes a “map” of your visual field. Your doctor uses the results to see where you have vision loss and how serious it is.
Repeat tests can gauge how IRD is changing your eyesight and how your treatment is working in relation to that.
You have light-sensitive cells in your eye. They’re called rods and cones. They send electrical signals from your retina to the part of your brain that processes vision. If you have IRD, these photoreceptors may not work very well.
ERG measures electrical activity in your retina in response to different kinds of light. It might show damage to your photoreceptors before you lose any vision.
The test usually takes about an hour. But you might be at your doctor’s office for several hours, especially if you need other IRD tests during the same visit.
You may get:
- Full-field ERG. This measures how well your entire retina responds to light or dark.
- Multifocal ERG (mfERG). This looks at how different parts of your retina respond to bright or dim light.
A technician will put numbing drops in your eye before the ERG. After that, they’ll give you a special kind of contact lenses. These use electrodes to record how your retina responds to light. None of this should hurt, but you might feel some discomfort.
You don’t have to do anything special to get ready for an ERG. Your doctor will ask you not to wear any eye make-up though. Kids who are very young may need to get this test while they’re asleep.
ERG isn’t always needed to diagnose IRD. You’re more likely to get this test if you see certain kinds of retina specialists.
IRDs are hereditary. The cause is a changed, or mutated, gene you inherit from one of your parents.
There are more than 300 known genes linked to IRDs. Your doctor can use a sample of your saliva or blood to find out exactly which one you have. Keep in mind that a “negative” test result doesn’t rule out IRD. It might mean the test wasn’t sensitive or specific enough to find the gene change that’s causing your vision loss.
Compared to a decade ago, it’s more common for doctors to order genetic tests early on. You may be able to get the results back in 2 to 4 weeks. Sometimes it may take longer.
A genetic counselor can help you weigh the pros and cons of genetic testing. Bring up any of your worries. You can also ask about how these results can:
- Confirm your diagnosis
- Help you plan for the future
- Steer family members toward testing
- Put you in the right clinical trial
- Guide future gene-therapy treatment
Your genetic information may also give clues about other health issues.
Talk to your doctor about the price of genetic testing. They may work with a sponsored program that’ll cover your costs. You can also check with your insurance provider to see if they’ll pay for your tests.
What Happens Next?
Your eye doctor will go over next steps once you have a diagnosis. You may or may not have a treatment option right now. But there’s ongoing research into gene therapies for IRD. You’ll likely have more choices in the future.
You can also join the My Retina Tracker Registry. That’s a research database for people with IRD and their families. It’s a free service provided by the Foundation Fighting Blindness, a nonprofit group. Researchers can’t trace the data that you give back to you. But they use it to understand more about IRD as they work to find better treatments and eventually a cure.
Photo Credit: MICROGEN IMAGES / Science Source
Michael Andreoli, MD, ophthalmologist and surgical retina specialist, Northwestern Medicine, Chicago.
Orphanet Journal of Rare Diseases: “Genetic testing and diagnosis of inherited retinal diseases.”
Foundation Fighting Blindness: “Vision Testing and Retinal Imaging in Clinical Trials: What Patients Can Expect,” “Why Genetic Testing is Important,” “Open Access Genetic Testing Program,” “My Retina Tracker Registry.”
American Academy of Ophthalmology: “Inherited Reginal Diseases,” “What is Optical Coherence Tomography?”
Prevent Blindness: “What are Inherited Retinal Diseases (IRDs)?” “Genetic Testing for Inherited Retinal Disease: The Time is Now.”
University of Iowa Health Care: “Color Fundus Photography,” “Fluorescein Angiography,” “Ophthalmic Electrophysiology.”
The University of British Columbia: “Autofluorescence Imaging.”
Massachusetts Eye and Ear (Mass General Brigham): “Inherited Retinal Disorders Service.”
Oman Journal of Ophthalmology: “Genetic testing in retinal dystrophies.”
Translational Pediatrics: “Retinal dystrophies, genomic applications in diagnosis and prospects for therapy.”