How Your Ophthalmologist Can Diagnose Retinitis Pigmentosa
Loss of peripheral (side) vision and night vision are early symptoms of retinitis pigmentosa (RP), although other eye disorders and conditions can also cause these issues. During a visit to the ophthalmology office, your eye doctor performs several tests that help determine if your symptoms are caused by RP.
What Is Retinitis Pigmentosa?
RP is a group of inherited eye disorders that cause gradual vision loss. The disorders affect the retina, a thin layer of tissue at the back of the eye. The retina contains light-sensing cells, called rods and cones. Rods are responsible for good side vision and the ability to see well in low light. Cones are needed for color and central vision and help you see well in brightly lit settings.
RP happens when a gene mutation causes the rods and cones to break down and die. Rods are usually affected first, which is why people often notice side and night vision problems initially. RP symptoms usually start during childhood, adolescence, or young adulthood. Sensitivity to light and color vision issues may also be symptoms of RP.
Over time, the disorder progresses, and the field of vision continues to decrease. Eventually, someone with RP may only have a small amount of central vision remaining or might be completely blind. The Foundation Fighting Blindness estimates that many people with RP have less than 20 degrees of central vision remaining by the time they're 40. Although there's currently no cure for RP, researchers are working to develop an effective treatment for the eye disorder.
Several inheritance patterns can cause RP, including:
- Autosomal Dominant. One copy of a gene that causes RP is inherited from a parent who has the disorder.
- Autosomal Recessive. Both parents must contribute a copy of the gene, although neither of them have RP.
- X-Linked. Mothers pass RP to their children through a mutated gene on the X chromosome. Females have two X chromosomes, while males have one. A healthy second X chromosome will counteract a faulty gene in the other X chromosome in females. Since males only have one X chromosome, they are more likely to be affected by RP.
Diagnosing RP
Your ophthalmologist may recommend several exams that make it possible to diagnose RP, such as:
- Dilated Eye Exam. Dilating your pupil with eyedrops makes it possible to see your retina and optic nerve easily. If you have RP, your ophthalmologist may see clumped pigments on your retina.
- Visual Field Test. The visual field test identifies blind spots anywhere in your visual field. During one type of visual field testing, you'll be asked to push a button when you see lights appear on a screen. Some lights will be directly in front of you, while others will be off to the side. If you have RP, you might not see the lights on the side.
- Electroretinography (ERG). Understanding how well your retinas react to light helps your eye doctor make a diagnosis. A tiny electrode placed on your cornea measures the electrical signs in your rods and cones when exposed to flashing lights during ERG. The test is performed after your eyes are numbed.
- Optical Coherence Tomography (OCR). This test measures the thickness of your retinas. Reflected light generates a series of pictures of your retina and optical nerve that are combined to form a 3-D map. You don't have to do anything during this test except for look at a target inside a special machine.
- Dark Adaptation Test. The dark adaption test measures how long it will take your eyes to adjust from bright lights to darkness. During this test, you'll push a button when you see a light on the screen.
- Genetic Testing. Genetic testing can help confirm the diagnosis if you have one of several identified RP gene mutations. The testing is performed using a blood sample.
Are you concerned that you may have RP? RP testing can help you determine if the disorder is responsible for your symptoms. Contact our office to schedule an examination with the ophthalmologist.
Sources:
Foundation Fighting Blindness: Retinitis Pigmentosa
https://www.fightingblindness.org/diseases/retinitis-pigmentosa
National Eye Institute: Retinitis Pigmentosa, 11/15/2023
https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/retinitis-pigmentosa
American Academy of Ophthalmology: What Is Retinitis Pigmentosa?, 9/9/2022
https://www.aao.org/eye-health/diseases/what-is-retinitis-pigmentosa
Healthline: Electroretinography
https://www.healthline.com/health/electroretinography
American Academy of Ophthalmology: Visual Field Test, 3/10/2022
https://www.aao.org/eye-health/tips-prevention/visual-field-testing