Welcome to the Rare Classroom, a new series from Patient Worthy. Rare Classroom is designed for the curious reader who wants to get informed on some of the rarest, most mysterious diseases and conditions. There are thousands of rare diseases out there, but only a very small number of them have viable treatments and regularly make the news. This series is an opportunity to learn the basics about some of the diseases that almost no one hears much about or that we otherwise haven’t been able to report on very often.
Eyes front and ears open. Class is now in session.
The disease that we will be learning about today is:
What is Retinitis Pigmentosa?
- RP is considered a rare disorder. It affects approximately 1/4,000 people in the US and worldwide. RP is mainly caused by gene mutations (variations) inherited from one or both parents.
- Loss of vision makes many independent activities of daily living challenging for affected individuals. Children affected by vision loss due to RPE65 mutations are often placed into sight assisted classrooms and use a cane or other visual aids, as compared to other children who are able to engage in normal childhood activities.
- Retinitis pigmentosa (RP) refers to a group of inherited diseases causing retinal degeneration
How Do You Get It?
- The result of mutations impacting the RPE65 gene
- It is caused by mutations in genes that are active in retinal cells.
- Because there are many gene mutations that cause the disorder, its progression can differ greatly from person to person
- RP is diagnosed in part through an examination of the retina. An eye care professional will use an ophthalmoscope, a tool that allows for a wider, clearer view of the retina. This typically reveals abnormal, dark pigment deposits that streak the retina. These pigment deposits are in part why the disorder is named retinitis pigmentosa.
What Are The Symptoms?
- Symptoms first start to appear in early childhood. In later stages only a small area of central vison remains along with slight peripheral vision.
- Loss of vision in both eyes results in some or all of the following:
- Poor night vision
- Loss of peripheral vision
- Distortion of color
- Tunnel vision
- Total blindness
- Reduced vision at birth
- Within first few months of life, parents usually notice a lack of visual responsiveness and unusual roving eye movements, known as nystagmus
- Eye examinations of infants with LCA reveal normal appearing retinas. However, electroretinography (ERG) tests, which measure visual function, detect little if any activity in the retina. A low level of retinal activity, measured by ERG, indicates very little visual function. ERG tests are the key to establishing a diagnosis of LCA
- By early adolescence, various changes in the retinas of patients with LCA become readily apparent. Blood vessels become narrow and constricted.
- Sometimes, pigmentary changes are similar to retinitis pigmentosa
- The appearance of the retina undergoes marked changes with age, vision usually remains fairly stable through young adult life
- Long term visual prognosis remains to be defined
- Visual acuity in patients with LCA is usually limited to the level of counting fingers or detecting hand motion or bright lights
- Some patients are extremely sensitive to light
- Patients with remaining vision are often extremely farsighted
How Is It Treated?
- Currently no effective treatments exist for loss of vision caused by mutations in the RPE65 gene
- Efforts to slow down the progression of RP, as well as gene therapy to cure the disease before it gets worse, are being actively pursued. However, once the photoreceptors die, the only options are to either transplant new photoreceptors or bypass them. Photoreceptor transplantation continues to be studied, but so far there are no results that show a clear benefit.
- Bypassing the photoreceptors is based on the finding that, although photoreceptors die in RP, their connections to the brain are mostly preserved.
- Bypassing photoreceptors is currently being attempted using gene therapy to make the remaining cells light sensitive but this has still not entered clinical trials.
- A second method to restore vision in eyes with RP is to use microelectronic chip technologies to convert light rays to neuronal impulses that can be conveyed to the brain via the preserved connections.
- This method, referred to as retinal prosthesis, artificial vision, retinal chip, and bionic eye has recently become available for individuals with RP in many parts of the world.
- Many novel methods have been proposed to connect a retinal prosthetic device to a blind eye. Multiple research groups around the world are working to find the best way to achieve artificial vision with retinal prosthesis So far, one device in the US and the EU and another device available only in the EU have received office approval for clinical use