The Rare360 Editorial Team

Sep 239 min read

Retinitis Pigmentosa: A Guide to Symptoms and Management

An image of a human eye with melanated brown skin, featuring a brown iris, depicted in a creative way.

Retinitis Pigmentosa (RP) is a group of inherited retinal disorders (IRDs) that cause the gradual breakdown of the retina, the part of the eye that is responsible for capturing light and allowing us to see. While a rare condition, RP is the most common type of inherited eye disease.

Over time, RP leads to vision loss, starting with night blindness and a narrowing field of vision, often described as tunnel vision. In some cases, people with RP may also experience loss of central vision, making everyday activities like reading or recognizing faces more difficult.

Retinitis Pigmentosa Causes

Retinitis pigmentosa (RP) is primarily caused by genetic changes that affect the cells in the retina, which is the light-sensitive layer at the back of the eye. These genetic mutations are usually inherited from parents. The genes involved in RP are crucial for the health and function of specialized cells in the retina called photoreceptors, which are responsible for capturing light and enabling vision.

There are two main types of photoreceptors: rods and cones. Rods are responsible for our vision in low-light conditions, while cones are responsible for colour vision and bright-light vision. When mutations occur in the genes responsible for RP, it leads to the gradual deterioration of these photoreceptors. This degeneration results in the typical pattern of vision loss seen in people with RP.

Initially, the rods are affected, which explains why individuals often notice difficulty seeing at night as the first symptom of RP. Over time, as both rods and cones continue to deteriorate, daytime vision and colour perception become compromised as well.

Interestingly, some genes linked to retinitis pigmentosa are also associated with other eye disorders, such as cone-rod dystrophy. In cone-rod dystrophy, the cones are damaged before the rods, which means that people experience issues with daylight and colour vision before they notice problems with night vision.

Other Potential Causes of RP

While genetic mutations are the primary cause of RP, in rare cases, other factors may lead to RP-like symptoms or worsen the condition. These include:

Medications: Some medications, particularly those used to treat autoimmune or inflammatory diseases, have been linked to retinal damage that mimics RP. For example, hydroxychloroquine (used to treat lupus or rheumatoid arthritis) has been known to cause retinal toxicity in some patients, leading to symptoms similar to RP.
Infections: Severe eye infections, such as cytomegalovirus (CMV) retinitis, may damage the retina in a way that resembles the degeneration seen in RP. While not a direct cause of RP, infections can cause long-term retinal damage.
Eye Injuries: Trauma to the eyes, such as a blunt injury or surgery-related complications, can sometimes lead to retinal degeneration or other vision problems. Although this is not a true form of RP, the resulting damage can create symptoms that look similar.

Types of Retinitis Pigmentosa

RP can be caused by mutations in more than 60 different genes, leading to various forms of the disease. These mutations lead to various forms of the disease, each with its own inheritance pattern and characteristics. Here's a breakdown of the main types:

Autosomal Dominant RP: This form of Retinitis Pigmentosa is caused by mutations in over 20 genes, with the RHO gene being the most common, accounting for 20–30% of cases. In this type, only one copy of the mutated gene from either parent is needed to cause the condition. Autosomal dominant RP typically progresses more slowly and tends to be less severe than other forms. If a parent has this form, there is a 50% chance of passing the mutation to their child.
Autosomal Recessive RP: This form is linked to mutations in at least 35 genes, with USH2A being the most common, responsible for 10–15% of cases. For autosomal recessive RP to develop, a person must inherit two copies of the mutated gene—one from each parent, who may be carriers without symptoms. This form usually progresses more rapidly, often leading to significant vision loss earlier in life.
X-Linked RP: X-linked RP is caused by mutations in genes located on the X chromosome, with RPGR and RP2 being the most common. This form is more prevalent in males because they have only one X chromosome, so a single mutation can lead to the condition. Females, who have two X chromosomes, are less likely to develop RP but can carry the mutated gene and pass it to their offspring. Males with X-linked RP typically experience more severe vision loss.

Prevalence of RP

Retinitis pigmentosa (RP) affects approximately 1 in 3,500 to 1 in 4,000 people in Europe and the U.S., with an estimated global prevalence of 1 in 3,000 to 1 in 4,000 individuals—impacting around two million people worldwide. In the U.S. alone, about 100,000 people live with RP. Although the prevalence of RP can vary between countries and populations, it affects individuals across all ethnic groups. Despite being a rare condition, RP remains one of the leading causes of inherited retinal degeneration and vision loss.

Symptoms of Retinitis Pigmentosa (RP)

Retinitis pigmentosa (RP) often begins in childhood, though the exact onset and rate of progression can vary significantly from person to person. For many, the early symptoms start in adolescence, with most experiencing substantial vision loss by early adulthood. By the age of 40, many individuals with RP are considered legally blind, typically having a central visual field of less than 20 degrees in diameter.

Early Symptoms:

Night Blindness: One of the first signs of RP is trouble seeing in the dark. For example, if you're in a dimly lit room or outside at night, your eyes might struggle to adjust, and it feels much harder to see compared to others around you.
Difficulty Adjusting to Darkness: Moving from a bright area into a dark one (like walking from a sunny street into a dimly lit room) may take much longer for your eyes to adjust. You might find it difficult to see anything for a while.
Blind Spots in Peripheral Vision: This refers to losing the ability to see things out of the corners of your eyes. At first, you might notice it when bumping into objects or people because your side vision is affected. You may still see fine when looking directly ahead, but the sides of your vision start to fade.

Progressive Symptoms:

As RP advances, vision loss continues and additional symptoms may develop, including:

Flashing or Twinkling Lights: Some people experience a sensation like tiny, flickering lights or flashes in their vision, which can be distracting or uncomfortable.
Tunnel Vision: Over time, you might lose more side vision and feel like you're looking through a narrow tube or tunnel. You can still see what's directly in front of you, but anything to the side becomes blurry or disappears completely.
Light Sensitivity (Photophobia): Bright lights can become overwhelming. You might squint, feel uncomfortable, or want to avoid sunlight and well-lit spaces because they feel too harsh for your eyes.
Loss of Color Vision: As RP progresses, you may have trouble seeing colors. Colors might appear faded or washed out, making it harder to distinguish between different shades.
Severe Vision Loss: In advanced stages, your ability to see can become very limited. You might struggle with daily activities like reading, recognizing faces, or navigating familiar places.

These symptoms usually progress gradually, but the timeline and severity can differ from person to person.

Diagnosing Retinitis Pigmentosa (RP)

Clinical Diagnosis

Early detection of Retinitis Pigmentosa is crucial in managing the disease and slowing its progression. Regular eye exams, especially for those with a family history of RP or experiencing early symptoms, are key to diagnosing the condition in its early stages. Diagnosing RP usually involves a series of specialized eye tests, including:

Electroretinogram (ERG): An ERG assesses the function of the retina by measuring the electrical responses of retinal cells to light stimuli. In individuals living with RP, the response is often reduced or absent, providing a clear indication of retinal dysfunction.
Optical Coherence Tomography (OCT): OCT uses light waves to capture detailed cross-sectional images of the retina. It helps detect any structural abnormalities in the layers of the retina that may be affected by RP, such as thinning of the retinal tissue.
Visual Field Testing: This test measures the peripheral vision, which is often one of the first areas affected by RP. As RP progresses, patients may experience a narrowing of their visual field, commonly referred to as tunnel vision.

These tests are crucial for assessing the extent of retinal damage and determining the stage of the disease.

Genetic Testing

In addition to clinical diagnostics, genetic testing plays a vital role in confirming a diagnosis of Retinitis Pigmentosa. Genetic counselling is recommended for individuals and families affected by RP to understand the hereditary nature of the condition. Genetic testing identifies the specific gene mutations responsible for RP, offering several important benefits.

While clinical tests can suggest RP, genetic testing provides a definitive diagnosis by pinpointing the mutations causing the condition. Certain genetic mutations can influence how severe the disease will be and how quickly it will progress, which is helpful for planning long-term care and treatment.

By combining clinical diagnostic tools with genetic testing, patients and healthcare providers can gain a clearer understanding of the disease, allowing for better management and more personalized treatment approaches.

Treatment of Retinitis Pigmentosa (RP)

Currently, there is no cure for RP, but various treatments can help slow disease progression and improve quality of life. The current treatment options aim to preserve remaining vision and assist with adapting to vision loss. Treatment plans are often tailored to individual needs and may involve a combination of the following approaches:

Gene Therapy: Although still in the experimental stages, gene therapy holds promise for treating certain genetic forms of RP. This approach aims to correct or replace faulty genes to restore or improve retinal function.

There is a Food and Drug Administration-approved gene therapy for only one gene (there are almost 100 genes) that causes retinitis pigmentosa — the RPE65 gene. The treatment is called voretigene neparvovec (Luxturna). Cases of RPE65 gene-related retinitis pigmentosa are very rare. At this time, there are no FDA-approved treatments for the other genetic variants that cause retinitis pigmentosa.

Retinal Implants: For individuals with advanced RP who have lost most or all of their vision, retinal implants, also known as retinal prostheses, provide a groundbreaking treatment option. Devices like the Argus II retinal implant bypass damaged retinal cells and stimulate the remaining healthy cells to create visual perceptions. While retinal implants do not restore normal vision, they can help patients regain basic visual functions, such as detecting light, movement, and large shapes, improving their ability to navigate daily environments.
Vitamin A Therapy: Research suggests that high doses of Vitamin A, when taken under medical supervision, may help slow the progression of RP in some patients. A long-term study suggested that a daily dose of 15,000 IU of Vitamin A palmitate might reduce the rate of decline in retinal function. However, this treatment must be monitored by a healthcare provider, as excessive Vitamin A intake can lead to liver toxicity and other health issues.
Low Vision Aids and Rehabilitation: For many patients with RP, adapting to vision loss is essential for maintaining independence and quality of life. Low vision aids, such as magnifying glasses, screen readers, and specialized lighting, can help individuals perform daily tasks. Additionally, vision rehabilitation services provide training on how to use these devices, as well as strategies for maximizing remaining vision and developing new ways to navigate the world. These services can include orientation and mobility training, home modifications, and assistive technology to support independence.
Assistive Technology: Technological innovations such as electronic visual aids and orientation and mobility training can help individuals adapt to vision loss. Tools like voice-controlled devices, apps for navigation, and screen readers can enhance independence and daily functioning.
Medication: In later stages of RP, macular edema (swelling in the central area of the retina) can reduce vision. Acetazolamide, a medication, can help alleviate this swelling and improve vision.
Sunglasses: Protecting the eyes from bright light and harmful ultraviolet rays is important for those with RP. Polarized sunglasses can reduce light sensitivity and help shield the eyes from further damage.

While these treatments may not cure RP, they offer hope for managing the disease and improving the lives of those affected. With continued research and advancements, future therapies may offer even more effective solutions for individuals living with Retinitis Pigmentosa.

Conclusion

RP presents significant challenges, as it leads to progressive vision loss and impacts daily life. Despite the current lack of a cure, the array of available treatments provides valuable support in managing the disease and enhancing quality of life.

As research continues to advance, there is growing hope for more effective treatments and potential breakthroughs. Gene therapy, for instance, holds promise for addressing specific genetic mutations, while ongoing innovations in retinal implants and assistive technologies offer new ways to improve daily functioning. The commitment to exploring new therapies and improving existing ones reflects a brighter future for those living with RP.

With every new discovery and development, the future for RP patients becomes increasingly hopeful. Continued research and clinical trials are essential in driving forward new treatments and ultimately finding a cure. The journey towards better management and understanding of Retinitis Pigmentosa is ongoing, and each step forward brings us closer to a world where effective solutions and improved quality of life are within reach for everyone affected by this challenging condition.