What is Retinal Dystrophies?

Retinal dystrophies (RD) refer to a group of eye disorders that cause damage to the retina, which is the part of the eye that senses light. These disorders vary greatly, and they can present a variety of symptoms and be caused by different genetic factors. Common symptoms include color blindness, difficulty seeing at night, changes in peripheral vision (what you can see on the side when looking straight ahead), and even complete blindness, particularly in more severe or progressive cases.

Research has shown that these conditions can be caused by defects in many different genes. Currently, we know of over 270 genes that can be linked to various types of retinal dystrophies. Interestingly, even within one family, different changes or mutations in the same gene can result in different types of this disorder. These genes are responsible for producing proteins that are vital to the function of photoreceptors (the cells in the retina that respond to light) and other cells of the retina, as well as for the process of converting light into a signal that the brain can understand (phototransduction).

What Causes Retinal Dystrophies?

Rods and cones are special cells in our eyes that allow us to see by transforming light signals into something our brain can understand. This process, named phototransduction, helps us to perceive images. During this transformation, our eyes create and recycle light-sensitive pigments. A condition known as Retinal Dystrophy (RD) happens when there are problems in rods and cones, or defects in the phototransduction process.

Retinal dystrophy can be categorized based on which cells – rods, cones, or both – are primarily affected. There are various types of RD – some occur as part of syndromes affecting multiple bodily systems, while others only impact the retina. These conditions can also occur randomly or be inherited from family members. In families, RD can be inherited in different ways, typically through dominant or recessive traits or connected to the X chromosome. Syndromic cases have symptoms affecting more than just the eyes while non-syndromic cases only affect the retina.

Risk Factors and Frequency for Retinal Dystrophies

Retinal dystrophies are eye conditions with unclear overall rates, however, we do know some specifics. The most common type, retinitis pigmentosa, affects about 1 in 5,000 people globally. There are other, even rarer forms like achromatopsia, which affect 1 in 30,000 people. These conditions mostly affect children and young adults, adding to financial and societal stresses.

Signs and Symptoms of Retinal Dystrophies

Rod dystrophies are a group of visual disorders that mostly affect the rod photoreceptor cells in our eyes. This includes conditions known as Retinitis pigmentosa (RP) and Congenital Stationary Night Blindness (CSNB).

RP is the most commonly seen rod dystrophy. It’s a condition where the rod photoreceptor cells are damaged first, leading to issues with vision. The symptoms and progression of RP can vary greatly from person to person. A common symptom is night blindness, although many people don’t notice it until their situation has advanced significantly. Additionally, patients may experience a slow and gradual loss in their peripheral field of vision. In the typical course, this proceeds at a slow pace, often unnoticed until it reaches a point, known as tunnel vision, where the person abruptly realizes the changes. Further, central vision may be affected due to formations like cystoid macular edema, epiretinal membrane, or retinal pigment epithelial defects.

CSNB, on the other hand, is a non-progressive type of night blindness. There are many different types of CSNB including ones where there are no changes seen in the fundus (the back of the eye) and others where there are changes – like Oguchi disease and fundus albipunctatus. Oguchi disease presents with a characteristic golden sheen over the retina that disappears following prolonged adaptation to darkness. Fundus albipunctatus is another form marked by tiny yellow-white dots over the back of the eye.

We also have Cone dominated diseases which are divided into diseases with early onset without progression, and those with late onset which usually progress. Conditions such as achromatopsia and blue cone monochromatism are examples. Patients with achromatopsia present with poor vision since birth, sensitivity to light, and problems distinguishing between colors. Cone Monochromatism on the other hand is a disorder where two of the three color-detecting cone systems in the eye are affected. Blue cone monochromatism, where both red and green systems are absent, is the most common variant.

There are also general diseases that affect the entire retina such as Leber congenital amaurosis (LCA). It’s a group of disorders that result in severe visual impairment or blindness from infancy due to certain gene mutations. Eye rubbing and keratoconus (an eye condition that results in thinning of the cornea) are associated with this condition.

Testing for Retinal Dystrophies

When it comes to conditions where the rods in our eyes are dominant and malfunctioning, we can often experience a loss in our peripheral, or side, visual field. This initially starts with a slight narrowing of these peripheral fields, which can get worse over time to the point of tunnel vision. People can usually see these changes in both eyes. For progressive diseases like Retinitis Pigmentosa (RP, an inherited and degenerative eye disease that can lead to severe vision impairment), it’s crucial to continually assess peripheral vision field, especially if the individual drives. For those with RP, night driving may need to be reduced and eventually stopped as the disease advances. These regular checks also help patients understand their visual limitations, which often aren’t noticeable otherwise.

On the other hand, if cones dominate our eyes and are not working correctly, peripheral field narrowing is rarely seen. If present, it stays the same over time. If the field defects worsen, it’s necessary to consider other conditions like cone-rod dystrophy or retinitis pigmentosa with a cone-rod pattern. In these diseases, visual field defects typically start around the central area and affect the peripheral areas in later stages.

Typically, retinitis pigmentosa patients can distinguish colors pretty well until the advanced stages when cones get affected. Once they start to struggle with visual acuity (clarity of vision) below 20/40, color vision abnormalities are noted. These abnormalities are particularly noticeable in disorders that primarily affect cones. Individuals with complete achromats, a condition characterized by the absence of color vision, are born color-blind, but they may train themselves to see different colors as varying shades of grey. Therefore, more advanced color tests might be needed for a proper diagnosis. Those with Blue cone monochromatism, as suggested by the name, can only distinguish the color blue, which can be tested through advanced color tests like Berson plates.

Electrophysiology, specifically a test called Full-field ERG (Electroretinogram, a test that measures the electrical responses of various cell types in the retina), is sensitive in diagnosing these eye disorders. In the early stages of RP, the test shows reduced rod responses, and as the disease progresses, responses from light-adapted (photopic) cells are affected too.

The ERG test is also the cornerstone in diagnosing ‘cone dystrophies’ or ‘cone-rod dystrophies’. Here, you would see reduced responses to the quick flicker of light. In later stages of the disease, responses to low light scenarios (scotopic responses) are also reduced. However, the reduction of scotopic responses in the early stages often points toward a diagnosis of retinitis pigmentosa. In achromatopsia and blue monochromatism, the differentiation can be done based on whether a cone signal can be received using a blue light flash on a yellow background.

Optical coherence tomography (OCT) is a non-invasive test that provides useful information about the retina. In RP, you could see thinning of retinal layers, specifically the outer retinal layers, a progression that can move towards the center of the retina (macula) and often spare the central area of the macula (fovea) till the late stages. OCT is also helpful in detecting cystoid macular edema (swelling in the macula) and epiretinal membrane (a thin, cellophane-like sheet growing on the surface of the retina). Moreover, OCT often eliminates the need for another test called fundus fluorescein angiography for detecting the swelling.

In some other disorders, like Night blindness with normal-looking retinas (CSNB) or Fundus Albipunctatus (a rare form of stationary night blindness), OCT often shows no changes. However, in achromatism (complete lack of color vision), OCT can show a range of changes from the disruption of light-sensitive cells in the central region of the retina to the presence of overly reflective particles in the light-sensitive cells layer, and in some cases, incomplete development of the fovea.

Treatment Options for Retinal Dystrophies

At present, there is no cure for retinal dystrophies, but there are several treatments that can improve a person’s quality of life. These include correcting vision with glasses or contact lenses, performing cataract surgery if needed, and recommending devices to assist with low vision. Additionally, for patients with macular edema (a condition where fluid builds up in the macula of the eye), medications that reduce fluid production in the eye can help.

For patients who have issues with night vision, aids for seeing in the dark or a simple flashlight can be very helpful. Similarly, those who have cone dystrophies (a type of eye disorder affecting the cone cells in the retina) and who are sensitive to light, can benefit from wearing tinted glasses. Glasses with an orange or red tint can be particularly useful as these colours are less likely to bother the rod cells (another type of light-sensitive cells in the retina). Similar coloured contact lenses are an alternative option. There are also a variety of tools and devices available that can help people with low vision to see better.

Gene therapy is another possible treatment for retinal dystrophies. In gene therapy, healthy genes are delivered to the retina to replace the faulty genes causing the disease. The retina is a good target for this type of therapy as it is easily reachable for the delivery of treatment and monitoring progress. It also maintains a static population of cells, which means only a small number of healthy genes need to be introduced. Subretinal injections are the preferred method of delivery for gene therapy as they allow the treatment to reach the exact location needed in the eye.

Stem cell therapy is also being investigated as a potential treatment for retinal dystrophies. This involves using pluripotent stem cells, which have the potential to become any type of cell, to replace the damaged cells in the retina. The advantage of the retina as a target for stem cell therapy is similar to gene therapy – it requires less therapeutic tissue compared to other organs. There are ongoing trials studying this approach for diseases like age-related macular degeneration, Stargardt disease, glaucoma, and retinitis pigmentosa.

Retinal prostheses, or devices that replace the function of damaged light-sensitive cells in the eye are another treatment option. These devices work by sending signals to the undamaged cells in the retina, which can process the information and send it to the brain. The U.S. Food and Drug Administration approved the use of a device called Argus II in 2013 for late-stage retinitis pigmentosa, an inherited degenerative eye disease.

After a diagnosis of retinitis pigmentosa or other retinal dystrophies, it’s important for patients to undergo genetic counselling. This helps to confirm the diagnosis and understand the pattern of inheritance. Genetic counselling involves collecting a detailed family history and conducting a clinical examination along with specific genetic tests. Understanding the pattern of inheritance can provide information on the risk of the disease being passed on to future generations.

Last but not least, patients should be connected to support services. These services are crucial when dealing with aspects like employment training and adjusting to life with visual impairment, especially for children who are going through the education system.

When dealing with retinal dystrophy, a type of eye disorder, it’s essential to diagnose it correctly because it often gets mistaken for other genetic or acquired eye issues. Misdiagnosing it can significantly affect the genetic and prognostic advice given to a patient. Also, appropriate diagnosis is crucial because acquired eye disorders can often be treated.

One form of retinal dystrophy, called Retinitis pigmentosa, must be distinguished from other conditions that also cause retinal pigment changes. These conditions include:

Rubella retinopathy, a condition caused by the rubella virus
Syphilis, an infectious disease
Autoimmune paraneoplastic retinopathy, an immune reaction to cancer in the body
Drug toxicities, which can be caused by medication overdose like Quinine

Moreover, other conditions like traumatic retinopathy and Diffuse Unilateral Subacute Neuroretinitis (DUSN) can sometimes be wrongly identified as unilateral Retinitis pigmentosa.

More advanced cases of retinal disorders such as choroideremia, Stargardt macular dystrophy, and cone-rod dystrophy often get misdiagnosed as Retinitis pigmentosa. Moreover, the conditions Retinitis punctata albescens and fundus albipunctatus also present similar symptoms which further complicates the diagnosis process. Therefore, electrophysiological findings are usually useful to make a definitive diagnosis when conditions share similar symptoms.

What to expect with Retinal Dystrophies

Retinitis pigmentosa, Leber congenital amaurosis and cone-rod dystrophies are all eye conditions that typically continue to get worse over time. It’s often the case that if these conditions develop early in a person’s life, they may have a more severe effect on the person’s sight. On the other hand, conditions like congenital stationary night blindness and achromatism, which involve difficulty seeing in low light and being unable to see color, respectively, generally don’t get worse with time.

Having the right information about these conditions, their potential impacts, and how they may progress, can really help patients and their families navigate the challenges these conditions can pose. This makes a clear understanding and discussions with medical professionals crucial.

Possible Complications When Diagnosed with Retinal Dystrophies

Retinitis pigmentosa, or RP, progresses at different speeds based on inheritance patterns and age when symptoms first appear. It often starts with peripheral vision becoming narrow (tunnel vision) and gradually leads to vision loss. It’s common for people with early-onset RP to have significant cataracts.

When these patients need cataract surgery, they have a higher risk of complications compared to the general population. These can include weak zonular fibers (the tiny fibers that hold the lens in place in the eye), tightening of the lens capsule (capsular phimosis), quick buildup of cloudiness back of the lens capsule (early onset of posterior capsule opacification), and swelling in the retina (cystoid macular edema).

Possible Progression and Complications of Retinitis Pigmentosa:

Begins with narrowed peripheral vision
Gradually leads to vision loss
Early presence of significant cataracts
Higher surgical risks for cataracts including:

Weak zonular fibers
Tightening of the lens capsule
Quick clouding of back of the lens capsule
Retina swelling

Preventing Retinal Dystrophies

Being diagnosed with retinal dystrophy, which is a type of eye disease that affects the retina and could potentially lead to vision loss, can be very worrying for the patient and their family. The idea of possibly losing their sight often triggers a lot of stress and fear. Retinal dystrophy conditions, aside from one called Leber congenital amaurosis (LCA), typically develop slowly, and some don’t worsen over time.

One common misunderstanding is that retinal dystrophies are ‘untreatable’. While it’s true that there is no cure, there are supportive treatments available that can greatly enhance a patient’s quality of life. These treatments include a thorough assessment of the patient’s remaining vision, access to support services, and learning new skills and strategies for living with reduced vision, which is termed as ‘visual rehabilitation’.

Frequently asked questions

Retinal dystrophies can have varying prognoses depending on the specific type of disorder. Some types, such as retinitis pigmentosa, Leber congenital amaurosis, and cone-rod dystrophies, typically worsen over time and can have a more severe impact on a person's sight if they develop early in life. Other types, like congenital stationary night blindness and achromatism, generally do not worsen with time. It is important for patients and their families to have a clear understanding of the prognosis and to have discussions with medical professionals.

Retinal Dystrophies can be inherited from family members or occur randomly.

Signs and symptoms of retinal dystrophies, including rod dystrophies and cone dominated diseases, can vary depending on the specific condition. However, some common signs and symptoms include: 1. Night blindness: This is a common symptom in many retinal dystrophies, including retinitis pigmentosa (RP) and congenital stationary night blindness (CSNB). Night blindness refers to difficulty seeing in low light conditions, such as at night or in dimly lit environments. 2. Peripheral vision loss: In RP, there is often a slow and gradual loss of peripheral (side) vision. This can progress over time and eventually lead to tunnel vision, where only a small central area of vision remains. 3. Central vision impairment: In some cases of RP, as well as other retinal dystrophies, central vision can also be affected. This may be due to the presence of certain formations, such as cystoid macular edema, epiretinal membrane, or retinal pigment epithelial defects. 4. Color vision abnormalities: Certain retinal dystrophies, such as achromatopsia and blue cone monochromatism, can cause problems with color vision. This may include difficulty distinguishing between colors or a complete inability to see certain colors. 5. Fundus changes: In some forms of CSNB, there may be visible changes in the fundus (the back of the eye). For example, Oguchi disease is characterized by a golden sheen over the retina that disappears after prolonged adaptation to darkness. Fundus albipunctatus, another form of CSNB, is marked by tiny yellow-white dots on the back of the eye. 6. Severe visual impairment or blindness: In general diseases that affect the entire retina, such as Leber congenital amaurosis (LCA), there can be severe visual impairment or blindness from infancy. This is often due to specific gene mutations. It's important to note that these signs and symptoms can vary greatly from person to person, and the progression of the condition can also differ. Therefore, it's crucial for individuals experiencing any visual changes or symptoms to seek medical evaluation and diagnosis from an eye care professional.

The types of tests that are needed for Retinal Dystrophies include: 1. Full-field ERG (Electroretinogram): This test measures the electrical responses of various cell types in the retina and is sensitive in diagnosing eye disorders like Retinitis Pigmentosa and cone dystrophies. 2. Optical coherence tomography (OCT): This non-invasive test provides useful information about the retina and can detect thinning of retinal layers, cystoid macular edema, and epiretinal membrane. 3. Genetic tests: Genetic counseling involves collecting a detailed family history and conducting specific genetic tests to confirm the diagnosis and understand the pattern of inheritance. It is important to note that these tests may vary depending on the specific retinal dystrophy and the individual patient's condition.

The doctor needs to rule out the following conditions when diagnosing Retinal Dystrophies: - Rubella retinopathy - Syphilis - Autoimmune paraneoplastic retinopathy - Drug toxicities (caused by medication overdose like Quinine) - Traumatic retinopathy - Diffuse Unilateral Subacute Neuroretinitis (DUSN) - Choroideremia - Stargardt macular dystrophy - Retinitis punctata albescens - Fundus albipunctatus

When treating retinal dystrophies, there can be some side effects or complications. These include: - Weak zonular fibers: Patients may experience weak fibers that hold the lens in place in the eye, which can increase the risk of complications during cataract surgery. - Tightening of the lens capsule: The lens capsule may tighten, leading to capsular phimosis, which can affect vision. - Quick buildup of cloudiness in the back of the lens capsule: This is known as early onset of posterior capsule opacification and can cause vision problems. - Swelling in the retina: Cystoid macular edema can occur, leading to swelling in the retina and potential vision impairment.

An ophthalmologist or a retinal specialist.

Retinal dystrophies have unclear overall rates, but the most common type, retinitis pigmentosa, affects about 1 in 5,000 people globally.

Retinal dystrophies can be treated in several ways to improve a person's quality of life. Treatment options include correcting vision with glasses or contact lenses, performing cataract surgery if necessary, and recommending devices to assist with low vision. Medications that reduce fluid production in the eye can help with macular edema. For issues with night vision, aids for seeing in the dark or a simple flashlight can be helpful. Wearing tinted glasses or contact lenses can benefit those with cone dystrophies and light sensitivity. Gene therapy, stem cell therapy, and retinal prostheses are also being investigated as potential treatments. Genetic counseling is important for confirming the diagnosis and understanding the pattern of inheritance. Support services are also crucial for employment training and adjusting to life with visual impairment.

Retinal dystrophies refer to a group of eye disorders that cause damage to the retina, which is the part of the eye that senses light.

Blindness Color Blindness Eye Health Night Blindness Retinitis Pigmentosa