What is Retinal Pattern Dystrophy?
Retinal pattern dystrophies are a range of eye conditions that develop slowly and are mainly passed down through families. These conditions mainly affect the macula, a part of the eye important for sharp central vision. They cause pigment to build up in the protective layer of the macula, known as the retinal pigment epithelium (RPE).
While these conditions often center on the macula, the pigment can also build up in the outer edges of the retina. There are several types of these conditions, depending on the pattern of the pigment in the eye. These include reticular dystrophy, fundus pulverulentus, butterfly-shaped pigment dystrophy, among others. Interestingly, the pattern in someone’s eyes could change over time, and different patterns can occur in each eye. A family genetic condition can result in different patterns within the same family.
People with these conditions usually have good vision, but because the pigment builds up in the macula, they could potentially lose some central vision or develop other complications like abnormal blood vessels in the eye or macular holes.
Most patients don’t notice any symptoms until they are in their forties or fifties, when they may start to notice changes in their central vision. These conditions can look like age-related macular degeneration (AMD), especially in later stages, leading to possible misdiagnosis. Further tests and follow up visits are needed to tell the difference between these conditions and AMD.
What Causes Retinal Pattern Dystrophy?
Pattern dystrophies, a type of eye condition, have been linked to changes or mutations in a specific gene, known as the retinal degeneration slow (RDS) and peripherin gene. This gene is found on chromosome 6 at a spot labeled as position 21.1. There are numerous types of these mutations, such as multiple missense mutations that have complex names like Arg172Trp, Lys197Glu, Tryp246Arg, and others, along with nonsense mutations such as Tyr285ter and Gln239ter.
The RDS and peripherin gene is vital because it helps in producing a protein called peripherin-2. This protein, a cell surface glycoprotein, may play an important role in developing and stabilizing parts of the eye’s light-sensing cells, known as photoreceptors.
Scientists believe that a mutation changing how this protein functions could lead to pattern dystrophy. This happens because the mutation may disrupt the photoreceptor’s structure, leading to this eye disease.
Risk Factors and Frequency for Retinal Pattern Dystrophy
Pattern dystrophies, a rare disease, have limited availability of widespread data due to their infrequency. From the available data, we know that it affects around 33,800 individuals in Northern France, translating to 1 out of every 1,490 people. In Europe, this number increases to over 300,000 people. Another similar condition, adult-onset vitelliform macular dystrophy, impacts people at a rate ranging from 1 in 7,400 to 1 in 8,200.
- Pattern dystrophies affect about 33,800 people in Northern France.
- This calculates to about 1 in every 1,490 people in that region.
- Across Europe, over 300,000 people have pattern dystrophies.
- Adult-onset vitelliform macular dystrophy affects between 1 in every 7,400 to 1 in every 8,200 people.
Signs and Symptoms of Retinal Pattern Dystrophy
Pattern dystrophies are often detected during regular eye check-ups. However, some patients might experience reduced vision and distorted visual perception, also known as metamorphopsia. In some rare cases, patients could even experience severe vision loss due to complications related to pattern dystrophies, such as abnormal blood vessel growth in the eye (choroidal neovascularization). During the eye exam, physicians will notice a unique pattern of coloured deposits within the layer at the back of the eye.
The exact pattern will help identify the type of pattern dystrophy that the patient is dealing with. In some cases, using additional imaging techniques such as fluorescein angiography, fundus autofluorescence, and Eye movement recording can provide more information to classify the dystrophy. It’s necessary to understand that the diagnosis of pattern dystrophy is based mostly on the clinical examination.
Interestingly, all pattern dystrophies show association with the pseudoxanthoma elasticum condition, but fundus pulverulentus pattern dystrophy is found to have the the strongest connection. Also, there is a significant correlation found between pattern dystrophies, and maternally inherited diabetes and deafness, with some estimates showing it to be over 80%.
Testing for Retinal Pattern Dystrophy
Butterfly-shaped pattern dystrophy is a condition named after the unique pattern of colored deposits which can be seen in an area of your eye known as the retinal pigment epithelium (RPE). The deposit’s color varies from black to yellow or white. These pigment deposits block the light, which makes the lesion – an area of slightly damaged tissue – easily visible, and helps differentiate this eye condition from others.
When using fluorescein angiography (FA), a test that uses fluorescent dye and a special camera to examine blood circulation in the retina, and Fundus autofluorescence (FAF), a diagnostic test which involves taking pictures of the back of your eye, you can see areas of both high and low fluorescence which correspond to lipid changes, a result of lipofuscin – a naturally occurring waste product in the eye. Electroretinogram (ERG) and Electrooculography (EOG), both tests that measure electrical responses in various cells in the eye, may reveal slight changes; however, those affected usually retain their normal vision and have good vision up until their fifties.
Reticular dystrophy, another type of eye condition, normally features a network of colored lines and knots that looks like a fishnet appearing in the RPE. These lesions can be up to five times the size of the optic disc – the circular area at the back of your eye where the optic nerve connects to the retina – from the macula, the small central area of the retina that provides the most detailed vision. While some lesions leave behind white dots and irregular atrophic changes – areas of tissue loss, FA can identify less fluorescent segments surrounding areas of hyperfluorescence with normal choroidal vessels – the layer in your eye that contains blood vessels.
Multifocal pattern dystrophy, similar to Stargardt disease or Fundus Flavimaculatus, shows multiple irregular white-yellow flecks scattered throughout the macula. The flecks seen in this condition are similar to those found in Stargardt disease. In addition to the macula, this type of dystrophy can affect the peripheral retina – the portion of the retina that is farthest from the center – and might impair your peripheral vision. In severe cases, full-field ERG abnormalities may be observed. Optical coherence tomography (OCT), a type of imaging test, will show these flecks as shimmery areas of localized swelling.
Adult-onset foveomacular vitelliform dystrophy (AFVD) is distinct due to its link to mutations beyond the peripherin/RDS gene, such as the VMD2 gene mutation. During an examination, the doctor might observe bilateral, symmetric, round, gray-white lesions in your macula. These lesions are usually a third to half a disc diameter and larger lesions can look similar to a condition called Best vitelliform macular dystrophy. But one way to distinguish AFVD from Best is through a normal ERG and EOG test.
Some patients with multiple drusen – small yellow deposits under the retina – can end up having drusen fluid, which can cause a small part of the retina to detach. This can get mistaken for an abnormal growth of blood vessels at the back of the eye known as choroidal neovascularization. But it’s important to note that those with AFVD won’t experience better vision after undergoing therapies aimed to reduce the growth of the blood vessels.
Finally, Fundus pulverulentus, a disease that creates a grainy look and small freckling of the RPE within the macula, can be mistaken for age-related macular degeneration due to RPE freckling. However, OCT imaging and follow-up can prove that they follow different disease paths. More than any of the pattern dystrophies, fundus pulverulentus has a common association with pseudoxanthoma elasticum – a disorder that causes calcium to build up in your body’s soft tissue.
Treatment Options for Retinal Pattern Dystrophy
Pattern dystrophies typically lead to slow changes in vision, the progression of which results in gradual vision loss. But you don’t need to worry too much because patients usually maintain good vision overall. There’s no established treatment to handle the pigment deposits and lipofuscin (a type of waste product) buildup that occur in pattern dystrophies.
However, for some people, vision loss can happen more quickly due to secondary complications like choroidal neovascularization and macular holes. Choroidal neovascularization is a condition where new, abnormal blood vessels start to grow in the eye, causing fluid and blood to leak into the retina. A macular hole is a small break in the macula, the part of your eye responsible for detailed, central vision. These secondary complications may require treatments such as anti-VEGF injections and surgery to repair the macular hole. Anti-VEGF injections are medications that help reduce the growth of these abnormal blood vessels in the eye.
In situations where vision loss is either slowly progressive or unexpectedly rapid, low vision therapy becomes the main option to help maximize vision function. This therapy involves a personalized plan to help you make the most of your remaining vision and improve your quality of life.
What else can Retinal Pattern Dystrophy be?
Pattern dystrophies, as a group, can appear similar to a condition known as AMD (Age-related Macular Degeneration). As a result, they need to be properly examined to ensure AMD is not actually the underlying condition. One significant look-alike to be aware of when diagnosing multifocal pattern dystrophy is a disease called Stargardt disease. This is because the formations, or ‘flecks’, seen in the central area of the eye (the macula) and beyond can look similar to those seen in Stargardt disease. Special imaging tests such as Fluorescein Angiography (FA) and genetic screening can help distinguish between these two conditions.
Other conditions that should be considered when examining someone with pattern dystrophies are Best disease and Choroidal Neovascularization. Using the same Fluorescein Angiography (FA) test along with another test known as Electrooculography (EOG), these two conditions can be ruled out.
What to expect with Retinal Pattern Dystrophy
Patients can be comforted knowing that pattern dystrophies, a type of eye disorder, usually do not have a significant adverse impact on their vision and any progression occurs slowly. Often because of difficulty in differentiating pattern dystrophies from another eye disease called Age-Related Macular Degeneration (AMD), many patients are mistakenly diagnosed with AMD. As a result, they are given treatments designed for AMD such as vitamin supplements, injections to impede the growth of abnormal blood vessels in the eye (anti-VEGF injections), and Photodynamic Therapy (PDT), a process which uses light to treat disease.
As patients grow older, there could be some developments of atrophy – a condition where tissues in the eye degenerate, affecting their central vision. However, in most cases, patients are still able to maintain their reading vision. The good news is, most of the patients will not require any sort of treatment or intervention and can be monitored over time.
Possible Complications When Diagnosed with Retinal Pattern Dystrophy
In rare cases, patients may face complications due to abnormal blood vessels in the eye, which can be treated with anti-VEGF therapy. It’s recommended to avoid Photodynamic Therapy (PDT) as it can hurt vision, especially for those with pattern eye disease, particularly AVFD. Furthermore, some people with AVFD may develop holes in the central part of their retina. Regrettably, a specific eye surgery called vitrectomy doesn’t work effectively for these individuals.
Possible Complications:
- Abnormal blood vessels in the eye (Treatable with anti-VEGF therapy)
- Negative impact on vision due to Photodynamic Therapy (PDT)
- Development of holes in the central part of the retina (macular holes) with AVFD
- Ineffectiveness of vitrectomy surgery in treating these conditions
Preventing Retinal Pattern Dystrophy
Although the majority of patients typically retain good vision and the condition progresses slowly, it’s important to have regular check-ups as well as thorough examinations to ensure there’s no co-existing condition like Age-related Macular Degeneration (AMD), a disease that damages the center of the retina and affects sharp, central vision. Some patients might experience a quicker loss of vision, in which case, they may need low vision therapy, a service that helps people with visual impairments function better. On rare occasions, patients can face complications like choroidal neovascularization – the growth of new blood vessels under the retina or macular holes – small holes or gaps in the retina at the macula (the part of the eye with the sharpest vision). Given these potential complications, it’s crucial to seek medical help if there is any experience of vision loss.
