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Their diagnosis doesn’t change who they are

Receiving a clinical diagnosis of an inherited retinal dystrophy, or IRD, such as retinitis pigmentosa, Usher syndrome, or Stargardt disease can be overwhelming. If your loved one is newly diagnosed, you may have a lot of questions.
We hope to provide you with some answers and make the process of learning about IRDs as easy as possible. Remember, a diagnosis may be challenging, but it can also bring people closer together. It’s all about taking small steps towards a better understanding of each other’s needs, and making adjustments over time to help life run smoothly.

About IRD

An introduction to what IRD is, what causes it, and how it can develop.

Recognising IRD

The process doctors use to diagnose IRD and how genetic testing can help.

Research into IRD

Information about ongoing research into IRD and its treatment.

Support and resources

Documents to help you understand more about IRD and how you can support your loved one.

About IRD

Learn about a collection of rare inherited diseases that affect the retina and cause vision loss.

What is inherited retinal dystrophy (IRD)?

As a family member, friend, or caregiver of someone with an IRD, getting your head around what IRD means will help you to support the individual’s understanding of their condition. Receiving a diagnosis can be a highly emotional experience, and they may struggle to take information in. This website can prepare you, so that you can be on hand to help. 

So, what is IRD?

IRD is used to describe a collection of rare eye conditions. IRDs can also be referred to as inherited retinal diseases or inherited retinal degenerations.1

There are lots of different types of IRD. Some names of the more common ones are retinitis pigmentosa (RP), Usher syndrome, Leber congenital amaurosis, and Stargardt disease, all of which you can find more information on here.

People with IRD have a mutation in one or more of the genes responsible for the function of the light-sensitive (photoreceptor) cells in the retina at the back of your eye. In IRD these cells begin to lose function or die, which leads to a gradual loss of vision and blindness.1

IRD can affect people at any age but it is a leading cause of vision loss in people of working age (15 to 45 years), and a common cause of visual impairment in childhood. It has been estimated that IRD affects more than 2 million people worldwide (about 1 in every 2000).2

As there are so many different types of IRD, while they affect the vision symptoms and progression are all different.

A quick guide to the retina

Retina: the back surface of the eye made up of two layers, full of cells that detect light (photoreceptor cells) and send signals to the brain to create images. Contains two types of photoreceptor cells: rods and cones.1

Macula: the most light-sensitive part of the retina, densely packed with photoreceptor cells, a central spot that is responsible for colour vision.1

Rod cells: mostly found around the edge of the retina, these cells are the ones that work in dim light and that help us see things that aren’t straight ahead.1

Cone cells: these are concentrated in the centre of the retina and are the cells that are mostly involved in seeing colour and that give us detailed vision.1

A diagram of the inside of an eye with the retina and macula labelled

Gene mutations and IRD

Learning about IRD in more detail can equip you with a better understanding in order to support the person coming to terms with their diagnosis. You may wonder about the link between gene mutations and IRD. The information below will provide an explanation.

All inherited retinal dystrophies are caused by mutations in genes. These genes are involved in the development and function of light-sensitive cells (photoreceptors) and other cells in the retina.1  More than 260 genes have been associated with IRD, which are thought to cause 60 to 70% of all cases.3,4


Some types of IRD are caused by a single mutation in an identified gene, whereas others can be caused by lots of different mutations but are known by the same name.2 For example, Stargardt disease is usually caused by a mutation in a gene called ABCA4, whereas we know of mutations in 84 different genes that can cause retinitis pigmentosa.2

In some cases the genetic mutation that causes an IRD isn’t yet known, but research is always being done to discover more. Genetic testing can confirm a genetic basis for the disease your child or loved one has and determine what mutation is responsible, how this might affect their progress, and what the likelihood is of passing it on to children of their own.

Common genetic terms

Medical language can feel very jargon-heavy and full of words you may not understand. Here are some of the most common words with quick definitions to make things easier.

  • Chromosomes: tight bundles of DNA in the nucleus of cells that store the genetic information of an organism. Humans have 23 pairs of chromosomes with half of each pair coming from each parent
  • Autosomal: a mutation not linked to sex (X and Y) chromosomes 
  • Allosomal: a mutation linked to sex (X and Y) chromosomes. Humans have one pair of sex
    chromosomes that determines biological sex; males have an X and Y chromosome while females
    have two X chromosomes
  • X-linked: a mutation that is on the X chromosome. 
  • Recessive: where that you need two copies of the mutated gene for the disease to cause symptoms
  • Dominant: where only one copy of the mutation is needed for a person to be affected
  • Carrier: someone who has a copy of a recessive mutation but is not affected by the disease associated with it. A carrier can pass the mutated gene onto their children

Inheriting IRD

You may wonder how your child or loved one came to have an IRD. Different types of IRD have different inheritance patterns depending on the type of mutation and the gene(s) affected.

Humans have 46 chromosomes in 23 pairs containing all the genes that make us up. Each parent contributes one half of a chromosome paring. Below are the different ways that mutations that cause IRD can be inherited. 

A diagram showing how autosomal recessive mutations are inherited. Two parents are carriers of the mutation, each with one affected gene have four children: one has no mutated gene, two are carriers and have one copy of the mutation, and one has two copies of the mutation and is affected by the disease.
A diagram showing how autosomal dominant mutations are inherited. One parent is unaffected and has two normal copies of the gene. One parent is affected and has one normal copy of the gene and one mutation. They have four children: two are unaffected and have two normal copies of the gene; two are affected and have one normal copy and one gene mutation.
A diagram of X-linked recessive inheritance. An affected father who has one copy of the mutation on his X chromosome and a mother who has two normal versions of the gene on her X chromosomes. They have four children, two sons who are unaffected and have inherited the normal x chromosome from their mother and two daughters who are carriers and have one normal version of the gene and one copy of the mutation each
A diagram of X-linked recessive inheritance: An unaffected father who has one normal copy of the gene on his X chromosome and a carrier mother who has one normal copy of the gene and one copy of the mutation. They have four children, one unaffected son and one unaffected daughter who have inherited normal copies of the gene. One affected son who has inherited the mutated gene on the X chromosome from his mother, and one daughter who has inherited a normal copy of the gene from her father and a copy of the m

Common types of IRD

There are a lot of different conditions that together are called IRDs, many named after the person who first described them. They can be caused by a mutation in one of over 260 genes that have been linked to the conditions and can develop at different ages depending on the type.3

IRDs can be described as syndromic or non-syndromic. Syndromic IRDs are ones in which the eye problems are associated with other symptoms (such as hearing loss in Usher syndrome) as part of a systemic disease, whereas non-syndromic IRDs don’t have these systemic symptoms.6

Some of the more common ones are described below. Other types of IRD can include – Bardet–Biedl syndrome, Joubert syndrome and primary ciliary dyskensia (among others).7

Retinitis pigmentosa (RP)7,9
Main symptoms and characteristics – Difficulty seeing in dim light
– Difficulty moving between light and dark
– Gradual loss of peripheral vision in both eyes
Who it affects Onset and speed of progression vary considerably: some people are affected as children, whereas others aren’t diagnosed until adulthood
Type of mutation Over 100 different genes have been linked to various forms of RP; mutations can be autosomal dominant (30-40%), autosomal recessive (50-60%) and X-linked (5-15%)
Usher syndrome10
Main symptoms and characteristics – Hearing loss (at an early age)
– Night blindness (nyctalopia) and poor peripheral vision or tunnel vision
– Problems with balance
– Exists as three clinical types (Type 1, Type 2, and Type 3) depending on severity and symptoms
Who it affects Usher syndrome affects around 1 in 10,000 people, either male or female, and is usually diagnosed very early in life
Type of mutation Caused by an autosomal (not located on the X or Y chromosome) recessive mutation in genes that are important for the function of both photoreceptors in the eyes and hair cells in the cochlea of the ear
Leber congenital amaurosis (LCA)11,12
Main symptoms and characteristics – Inability to focus or nystagmus (involuntary jerky eye movements)
– Photophobia (sensitivity to light)
– Slow pupil response to light
– Pressing or rubbing the eyes
Who it affects LCA is a rare form of retinitis pigmentosa that affects around 1 in 33,000 to 1 in 50,000 people and is usually diagnosed a few weeks or months after birth. Children with LCA usually have severe vision loss early in life
Type of mutation Caused by a number of different mutations, usually autosomal (not located on the X or Y chromosome) recessive, but can sometimes be autosomal dominant
Stargardt disease13,14
Main symptoms and characteristics – Difficulty seeing fine details or distance
– Black, hazy, or wispy spots in central vision
– Slow adjustment to bright or low light
Who it affects Stargardt disease is the most common form of inherited juvenile macular degeneration and affects around 1 in 10,000 people. It is usually diagnosed in childhood or in teenagers
Type of mutation Stargardt disease is caused by mutations that affect the central part of the retina (the macular) that lets us see colour and fine detail. These mutations are usually autosomal recessive. Different gene mutations cause different types of Stargardt disease

 

Disease progression

The thought of a condition progressing can be unsettling for both you and the person you are caring for. But knowing the facts and what to expect can put you both at ease and help you plan for the future. How quickly an IRD is likely to progress and what symptoms they will develop can depend on what form and mutation a person has. Even the same IRD can progress differently in different people.

Many conditions start with difficulty seeing in low light levels, before leading to further vision problems. Loss of vision can be slow and gradual or can happen more suddenly. The different examples of visual impairment below help you to understand how the disease can develop.

An image of a landscape with a road running through, split into two. One side shows a clear view	, and the other shows black shadows at the top and bottom of the image, obscuring the view.

Tunnel vision or loss of peripheral vision

An image of a woman lifting a smiling child. The image has a black blob in the centre with blurred edges, obscuring the centre of the image.

Spots in the centre of vision

An image of a black Labrador. The image is split into two parts. The left part shows a clear picture, and the right shows a distorted paler version of the picture.

Blur in the centre of vision

Although their vision may worsen, there are a number of things you can do to help the person you are caring for adjust and make changes so that IRD doesn’t stop either of you from living your lives. See more in our section on Support and resources.

IRD can progress differently in different people, and so it’s important to get the most accurate diagnosis you can. For more information on clinical diagnosis and genetic testing click here.

References
1.
Retina International. Available at https://www.retina-international.org/educate/ Accessed February 2021. 2. Cremers FPM, et al. Genes 2018; 9(4): 215. 3. RetNet. Available at: https://sph.uth.edu/retnet/sum-dis.htm Accessed February 2021. 4. Hafler BP. Retina 2017; 37(3): 417–423. 5. Genetic Alliance. Understanding Genetics: A District of Columbia Guide for Patients and Health Professionals; District of Columbia Department of Health. Washington (DC): 2010 Feb 17. 6. Pierrottet CO, et al. Gen Med Res 2014; 13(4): 8833. 7. Berger W, et al. Prog Retin Eye Res 2010; 29; 335–375. 8. Menghini M, et al. Expert Opin Orphan Drugs 2020; 8(2–3): 67–78. 9. Sahel JA, et al. Cold Spring Harb Perspect Med 2015; 5(2): a017111. 10. Mathur P & Yang J. Biochim Biophys Acta 2015; 1852(3): 404–420. 11. Kumaran N, et al. Br J Ophthalmol 2017; 101: 1147–1154. 12. Chacon-Camacho OF, Zenteno JC. World J Clin Cases 2015; 3(2): 112–124. 13. Tsang T, Sharma T. Adv Exp Med Biol 2018; 1085: 139–151. 14. Tanna P, et al. Br J Ophthalmol 2017 Jan; 101(1): 25–30.

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Recognising IRD

There are lots of different types of IRD and lots of tests doctors can use to diagnose them.

Signs and symptoms

There are a range of different signs and symptoms that your child or loved one might experience, beyond problems with their vision. These vary because of the number of diseases that are included in the term inherited retinal dystrophy. Some of the ocular signs to look out for that can suggest your child or loved one might have a problem with their vision and that can prompt a doctor to arrange further tests are:

Cartoon illustration of a woman and a young black girl high-fiving

In babies and young children:

  • Nystagmus (uncontrolled eye movements)1
  • Photophobia (sensitivity to light)1,2
  • Poking or rubbing of the eyes1
  • Problems with hearing and balance (mostly associated with Usher syndrome)3
Cartoon illustration of a woman sat on an armchair, reading a book.

In older children and teenagers:

  • Difficulty reading and seeing things at a distance
  • Loss of visual acuity2
  • Night blindness (nyctalopia) or problems seeing in dim or low light1,2
  • Slow eye response when switching from bright to dim light

In children and adolescents, signs of a potential issue with vision can show up in other ways:

ADHD
Difficulty paying attention that may seem like ADHD (attention deficit hyperactivity disorder)4
Avoiding reading
Avoiding reading or losing place when reading4
Eye discomfort
Complaints of eye discomfort or tiredness4
Eye rubbing
Frequent eye rubbing or blinking4

This video gives an idea of what it can be like to live with an IRD, to care for someone who has it and also highlights some of the symptoms

How is IRD diagnosed?

Receiving a diagnosis for an IRD can be daunting for both you and your loved one, but knowing the process of a diagnosis is important in understanding your options. 

There are two types of diagnosis for IRD: clinical diagnosis and genetic (or molecular) diagnosis.5

Clinical diagnosis

Clinical diagnosis
A clinical diagnosis is made based on the signs and symptoms on display as well as tests done in the doctor’s office. It is an assessment of whether a person has an IRD and, if so, what type. It might involve a number of different clinical tests carried out by a doctor or ophthalmologist. Some of these tests are outlined in more detail below.6

Genetic diagnosis

Genetic diagnosis
A genetic diagnosis is where genetic testing is used to find out exactly what gene mutation is causing an IRD. It’s used to validate and confirm the clinical diagnosis and find out exactly what is wrong. Not all of the mutations that cause IRD have been identified yet, but a large proportion have, and a genetic test should be able to tell you more and help inform the management of your child or loved one’s IRD.7,8

Clinical tests for IRD

Beyond normal sight tests, there are a number of different tests that a doctor or ophthalmologist might carry out to identify IRD and get more information.

Visual field testing: Uses a machine to check how much of the peripheral vision has been affected.9 This is non-invasive and involves the person indicating when they see a given stimulus, such as a flashing light.9

Retinal imaging: Uses a special camera to take images of the back of the eye including small structures and any abnormalities.10 This can be used to confirm a suspected clinical diagnosis and help guide further testing.

  • Fundus photography: A fundus photo is a picture of the retina that can be used to detect abnormalities. Fundus photography can be combined with autofluorescence imaging to give more information and makes it possible to diagnose IRDs such as Stargardt disease more easily.6
  • Optical coherence tomography (OCT): A scanning device that works by bouncing light waves off the retina to get a better picture of what is going on in the layers of the retina.6

Electroretinography (ERG): Measures the electrical response of rod and cone cells to light, using an electrode placed on the cornea. This helps see if the photoreceptor cells are functioning as they should be.6

Genetic testing

What is genetic testing?
A genetic test can be done after your child or loved one has been given an IRD diagnosis to give more information about the mutation causing it and what their disease progression is likely to be. Genetic testing is usually done via a blood sample, and involves sequencing the genes in a laboratory and comparing them to mutations that are already known to relate to IRD.9 It’s done to give a more precise, genetic diagnosis of your condition and can help guide future management.

Why is genetic testing useful?
Genetic testing can help identify definitely if the patient has an IRD or not and, if so exactly what gene mutations are causing an IRD. This can help give a better idea of how the disease is likely to progress and can give the doctor more information to help guide disease management. A genetic diagnosis can also identify if your child or loved one might be a candidate for any ongoing or future clinical trials or approved treatments of IRD (see more here) and can help provide information that can guide further research into the treatment of different IRDs.10

As well as this, a genetic diagnosis helps to provide your child or loved one with reassurance about their condition, and give them important information about the likelihood of passing it on to any children they may have in the future.9

Getting referred for genetic testing
Your child or loved one’s doctor or ophthalmologist will usually want to make a full clinical diagnosis before proceeding to genetic testing. They may also want you to speak to a genetic counsellor before referring for genetic testing, as they can help you make sense of the results.9

If you think a genetic test could be the right option for your loved one, you should speak to their healthcare practitioner about the possibility.
References
1.
Kumaran N, et al. Br J Ophthalmol 2017; 101: 1147–1154. 2. Gill JS, et al. Br J Ophthalmol 2019; 103: 711–720. 3. Mathur P & Yang J. Biochim Biophys Acta 2015; 1852(3): 404–420. 4. American Optometric Association. School Age Vision. Available at https://www.aoa.org/patients-and-public/ good-vision-throughout-life/childrens-vision/school-aged-vision-6-to-18-years-of-age Accessed February 2021. 5. Menghini M, et al. Expert Opin Orphan Drugs 2020; 8(2–3): 67–78. 6. Henderson RH. Paediatrics and Child Health 2019; 30: 1. 7. Hafler BP. Retina 2017; 37(3): 417–423. 8. Duncan JL, et al. Trans Vis Sci Tech 2018; 7(4): 6. 9. RNIB and RCOphth. Understanding Retinitis pigmentosa and other inherited retinal dystrophies. 2017. Available at: https://www.rnib.org.uk/eye-health/eye-conditions/retinitis-pigmentosa Accessed February 2021. 10. Lee K, Garg S. Genet Med. 2015;17(4): 245–52.

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Research into IRD

Ongoing research into treatments for IRD and how to get involved

IRD clinical trials – ongoing research

Although there aren’t currently treatments available for many forms of IRD, there is a lot of research happening to try and find new options to treat these diseases. Most clinical trials are run at specialist centres and only include patients who have a particular diagnosis or specific genetic mutation and some only run in specific countries. Most clinical trials across all different types of diseases are registered on the clinicaltrials.gov website.

If you think your loved one might be a candidate for a clinical trial, you should talk to their doctor about the possibility and what their options might be.

You can find a list of trials that are currently recruiting patients for treatments of inherited retinal dystrophy here.

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Support and resources

 

Helpful information about IRD and what a diagnosis means for you.

As someone caring for a person with an IRD it can be difficult to know where to go for help, but there are patient support and advocacy groups out there. These may be able to offer advice for supporting your loved one and can also help you in managing your journey with them. Some examples of these are listed below.

Useful websites

Downloadable resources

Leaflet - IRDs