What is an inherited retinal disorder (IRD)?
An inherited retinal disorder (IRD) alters the structure and function of the retina and impairs vision.
In some children with IRDs, visual impairment is mild, but in others it is more severe. IRDs are rare. There are many types. Most IRDs affect the light-sensitive cells that are known as photoreceptors, reducing or preventing responses to light in the retina and leading to vision impairment. IRDs are inherited and cannot be prevented. Some are degenerative, meaning they will worsen over time, but some remain stable throughout life.
What are the most common inherited retinal disorders?
The most common types of inherited retinal disorders include:
Leber congenital amaurosis (LCA)/early onset retinal degeneration
Leber congenital amaurosis (LCA) causes severe visual impairment that starts as early as infancy. Children with LCA may also have extreme farsightedness and crossed eyes. An FDA-approved treatment for the RPE65 form of LCA helps with vision.
X-linked retinitis pigmentosa (RP)
Retinitis pigmentosa is a group of related sight disorders. The common attribute is the slow deterioration of the photoreceptor cells in the retina that respond to light. Loss of night vision is often an early sign of X-linked RP, along with some visual acuity deficits, followed by the loss of peripheral vision.
Children with achromatopsia have limited or no color vision, low vision acuity (typically at a legally blind level), and extreme sensitivity to light. Achromatopsia is different from congenital “common” color vision deficiency (sometimes known as color blindness) in that it also causes low vision and sensitivity to bright light. Fortunately, symptoms usually do not worsen over time.
Stargardt disease damages the macula, a part of the retina that provides straight-ahead vision — the vision for seeing details such as small letters. The onset of the disease is typically during childhood, but it might not be detected until adulthood. It causes the loss of the central vision field. The loss of all vision is uncommon.
Cone-rod dystrophy (CRD)
Cone-rod dystrophy is a group of related IRDs that involve the deterioration of the photoreceptors that are known as rods and cones. Vision loss occurs over time, usually starting in childhood with symptoms such as poor vision and sensitivity to light. Later symptoms include blind spots in the center of vision, loss of peripheral vision, and difficulty distinguishing colors.
This condition affects males and is caused by a loss of retinal cells. Choroideremia causes progressive vision loss: usually night blindness in childhood, followed by a gradual loss of peripheral vision, and eventually an inability to make out details. Tunnel vision or complete blindness by adulthood are possible.
This condition affects males and causes an early loss of central vision because the retinal layers split apart. Vision may slowly deteriorate with age.
Congenital stationary blindness
Typical features are early severe nearsightedness (high myopia), low vision even with glasses on, and noticeable difficulty seeing in dimly lit conditions. There are many forms of congenital stationary night blindness; the specific form is determined through genetic testing.
Inherited Retinal Disorders | Symptoms & Causes
What are the causes of inherited retinal disorders?
Inherited retinal disorders are passed down from a family member and cannot be prevented. The disorder develops when there is a change in one or more genes that govern retinal cell structure and function. If one or more of those changed genes don’t work properly, retinal cells are altered in their function, and often in their structure. These alterations lead to vision loss. The severity of genetic mutations varies. Some IRDs can be more severe than others.
What are the symptoms of inherited retinal disorders?
The symptoms of an IRD depend on the type and severity. While some IRDs might be quite stable, others cause loss of vision over a lifetime and some cause blindness. For those IRDs that are stable, or non-degenerative, they will not worsen over your child’s life. Here are symptoms of inherited retinal disorders you can look for in your child:
- vision problems that are not corrected with glasses
- not wanting to go outside during the daytime and sensitivity to light
- having difficulty navigating in low-light conditions
- bumping into objects and speaking about not seeing things to the side (impaired peripheral vision)
- unsteady eye movements, such as a roaming or shaking eye
- difficulty discriminating colors
- a family history of IRDs
Inherited Retinal Disorders | Diagnosis & Treatments
How is an inherited retinal disorder diagnosed?
Inherited retinal disorders are not always easily diagnosed. Because symptoms from different eye conditions overlap, extensive testing and time are often needed to pinpoint a diagnosis. At the Department of Ophthalmology, we develop a diagnostic plan that’s right for your child.
First, we give your child an eye examination. For some patients, we conduct an electroretinogram (ERG), a test of retinal function that measures the electrical response of an eye’s light-sensitive cells (photoreceptors). We can also measure your child’s ability to see in low light (dark adaptation testing), and determine their extent of vision (visual field testing). To assess the structure of the retina, we conduct retinal imaging. By characterizing the function and structure of the retina, these tests help in the diagnosis of an IRD. They also give us an idea of how to best support your child’s vision needs.
Genetic testing is also critical to reach a specific diagnosis. Collaborating with the Division of Genetics and Genomics, we examine your child, ask about your family history, and conduct specialized genetic testing — all to help guide an IRD diagnosis. We also work with other specialists if your child’s eye condition is related to other conditions. In infancy and early childhood, an IRD may have only subtle signs and only later will fully develop or stand out from other eye conditions. That’s why it is important to stay engaged with your ophthalmologist and report any new symptoms so your child can be further evaluated.
How we care for inherited retinal disorders
Unfortunately, there are no cures for most IRDs. Depending on the condition, there may be care options such as prescription glasses to improve visual clarity, tints and filters that can lessen your child’s sensitivity to light, or surgery to repair the retina for those with advanced X-linked retinoschisis or those associated with complications from very high myopia.
We now offer gene therapy for children who have LCA associated with the genetic Biallelic RPE65. This tremendous breakthrough offers hope that ongoing research — including a current clinical trial at Boston Children’s to treat X-linked RP and an anticipated one for X-linked retinoschisis — will someday identify therapies that benefit children with other IRDs.
What is retinal gene therapy?
Retinal gene therapy provides a working copy of the RPE65 gene to the retinal cells of the eye. A copy of the working gene is injected beneath the retina (the thin layer of tissue in the back of the eye). This enables the retinal cells to make the RPE65 protein, which allows the visual cycle to continue and for light to be converted to electrical signals to be interpreted by the brain.
Who is eligible for Luxturna™?
The retinal gene therapy Luxturna™ is available for children 12 months and older who have a genetically confirmed mutation in both copies of the RPE65 gene. Patients must undergo a clinical examination and evaluation at our clinical site to determine if there are enough retinal cells to receive the therapy.
For more information about whether Luxturna™ is right for you or your child, or to refer a patient, please contact:
Hanna De Bruyn
Retinal Gene Therapy Coordinator
Inherited Retinal Disorders | Resources
Resources and services for inherited retinal disorders
No matter your child’s type of IRD, we will closely monitor their condition to track how it is progressing and will recommend resources and services for living with diminished eyesight, including:
- Boston Children’s Low Vision Service, which will recommend visual aids that can help your child best use their remaining vision to its fullest potential
- Boston Children’s Social Work Program, which offers a wide range of social services to help your family manage your child’s condition
- genetics counselors at Boston Children’s, who can help your family understand the genetic tests that are recommended to diagnose your child’s IRD
- teachers of students with visual impairments, who will understand your child’s visual impairment and can help them participate in a school setting
- orientation and mobility experts, who will help your child learn how to safely move within their everyday environment
- Massachusetts Commission for the Blind, which can connect your family to social rehabilitation and other services
- social workers from outside agencies, who can advocate on your child’s behalf at school and other settings