What is Stargardt’s Macular Dystrophy?
Stargardt’s Macular Dystrophy is the most common hereditary macular dystrophy with an estimated incidence of 1 in 10,000. It affects the macula, this is a specialised region of the eye that we use for seeing straight ahead and in detail. The typical person presents with visual symptoms between the first and third decades of life.
What are the symptoms of Stargardt’s Macular Dystrophy?
Symptoms of Stargardt’s usually start between childhood and early adulthood. They are most likely to include loss of central vision (including some blank spots) in both eyes, problems with colour vision, being sensitive to light and being slow to adapt to the dark. The symptoms vary from person to person depending on the exact genetic fault. It is rare for people with the disease to become completely blind. For most people, vision loss progresses slowly over time to 20/200 or worse.
How is Stargardt’s Macular Dystrophy inherited/caused?
Stardgardt’s is autosomal recessive, it takes two copies of the mutant gene to give rise to the disease. An individual who has one copy of a recessive gene mutation is known as a carrier. When two carriers have a child, there is a:
- 1 in 4 chance of having a child with the disease,
- 1 in 2 chance of having a child who is a carrier,
- 1 in 4 chance of having a child who neither has the disease nor is a carrier.
Autosomal recessive mutations in the ABCA4 gene account for about 95 percent of Stargardts Macular Dystrophy. The other five percent of cases are caused by rarer mutations in different genes that play a role in lipofuscin function. Some of these mutations are autosomal dominant.
How is Stargardts Macular Dystrophy diagnosed?
The diagnosis of Stargardts is based on detailed eye examination with findings of typical pigmentary changes predominantly in the macular area e.g beaten metal, flecks or bull’s eye maculopathy, in conjunction with findings of abnormal pattern ERG which tests mainly the function of the macular.
How is Stargardts Macular Dystrophy treated?
Currently there is no treatment for Stargardts disease. Some ophthalmologists encourage people with Stargardts to wear dark glasses and hats when out in bright light to reduce the build-up of lipofuscin. Cigarette smoking and second hand smoke should be avoided. Animal studies suggest that high-dose vitamin A may increase lipofuscin accumulation and potentially accelerate vision loss. Therefore, supplements containing more than the recommended daily allowance of vitamin A should be avoided or taken only under a doctor’s supervision.
Behaviour and Conditions that might indicate Stargardts Macular Dystrophy
Symptoms vary from person to person depending on the exact genetic fault and progresses slowly over time. It is rare for people with Stargardts Macular Dystrophy to become completely blind.
- Symptoms usually begin between childhood and early adulthood.
- Loss or blurriness of central vision in both eyes.There may be blank spots or scotomas, which may affect how the child views material or his environments. They may move or turn their head to compensate for the loss or blurriness of central vision.
- Coming in closer to view finer, smaller or subtler details in print and non-print materials.
- Difficulty with colour vision, which may exhibit itself in colour confusion.
- Difficulty with bright lighting or sunlight; avoidance of bright places; squinting or closing eyes when outside.
- Difficulty with glare on reflective surfaces such as whiteboard, laptop screen, puddles and wet surfaces on footpath.
- Needing time to adjust or adapt when going from a brighter environment to a darker one or vice versa.
What to do
- The young person should visit an optometrist or ophthalmologist to determine diagnosis and cause.
- A Functional Vision Assessment will review the child or young person’s use of vision. This will include observations and assessments of how he/she uses vision in real life situations and for learning and access to Te Whāriki, the New Zealand Curriculum, the Blind and Low Vision Education Network, NZ (BLENNZ) Curriculum and the Expanded Core Curriculum.
- Adaptations or modifications to the environment and materials used may be required. Some of these can include lighting review, monitoring glare to reduce fatigue and to maximise access and reviewing and organising spaces to encourage play and movement.
- Strategies and suggestions for low and high tech devices later in life to assist the learner’s functional vision are also included in the functional vision assessment. Some of these suggestions can include a review of print size, contrast levels and the effects of clutter. Slope boards, magnifiers and other tools to assist with posture and near and distant access are assessed.
- A Developmental Orientation and Mobility assessment will assess how the infant, child or young person moves purposefully, safely and confidently in the environment and how they understand where they are in space and what is around them.
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