How is vision affected in Batten disease?
The retina is a thin layer that lines the back of the eye and contains photoreceptors, which are structures that change light into electrical signals. These signals are sent through the optic nerve to an area of the brain that processes vision. This part of the brain pieces these signals together to form the images we see.
In people with Batten disease, a toxic compound known as lipofuscin accumulates inside cells, including those of the brain and retina. This buildup damages the photoreceptors in the retina, optic nerve, and area of the brain that processes vision.
Signs of worsening vision
Deteriorating vision is often the first sign of Batten disease and usually begins around the age of 5, with blindness occurring by 6 years old. Changes in vision may develop alongside other early signs of the disease such as clumsiness and slow learning, as well as behavioral and personality changes.
Children with worsening vision may adopt an “overlooking” eye position characterized by looking above the object of interest instead of directly at it. Other symptoms may occur, such as headaches, frequent eye rubbing, squinting or blinking, covering one eye, and head tilting.
Children may avoid reading and appear to have a shorter attention span. While they may still attempt schoolwork, they do so with a lower understanding and retention of the learning material.
In younger children, achieving developmental milestones later than expected may be observed as a result of impaired vision.
Color blindness is not uncommon in childhood forms of Batten disease, with patients having difficulty in telling colors apart or making frequent mistakes in identifying colors.
Evaluating changes in vision
The time when vision loss occurs and how fast it progresses can be very different from one person to another with Batten disease.
A visit to the ophthalmologist, who will perform a series of eye tests, is the first step in evaluating the degree of vision loss. Patients may be required to undergo an electroretinogram, a test that measures electrical signals generated by the retina.
A biopsy of the conjunctiva, or the inner lining of the eye, will reveal characteristic fluorescent lipofuscin deposits that are the hallmark of Batten disease.
Managing vision impairment
There is currently no effective treatment to prevent vision loss in Batten disease patients. However, early diagnosis of vision impairment is important so that interventions can be put in place to allow children to achieve their full developmental potential.
Vision aids such as glasses and contact lenses may be able to correct less severe vision impairment. Orientation and mobility training is necessary for patients with total vision loss. This training teaches the patient to use hearing, smell, and touch to navigate the world.
Children with impaired vision need special care and attention since the inability to see may cause feelings of anxiety and frustration. Behavioral problems such as pushing, grabbing, and throwing commonly occur, and should be managed gently with kindness and understanding.
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