What is Lebers Congenital Amaurosis?
Lebers Congenital Amaurosis (LCA) is a spectrum of inherited conditions that causes poor vision in early childhood. Symptoms commonly first appear around 2-3 months of age.
How is LCA inherited?
LCA is usually autosomal recessive. Both parents carry one copy of a recessive gene. If both parents are unaffected but carry the recessive gene, there is a 25% chance that each of their children will have LCA. A number of genetic defects have been found that cause LCA — most of which are inherited in a recessive fashion. However reportedly a couple of genes have been involved in a rare form of dominant inheritance. In the latter case, one mutated copy of the gene from an affected parent or a new mutation in the child would lead to LCA.
What are the symptoms and signs of LCA?
The most common early symptom is nystagmus (shaking of the eyes) and it is usually evident within the first few months of life. As a child gets older, poor vision/tracking, sensitivity to light and poking/rubbing of the eyes with a fist or finger may also be noted.
How is LCA diagnosed?
LCA is usually diagnosed by an ophthalmologist based on family history and the physical findings at the examination. An electroretinogram (ERG) is often utilised to confirm the diagnosis however ERG is usually very poorly defined or unrecordable due to damage of the retinal rod cells.
How is LCA treated?
There are currently no treatments for most types of LCA. Routine examinations by an ophthalmologist are recommended for all LCA patients to diagnose/treat other eye problems and prescribe glasses. Low vision aids to maximise visual function can be very useful for patients with LCA. There have recently been experimental successes using gene therapy for one type of LCA (involving the RPE65 gene) in both animal models and humans but this therapy is still in the research phase.
Behaviours or conditions that might indicate Lebers Congenital Amaurosis (LCA)
- Usually a significant vision loss is noticed during infancy.
- Eyes may wobble or show involuntary movement (nystagmus).
- The infant may not give consistent, deliberate or prolonged facial regard.
- The infant may remain sensitive to bright light.
- The infant may find it challenging to focus and track moving objects.
- Visually guided reaching may not occur when developmentally expected.
- The infant may not recognise their parents across a room.
- Crawling may be delayed.
- Looking and reaching for objects for further investigation may be delayed or the infant may rely on sound to locate the object or voice to turn to familiar people.
- Extreme hypermetropia (farsightedness) might be diagnosed and prescription glasses to assist some of the clarity issues might be recommended.
What to do
- The young person should visit an optometrist or ophthalmologist to determine diagnosis and cause and possible prescription glasses.
- A Functional Vision Assessment will assess the infant, 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 maximise access and defining 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 strategies can include a review of print size, contrast levels and the effects of clutter.
- 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.