Vision problems are not always confined to the eyes. Our brain develops the ability to process increasingly complex information based on the visual and tactile information it receives. Vision difficulties can, therefore, be the source of learning disabilities. These conditions are very common, particularly in premature babies, and are on the rise. How should they be dealt with? How can they be diagnosed? How can we help parents support their children? IAPB Italy has recently published an insight series by the National Low Vision Center on this theme on its website.
Interview with Dr. Daniela Ricci, pediatric neurologist at the National Low Vision and Vision Rehabilitation Center.
We first need to debunk a popular myth, which is also widespread among ophthalmologists: vision problems are not confined to the eyes only. Vision difficulties have an impact on our motor, cognitive and social skills, especially during childhood, because they heavily affect the way our brain learns to process and interpret information from the outside (space, sensations, etc.)
“Our brain development is strictly connected to sensory information, and visual inputs are paramount,” says Dr. Ricci, pediatric neurologist at the National Low Vision and Vision Rehabilitation Center. “I’m not referring to physiological functions only. Since new magnetic resonance imaging techniques opened the door to the investigation of brain connectivity, we have started to assess the impact of prematurity and sensory deficit on the development of connections among various brain areas, that is, the mechanism enabling the quick decoding of information and the programming of complex actions or tasks. The brain of sighted people and of people blind since birth show a tight pattern of neural connections. That’s because sensory inputs coming from sight, or from other senses that have compensated for its loss, have granted a constant flow of information. However, in the presence of congenital or genetic damage, such information doesn’t reach the brain, or is incorrectly processed, leading to a reduced development of brain connectivity.
What happens when the correct exchange of information between our brain and our senses is impaired?
Information is acquired and processed more slowly. Not all forms of brain impairment cause visual impairment. However, all (severe) visual impairment affects a child’s neurological and psychomotor development because it reduces the quantity and quality of information through which our brain evolves and builds its own experiences. Visual impairment may result from brain ‘lesions or malformations, whether genetic or not. Other forms of visual impairment stem from eye diseases.
Starting from this assumption, we examine the relationship between sight and neurological development by looking at:
- nystagmus and strabismus;
- learning disabilities
- Syndromes
- Brain injuries
1 – NISTAGMUS AND STRABISMUS
Nystagmus is a rhythmic and involuntary oscillation of the eyes. Physiological nystagmus is related to the way we look at moving objects: a typical example is that of a person on a moving train, who is looking out of the window and focusing on the poles or trees along the railway line, one at a time, (a slow movement of the eyes is soon followed by a rapid or jerking movement). In pathological nystagmus, however, every oscillation cycle tends to move the object of observation away from the fovea (center of the retina), excluding it from the central area of the visual field, and thus causing severe vision issues.
Strabismus is a condition in which the visual axes of the two eyes do not align. If developed in adult age, it may cause double vision (diplopia). When present at birth, or if the onset is in the first years of a child’s life, our brain spontaneously excludes images coming from the deviated eye: the unused eye is automatically deactivated to avoid doubling the image. Early diagnosis is very important in these cases, otherwise the deviation may cause a significant permanent reduction of visual acuity in children (amblyopia).
What is the relationship between nystagmus, strabismus, and neurodevelopmental deficit?
Neither condition, if isolated, necessarily poses a risk to neurological development. Children with benign congenital nystagmus or with isolated strabismus show adequate psychomotor and cognitive development. When combined, however, they may threaten a child’s cognitive development, because they are typically associated with eye or brain disease or both, as is the case with premature babies who develop preterm retinopathy.
How?
It is not so much visual acuity that is threatened, but the ability to observe and perceive objects, people, and space. Children affected at the same time by severe nystagmus and strabismus do not develop binocular vision and, therefore, do not easily obtain information regarding distance, depth, and tridimensionality from their eyes. All eye movements are hindered: saccades (quick jerks), movements in between saccades and smooth pursuit (larger gaze-shifting movements along a sequence of fixation targets) and smooth pursuit (slow tracking movements). Children have difficulty in assessing distances, they seem clumsy and uncoordinated, even when picking up an object with their hands, also because they don’t perceive its volume well. Visual impairment implies a poor ability to identify details of images or objects, with the consequent inability to make out one object from another, as well as to draw them or interact with them. Yet another problem adds on to this: our brain tends to favour sight over other senses anyway. The result is that, while blind children reach out with their hands to compensate for the absence of visual information (i.e., they use other senses), visually impaired children tend to use their sight regardless. In short, their brain processes visual information that is wrong or misleading.
What can be done to treat these children?
There is no standard protocol, although we are aiming to implement one, here at the National Low Vision Center. There are different and effective forms of training and tests to assess and correct the impact of visual impairment on learning. In many cases, with the correct support, children can develop appropriate strategies that help them obtain reliable information and build up a database of experiences, upon which they can participate in all the typical activities of their age group. Early diagnosis, as in almost every aspect of eye care, determines the effectiveness of rehabilitation.
What’s the situation like in Italy?
Unfortunately, awareness of the relationship between visual impairment and brain development is not widespread. Too often, we examine children aged two or three with an eye problem, who have never been previously checked by a neurologist. This is due to a widespread misconception that vision problems are confined to the eyes only. This is not true. Vision problems, especially among children, can lead to a brain issue that needs rehabilitation and special training in order for it not to interfere with growth and learning.
