Vision Blindness Part 1 – What we can’t see.

3d render of man carrying book on his back. Concept of learning difficulties.

(See the Introduction here.) For many years, researchers have asked, ‘Why is it that nearsighted children seem to fare better in academics than farsighted children?’ Some have even gone so far as to suggest myopic IQ’s are higher than hyperopic IQ’s, and that there is some epigenetic and / or pleiotropic link between refractive state and intelligence. A recent discussion of certain refractive states as physical disability expands on this. In short, children with farsightedness and/or astigmatism experience a much greater physical strain than their nearsighted peers: In other words, it has less to do with intelligence than the physical and toxic burden of these conditions in a heavily vision-based instructional model.

For those behavioural optometrists working with pediatric patients, it is clear to see that refractive state is fundamental to how a child learns, behaves, and struggles. The numbers in the glasses prescription, as limited as they are in the description of the entire visual status of a child, represent key information that should be understood by anyone managing the child’s health or education. It is of no practical use, for example, to have the child undergo a psychoeducational assessment battery if we have no concept of what their refractive status is: Children with nearsightedness tend to do better in academic and cognitive testing, farsighted and astigmatic children will do worse if uncompensated, especially if they’d never been compensated. The number’s parts represent very real information that impacts on how a child functions and behaves, to a great degree, how they will develop.

The medical-mechanical view of refractive state reduces it to a matter of relative blur, and nothing more: So long as a child can read a picture eye chart at 10 feet, they are ‘fine’. Likewise, the pronouncement of good health from a family doctor or pediatrician is often taken as a sufficient assessment of ‘vision’, which is very different from eye health.

Not to belabor the point, but asking the family practitioner about a child’s vision is roughly equivalent to asking them about your car’s engine, your accounting and taxes, or the law. We use professional specialties because we intuitively understand that no one person can be expert in all fields.

From a summary paper I co-wrote on VILD, here are the basic elements of a vision exam all children should have prior to starting school. Your family doctor and pediatrician are unlikely to even have a record of the very basic refractive state (eyeglasses prescription) on file, let alone all of these key markers in vision function. Likewise, even the basic measurement of visual acuity is often done by untrained personnel at distance (while most learning occurs at near distance), using imprecise charts (picture charts), and no notes are made with respect to the child’s response to doing the test itself: Are they straining? Do they turn or tilt the head? Do the eyes turn? See also this monograph on pediatric vision assessment.

1. Visual Health: Includes eye health, visual nervous system pathways, and reflexes.
2. Refraction and Accommodative Status: Assessment of nearsightedness, farsightedness, and astigmatism, as well as how these compare right to left. Near refraction as well as distance refraction are recommended. Accommodative range and facility.
3. Cycloplegia on borderline cases. ‘Wet’ or ‘drop’ exams, where the focusing system is relaxed by medication.
4. Visual Acuity @ distance and/or at near. Where the chart lies will determine performance and reveal different findings. Farsighted children are much more likely to show signs of facial muscular strain at near, but not so much at far distances.
5. Ocular Motility: Includes range of movement, binocular alignment, pursuits, fixations, saccades, and vergence.
6. Colour: Rarely a significant finding, but should be done. Determines to some extent career options and can be diagnostic in some medical cases.
7. Stereopsis: To what extent can depth be perceived (3D).

Here’s a typical example from clinical experience as to the extent of most medical eye exams related to child learning concerns. This is a repeated observation many times daily in other clinics that treat vision-related learning and behaviour problems:

1. Parent, usually Mom, is told their son, say, is having trouble in school. They are advised to ‘see a doctor’ by school personnel, and this usually means an MD.
2. The family doctor (General Practitioner Medical Doctor, or GPMD) recommends various testing that can a basic assessment of cranial nerve function, perhaps blood work, and frequently brain imaging. In many cases, if there is even a whiff of concerns around attention (whatever that might be*), there is a paper survey circulated to already heavily-biased staff at school: Does this child appear to have trouble with attention and hyperactivity? The answer, to those referring the child, will almost always be in the affirmative.
3. In many cases where the child is showing significant differences in behaviour and learning from his peers, Mom will also be advised to seek a psychoeducational assessment.
4. The GPMD may refer to a pediatrician to ‘confirm’ findings, which is most often a matter of reviewing the chart, and confirming that the parents are in favour of some sort of intervention, usually stimulants.
5. As the child most often has no obvious ocular health problem or a frank strabismus, good ‘eye health’ is most often taken as ‘good vision’.

No where along the line of recommendation and assessment is anyone asking, ‘What about visual function?’. We know that GPMDs and pediatricians are not trained in visual functional assessment and so they are not looking: The rationale seems to be ‘If it were worth looking for, I would look for it and be trained to do so’. Still, we know that of those children who struggle in school, by far most of them struggle with these ‘invisible’ vision issues.

Vision function is complex and so describing it in detail is clearly beyond the scope of this post. Still, it is important that we do consider some of what is involved so that basic principles might be presented.

Non-medical vision dysfunction (aka visual impediments to learning and development, or VILD) take many forms but can be roughly divided into two broad categories: Elements of visual signal acquisition (VSA) and visual signal processing (VSP). VSA can be viewed as comprising all those elements that lead to fixation of a target and clarification of a single image on corresponding retinas; these are the physical ‘moving part’ elements of vision and are driven by the brain using the eyes. VSP is everything that happens with the signal after it has been captured through VSA, ranging from spatial computation, identification of objects, motor planning, memory, and so on.

Visual impediments to learning and development (VILD) are summarized in this paper. VILD are much broader than simple visual acuity, which is taken to represent the inoffensive and inoccuous ‘blur’ of the medical-mechanical view of vision function. Vision dysfunction is more likely to present as head pain, confusion, frustration, and emotional outbursts than a subjective report of blur. Indeed, one of the reasons all children should have a comprehensive eye exam early is that for them, their vision is absolutely normal, regardless of the extent to which they might be affected.

It is clear to see that expertise counts when it comes to vision, and that family doctors and pediatricians are not taking a serious look at vision in large part because they have not been trained to pay it any heed. This is a reasonable reason for not looking into it, if not misguided and narrow. But, as vision is critical to child development and behaviour, and given that we are largely visual animals, it would only make sense that the child’s visual functional status be noted on a child’s chart, at the very least prior to prescribing of drugs for behaviour or learning, and certainly before any additional invasive testing, including brain scans and psychoeducational assessment.

The next part in this series will consider in brief what we miss when we disregard visual functional assessment.

*A note on ‘attention’. Teachers and family doctors are not trained to appreciate all the elements involved in what drives a student’s attention. When teachers complain about a student’s attention, most often they are referring to their own attention, as in, the student is busy or struggling and requires more of the teacher’s attention. The child’s concern, then, is often really a classroom management concern. While it appears to be very easy to obtain drugs for modifying a child’s behaviour in class, there is never any discussion about how the school and teacher might modify programming to suit the child’s needs (i.e. a move away from more multisensory experiences rather than simply computer- or reading-based instruction). There is no doubt that in many cases the drive to seek a ‘diagnosis’ for learning disability is a deflection, or redirection, from a profound ‘teaching disability’, or inability to modify instruction according to student needs. The fact that we still insist on a text and computer-based instructional model while disregarding a child’s visual functional status is a testament to this.