hyperopia in young children

New England College of Optometry, Boston, Massachusetts, USA

Abstract

BACKGROUND:

Hyperopia is the most common refractive error of children. Children with mild (or even moderate) levels of hyperopia usually do not experience visual problems resulting from this hyperopia. However, children with moderate-to-high degrees of hyperopia are at significantly increased risk for the development of amblyopia and strabismus. It is this association with these visually threatening disorders that makes hyperopia in children an important public health problem. In addition, even lesser degrees of hyperopia may affect the child's ability to perform well in near-related tasks, such as reading. The effect hyperopia has on an individual child is dependent on a variety of factors, including the magnitude of hyperopia, the age of the individual, the status of the accommodative and convergence system, and the demands placed on the visual system. Early detection and treatment of hyperopia may help prevention of potential complications from adversely impacting the child's vision. Although much is known about childhood hyperopia and its effects on vision, there is also much that is not known. The natural history, ocular biometry, relationship to accommodative function, the indications for treatment, and the most effective treatment modalities are among the underlying issues and clinical considerations awaiting more complete understanding.

Myopia and Hypermetropia

Myopia and Hypermetropia are common refractive errors which are usually corrected by glasses and contact lenses. Moderate degrees of myopia may also be corrected by refractive surgery, RK and PRK or by orthokeratology.

Myopia is characterised by a slight elongation of the eyeball, causing the image to fall in front of the retina, while hypermetropia is characterised by a slight shortening of the eyeball, causing the image to fall a little behind the retina. In both cases, blur circles are formed instead of image points leading to blurring of the overall image.

The classical view

In traditional optometry it is held that both these conditions are congenital and unalterable. Wearing glasses is not supposed to either improve or worsen the condition, but it is held that correction is essential in hypermetropia to prevent squint and eyestrain which would otherwise be caused by excessive efforts to shorten the focus.

The Bates view

Dr Bates held that these errors were caused by strain. Tension of the extraocular muscles would interfere with the operation of central fixation causing the eye to become, in effect, semi-amblyopic (see article on amblyopia). Further efforts to see clearly would have a negative effect on the ability to focus. Glasses, by alleviating the symptom without removing the cause, would confirm a bad habit and make it worse

Latest research

Current physiological research confirms and goes beyond Dr Bates in establishing that in a wide range of species, introducing lenses, among other visual distortions, influences the development of the eye whereas most errors observed in the early stages of development correct themselves if left alone.

Research in hypnosis with human subjects has shown that persons experiencing multiple personality states manifest different degrees and kinds of refractive error at different times - demonstrating that it cannot be an attribute of the physical structure.

The experience of Vision Education

Both myopia and hypermetropia are regularly found to respond well to Bates teaching at all ages. Reductions in manifest hypermetropia of up to 7D (+7 to normal) have been experienced without any adverse sequeliae such as squints or strain - on the contrary, parallel improvements have been noted in other areas of performance. Reductions in manifest myopia of at least 8D (-16 to -8, -6 to normal) have been found. Generally the improvement in actual vision is in excess of what the measurable results would suggest

By PeterMansfield