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These figures show that out of 405 children there were only 7
whose vision remained the same or was improved after the addition
of + 1 sphere to the reading eye. According to the Report, therefore,
these children are hypermetropic, whilst the remaining 398
have normal vision or are slightly myopic, and we have then to
distinguish between the normal who need nothing further and
the slight myopes who do need to be followed up and refracted
if possible.
I cannot feel, however, that emmetropes and slight myopes
account for all those children whose vision was adversely affected
by the +1 sphere. If one were dealing only with simple hypermetropia,
normal vision and simple myopia this would undoubtedly
be the case, but there are also the small astigmatic
errors to be considered. I feel certain that cases of simple
hypermetropic astigmatism of less than one diopter would have
their visual acuity considerably decreased by the addition of a
+ 1 sphere. Yet many of such cases would have good vision with
no subjective symptoms, and would therefore come into the
category of those who were to be tested again with the + 1 sphere.
If this is so, and at present I can produce no figures in proof
of it, one would have to distinguish between normal vision, slight
simple hypermetropic astigmatism and slight myopia.
It is difficult to see how this can be done except by refraction,
which would be impossible if my figures are correct, on account
of the large numbers.