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94
Subjective testing with a +1.0D. sphere.—In the report of the Committee of Inquiry into problems
connected with Defective vision in School Children (published by H.M. Stationery Office, 1931)
there appears a suggestion (p. 53) that with a view to minimising the possibility of the preventible
occurrence of Myopia the subjective testing of the visual acuity of school children should include
the following procedure. If a child has no subjective symptoms, and reads the requisite 6/6 or 6/9
on Snellen's type, a +1.0 D. sphere should be placed before the eye to be tested and the effect of
this artificial myopia recorded. The object aimed at in this procedure is the elimination of all
emmetropes and low myopes who would otherwise escape detection.
An extended trial of this method of testing was made by the School Medical Officers ; the result
was the provision of a mass of material for refraction, which was passed on to me and made the subject
of study. During the course of the year I reported to Dr. Buchan as follows :—
1. Dated April 19th, 1932.
"I enclose an analysis of 52 cases sent to me under the ' +1-0 D. scheme,' on the strength
of which I propose that the scheme be abandoned.
Total 52
Emmetropia 29 =60%
Hypermetropia 9\l4 =28°/
Hypermetropic Astigmatism 5 J
Myopia 1 = 2%
Those with the two eyes different:—
Hypermetropic Astigmatism and Mixed
Astigmatism 2
Hypermetropic Astigmatism and Emmetropia
1
Mixed Astigmatism and Emmetropia 1
Myopia and Emmetropia 1
" Did not attend." 3
52
2. Dated September 23rd, 1932.
"After further prolonged trial of the Scheme of testing the visual acuity of school children with
the use of a +1.0 D. sphere, I unhesitatingly reiterate the opinion I expressed to the representative
of the Board of Education some months ago, namely, that it should be abandoned. My reasons
for this are as follows:—
1. That it fails in its object of selecting the low myopes for correction, and that these are
eliminated by the ordinary subjective tests.
2. That it selects the vast majority of low hypermetropes, who have no manifest
metropia, and who need no correction.
3. That as a consequence the numbers are becoming unwieldy, and scores of children are being
prevented from school work for about two weeks without good cause. As an example of
this, in the last 32 refractions done at Clinic 3, no glasses were prescribed in the case
of 19 of them.
4. That the confidence of some parents in the Clinics is being undermined by the fact that, as
they see it, the decision of a nurse or doctor is being over-ruled and negatived by that
of another doctor.
It will be seen that, in 52 unselected cases sent up as a result of this method of subjective
testing, but one Myope was discovered, with in addition one patient with one Myopic eye. It is
evident from this that the leakage which obtains in the ordinary methods of subjective testing is
minimal. The arguments outlined in my second report need no further explanation.
In considering a scheme such as this it is necessary to put upon record my opinion that but
slight value should be attached to subjective results in school children. So many different factors,
extraneous to actual visual acuity, come into play in determining how much a child shall read to
a medical examiner ; and the discovery of the varying subjective results obtained from the separate
members of a group of children with identical refractive errors is a matter of common experience to
an ophthalmologist. It is my experience that, whatever the optical result, the placing of a lens
before a child's eye very frequently results in diminished visual acuity. In dealing with children
it has always been my rule—I am speaking now with regard to refractive errors pure and simple,
uncomplicated by any condition such as a squint—to correct with glasses those cases, and only those
cases, who either (1) have demonstrably defective vision, or (2) present objective signs or subjective
symptoms of Eye-strain ; and, a fortiori, those cases who come into both categories.