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93
by this means increases proportionately as the magnitude of the refractive error diminishes. Accordingly,
differences of J Dioptre were taken account of in the cases with low refractive errors, and
differences of ¼ Dioptre in those with high errors, the dividing line being in the neighbourhood of
5 Dioptres.
The abbreviations employed are as follows:—
E Emmetropia.
H Hypermetropia.
M Myopia.
HA Hypermetropic Astigmatism.
MA Myopic Astigmatism.
CHA Compound Hypermetropic Astigmatism.
CMA Compound Myopic Astigmatism.
XA Mixed Astigmatism.
I Irregular.
Total number of Refraction attendances 1,546
Of these there were : Isometropic 615
Anisometropic 931
The Refractive errors were as follows:—
CHA 477 Cases.
H 227 „
E 168 „
CMA 116 „
M 106 „
HA 75 „
H. & CHA 65 „
M. & CMA 32 „
HA. & CHA 32 „
MA 29 „
XA 27 „
HA. & XA 24 - „
MA. & CMA 14 „
H. & HA 9 „
HA. & MA 7 „
HA. & CMA 7 „
M. & MA 6 „
E. & M 6 „
E. & XA 5 „
E. & CHA 4 „
E. & HA 4 „
MA. & XA 4 „
CHA. & XA 4 „
M. & HA 3 „
E. & H 3 „
CMA. & XA 3 „
CHA. & MA 3 „
CHA. & CMA 3 „
H. & MA 2 „
E. & MA 1 „
CHA. & M 1 „
CMA. & H 1 „
E. & I 1 „
H. & M 1 „
E. & CMA 1 „
In addition there were:—
Not under Atropine 70 ,,
Behaviour prohibited Examination 5
1,546 „
To one engaged in Refractive work these figures are of considerable interest. The abnormally
high percentage of Emmetropes is accounted for by the operation of the scheme for testing school
children subjectively with a +1.0 D. sphere, to which reference is made on next page. Compound
Hypermetropic Astigmatism is by far the commonest refractive error, the proportion of the total
being 30 per cent. Myopia, the most important refractive error in the child on account of its grave
possibilities, may be taken as represented by the sum of M., MA., CMA., M. & MA., M. & CMA., and
MA. & CMA., which gives a figure of 303 cases, or 19 per cent ; the total of Hypermetropic errors
calculated in a similar fashion is 88-5, or 57 per cent.