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and the only other child wearing glasses was the 1st; in case 22 the myope was
the 4th, and the only other child with glasses the 2nd. In case 9, the first child
was an imbecile and the 5th an infant, so that the whole family might possibly be
myopic, and in case 23 the 7th child was an infant so that here again almost the
whole family might be myopic.
The tendency to grouping of children within the family is very interesting and
suggests that in some families there is a genetic factor causing myopia in consecutive
children, though in others there is no such evidence.
Increase of
myopia.
Twenty-two of the 104 children showed a mean increase of over 0.5 dioptre a
year. Of these, the increase in 13 cases was from 0.5 to 0.75 dioptre; in six, from
0.75 to 1; in two, from 125 to 15; and in one it was 1.75 dioptres per year.
A noteworthy feature is the large proportion of children, 17 out of 22 or 77 per cent.,
as compared with 55 per cent in the group with an increase of less than 0 5 dioptre
a year, who had enlarged tonsils and adenoids at the time of the inquiry or who had
already had them operated upon. Of eight who had had an operation, one child was
awaiting a second, another still had catarrh and mouth breathing, a third had some
enlargement of the tonsils, and a fourth had had an operation both before school age
and at ten years old. Two others had not had tonsils and adenoids removed untilten.
The remaining two had had operations at six and showed no signs of recurrence.
Deducting these two, in 15 out of 22 or 68 per cent, of the cases, tonsils and adenoids
were a factor possibly operative in the increase of myopia during the periods spent at
sight saving classes.
Eight of the 22 or 36 per cent, had a definite family history of myopia as compared
with 23 per cent, in the group with the lesser increase. Nearly always this wasassociated
with other possible causes such as tonsils and adenoids, the one exception
being the case which showed the greatest increase (1.75 dioptres per year) where
it was the only factor known. It is noteworthy that of nine children whose increase
per year was over 075 dioptre, six had a definite family history of myopia.
As regards position in the family, 26 per cent, ranged from 6th to 10th, as
compared with 13 per cent in the group with the lesser increase.