ittle
disturbance to the sight of the other: when the inequality consists
in the difference of convexity, or difference of the limits of
distinct vision, having the limits of distinct vision in each eye
given, it may be calculated with some degree of accuracy what degree
of inequality is necessary to produce squinting. It seems then that
there are certain limits with regard to the inequality of the eyes,
necessary to produce this deformity; and that if the inequality be
either greater or less than these limits, the person will not squint.

Having now endeavoured to show what is the most common cause of
squinting, I shall briefly attempt to point out those cases in which
we may expect to effect a cure, and afterwards give a very short
account of the most likely methods of doing it.

We cannot have great hopes of success, when there is a very great
defect in the distorted eye. When the eyes are of different
convexities, there is no other way of removing the deformity, than by
bringing them to an equality by means of glasses, and then the person
would only look straight when he used spectacles. When this defect is
owing to a weakness in the distorted eye, it may sometimes be cured:
M. Buffon observes that a weak eye acquires strength by exercise, and
that many persons, whose squinting he had thought to be incurable, on
account of the inequality of their eyes, having covered their good
eye for a few minutes only, and consequently being obliged to
exercise their bad one for that short time, were themselves surprised
at the strength it had acquired, and on measuring their view
afterwards, he found it to be more extended, and judged the squinting
to be curable. In order therefore to judge with any certainty of the
possibility of a cure, it ought always to be tried whether the
distorted eye will grow better by exercise; if it does not, we can
have little hopes of success; but when the eyes do not differ much in
goodness, and it is found that the distorted eye acquires strength by
exercise, a cure may then be attempted: and the best way of doing it,
(according to M. Buffon) is to cover the good eye for some time, for,
in this condition, the distorted eye will be obliged to act, and turn
itself towards objects, which by degrees will become natural to it.

When the eyes are nearly brought to an equality by exercise, but
cannot both be directed to the same point, Dr. Jurin's method may be
practised, which is as follows.

If th