accommodation is impossible, and certain lines of a radiating chart must be blurred, and the vision reduced.

But it is the common experience of all oculists to find the most serious cases of eye strain among those who can, by a contortion of the lens, overcome the deformity and secure good vision. It is not the lessened sight which causes the strain, but the nerve energy wasted in securing better sight. So it is that the high degrees ef error, which the ciliary can in no way overcome, cause less strain than the lesser errors.

Instead of saying that eye strain exists notwithstanding normal visual acuity, it would be more exact to say of these cases that eye strain exists because of normal visual acuity.

Instinctively we endeavor to secure a clear retinal image. As nature adhors a vacuum, so the retina abhors blurred outlines. "Good vision does not necessarily mean good eyes."

So far we have been speaking of the single eye, but the fact that ability to see does not exclude eye strain must be much more apparent when it is remembered that normal sight is binocular.

Each eye sees separate pictures, and unless the two eyes are so directed that the image falls upon corresponding parts of the two retinas, double vision is the result.

True binocular vision requires the co-ordination of the six muscles which turn each eye, and the two ciliary muscles.

When each eye accommodates for a near object, the internal recti must converge the eyes till the visual lines meet at the point looked at, A Fig. 5. Failing in this there occurs. either double vision, shown by dotted lines Fig. 5, or a tendency toward doubling, which causes more or less blurring.

Normally the brain abhors double vision with the confusion which it occasions.

Any tendency of the eyes to turn in a wrong direction is overcome by excessive nerve energy to the lagging muscle which "whips" the eye into line. This not only occasions a waste of nerve energy, but seriously disturbs the primary visual

centres which preside over the co-ordination. These patients are often conscious of the excessive effort to fix the eyes on a given object for any length of time.

This function of co-ordination has through development been relegated to the sub-conscious. This leaves the higher nerve centres free for their proper cerebration. Now when these higher nerve centres are obliged to exercise a conscious con

trol over sub-conscious functions, it is as disastrous to the proper economy of energy as when the manager of a great business is obliged to attend personally to details which he had delegated to subordinates. Let it not be forgotten that each eye separately may be absolutely perfect and may possess normal visual acuity, and yet a lack of balance of these muscles which turn the eyes cause severe strain. Unfortunately, a refractive error in each eye often co-exists with a tendency of the eyes to deviate. It should be borne in mind that when one eye is noticeably turned, binocular vision no longer exists except in cases of sudden paralysis.

The tendency to turn is like the fractious horse which never completely frees himself from his mate but gives his driver no end of trouble to make the team "pull together."

Lenses for the correction of eye strain relieve by supplying in a glass lens the necessary refractive power, leaving the accommodative function to do only its normal amount of work.

For astigmatism the correcting lens produces its effect only in the direction of the defective meridian. Deviating tendencies are corrected either by gymnastics, prismatic lenses, or by operative measures. The latter include sections of the strong, or advancement of the weak muscles. Just as an eye strain may exist without any reduction of vision, so lenses may give perfect relief without any improvement of vision. Moreover, it is necessary in certain conditions to prescribe glasses which cause an actual blurring of distant objects. These two facts go hand in hand and emphasize the statement that has been previously made that neither eye strain nor its correction depend upon the amount seen, but the effort expended in the act of seeing.

A simple means of excluding eye strain is much to be desired, and it is to be regretted that such a thing is absolutely impossible. It requires just as much technical skill to decide this point as to prescribe the necessary lenses for its correction. Patients with large pupils are very susceptible to ocular disturbances. The dilator muscle of the iris is enervated by the sympathetic, and any irritation of the sympathetic system may cause dilation. Moreover, peripheral portions of the cornea are very irregular, and any error of curvature is much more noticeable in a large than a small arc. The small pupil acting as a diaphragm, "stops down " the lenticular system. It is frequently noted that the correction of slight refractive errors is very important if the case presents large pupils. Inattention and backwardness in school children is often indicative of faulty vision, and this symptom alone justifies a thorough examination. A case referred to me by Dr. Batchelder a few weeks ago is a good

illustration. Freddie C. Very backward at school, frequent complaints being sent to the parents. Distant vision was nearly normal but the boy complained that the "words jumped round." Glasses for far sightedness gave almost immediate relief. Not only did the complaints from the teacher stop, but in less than three weeks he brought home a special note of commendation of his progress.

There are certain facial expressions which may lead one to suspect that vision is not accomplished easily. Spasmodic working or twitching of the face or a wrinkling of the forehead are quite common. It is not claimed that each particular disease has its characteristic "facies" but that a certain trouble, worried or pained expression is often indicative of some form of eye strain.

To advise the general practitioner when to send his patient to an oculist is perhaps a rather delicate matter, and the writer's only excuse for assaying the role is his daily experience of curing by optical means some case of long standing, where eye strain was not suspected. The eye headache is usually a dull pain, generally referred to forehead temple on occiput, but any attempt to differentiate headaches and to decide by the location and character of the pain, whether it be a reflex from eye strain or not, would seem to be thoroughly impracticable. Every case of chronic headache, whether temporal, frontal, vertical, or occipital, merits ocular investigation. The same may be said of every case of migrane though the cure of this malady is not so general. Every case of epilepsy, preferably before it gets beyond the stage of petit mal should be examined, not only with the usual care, but a paralysis of the accommodation. insisted on, lest there be some latent error. Intractible cases of chorea, insomnia, vertigo and dyspepsia should be examined. All children whose vision is below .7 of the normal, or who are extremely irritable or backward and inattentive at school, even if the "sight is perfect." All children with atrabismus, if possible, while it is periodic. All forms of inflammation of the eyes which do not quickly yield to

The two photos were taken upon the same day, two weeks after he began to wear glasses. Simply leaving off the glasses for a few minutes caused a return of the old scowl,

Fig. 7, Harold G. Both corneas scarred by old ulcers. of astigmatism. Even with glasses vision was only .3 normal, and yet there is complete relief of the old "strain."