weaker glasses will be required, but the strength should be gradually increased until he has arrived at the glass which really neutralizes his hypermetropia. These spectacles should be worn both for far and near objects, should indeed, be always worn when the eyes are used. If the hypermetropia is great, or if a presbyopia co-exists, two pairs of spectacles will be required, a strong pair for reading, &c., a weaker for distance.

"Hypermetropia is a very frequent cause of asthenopia and also of convergent strabismus. The asthenopia is produced by the overstraining of the accommodation apparatus in reading, writing, &c., without the proper spectacles. We have seen that the hypermetropic eye has already to exert its power of accommodation more or less for distant objects, in viewing which the normal eye hardly uses its accommodation at all. How much greater must this exertion be when the hypermetropic eye looks for any length of time at near objects, the rays from which are strongly divergent. The eye cannot keep up this great strain of its powers of accommodation for any length of time, and hence symptoms of asthenopia soon arise.

Hypermetropia often causes convergent strabismus. As the power of accommodation increases when the convergence of the optic axes is augmented, a person suffering from hypermetropia often squints involuntarily, in order to see more distinctly. This squint becomes permanent, if the hypermetropia is not treated, and a strabismus operation will then be required.

9. ASTHENOPIA.-HEBETUDO VISUS. AMBLYOPIA PRESBYTIQUE.

The eye presents a perfectly normal appearance; its movements are restricted; convergence of the axes of vision takes place without difficulty; the perception of objects is generally as perfect as ever; and yet in spite of all this, reading, writing, or any other employment requiring near objects to be viewed, induces fatigue; objects become confused and indistinct, and a sense of tension is felt above the eyes. Such a height does this reach that temporary relinquishment of the employment is rendered necessary. After resting a few moments vision becomes again distinct, but the same symptoms develop themselves again sooner than before. The amount of labor that can be performed is directly proportional to the amount of rest that has been taken.

So long as the eyes are not employed on near objects vision appears normal, and no disagreeable sensation is experienced. No sooner, however, does the patient, regardless of what he has experienced, attempt to continue his previous occupation, than the symptoms become more and more pronounced; the pain in the forehead grows more intense; the eyes become red, the tears flow freely, yet the eyes them

selves are rarely painful. As this condition becomes more aggravated, the patient is obliged to close his eyes and pass his hand over his forehead. Has too persistent an effort been made, all work on near objects must be given up for a considerable period.

PATHOLOGY.-This is little understood. Mackenzie thought the seat of the disease must be sought in the organs by the operation of which the eye adapts itself to different distances. Dr. Derby,* regards "an abnormal structure of the eye as lying at the root of the whole matter." He says:

The results of modern investigation show:-That the agent in the act of accommodation is the crystalline lens, which varies its convexity, without changing its position. That where objects are so distant from the eye that the rays coming from them may practically be regarded as parallel, such rays are brought to a focus on the retina without any accommodative effort; and that the nearer the object approaches the eye, the greater will be the strain on the accommodation.

And while the far-point, or limit of distinct vision of a normal eye, may thus be said to lie in infinity, (rays coming from an infinite distance being parallel) the near point of such eye-i. e. the nearest point for which it can accommodate progressively recedes with advancing age, constituting presbyopia when it has increased its distance from the eyes so much so as to cause inconvenience.

Thus in an ideal eye the farthest point of vision should lie in infinity, that is, the eye, when adapted for its farthest point, should possess the power of bringing parallel rays to a union on the retina without accommodative effort.

Relatively few eyes, however, correspond to this ideal. Parallel rays, entering some eyes adapted for their farthest point, are brought to a union before the retina, so that only divergent rays, proceeding from objects relatively near can form perfect images on its surface. And parallel rays entering other eyes whose accommodative power is similarly relaxed, find their place of union behind the retina, to form perfect pictures on which the rays should enter the eye converging.

Both of these conditions depend on a defect in the structure of the eye. The first constitutes myopia. The second is called by Donders Hypermetropia (which see page 137.) Presbyopia may exist in connection with either. In the first case the far-point lies this side of, in the second beyond infinity. The first requires a concave, the second a convex glass to give power of distinct vision at a distance. In 1858, Donders announced the general association of asthenopia with hypermetropia and this abnormal structure of the eye. In 1860, he said of the last hundred cases he had examined of asthenopia, hypermetropia existed in every one.

* Medical and Surgical Journal.

According to Donders "the amount of accommodation we can bring to bear on an object at any distance, depends, in a great measure, on the angle at which it is necessary to converge the axes of vision in order to regard the object; the rule being that the two go, to a great extent, hand in hand, and that the greater the convergence the more accommodation we can bring into play. We distinguish between absolute and relative accommodation; absolute being the whole amount of accommodation that exists under the most favorable circumstances, the near-point being taken at the greatest possible convergence of the visual axes, and the far-point at their nearest approach to parallelism; while relative accommodation is the amount that can be made use of at any fixed convergence of the axes of vision. Now it is found by experiment and observation that where normal eyes need, for a given convergence, half their relative accommodation, hypermetropic eyes are obliged to use or even more, which greatly fatigues them; and the cause of the asthenopic symptoms is thus simply a want of proportion between the convergence of the axes of vision and the amount of relative accommodation that is obliged to be brought into play.

TREATMENT.—It was formerly the practice to prohibit the use of positive glasses for the concentration of the vision on distant objects and only those very weak were used for near ones. The relief they afforded was therefore but trifling. Now the nature of the disease being understood, we only regard the effect desired, viz., the relief of the accommodation from its unnatural strain, and the restoring of the proper harmony between it and the convergence of the axes of vision. The treatment, therefore, consists in giving the patient glasses that correspond with the degree of abnormal condition and structure of his eyes. "The strongest convex lens with which he can see distinctly at a distance reduces his eye to one which needs no glass for either near or remote objects." In some patients who possess only a limited power of accommodation, a stronger lens will be needed for work on near objects; "and a simple mathematical process enables us to compute the glass with which he shall be able to work in a given distance, and in so doing bring into play not more than one-third of the whole amount of his accommodation."

In ascertaining the "strongest glass with which the hypermetrop can see in the distance," Donders employs a solution of atropia, sufficiently strong to paralyze the accommodation, dropping this into the eye before the trial is made. The patient who first thought himself suited with a glass of twenty-four inches for distant objects; "after the employment of atropia, found one of six inches to be the glass re quired."

10. FUNGUS HÆMATODES, AND CANCER OF THE EYE.

DIAGNOSIS.-Fungus Hæmatodes had always been confounded with scirrhus or cancer until Burns, Hey, and Abernethy pointed out the characteristics of the two diseases, both in respect to their formation and development, as well as their pathology. They possess several qualities in common, like malignancy, inevitable tendency to the destruction of the affected parts, the power of contaminating the whole system, and giving rise ultimately to fatal constitutional symptoms; but in other respects they are entirely dissimilar.

Fungus hæmatodes is not usually attended with the severe stinging and lancinating pains of cancer; its texture is spongy and elastic, and is soft and apparently fluctuating under the touch, while scirrhus is hard and stony. When fully formed the fungous tumor is of the consistence of brain, is of a dark and livid hue, and bleeds on the slightest touch, while the substance of the cancer is hard, fibrous, and cartilaginous; at its commencement and during its development, the fungus is knotty and unequal, and thus affords a sign which distinguishes it from cancerous and other tumors. Fungus is more prone to occur in young subjects, while cancer is for the most part confined to persons past the middle age. Fungus of the eye commences in the posterior chamber, while cancer of the eye attacks primarily the conjunctiva or lachrymal gland. The progress of fungus is more rapid and destructive than that of cancer.

The first symptom observed in fungus hæmatodes is defective vision, and, on looking into the eye, a small shining spot is perceived at the bottom of it. This nucleus of the disease commences in the retina and optic nerve, is traversed by branches of the central artery of the retina, absorbing it in its course, until it arrives near the iris, when it presents a dark amber or greenish hue, and is apt to be mistaken for cataract.

As the enlargement increases, the ball of the eye becomes prominent, irregular, and knotty, the cornea ulcerates, and the disease displays itself externally in the form of a soft, medullary, and purple fungus, bleeding at the least touch. The pupil becomes dilated and immovable in the early part of the disease, and also somewhat changed in color, which becomes a strongly-pronounced amber or brown when the swelling arrives at the iris. The sclerotica soon acquires a dark blue color, is crossed by dilated veins, and is sometimes attacked by the malady as well as the cornea. After the fungus has shown itself externally, the absorbent glands of the jaw and neck become affected with a medullary degeneration; the countenance assumes a sallow and cadaverous appearance; general debility and nervous irritation occur; loss of appetite, impaired digestion; nausea; irritable

stomach; restlessness, and the usual symptoms of hectic fever terminate the patient's existence.

Cancer of the eye, as we have before remarked, generally attacks persons advanced in life. This disease, unlike fungus hæmatodes, commences in the conjunctiva, caruncula lachrymalis, or lachrymal gland, in the form of a hard warty excrescence, which continues for an indefinite period, sometimes attended with twinging and lancinating pains, at other times free from all uneasy feelings, until finally its interior structure becomes altered in texture, an ichorous matter forms within the swelling, which gradually makes its way to the surface, and thus develops the first stage of ulceration. When arrived at this point, vision is destroyed, an irregular fungous mass shoots up from the ulcerated point, highly vascular, of a red, brown, or livid color, and easily excited to hæmorrhage. As the mass increases, the tissues of the eye become distended; the ulceration and sloughing advance; severe lancinating pains dart through the globe; the appetite is impaired; the patient loses flesh, strength, and courage; sleep is disturbed; the countenance assumes an anxious, distressed, and sallow appearance; hectic fever sets in, and the sufferer speedily yields to the result.

Hitherto the diseases under consideration have usually been deemed incurable by internal remedies, and on this account surgeons have advised the early extirpation of all suspected tumors, hoping in this way to eradicate the affection while it is local, and before the mass of blood becomes contaminated. But it must be admitted, even when the operation has been resorted to early, and under the most favorable circumstances, that a lamentable want of success has for the most part, followed all surgical measures. Stealthy and insidious at their com mencement they gradually glide along, depositing in all surrounding textures their destructive and fatal poison, until disorganization begins, when the livid, foul, and destructive phenomena appear in their hideousness, rapidly communicating their influence through the whole organism, and baffling all efforts of the physician and surgeon.

But though experience has so little of promise, we can not admit that there are no remedies in the whole range of the materia medica capable of counteracting this morbid influence. We may yet find some medicine sufficiently specific to cure these diseases during their forming stage. We believe, indeed, that homoeopathy will, ere long, accomplish all that we require in this matter. Only a limited number of well-authenticated homoeopathic cures of true medullary fungus, or of cancer, have been reported; but the results in these few cases should inspire us with some confidence of success, especially during the early period of the maladies.

CAUSES. The immediate cause of medullary fungus and of cancer is involved in doubt. Some have suggested the operation of animalculæ,