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that there should be a relatively constant flow of nervous stimulation to the extrinsic ocular muscles sufficient to keep the visual lines parallel without conscious effort. This state may exist and at the same time the different muscle tests, which have as their modus operandi the exclusion of the desire for binocular single vision, may show heterophoria. Unquestionably in many instances the heterophoria may not be of a purely functional nature, but may be due to faulty insertion of the muscles, abnormalities in their shape and size; or to peculiarities in the development of the orbit. As these defects are of a long standing, nature ofttimes learns to compensate for many of them provided they are accompanied by good vision. Our understanding of binocular single vision is very imperfect, and our progress towards a thorough knowledge of it slow. One thing, however, that we have learned, through careful study of our cases, is conservatism in operative treatment, and the next ten years will show fewer secondary squints than the past.





1. Dislocations.

1. Dislocations.

2. Direct injuries of capsule.

3. Indirect injuries to lens.

There is no surgical condition in the entire domain of ophthalmology that requires more careful discrimination than traumatic affections of the crystalline lens. The surgical procedures indicated for the well established diseased states of the eye, such as senile cataract, pterygium, strabismus, entropium and glaucoma are generally very plain and are in accordance with fixed rules and the question of individual judgment does not play so important a part. But with regard to the injuries of the lens, there are so many possibilities to be considered that one must weigh well his words before giving a dogmatic opinion as to the issues of a given case. I have seen the snapping of a mandolin string in the hands of a young girl, even without perforation of the cornea, lead within a few hours to extreme swelling of the lens with complete opacity followed by all the features of a fulminating glaucoma, and demanding a speedy operation for her relief. And on the other hand I have seen a man who, while engaged in a fight, had his eyeball cut wide open by a rusty pocket knife that entered at the cornea and severed all the tissues intervening between the point of entrance in the cornea and the distal opening near the optic foramen, and with extensive loss of vitreous in addition to the laceration of cornea, iris, ciliary body, choroid, retina, scelera and the periphery of the lens; and yet under appropriate treatment he would recover excellent vision without pain or inflammatory reac

tion. And thus the cases might be indefinitely multiplied to illustrate that the final result is not proportionate to the extent of the original injury. And yet we would be safe in asserting that all traumatic affections of the lens are serious in their very nature, as will be easily understood from a consideration of the parts involved.

The lens in its normal state is composed of transparent layers of elastic proteid matter arranged in concentric order and securely inclosed in a thin capsule of fibrous tissue, which is held in place in the fossa by the suspensory ligament which passes from the equator of the lens to the ciliary processes. As no blood vessels enter the normal lens its nutrition is obtained through the neighboring lymphatics. And whenever these avenues of nourishment become interrupted in any marked degree the lens undergoes degeneration with resulting opacity. And thus an injury apparently insignificant may sometimes lead to traumatic cataract by the influence produced in the channels of lymph from surrounding structures.

In this way lenticular opacity may follow a dislocation of the lens even where there has been no visible rupture of the capsule, and also injuries to the ciliary region not directly implicating the lens may lead to lenticular changes on account of the impaired function of proximal tissues. But by far the most frequent and most important traumatism of the lens is that dependent upon a rupture of the capsule, which may occur either by direct entrance of a penetrating instrument or by the indirect influence of concussion.

The character of the lens substance is such that it will swell up and become opaque when brought in contact with the aqueous and vitreous humors of the eye. And thus a rupture of the capsule that is not speedily closed will invariably lead to an opaque condition of those lens fibers that have been subjected to the action of the aqueous or vitreous, but especially the former. The extent and rapidity of the lens involvement will depend upon the character of the lens substance and upon the facility with which it

becomes permeated with the fluids of the globe. And thus we find that an extensive laceration of the capsule, other things being equal, will be attended by a more rapid development of traumatic cataract. When the aqueous gains access to the lens fibers they swell up, become opaque, degenerate and become absorbed, if the lens is sufficiently soft, as in childhood, and provided the swollen fibers are not presented in such large quantities that the small amount of the aqueous can not dispose of them. In the earlier years of life a traumatic cataract can be made to undergo almost complete absorption. But in the middle and later years of life there is very apt to remain an opaque remnant of the lens associated with the capsule and totally preventing the entrance of light even if the swelling of the lens should not result in serious inflammatory reaction.

The chief danger in the case of traumatic cataracts is that the lens fibers undergo rapid swelling, with pressure on the iris and ciliary body, leading to a severe irido-cyclitis with all its attendant possibilities, even to the point of producing sympathetic ophthalmia in the fellow eye.

The diagnosis of an opaque, dislocated lens does not involve any difficulty, provided intraocular cloudiness from hemorrhage or exudates does not obscure the field.

But an imperfect examination may sometimes fail to reveal the luxation of a transparent lens. Of course the anterior luxations are so very apparent that a direct inspection will establish the condition. But the posterior luxations are best determined by the ophthalmoscope, which will show certain characteristic modifications in the refraction according as the lens does or does not lie between the observer and the fundus. Again, if the periphery of the lens should lie in the pupillary area it will be seen as a crescentic shadow upon the red background of the fundus. And in every case where the backward dislocation is very pronounced the iris having lost its normal support will present a tremulous motion and receding from the cornea will deepen the anterior chamber. The shrunken remains of a dislocated lens may sometimes move

with great freedom within the globe, and I have seen them play hide and seek through the pupil, now plainly visible in the anterior chamber and now securely concealed behind the iris in the posterior chamber.

The management of dislocated lenses will vary greatly according to the circumstances of the case. If the luxation is partial and the lens continues clear, gentle massage may be applied to the globe with a view of inducing the lens to slip back into the fossa, and no operation would be indicated. If the lens is located entirely in the anterior chamber it will generally be best to extract it at once from this situation. If the lens is displaced into the vitreous an expectant plan should be adopted, and if the lens remains clear and does not cause inflammation of the globe it might be allowed to remain. But if the inflammatory features develop it will be best to extract the lens if it is sufficiently opaque to render the operation easy of accomplishment. It is sometimes exceedingly difficult, in fact, as Agnew has said, the most difficult operation in ophthalmic surgery to successfully extract a lens from the deeper regions of the vitreous. In some cases the lens is driven through a ruptured sclera and may be found beneath the ocular conjunctiva from which it may be readily removed.

In severe injuries and even in extensive ulceration of the cornea the lens may be extruded through the corneal wound.

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