THE STUDY AND CORRECTION OF HETEROPHORIA



It is questionable what internal remedies can do for the relief of hyperphoria. The late Geo. S. Norton, M.D., in 1889, called attention to the provings of Senega and Onosmodium, and their usefulness in affections of the ocular muscles, and reported a number of cases in which these drugs had been used with apparent benefit.

The value of Senega in hyperphoria has been made the subject of a recent communication by Linnell, but as I have elsewhere endeavored to show, [Jour. O., O. and L., April. 1893.] the usefulness of the remedy in this disorder is by no means proven by the cases related. Indeed, the provings of Senega do not show any special adaptability of the drug to hyperphoria, so far as we understand the symptoms of this affection. Nevertheless, it might have an empirical or clinical value, but the evidence even here is defective. Norton says that the symptoms calling for Senega, are “dull, tired, aching, pressing pains in the eyes, or throughout the whole head, with smarting and burning in the eyes, always worse after using them and often accompanied by catarrhal symptoms of the conjunctiva.”.

Onosmodium has many symptoms of heterophoria in its proving, e.g., occipital headache; a dull aching pain extending down the back of the neck, or over one side of the head, generally the left; vertigo, with strained or stiff sensation in the eyes, aggravated by use of the eyes for near work. Gelsemium has a transient vertical diplopia, and may be of value in those cases of hyperphoria accompanied with the paretic or other characteristic symptoms of the remedy. Stramonium shows a marked vertical diplopia in its provings. The importance of this symptom in the proving of a drug, is simply that it indicates that the drug has a direct influence upon these muscles which are concerned in the production of hyperphoria.

We do not find diplopia (unless it be transitory) in heterophoria. But as a drug-symptom, diplopia is an indication that the remedy has an action along the line in which we seek for curative effects, and suggests that it may possess valuable therapeutic properties in the treatment of affections of the upward and downward turning muscles of the eyes.

So far as the applicability of these or other drugs to the cure of hyperphoria, is concerned, the evidence in their favor, is at the best, obscured by the fact that in almost all of the cases reported, other treatment than the medicinal was given the patient, so that the action of the remedy is not clearly shown. Norton, himself, limits all attempts at a cure by remedies to hyperphoria of less than 2 degree. In higher degrees, an immediate tenotomy was advised.

Systematic exercise of the affected muscles by means prisms, has been used and recommended as a cure for hyperphoria, and the clinical evidence in our hands is favorable to its usefulness. In hyperphoria of 1 degree and perhaps 2 degree, if persisted in, it may effect a cure, but in higher degrees it does not seem to be of much value.

In a case where there is a manifest hyperphoria of say 1 degree, circumstance often suggest that there is an additional amount that is latent, and a correcting prism is prescribed, to be worn constantly, for the purpose of revealing this latent defect. Under these circumstance, in many instances, the daily examination will show an apparent increase in the hyperphoria, until we may have developed in the course of a week, beginning with 1 degree, as much as 5 degree or more. This final amount is then accepted as the total of the real hyperphoria present, and made the basis of an operative correction.

Now while it may happen that latent hyperphoria can be made manifest in this way in some instances, we must not lose sight of the fact that under the constant influence of a prism, the normal equilibrium of the eyes will often be temporarily changed so as to generate a species of false heterophoria. Thus it is possible to produce at will exophoria or esophoria in the same eyes, by wearing prisms with the base in or out, as the case may be, and either right or left hyperphoria, as we please, in a similar manner. The heterophoria thus produced is of variable duration, but always temporary.

It may not be possible always to distinguish between the factitious and the real defect. The increased relief of concomitant symptoms, by the corrected increase in the manifest heterophoria, if it occurs, or the greater permanency of the disordered equilibrium, might serve as distinguishing marks, but if we accepts as the true state of muscular equilibrium, that shown while the eyes are under the influence of prisms constantly worn, we are treading upon dangerous grated, and if it is taken as the guide to the extent of the operation, we are apt to afflict our patients with an over-correction.

With regard to the details of the operation itself, I have little to say, except that in tenotomy of the rectus superior, care must be taken to make the incision high enough, so that the tendon of the muscle will lie in the wound. Rather than to fail in this respect, the operator should measure the necessary eight mm. from the corneal margin with exactness. In my experience, complete section of the tendon is often required for the correction of even low degrees of hyperphoria. The lid retractor, held by an assistant is much more comfortable for the patient than the spring speculum. At the end of the operation, the correction should be as nearly perfect as possible. If an over- correction is made, an appropriate advancement is easily done.

Exophoria and Esophoria.-As in the treatment of hyperphoria, we have here a variety of methods to choose from; surgical, gymnastic, hygienic and medicinal. As indicated above, we are to be guided by the causes lying back of the particular troubles in question, so far as we are able to discover them. There is associated with most cases of disturbed muscular equilibrium a defective ratio of abduction and adduction, as well as positive deficiencies in muscular power. Thus in a typical case of exophoria, we may find that the adduction is abnormally low, or the abduction excessively high.

In the exceptional and irregular cases this dose not obtain. We may have exophoria with an adduction of 40 degree or 50 degree. Or there may be exophoria in remote vision and esophoria for the near point; or the reverse may be true. Out of two hundred and twenty-nine cases of exophoria, Norton found ten with esophoria in accommodation; in one hundred and fifty-eight cases of esophoria there were sixty- eight with exophoria in accommodation. These atypical cases are credited to the disturbing influence of hyperphoria, and the recommendations made to correct this before undertaking the correction of the lateral disturbances.

In some cases clinical experience seems to justify this assumption. Upon theoretical grounds however, there would not seem to be any satisfactory explanation of what we may call “crossed heterophoria,” in a faulty innervation of the superior or inferior recti muscles. It is true that there is a slightly increased tension of these muscles in the act of convergence, but this seem hardly enough to account for the abnormal conditions so frequently met with. As I have elsewhere suggested, a more rational and satisfactory explanation of “crossed heterophoria” may be found in the relations between accommodation and convergence.

If we have a case of slight esophoria in remote vision, for example, it is easy to conceive that in convergence for the near point, exophoria might result from an enfeebled power of accommodation, by which the added stimulus of the accommodative act was not adequate to maintain the necessary convergence. This is easily shown in an experimental way, by observing the effect of convex and concave glasses upon the position of equilibrium of the eyes in fixation for the near point. If we have orthophoria, or a low degree of esophoria for distance, we can obtain exophoria at the near point, by decreasing the amount of accommodation in use for that point by means of convex glasses. Exophoria may be transformed into esophoria or into orthophoria in a like manner, by means of concave glasses.

These experiments show very clearly the case with which “crossed heterophoria” may be explained independently of a real or hypothetical hyperphoria. They also suggest a possible method of treatment in some cases by such exercise of the accommodation as will increase its positive range. Clinical experience to justify this suggestion is wanting, as cases entirely appropriate to it have not come under my observation since the idea occurred to me. I am satisfied however, that the key to the explanation and treatment of a good many puzzling cases of heterophoria will be found in a study of the relations between relations between the accommodation and convergence, and in the relative amplitude of accommodation.

Tenotomy of the stronger muscle after the method of Stevens is a familiar method of treatment. The extent of the operation is determined by the amplitude of convergence. If we have exophoria with subnormal abduction for the far point, it will be improper to tenotomize the already weak muscles. In fact, it may be laid down as a general rule, that a tenotomy is indicated in exophoria only when there is an absolute or relatively excessive abduction. In the contradictory cases, the treatment must first be directed to increasing the power of the weak muscles, and of the accommodation, if necessary.

Harold Wilson