DIVERGENCE INSUFFICIENCY: A CLINICAL STUDY* Anomalies of ...

DIVERGENCE INSUFFICIENCY: A CLINICALSTUDY*

AVERY DE H. PRANGEN, M.D.Rochester, Minnesota

AND

(By invitation)

FERDINAND L. P. KOCH, M.D.Rochester, Minnesota

Anomalies of the convergence-accommodative mechanismhave long been recognized as a source of ocular discomfort.The importance of pathologic divergence, particularly di-vergence insufficiency, has not been fully stressed. In ourexperience, divergence insufficiency is a definite clinicalentity which causes much asthenopia. It also appears to beamenable to treatment.

Divergence insufficiency is distinguished from other typesof esophoria by the fact that in the former condition theesophoria is greater in distant vision than it is in near vision,and the power of divergence or abduction is definitely belowthe normal. These cases may be divided further into thosein which there is insufficiency, paresis, or paralysis, thedifferentiation here being largely a matter of the degree ofseverity, clinically, of the divergence difficulty. A similarclassification is used clinically to describe various degrees ofaccommodative weakness. Embarrassment of divergencevaries from a low-grade insufficiency to an actual paralysisof the function.Dunphy and Dunnington' reported cases of divergence

paralysis and also mentioned cases reported by Parinaud,Theobald, Duane, Holden, Cutler, Wheeler, Alger, and Zent-mayer.

* From the Section on Ophthalmology, The Mayo Clinic, Rochester,Minnesota.

136

PRANGEN AND KOCH: Divergence Insufficiency 137

The typical findings in divergence paralysis are the pres-ence of a homonymous diplopia in distant vision but not innear vision; the ocular excursions are normal, and there is aloss of diverging power. Convergence is unaffected. If thesecases are to be accepted as cases of divergence paralysis, onemust assume the existence of a center for divergence similarto the accepted center for convergence in Perlia's nucleus.Bielschowsky was of the opinion that a divergence innerva-tion is required not only to divert the visual lines from con-vergence into parallelism, but also to overcome an esophoria.This writer observes that vergence tests tend to prove this.Duane also believed that such a center existed in the vicinityof the nucleus of the sixth cranial nerve. Bergmann, Pugh,and Duke-Elder believed that divergence is accomplished byrelaxation of convergence through reciprocal innervation.Maddox assumed that divergence paralysis occurs. Rileyheld that a center for divergence can be suspected on clinicalgrounds, although its anatomic site is as yet unknown. Assuggested by Bielschowsky, it would seem difficult to con-ceive why only convergence should lack an antagonistic in-nervation. It seems that there must be a definite center fordivergence in order to carry out the refined control whichis exhibited clinically over the all-important convergence-divergence relationship. This is so carefully balanced afunction that its operation by a one-sided control-that is,by convergence only-is difficult to visualize.

Cases of divergence insufficiency were reported by Dun-nington,7 Davis, Peter, Maddox, Pugh, and Bielschowsky.These authors pointed out the discomfort caused by the con-dition, the association of physical and psychic disturbances,the exaggeration of the condition by presbyopia, the lack ofresponse to orthoptic treatment, and the possibilities forrelief by the use of prisms base out. On the last point,opinion was divided. Operation was advised in cases in whichthe condition did not respond to other forms of treatment.

In diagnosing divergence insufficiency, it is first noticed

138 PRANGEN AND KOCH: Divergence Insufficiency

that the eyes show an esophoria both in distant and in nearvision. It is further observed that the esophoria is definitelygreater in distant vision than it is in near vision. Whenreadings of vergence are taken, it is seen that divergence iswell below normal, whereas convergence is above normal. Ifone determines the rest position, or phoria, slowly, thusfatiguing binocular fixation, when the cells of the phorometeror trial frame are cleared, and, preparatory to taking readingsof vergence, the eyes fix the light at six meters, they willoften exhibit a homonymous diplopia, which at once willshow their deficient diverging power. This diplopia maydisappear quickly on resumption of binocular fixation, butit will usually reappear as one proceeds to fatigue divergenceby repeated tests of ability to overcome prism base in. Sucheyes may overcome four to five degrees of prism base inat first, but as the test is prolonged this amount quicklydrops to 0 or one or two degrees of prism base in. As thediplopia is elicited in this manner by fatigue, it will often befound that a prism base out, of from two to six degrees, isrequired in order to maintain single vision at six meters.Incidentally, this is a good way to determine how muchprism base out is needed for distant use. Convergence beingunopposed is usually high-between 20 and 30 degrees. Whenreadings of vergence are taken in near fixation, the same re-lations are found, but we have come to regard divergence asa significant finding for distant fixation only, and to regardconvergence as a significant finding for near fixation only.In other words, divergence is typically a function of distantvision and should be so measured, and convergence should bemeasured for near vision.

In our experience the phenomenon of homonymous diplo-pia on fatigue of fixation has not been found frequently innear vision. In the cases of divergence paralysis, homony-mous diplopia for distance is, of course, a constant finding.In a typical case of divergence insufficiency (Case 52 in ourseries), when the ametropia was corrected there was an eso-


phoria of ten degrees at six meters and of five degrees at0.33 meter. Divergence at six meters was one to two degrees,whereas convergence at 0.33 meter was 25 degrees. Therewas also a left hyperphoria of three and one-half degrees forboth distant and near vision. When fixation was fatigued atsix meters, homonymous diplopia was elicited and five de-grees of prism base out were required to maintain single vi-sion. Inasmuch as this corresponded to the amount ofesophoria found in near vision, five degrees of prism base outwere prescribed to be worn constantly, together with threeand one-half degrees of vertical prism. The eyes were hy-peropic, and the patient was thirty-one years of age. He hadhad much difficulty with near work and had left college.With this correction he was greatly pleased, he returned tocollege, and graduated.In the present study we are reporting 54 cases of esophoria

in which an analysis of the findings seemed to indicate adivergence insufficiency. Thirty-seven of these were cases offrank divergence insufficiency, 10 ekhibited functional eso-phoria, four were cases of paralysis of divergence, and twowere cases of paresis of divergence; one case of excessiveconvergence was included because relief was obtained bythe use of prisms base out. In all but seven cases in thisseries the patients were between twenty and forty-five yearsof age-a period of life when the greatest demand is made onthe eyes for intensive close work. Among younger peoplethere is less demand on the eyes and greater reserve power,whereas elderly persons are aided by presbyopic additions.As to sex, the patients were about, equally divided: 25 weremales and 29 were females. Occupation seemed to play adefinite role, as 34 patients were engaged in performing nearwork. Normal vision was found in all cases; no amblyopiceyes were observed. Accommodative power was low in 11cases, and in five it was definitely subnormal. In 14 casesthe patients were wearing glasses that afforded very incom-plete correction of the ametropia, this adding to the strain


of an already defective ocular apparatus. Hyperphoria wasseen in 34 cases; it was often of a changing and fluctuatingtype. It was found for distance only in eight cases. Thehyperphoria averaged one degree, and the most marked waseight degrees. In one case the hyperphoria was 11 degreesfor distant vision and seven degrees for near vision; thisappeared to be the primary difficulty, the divergence weak-ness being of secondary importance. Divergence averagedfrom two to four degrees; it was 0 in 11 cases, although thecondition seemed to be frankly paralytic in only four cases.In the paralytic group the patients complained of a persistenthomonymous diplopia at a distance and in all fields of vision,but not in near vision. There was, as a rule, more than 20degrees of convergence. Hyperopia occurred in all but 10patients, myopia was present in eight cases, mixed astig-matism was present in three, and antimetropia occurred inone case. Anisometropia, which was found in 26 cases, wasa somewhat constant source of annoyance to these eyes. Theesophoria recorded was from 3 to 18 degrees at six meters,and from 2 to 10 degrees at 0.33 meter.

In 20 cases functional derangements, such as chronicnervous exhaustion, functional disorders of the stomach,of the genito-urinary tract, biologic inferiority, asthenia,and menopausal disturbances, were present. Exophthalmicgoiter was noted in one case, and migraine was present intwo cases. In the cases in which paralysis occurred, vasculardisease was found in one case, ovarian dysfunction in one,mental depression in one, and exophthalmic goiter in onecase. From a neurologic point of view, 12 instances ofpsychopathic personalities were noted; 26 patients were neu-rasthenic in type, and 10 patients were obviously tense andhigh strung in their make-up. In several instances, the onsetof presbyopia aggravated the symptoms of the divergenceweakness, which substantiates the observation of Davis.The symptoms complained of were, for the most part,

asthenopia associated with use of the eyes in near vision,


fatigue, smarting, burning, and headaches. Some patientshad difficulty in focusing the eyes on looking from near tofar distances, and others felt as though their eyes were cross-ing and out of focus, or experienced eye-strain. Homony-mous diplopiawas present in 13 cases. Except in patientswithparalysis and paresis, this diplopia was often fleeting andintermittent in character, and was observed most often indistant vision. In about half of these cases the diplopia couldbe induced in near vision with fatigue of binocular fixation.It was interesting to note that in practically all the cases ofinsufficiency the symptoms complained of were most markedin near vision, in spite of the fact that the anomaly is pri-marily one of distant vision. We believe this is logical,however, since much greater demand is made on the fixatingmechanism of the eyes when they are engaged in near work.Hence the symptoms of all forms of accommodative andmuscular imbalances are exaggerated in near vision. Theactual physical data, however, vary, of course, with the posi-tion of the eyes when measured. Phoria and diplopia indivergence anomalies are greater at a distance, whereas inconvergence anomalies they are greater in near vision.

Concerning the nature of divergence insufficiency and thepathologic changes involved, we can but theorize. It wouldappear that in this condition there is an essential and in-trinsic defect in the fixating mechanism of the eyes. Whetherit is congenital or acquired is an open question. In eithercase it seems to be found in association with other defects ofthe central nervous system and the eyes. Psychic and ner-vous instability and irritability were marked features in ourseries of cases. Anisometropia was observed in a high per-centage of these cases, and anisometropic eyes are known fortheir instability and inherent irritability, especially whenforced to do much near work. Hyperphoria was seen oftenand is a frequent source of ocular fatigue. Subnormal ac-commodation and beginning presbyopia were found fre-quently; these conditions naturally added 'to the difficulty


already present. It is seen, therefore, that there is an asso-ciation or a combination of errors which go to make up anobvious and essentially defective mechanism for fixating theeyes. Therefore, given the presence of these defects of thecentral nervous system and the eyes, plus excessive demandson the eyes, it is not difficult to understand why the patientshould have marked symptoms of asthenopia. Except forthe cases of paralysis, we doubt very much if there is anydefinite cause for divergence insufficiency. It appears to bean essential defect which, when associated with these otherfactors, causes asthenopia.

In the treatment of divergence insufficiency a careful diag-nostic study is the first essential. So-called esophoria shouldbe checked repeatedly, and the degrees of esophoria foundin distance and near vision should be compared. When theesophoria is persistently greater for distance, divergence weak-ness should be suspected. Repeated readings of vergencewhich show divergence is decreased and convergence is in-creased, in association with this type of esophoria, will con-firm the diagnosis. If, in addition, homonymous diplopiais elicited in distant vision during vergence tests, the diagnosisis still more positive. When such diplopia requires a prismbase out to maintain single vision, the diagnosis is estab-lished. Refraction should be performed carefully, and theneeds for balanced vision, distance and near, should be de-termined. It is well to appraise the mental, the nervous, andthe physical status of the patient, because these factors fre-quently determine the ability of the patient to meet hisdemands successfully with any form of treatment. If thesefactors are not too unfavorable, we have found the outlookfor successful treatment good, and vtice versa.

In our series of 54 cases, in all but nine cases we haveprescribed prisms base out incorporated in the prescriptionsfor glasses. The amount of prism base out prescribed wasdetermined (1) by the minimal amount needed to maintainsingle vision and" (2) in those cases in which no diplopia was


found we ordered the approximate amount necessary to offsetthe esophoria present in near vision. This left the eyes stillesophoric for distance. The average amount of base-outprism ordered was four degrees, the greatest being eightdegrees. The amount of prism was divided equally betweenthe two eyes. In seven cases of hyperesophoria a verticalprism was placed before one eye-usually the nondominantone-and the base-out prism was placed before the dominanteye. In our opinion this should have been done more fre-quently; in other words, we should have taken greater cog-nizance of existing hyperphoria, as it occurred frequently.We are aware of the general prejudice against the prescribingof prisms base in and base out, but we can see no logicalreason why they should not be prescribed when they areindicated, just as any other type of correcting lens is pre-scribed. That the patient becomes dependent on them orthat the prisms must be increased at times does not seem avalid excuse for failing to prescribe them when ocular comfortand visual efficiency demand them. It is true that theyshould be given only in carefully selected cases. In our ex-perience the use of a minimal amount of prism base out incases of definite divergence weakness has proved most help-ful. In practically all our cases only one pair of glasses,either single vision or bifocal, was ordered. By prescribingthe minimal amount of prism, the same amount was usedboth for distant and for near vision; this apparently wassatisfactory.In the functional esophorias prolonged use of atropin

proved beneficial. It did not, however, alter the esophoria,symptomatically. It seemed to be characteristic that inmany of the cases of insufficiency there were periods of ex-acerbation of the irritability. When these exacerbationsoccurred, atropin served to place the eyes at rest, after whichthey would be more comfortable for a time. It would appearthat therapeutic cycloplegia should be used more often in the


various irritable, asthenopic cases, even in the presence ofdefinite presbyopia.Inasmuch as we are dealing with an insufficiency, one

would assume that it might be amenable to orthoptic treat-ment. Maddox and Pugh obtained indifferent results withthis method of treatmyent. We have had no experience withthis form of treatment, but will experiment with it in selectedcases.Dunnington7 has recommended operation for the more

refractory types of this condition. This is undoubtedly thecorrect procedure. We have perhaps been unduly conserva-tive in not attempting surgical treatment in these cases be-cause of the somewhat conflicting and disturbing factors thatwere present. As a group, the patients appeared to be poorsurgical risks. The psychic and neurologic traits and theintrinsic irritability exhibited by many of these patients ledus to hesitate to employ surgical treatment. It may be thatin the future, as we study these cases more intensively anddifferentiate them more closely, we may be able to selectmore patients for surgical treatment. One patient who wastreated surgically did well objectively and obtained normalmuscle balance, but subjectively he showed no lasting im-provement. Those who have severe functional disturbanceswill probably not improve under any form of treatment.Theoretically, the operation of choice should be a reenforce-ment of the external recti muscles, but perhaps recession ofthe internal recti muscles plus exercise of the external muscleswould have the same effect.The results of nonoperative treatment, as here outlined,

were satisfactory in this series. Fifteen patients were ob-served for more than two years. In 24 cases in which we wereable to observe the patients, a reasonable degree of ocularcomfort was secured. In many of these cases the relief ob-tained was striking. In the group of cases in which therewas nervous and mental involvement the results were notgood, whereas in others they were unknown or of questionablevalue.


SUMMARYDivergence insufficiency is a definite clinical entity that

causes considerable asthenopia, particularly in near vision.Four cases of divergence paralysis were observed. It wouldappear clinically that there is probably a cerebral center foractive control of the divergence mechanism. In many casesof this series the incorporation of prisms base out in the cor-recting lenses was most useful. Hyperphoria occurs fre-quently in association with the esophoria in these cases, andtherefore we should probably correct this by adding a verticalprism. These eyes seem to show a combination of pathologicstates, such as decreased divergence, anisometropia with ir-ritability, vertical imbalance, subnormal accommodation,beginning presbyopia. Such conditions are associated withfunctional disturbances and an unstable nervous system.With such a combination, ocular discomfort is unavoidable.Nonoperative treatment, as here outlined, has been of def-inite assistance to 50 per cent. of the patients reported in thisseries of cases. Orthoptic training and operation probablyshould be tried more frequently in selected cases.

REFERENCES1. BerSmann: Wilbrand and Saenger, Die Neurologie des Auges, 1921,

viii, p. 17.2. Bielschowsky: Arch. Ophth., 1935, xiii, p. 569.3. Davis: Arch. Ophth., 1933, x, p. 455.4. Duane: Arch. Ophth., 1899, xviii, p. 261.5. Duke-Elder, W. S.: Textbook of Ophthalmology, C. V. Mosby Company,

St. Louis, 1933, i.6. Dunnington: Arch. Ophth., 1923, lii, p. 39.7. Dunnington: Virginia M. Monthly, 1934, lxi, p. 515.8. Dunphy: Am. J. Ophth., 1928, xi, p. 298.9. Maddox: Tr. Ophth. Soc. U. Kingdom, 1929, xlix, p. 2.

10. Peter: Conrad Berens, The Eye and Its Diseases, W. B. Saunders Com-pany, Philadelphia, 1936, p. 862.

11. Pugh: Squint Training, Oxford University Press, London, 1936, p. 54.12. Riley: Tr. Am. Acad. Ophth. & Oto-Laryng., 1936, xli, p. 82.

DISCUSSIONDR. JAMES WATSON WHITE, New York: Dr. Prangen's paper

deals with a condition troublesome to both the patient and theophthalmologist.

146 PRANGEN AND KOCH: Divergence InsuffliciencyI have not found, as Dr. Prangen has, that the symptoms are

more marked at the near-point. Rather the panorama asthenopiaand double vision are much more annoying for distance. There isalways an esophoria or esotropia for distance, but at 33 cm. theremay be only a trace of esophoria. Frequently there is an exophoriaat 25 to 30 cm., and at 20 cm. there is practically always an exo-phoria. The convergence near-point is rarely excessive, and ismore likely to be remote. The esophoria or esotropia, as well asthe diplopia for distance, grows progressively less as the light ap-proaches the eyes, and both disappear at some point within 1 M.,depending on the amount of the deviation. It is an interestingobservation, although usually not necessary to a diagnosis, tomeasure the amount of the esophoria, also the diplopia, at 6 M.,3 M., 1 M., 0.50 M., 0.25 M. In doubtful cases the deviation fordistance should be measured at 25 to 50 M. also. The diplopia testis not so dependable as the actual measurement of the amount ofdeviation by the screen test.

I have found, as Dr. Prangen has, that there is some degree ofhypocyclosis for which a plus lens must be added for reading. Thisplus lens, however, does not reduce the esophoria for distance ifthe esophoria is due to a divergence insufficiency. However, if theesophoria is due to a convergence excess, the esophoria for near isdefinitely lessened. If the esophoria is about the same for distanceas for near, and if atropin or plus lenses will definitely reduce it,the condition is probably a convergence excess; but if the esophoriafor near is considerably reduced, or if it is changed to an exophoria,and the esophoria for distance is practically unchanged, then aprimary divergence insufficiency probably exists.

It is possible that some of the patients observed by Dr. Prangenwere primarily cases of convergence excess. This would seem prob-able, since the symptoms for near work, instead of for distance,were so much increased, as in a typical divergence insufficiency.Prism divergence for distance is below normal and may be nil,

whereas for near the prism divergence may be quite normal. Ihave not found a prism divergence as much as 3 D. to 4 D., as Dr.Prangen has.

Prisms base out in the distance glasses are well borne, but in closework if used for near as well they may increase the symptoms.The prisms in the reading correction tend to act as a prism con-vergence exercise and to increase the esophoria for near. This isproved by the fact that if the patient is using prisms base out whenfirst seen, by removing the prisms the esophoria for distance will


remain unchanged, whereas the esophoria for near will be definitelylessened. The esophoria for near was changed to an exophoria.No form of divergence exercises has been of any aid in my cases

of divergence insufficiency. However, if the condition is one ofconvergence excess, diverging exercises are a definite aid. I havenot found the high incidence of nervous symptoms and constitu-tional conditions which Dr. Prangen has found.The following cases are typical:CASE 1.-J. P. H., male, aged thirty-eight years, was seen in

August, 1919. At the age of thirty-two he began to have headachesand asthenopia. He did not recall having seen double at first. Hewas wearing +0.75 sph. c 3Y2 A prism base out, both eyes, vi-sion = 20/15. P. = 6.5 D., right and left. Homonymous diplopia,4 A at 16 feet; 3 A at 10 feet; 1 A at 15 inches. Fuses at 10 inches.Esophoria for distance, 8 A.; for near, 6 A. Exophoria, a trace inlooking to the right or left at 33 cm.On adding +2.25 sph. to his correction, the esophoria was 5 A

for distance, with 2 A of exophoria for near. The prism divergencewas nil, a 1 A prism producing diplopia at 20 feet.

Since many forms of treatment had been used by those who hadpreviously treated him, and since complete tests had been made todetermine the etiology, these were not repeated.The left external rectus was resected at once, and on removing

the first dressing on the second day the patient said that his distantvision was comfortable for the first time in eight years. The firstrecorded tests were made two weeks after the operation, and showedan exophoria of 1 A for distance and 3 A for near. Prism di-vergence, 7 A; PcB = 75 mm. Six months later there was anesophoria of less than 1 A; prism divergence, 7 A; exophoria fornear, 3 A. Four years later (1923) there were headache, nausea,and asthenopia. He had orthophoria for distance, prism divergence5 A; PcB = 60 mm. A change in his glasses relieved the symptoms.

July, 1927. Exophoria, a trace only, for distance and near;prism divergence, 3 A.

In 1933, fourteen years later, there was an esophoria of 6 A fordistance; exophoria, a trace for near. Divergence, 3 A. An in-crease in the presbyopic correction with an addition of 1 A prismbase out, entirely relieved the symptoms.

In 1935, with R. E. +1.00 sph., L. E. +0.75 sph. C +0.25 cyl.ax. 180°, he had 20/10 vision. Esophoria, 2 A for distance;exophoria, a trace for near. Trifocals were prescribed with 1 Aprism base out and +2.50 sph. added for reading. These weremost satisfactory. This case is interesting because it was so typical,


was relieved of symptoms by operation, and ran an uneventfulcourse for sixteen years, during which time the prism divergencewas never less than 3 &.

CASE 2.-Mrs. M. B. C., aged seventy-two years, R. E. +3.00sph. C. +0.37 cyl. ax. 180°, 20/15; L. E. +3.00 sph., 20/15.Esophoria at 6 M., 9 A; at 3 M., 9 A; 1 M., 5 A; 0.50 M., 2 A. At25 cm. there was an exophoria of 2 A. She fuses at 20 feet with 2 Aprism base out, right and left. This is not enough for a distance offrom 200 to 500 yards, and is too much for a distance within 10feet. In this case a prism base in may be placed in the readingsegments to counteract the prism for distance. With the markedchange in esophoria or esotropia, as the distance varies, it is im-possible to relieve the symptoms entirely by prisms, and, as in thefirst case, resection of the externus or occlusion of one eye wouldgive the greatest relief.DR. THOMAs D. ALLEN, Chicago: This is a very important

contribution, I think. The fitting of glasses and the fitting ofprisms are troublesome to most of us. Many ophthalmologistshave stopped the fitting of prisms entirely because they are sounsatisfactory.

I think one of the tests which Dr. Prangen did not have timeto speak about should be emphasized, and that is whether or notthere is the ability to fuse. If a person obviously has no abilityto fuse, prisms will do no good. We may demonstrate all sorts ofphorias, and if the patients do not fuse, of what use are prisms?Occasionally prisms may be of some use when there is weak fusionalability; but we usually-and I presume Dr. Prangen always-test for stereopsis. We have now at hand one of the Keystone setsof about a dozen charts showing letters and numbers at differentdistances apart, and as a result of testing with these charts we cantell the relative stereopsis. We find also, when we are a littlehesitant about fitting prisms, that it is of great value to put in alight-weight frame the glasses that we believe should be used, andthen add or subtract the prisms, and let the patient wear the glassesfor a half-hour or longer in the office. Occasionally patients mustcome back a second time for this little test. I was very much in-terested in this paper, and it seems to me that it ought to provokeconsiderable thought.DR. AVERY DE H. PRANGEN, closing: I thank the gentlemen

for their discussion, and I am particularly gratified that there issome difference of opinion, because it makes one feel that he hasstirred up an interesting subject.

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