The effect of forced vergence on heart rat

Eberle, James E.

Murphy, John H.

Zoller, Richard L.

English

CommonKnowledge

Pacific University 
CommonKnowledge 
College of Optometry Theses, Dissertations and Capstone Projects 
5-1973 
The effect of forced vergence on heart rate 
James E. Eberle 
Pacific University 
John H. Murphy 
Pacific University 
Richard L. Zoller 
Pacific University 
Recommended Citation 
Eberle, James E.; Murphy, John H.; and Zoller, Richard L., "The effect of forced vergence on heart rate" 
(1973). College of Optometry. 353. 
https://commons.pacificu.edu/opt/353 
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The effect of forced vergence on heart rate 
Abstract 
The effect of forced vergence on heart rate 
Degree Type 
Thesis 
Degree Name 
Master of Science in Vision Science 
Committee Chair 
Niles Roth 
Subject Categories 
Optometry 
This thesis is available at CommonKnowledge: https://commons.pacificu.edu/opt/353 
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THE EFFECT OF FORCED VERGENCE 
ON HEART RA'l'E 
THE EFFEC'.r OF F'ORCED VERGENCE ON HEART RATE 
by 
James E. Eberle 
John H. Murphy 
Richard L. Zoller 
Submitted In Partial Fulfillment Of 
The Requirements For The Degree 
of 
Doctor of Optometry 
of 
Pacific University 
May 1973 
ACKNOWLEDGEMENT 
The authors wish to express their sincere a_ppreciation 
to Dr. Niles Roth, 0.0., Ph.D., Associate Professor of Physio-
logical Optics and Optometry, for his interest and assistance 
in this study and to Sharon Zoller for her hel_c; in pr1.::para.-
tion of this work. 
J. E� 
J .. M. 
R. z. 
.-
THE EFFECT OF FORCED VERGENCE ON HEART RATE 
INTRODUCTION 
The human body is a. very complex, yet highly coordinated 
organism. Interactions of parts within the human body are 
such that change in one can have a profound effect on any 
number of other parts of the body. One of thewe int.erac ti ve 
relationships provides a basis for our thesis. 
The oculocardiac re flex is a well known and stu'died 
relationship between the eye and heart. According to Adler,1 
mechanical pressure on the eyeball, slows the heart rate. The 
afferent path ot this reflex is 'mediated by the opthalmic 
division of the trigeminal nerve, while the efferent pathway 
is via the vagus nerve. It is most noticeable when the person 
is under the effects of a general anesthetic. 
With regard to the oculocardiac reflex the results of 
two studies should be ,mentioned. The first is a study by 
Gil�espie, Richter, and Wang2 who found that normal heart rate 
usually returned within 20 seconds after release of pressure. 
The second experiment was performed by Sorenson and Gilmore3, and 
confirmed in a study by Kirsch, Sarnet, Virgil, and Axelrod4 
which led to the cc,nclusion that traction on the medial or 
lateral rectus muscle, along with s�veral other types of pressure 
lead to a decreased heart rate, and sometimes cardiac arrest. 
Direct mechanical pressure on the eyeball is not necessary. 
Introduction J.E., J.M., R.Z. 
The final point to be made i_n connection with the oculo-
cardiac reflex is that incre ased pressure on the eyeball 
invariably reduces, rather than increases, heart rate. 
Doctor John <P:i.erce5, in his doctoral research concerned 
himself wi'th a problem very similar to ours . He studied the 
re lationship between performance and physiological activity as 
a function of near point lense s, working dist:_ance a,nd posture . 
One of the relationships that he st udie d in his the�i� was the 
correlation between nl9ar point lenses and change in heart 
rate. In his stud.y , Doctor Pierce used near point lenses of 
Pl ano, +0.50 and +1 .00 OU with four trials through each lens 
power on each of his twenty-two sub;j ects . His results showed 
that the heart rate changed acc ording to the following table 
from his study. 
Lens Power Plano +1 .oo 
Mean Heart Rate 79 .3 82.2 
In his study, Doct or Pierce showed that several physio­
logical indicators changed in a similar manner as a function 
of hear point lenses, body pqsture and workinr;: dist0anc e • 
.An article and lecture by Doctor B. Grolman6 is the 
primary reason we became interested in this problem. Doctor 
G�olman discussed binocular refraction and fixation disparity 
as measured with his near point polarized cards. 
2 
Doctor Grolman notes that two of his colleagues, S. Emery 
and D. DePediV!D of AO' S Resec-,rch Department made the following. 
Introduction J.E., J.M., R.Z. 3 
observations during a study of the effect of induced oculomotor 
stress on th® visually evoked cortical response. 
"With the gradual progressive introduction of BI or 
BO prism (divided between both eyes), subjects; while 
maintaining single simul tanious binoc ular vision , ; 
demonstrated progreasive increases in cardiac rate. 
Addi tional prism, precipitating diplopia, produced a 
reduction in heart rate which , however, remained 
above th.e initial base line. 
11Twelve prism diopters base in produced, for these 
subjects, 20-30% increase in heart rate. In .all 
cases, these subjects manifested fixaticm disparities 
at this level. As little as 1t prism diopters BI, 
divided betwe-en the two eyes produced readily measur­
abl e increases. 
Doctor Grolman mentioned this observation in his guest 
lecture at Pacific University in the winter of 1973 noting that 
it wos just an observation and, as they were studying other 
phenomena at the time, they were no t able to pursue it further. 
Knowledge of the oculocardiac reflex, the unpublished Ph.n 
thesis _by Doctor Pierce· and the above-mentioned a!'ticle and 
lecture by Doctor Grolman led us to investigate further the 
effects of forced lateral vergence on heart rate. 
HYPOTHESIS 
The hypothesis taken for this study is that forced vergence 
has no effeGt on heart rate. (Null hypothesis.) 
METHOD 
The number of subjects for this heart rate-vergence study 
was twenty-seven. Twenty-six of these subjec ts were Optometry 
students at Pacific University. Twenty-five of the subjects 
Method J.:C., J.M., R.Z. 4 
were males and two of the subjects females. Of the twenty-seven, 
the twenty-six Optometry students .all had experience with forced 
vergence techniques. The age range of these subjects was 
twenty-one through twenty-five years of age. All subjects had 
normal binocular vision according to previous clinical tests. 
The experimental design consisted of three stages: 1) determin-
ation of initial heart rate, 2) monitoring of heart rate at 
each of two levels of forced negative (base in ) and forced 
positive ( base out) vergence, and 3) determination of heart 
rate at the end of testing.' 
The equipment used for the experiment included 1) a 
phoropter with rotary prisms , 2) a reading rod, 3) a reduced 
Snellen acuity card, 4) a stethoscope, and 5) a timer. The 
method of measuring ( me te ring ) heart rate was designed to be 
as free as possible of influences on heart rate; An electro-
cardiogram eould very likely h�ve influenc�d he art rate more 
than the actual methods used. Two methods of monitoring heart 
rate were used; a stethdscope placed on the chest, an� counting 
. . 
the pulse at the patient's wrist. In both methods, beats were 
counted for a period of sixty seconds. In general, the find-
ings reflect the combined results of both me thods used 
simultaneously. When the stethoscope and pulse ra.te disagreed 
by more than one beat, the finding was considered invalid. 
When results differed by only one beat the finding was recorded 
as the average of the two valued. There were instances, however, 
Method J.E., J.M., R.Z. 
when one m e ti1od may have broken down during a test such a.s 
losing the pulse. In such a case, the other method supplied 
the recorded value. 
The subject after being seated in an examining chair had 
his near pupillary distance and his habitual near point 
5 
prescription placed in the phoropter. At this time the subject 
was allowed to rest for a pe riod of a few minutes before pro-
ceeding. This was to cancel the effects of any kind of exer:-
cise such as walking into the room. :Heart rate was then 
monitored with the rotary prisms in place with zero prism 
diopters involved. During this t1m� the subject viewed the 
re_duced Snellen ·acuity card at a distance of forty centimeters. 
This rate was considered the base value for the experiment in 
computing statistics. After the base heart rate measurement, 
a near point lateral phoria was taken through the habitual Rx. 
-. 
This was done with vertical dissociation prism before the left 
eye and lateral measuring prism before the right eye. Also at 
this time forced vergence tests were done at· the near 
point test distance. Base out prism was first used to establish 
a break, and then a recovery value was found. The duction was 
repeated in the base in direction. 
The rotary prism was next re turned to the zero position 
and the subject allowed to rest for app±-oximately one minute. 
After resting, base out prism was applied in an amount equal 
to half the total base out value (BO to break). With this 
Me thod J.E., J.M., R.Z. 6 
amount of prism in place, the subj ect was instructed to keep 
the 2 0/20 line of the reduced Snellen card single and as clear 
as possible. Under these condition�, the heart rate was 
measured, as described earlier, for a pe riod of sixty seconds. 
The next trial used an amoun� of base out prism just 
under the break value .  Generally, this was two to three prism 
diopters less base out than the break value obtained earlier. 
There was no scheduled rest between the first and second trials. 
Heart rate was again measured as in the first trial. 
Follo:ving the two base out trials the rotary prisms were 
returned to zero and the patient was allowed a rest period of 
about one minute. Th� two base in prism trials were performed 
in the same wa.y as the base out trials, obtaining sixty 
second heart rates for both one half the base in to break 
value and a base in value just under the break point. 
Following these four trials, another re st period of about 
two to thr e e  minute.a was introduced be fore obtaining the final 
heart rate. During this final count, the rotary prisms were 
returned to zero while the subject vi�wed the 20/20 line as 
before. Any subject who -ha� a final heart rate that differed 
by more than two beats from the original base rate was consi­
dered by the experimenters to be insufficiently stable for 
this study, and the data were not used. 
Data Processing and Analysis J.E., J.M., R.Z. 7 
DA'rA PROCESSING AND ANALYSIS 
Of the twenty-six sub jec ts originally involved in the 
study, seven were screened out because of a final heart rat e 
that differed by more than two counts per minute from the 
initial heart rate. Data from the remaining nineteen subjects 
were divided into two groups according to amount of near point 
lateral phoria. In one group, phorias ranged from five �xo 
to five e so. In the second group, phorias were greater than 
five exo or five eso. There were fourteen subjects in the 
first roup and five in the second. 
In both groups the raw de.ta from the four trials were 
proc@ssed further by calculating the percentage change of 
each finding from the initial base rate� These percent change s 
for all subjects in a given group were averaged for each trial. 
Thus, the fourteen sub j ect s of group one provided four average 
percent changes, one for each of the prism levels. In group 
two, thi& fi_rst base in pri sm trial was not included in the 
ste_tistical work up because the members of this group were 
mainly high exophores, and half the base in to break value 
WOLl d have been so near the phoric posture that the amount of 
forced vergence would have b ee n negligible. 
For statistical purposes, an analysis o f variance test 
was employed7. The method of analysis chosen was that of 
treatment by subjects design where ·2.. . .. 
F- m e an_ · tre &tments - m e an2 error 
L Results J.E., J.M., R.Z. 
RESUL'I'S 
The results, indicated by the mean percent change from 
the baseline for each prism application, appear to show that 
heart rate did, on the average, increase for both groups 
( 14 subj ects with phoria w/in :!:: 5 �of ortho and five subj ects 
I i . f . f t b th +_ 5 � ) . w phor as di fering ·rom or ho y more - an 
The per�ent difference from baseline, computed to norma­
lize th• data, showed somm subj ects with increased rates and 
others with decreas�d rates. The range of variation is shown 
below. 
% Change t BO 
Max. ine-r.ease +8.8 
Max, decrease -4.9 
Mean +1 .49 
JLCha:rige t BO 
Max. increase + 10.3 
Max. decrease -2.5 
Mean +2.40 
G;IDoup I 
1 BO 
+9.6 
-5-5 
+3. i 2 
Group II 
1 BO 
+ 13. 1 
-2.4 
+5.54 
t BI 
+ 11 • 2 
-1 �2 
+3.61 
1 BI 
+12.9 
-3.8 
+l+.67 
1 BI 
+14.5 
+2.4 
+8.92 
The mean de.ta shows an increase in the heart rate with 
each prism application, larger for BI than for BO, and larger 
for the greater amounts of prism. 
Statistical Analysis of the data, using the Treatment by 
Subj ects Design, shows that the change in heart rate is 
significant at the G.025 l�vel . 
8 
Results J.E., J.M., R.Z. 
For group one the F value is 2.9202. The significance 
range at the proper level of degrees of freedom is 1.57 to 
5.70 (20% to 0.1% level. 
9 
Originally, we had intended that there be only one group 
of subjects; however, the variance of phorias made it necessary 
to divide the subjects into two groups. Statistical analysis 
was not applicable to group two because of its small size. 
DISCUSSION 
The results of our work show a consistent change in heart 
rate from the baseline with addition of prism. The greatest 
change occurred with full BI value, and the smallest change 
was with t the maximum BO value. Doctor Grolman's study 
alluded to the fact that the heart rate increases 20-30 per­
cent with the additi on of prism. While our data was signifi­
cant at the 2.5% level of probability, we were not able to 
find resul ts of this magnitude. Individual results did show 
increases of up to 13 percent with forced verge�ce. 
Grolman's study also indicated that once prism was remove� 
heart rate remained above the bci.se re.te. Our results also 
showed t hat , after prism was removed, heart rate remain®c,l 
above base rate in all but two of our subjects . 
Our results contrast with effects of oculocardiac reflex 
due to stress on the eye, where heart rate decreases. Thus, 
if there is a significant effect due to prism, it is possibly 
L 
L 
Results J.E•, J.M., R.Z. 
not related to the oculocardiac reflex. Viewing Doctor 
Pierce's study, which showed heart rate increases with near 
point lens application, in conjunction with our stud� it may 
indicate the possibility of a mechanism other than the oculo­
cardiac response. 
A more sensitive experimental design to study this rela­
tionship further might include some of the following factors: 
relating the pho ria to the prism application rather than 
dividing the duct.ion ranges around the zero prism diopt@r 
le ve l , and choosing subjects with a larger age variance . The 
monitoring of heart rate might have been L�proved through the 
use of a more sensitive instrummnt such as the electrocardio­
gram. A nevi. experimental design might also allow longer rest 
periods between trials monitoring heart rates over longer 
periods of time. 
CONCLUSIONS 
The null hypothesis must be rejected for this study 
since analysis shows that increased heart rate with forced 
vergence is significant at the . 025 percent level. Further 
study is indicated with the possible retinements discussed 
above. 
10 
Data J.B., J.M., R.Z. 11 
L DATA 
SUBJECTS WI'l'H PHORIAS OF !5 A 
Percent Clrnnge from Baseline 
i BO 1 BO �BI l..fil 
1 . 8.8 5.9 5 0 • ,,I 7.4 
2. 1 • 2 1 • 2 -1.2* .6 
3. 2. 1 1.4 2. 1 5.6 
4. 3.4 - .34 5. 1 1.7 
5� 0 6.5 3.2 7.3 
6. .76 o· 0 -3.8 
7� 0 9.6 1L2 12.9 
8-. 
-
3 . 5. t>.4 2. 1 5.7 
9. 4.4 6.6 4�4 2.2 
1 o. -1.3 -5-5 o;6 2.7 
1 1 • 2.3 1. 1 2 .3 · o  
12. 3 . 9 6.2 10. 1 12.5 
13. -4-9 0.9 2�9 4.9 
14. 3 .8 3.8 1.9 5.7 
¥ean Value: 1 .497 3. 12 3.61 4.67 
( "-" denotes Heart Rate that decreased from B-aseline. ) 
Data J.E., J.M., R.Z. 12 
SUBJECTS WITH PHORIAS > ! 5 � 
Perc©nt Change from Baseline 
�BO 1 BO 1 BI 
1 • 1 .8 7.4 6.5 
2. 10.3. 13. 1 14.4 
3. -2.5* 7.6 14.5 
4. 4.8 2�0 6.8 
5. -2.4 -2.4 2.4 
Mean: 2.40 5.54 8.92 
( 11-11 denotes Heart Rate that decreased from; baseline.) 
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BIBLIOGRAPHY 
lMoses, Robert A. (Editor), Adler's Physiology of the· E;Ye, Mosby 
Co., St. Louis, 1 970, p. 70. 
2Gi llespie , R.; Richter, . C. ; and Wang, G., "The Oculocardiac 
Re flex: Its Clinical Significance," J. Ment. Sc. 72:321 -325, 
1926. 
3sor0nson, E. J., and Gilmore, J. E. "Cardiac Arrest During 
Strabismic Surgery 11 ,_ Am. J. Ophth. 4 1 :748-757, 1956. · 
'+Kirsh, R.; Samet Pq Kugel,- V.; and Avelrod, S.;"Electrocardio­
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Retrobulbar Injectionn, Arch. Ophth. 58:348-356, 1957. 
5pierce, J. R., "A Study o f the Relationship between Performance 
·and Physiological Activity as a Function of._Nearpoint 
Lenses, Working Distance and Posture", Unpublished Ph.D. 
thes:j;.s, Univ ersity of Portland, OR, 1970. 
6Grolman, B., ''Binocular Refraction--Fixation J)isparity"; !£!. 
Optician, Sept. 17, 1971, p. 1 6-19. 
7B,runi_ng, J. L.; and Kintsz, B .• L., COmJJUtational Handbook of 
Statistics, Scott, Foresman and Ce., Ill., 1968, p. 47-54· 


The effect of forced vergence on heart rate

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The effect of forced vergence on heart rate

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