This was a study of the effect of prolonged maintenance of a rotated head position on the apparent frontal plane, as determined by using a rotating-plane apparatus, Measurements of the apparent frontal plane were obtained before and after a forty-five minute adaptation period in which the subject\u27s head was restrained in a rotated position, by means of a surgical collar. Stereoscopic information was withheld during this time by covering the dominant eye with a white patch. In both test and re-test conditions the plane of the subject\u27s face was congruent with the frontal plane of his body, Results showed that relative to the  before  settings the apparent frontal plane was rotated toward the subject on the side toward which his head had been rotated

Stakston, Malin C

Williams, David I

English

CommonKnowledge

Pacific University 
CommonKnowledge 
College of Optometry Theses, Dissertations and Capstone Projects 
5-1970 
Effect of head rotation on the apparent frontal plane 
Malin C. Stakston 
Pacific University 
David I. Williams 
Pacific University 
Recommended Citation 
Stakston, Malin C. and Williams, David I., "Effect of head rotation on the apparent frontal plane" (1970). 
College of Optometry. 318. 
https://commons.pacificu.edu/opt/318 
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Effect of head rotation on the apparent frontal plane 
Abstract 
This was a study of the effect of prolonged maintenance of a rotated head position on the apparent 
frontal plane, as determined by using a rotating-plane apparatus, Measurements of the apparent frontal 
plane were obtained before and after a forty-five minute adaptation period in which the subject's head 
was restrained in a rotated position, by means of a surgical collar. Stereoscopic information was withheld 
during this time by covering the dominant eye with a white patch. In both test and re-test conditions the 
plane of the subject's face was congruent with the frontal plane of his body, Results showed that relative 
to the "before" settings the apparent frontal plane was rotated toward the subject on the side toward 
which his head had been rotated. 
Degree Type 
Thesis 
Degree Name 
Master of Science in Vision Science 
Committee Chair 
C. B. Pitbaldo 
Subject Categories 
Optometry 
This thesis is available at CommonKnowledge: https://commons.pacificu.edu/opt/318 
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.. 
. , 
EFFECT OF HEAD ROTATION 
ON THE 
APPARENT FRONTAL PLANE 
SIXTH YEAR OPTOMETRY PROJECT 
PRESENTED to FACULTY OF 
THE COLLEGE OF OPTOMETRY 
PACIFIC UNIVERSITY 
In Partial Fulfillment Of 
Requirements for The Degree 
Doctor of Optometry 
by 
Malin c. Stakston 
David I. Williams 
l'llay 1970 
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D'r. c. 86 Pitblado, Thesis - Advisor 
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ACKNOWLEDGEfn.ENT 
It is with sincere appreciation that 
the authors thank Dr. Pitblado for 
his guidance and many sugg~stions in 
the design and analysis of this study, 
~l. C. Stakston 
D. I, LVilliams ; 
ABSTRACT 
This was a study of the effect of prolonged 
maintenance of a rotated head position on the apparent 
frontal plane, as determined by using a rotating-plane 
apparatus, Measurements of the apparent frontal plane 
were obtained before and after a forty-five minute 
adaptation period in t1Jhic.h the subject's head was re-
strained in a rotated position, by means of a surgical 
collar. Stereoscopic information was withheld during 
this time by covering the dominant eye with a white 
patch. In both test and re-test conditions the plane of 
\ 
the subject's face was congruent with the frontal plane 
of his body, Results showed that relative to the "before" ( 
settings th~ apparent frontal plane was rotated toward 
the subject on the side toward which his head had been 
rotated. 
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INTRODUCTION 
This thesis is not the only study on stereoscopic 
after-effects. Experiments on this subject have been 
done by Kenneth N. Ogle and his associates. These dealt 
with the apparent rotation of the binocular visual field 
that was caused by the use of a meridion a l lens before 
one eye. Ogle was concerned with disparity as the 
independent variable. 
No data on after - effects of head rotation, under 
conditions that had no effect upon disp a rity, could be 
\_. 
1 
found. The following study deals with the effect of 
head rotation on the apparent frontal plane. 
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METHODS 
APPARAT~~ 
The apparatus consisted of a BO X 65 cm. panel of 
glass rotatable about a vertical axis. The surface 
facing the subject was spray-painted flat black to cut 
down on reflections. Twenty to twenty-five dots were 
randomly scratched on the front surface of the rotatable 
plane at eye level. The plane was held in a 2 X 4 frame 
with .a pivot point located in the vertical axis. The 
vertical axis of the rotatiny plane was in the subject's 
median plane, The degrees of rotation were plotted on 
0 
the left side of the base with the 90 mark indicating the 
~ 
objective frontal plane. (The 95 mark was closer to the 
0 
subject and the 85 mark was further from the subject.) 
Attached to the base was a face plate with an aperture 
of 2.5 X 5.8 cm. This was large enough so it would not 
interfer wit h the subject's view of the dots. The plate 
also included side blinders which eliminated peripheral 
cues and stray lighte The aperture was located 6 cm. 
behind the head and chin rest, and 34 cm. in front of the 
axis of rotation of the rotating plane. In turn, the 
rotating plane was 100 cm. from a white beaded screen on 
the laboratory wall. The center of the screen was illu-
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minated by a sixty watt bulb which provided 1 fc of 
illumination onto the center of the screen, The 
apparatus ~as spray-painted a flat black and enclosed 
by black cloth to keep stray light from interfering with 
the test. 
The stool, head and chin rests were adjustable to 
accommodate each subject. While the subject viewed the 
rotating plane no part of itcs frame was visible. The 
measurements were obtain~d in a room in which the window 
was covered by two sheets of black polyethylene plastic, 
All of the experiments were done in the evening after 
dark so there was no possibility of extraneous light 
entering the room. The only illumination was that of the 
single light source used ta illuminate the screen. 
PROCEDURE 
Using the multi-stereo S-2 Keystone card the twelve 
subjects were screened for stereopsis. Any subject with 
less than BO% stereopsis was rejected. 
The subject was positioned in the chin rest, before 
the viewirg aperture. He was then tested binocularly on 
the apparatus to determine his apparent frontal plane. 
The subject was instructed to respond by saying, "now" 
when the rotating plane appeared to be parallel to the 
plane of his face. The starting position for the rotating 
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0 Q plane was at 75 + 2, it was then rotated toward the 9cf 
position. After the subject responded he was then 
instructed to close his eyes, The experimenter then 
recorded the scale reading, and re-positioned the rotating 
0 0 plane at 105 + 2. The subject was then instructed to open 
' his eyes and the exp e rimenter slowly rotated the plane 
toward the gif setting, Ten observations were taken, The 
first t wo observations were not record ed, so the subject 
was able to become familiar with the proce du r e. The 
ave r age of the remaining eight trials designated the 
subj ect's apparent frontal plane before the adaptation 
period. 
After the pre-exposure test the dominant eye was 
patched using white tissue as an occluder. The purpose 
of the occlusion was to eliminate stereoscopic cues. The 
eye dominance was determined by a conventional clinical 
method (hole card). The head was rotated in the direction 
opposite the occluded eye • • Ta clarify this, when the right 
eye was occluded, the head was rotated to the left and 
vice versa. The head was held in the rotated position by 
a surgical collar. 
The adaptation period lasted forty - five minutes. 
During this period the subjects were allowed to wander 
in the corridors or in the lab area, but they were 
instruct e d not to do any rea ding, since it could induce 
5 
vertical head tilt. 
After this adaptation period the subject was 
returned to the apparatus and seated. He was instructed 
to close his eyes and the experimenter then remo ved the 
eye patch and surgical collarc His head was then placed 
in the chin and head rest and the room illumination was 
turned off, except for . the light on the screen. The 
post -adaptation test procedure was then conducted in the 
same manner as the pre-test procedure described previously. 
The average of these trials designated the subject's 
apparent frontal plane after the adaptation period. 
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RESULTS 
After adaptation with the head rotated to the left, 
the subject reported the rotatable plane to be physically 
closer to his body than it had been in the pre- test. The 
reverse was true for subjects whose heads had been turned 
to the righte mean settings before and after exposure 
are presented in Table #1. 
In the following table under the heading 'sign', the 
data from left and right "head tu r ners" are combined in 
order to obtain a single statistic, The plus repres ents 
rotation toward zero on the side to which the head had 
been turned while minus represents rotation away from 
zero on the side to which his he ad had been turned. 
0 
The mean change in settings was 3.74. The standard 
deviation was 1.0~. A 't' test (related samples) with 
eleven degrees of freedom yielded a value of 12.03 
l l (p< .005). 
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) AB LE #1 
Direction 
of 
Subject Head Turn Before After Difference Sign* 
91 • 50° 
6 ~- 0 c.s. Left 95.38 3.88 +3.88 
J.C. Left 90. 50° 95 .12° 4 o 62CI +4.62 0 
L.S. Right 90. 87° 85. 00° 5. 87~ +5.87 Ii 
J.J. Left 91.5d' 95.,251:) 3. 75° +3.75 0 
C.P. Left 87. 88° 90. 75° 0 'O 2.87 -1-2. 87 
m.s. Left 0 90.12. 95. 00° 4. 87° ' +4.87 
0 0 0 Q 
D • ~J • Left 92.00 95.00 3.00 +3.00 
r11. A • Left 90. 75° 93 .12° 2. 3711 +2.37 Ci 
T.J. Right ~ 92.87 0 3. 87() (l 89.00 +3.87 
C,J. Left 0 91 .oo 93. 25° 2. 25° 0 +2.25 
c.s. Left 0 91 • 75 96 .12° 4.37 0 0 +4.37 
I<. 8 • Left 90. 25° 93. 37° 3 .12 0 
0 I +3 .12 
* 
+ ::: rotation tmllard 0 on the side to which the head 
had been turned 
::: rotation away from 0 on the side to which the head 
had been turned 
DISCUSSION 
Under reduction conditions, judgments of ·the 
orientation of a plane with respect to the frontal 
position should be based on binocular disparity between 
different points on the plane. Rotating the plane alters 
this disparity until phenom enal frontality is reported. 
The disparity now measurable is the geometrical- optical 
correlate of the apparent stereoscopic frontal plane. If 
a subject is trying to set this plane in a frontal position 
the positions of his own body and head must somehow be 
taken into account. An objective frontal plane with 
respect to the body does not present the same disparity 
pattern for all possible head positions. This suggests 
that there is more than a single binocular disparity 
pattern associated with the apparent stereoscopic frontal 
plane. These patterns should be coded according to the 
head position. This also assumes that when the term 
"frontal" is used, subjects refer to it as a position 
parallel to the frontal plane of the body, rather than 
the face. 
Based on the above discussion such a change might 
have been expected if the position of the head relative 
to the body had changed during the adaptation period. 
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Such adaptation would mean that the primary position 
might no longer be positioned as such, The subject 
should then seek the disparity pattern which would 
norma~ly accompany the "new" coded head position, rather 
than the primary position. 
After the head was returned from a leftward rotation 
to the primary position the objective frontal plane 
appeared to be rotated on the left. away from the 
observer. To compensate fbr this, the plane was then 
rotated toward his left side so it would appear to be in 
the frontal position. 
It is noted that the method chosen for withdrawing 
stereoscopic input created a concomitant variable (an 
accompanying variable), i.e., exposure only of non-
dominant eye. There is no evidence whether these variables 
are related to the stereoscopic after-effect. We do not 
believe that it matters which eye would be occluded; how-
ever, this should be investigated further in order to 
determine this point. 
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APl?ENDIX 
1.) C. S.---Occluded O. D. 
Before 
88° 
95° 
90° 
92° 
90° 
. 93° 
go" 
94" 
91I5i:Y" AVERAGES 
After 
--
Cl 95 
93° 
99° 
93° 
96° 
96° 
95° 
96° 
95:38'1 
0 Difference +3.88 
2.) J. C.---Occluded O. D. 
Before 
89Q 
92° 
90" 
89'" 
93° 
89~ 
90° 
92~ 
9~ AVERAGES 
After 
98° 
92<.> 
97., 
98' 
95° 
91 "' 
95" 
94~ 
95 .12° 
Difference +4,62 0 
3.) L. S.-- - Occluded O. S. 
Before 
90° 
92° 
89° 
88(> 
94() 
92~ 
91() 
91° 
90 0 87~ AVER AGES 
After 
-
0 85 
82° 
88c 
86° 
871) 
85° 
83" 
84° 
---:;i;-85. 00 
Difference -5.81 
4.) J, J.-- - Occluded O. D. 
Before 
90~ 
90Q 
93<J 
88~ 
87° 
92° 
98° 
94" 
91.50v- AVERAGES 
Afte r 
--
94G 
95" 
95~ 
90° 
100(' 
98° 
94° 
96.:. 
9"5,25-c 
Difference +3.75 0 
12 
5.) c. P.---Occluded O. D, 
Before 
86° 
90° 
88~ 
90° 
87° 
87° 
87° 
88 !.> 
87.87T" AVERAGES 
After 
85° 
97° 
85~ 
95° 
88° 
94° 
87~ 
95° 
90.75° 
!() Difference +2,87 
6.) m. S.---Occluded O. D. 
~for~. 
8i' 
94<1 
90° 
92° 
89G 
92° 
871> 
90~ 
9~ AVERAGES 
After 
Difference +4.87Q 
13 
--
7.) D. W.---Occluded D. D. 
Before 
871> 
95° 
86° 
97° 
91(! 
939 
92° 
95<) 
92. OlF AVERAGES 
After 
---
91° 
97° 
98° 
95° 
92° 
98° 
94<.I 
95~ 
95.00'S 
Difference +3.00 II 
8.) m. A.---Occluded D. D. 
Before 
95° 
971:> 
86° 
8Bc. 
89° 
87° 
92° 
92fl 
90. 75° AVERAGES 
After 
92° 
93° 
91° 
96° 
92° 
95° 
92° 
94t1 
93 .1 2° 
Difference +2.37° 
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·:·-, 
9~) T. J.---Occluded 0, S. 
Before 
92.., 
91t) 
92" 
92!:1 
98" 
95° 
91Q 
92° 
92,87° AVERAGES 
After 
92G 
87(} 
87° 
sd' 
92'' 
92 13 
87° 
91Q 
89 ."oo 'J" 
() 
Difference .. 3.87 
10.) C. J.---Occluded O~ D. 
Before After 
95° 
89? 
95<;) 
88" 
95~ 
89° 
100° 
95Q 
93.25° 
Difference +2.25 0 
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11,) C. S.---Occluded o. D. 
Before After 
Difference +4.3~ 
12.) K. B. ---occluded o. D. 
Before 
---
After 
I. 
Difference +3,12~ 
-~ - I 
·. 
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E..D = 44. 84° 
Average = €.D/n = 3. 74° 
t = 6/.std Dev 
v-n 
std Dev = \)~2 - {£D)2Tn 
n- 1 
= vlloe36 - 2 010. §.~lJ 2 
11 
= t/180.36 - 167.55 
1 1 
.)12.81 = 
. 11 
= V1 .164 
= 1.079 
t ::: D 
std Dev/ Vil 
"" 
= 3. 74° 
1.0797ffZ 
= 
1.079'/'3.46 
= 12.027 


Effect of head rotation on the apparent frontal plane

https://commons.pacificu.edu/cgi/viewcontent.cgi?article=2305&amp;context=opt

Effect of head rotation on the apparent frontal plane

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