Investigations on Subjective and Objective Cyclorotatory
Changes After Inferior Oblique Muscle Recession
Hermann Dieter Schworm, Silvia Eithoff, Markus Schaumberger, and Klaus-Peter Boergen
Purpose. To determine subjective and objective cyclorotatory changes after surgery for oblique
muscle disorders and to analyze the mechanisms of the well-known, long-term, postoperative,
subjective cyclotorsional changes.
Methods. Twenty-six patients underwent unilateral inferior oblique muscle recession for strabismus sursoadductorius (inferior oblique overfunction). Subjective and objective cyclodeviation
were examined before surgery with and without diagnostic occlusion, as well as 1 day, 3 days,
and 4 months after surgery. Subjective cyclodeviation was assessed by Harms' tangent scale.
Objective cycloposition was measured by means of fundus cyclometry, a novel method using
an infrared scanning laser ophthalmoscope.
Results. Diagnostic occlusion did not lead to significant changes in either objective or subjective
cyclodeviation. Preoperative objective excycloposition was nearly equally distributed between
affected eyes and fellow eyes. Early surgically induced incyclorotatory effects were more pronounced objectively than subjectively. On long-term follow-up, a reduction in the incyclorotatory effect was found to be smaller subjectively than objectively. A significant difference
between subjective and objective cycloposition was seen early after surgery, and a significant
difference between subjective and objective cyclorotatory change was found immediately after
surgery and on long-term follow-up.
Conclusions. Long-term regression of the incyclorotatory effect after inferior oblique muscle
recession was confirmed objectively and subjectively and can be explained as a cessation of
preoperatively required binocular compensatory innervation. The authors conclude that the
difference between objective and subjective regression is caused by sensory cyclofusion. Invest
Ophthalmol Vis Sci. 1997;38:405-412.
Subjective cyclodeviation, when tested on orthoptic
examination, can differ from real objective cycloposition of the globe.1'2 It has been pointed out by Hessel3
that the relation between sensory and motor cyclofusion in fusional cyclovergence is 3:1. In objective measurements of human cyclofusional response, Kertesz4
found a fusion of disparities up to 5° without rotation
of the globe. In Bielschowsky's head tilt test, sensory
elements seemed to play an important role because
pure motor compensatory counterrolling was found
not to exceed 50.5 After surgery of the oblique muscles,
torsional phenomena can be found that are still not
From the Eye Hospital, Ludwig-Maximilians-University, Munich, Germany.
Submitted for publication April 11, 1996; revised July 22, 1996; accepted September
30, 1996.
Proprietary interest category: N.
Reprint requests: Hermann Dieter Schiuorm, University Eye Hospital,
MathUdmislrasse 8, 80336 Munich, Germany.
clearly understood. As described by Herzau,6 some
persons complain of a postoperative subjective cyclorotatory overcorrection that disappears after a certain
period of time. Others reveal a regression of the surgery-induced rotatory effect by recurrence of a certain
amount of subjective cyclodeviation without having
shown an overcorrection. Litde has been reported
so far on objective cyclorotatory changes after
oblique muscle surgery, and little is known about the
relation between subjective and objective cyclorotatory changes.7'8
It was our aim to determine motor and sensory
torsional elements in patients who underwent surgery
of the oblique muscles to find an explanation for the
above-mentioned phenomena. To that end, objective
cycloposition and subjective cyclodeviation were measured in patients with oblique muscle disorders before
and after surgery. In addition, we tried to quantify the
Investigative Ophthalmology & Visual Science, February 1997, Vol. 38, No. 2
Copyright © Association for Research in Vision and Ophthalmology
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Investigative Ophthalmology 8c Visual Science, February 1997, Vol. 38, No. 2
influence on cyclotorsion of binocular conditions in
comparison to monocular conditions before and after
surgery.
METHODS
Subjects
This research adhered to the tenets of the Declaration
of Helsinki; informed consent was obtained from all
patients after the nature and possible consequences
of the study were explained. Twenty-six patients (17
males, 9 females) with unilateral strabismus sursoadductorius (inferior oblique overfunction) were included in the study. Mean age was 39 years; the age
range was 9 to 74 years. Patients were excluded if they
had any other squint or serious ocular disease. The
right eye was affected in 11 patients, and the left eye
was affected in 15 patients. Unilateral inferior oblique
muscle recession was performed on the affected eye
only. Seven patients underwent recession of 8 mm, 9
patients underwent recession of 10 mm, and 10 patients underwent maximum recession (the technique
for this has been described elsewhere).9
Assessment
Full orthoptic examination with assessment of subjective cyclodeviation and objective cycloposition was performed before and after surgery. To detect the influence of binocularity on cyclotorsion, subjective cyclodeviation and objective cycloposition were assessed
before surgery both without diagnostic occlusion and
then after 3 days of diagnostic occlusion. Subjective
cyclodeviation and objective cycloposition were measured on the first postoperative day immediately after
removal of the bandage and before binocular stimulation had been applied, on the third postoperative day
after 2 days of binocular vision, and 4 months after
surgery for long-term assessment. Evaluation of preoperative cyclodeviation without diagnostic occlusion
was hampered in three patients because objective and
subjective data were missing and in one patient subjective assessment was available only with fixation of the
affected eye.
Subjective cyclodeviation was assessed binocularly
under complete dissociation by the tangent scale devised by Harms10 and further described by Mackensen" (Fig. 1). This method is applied in Germany
for simultaneous assessment of horizontal, vertical,
and cyclotorsional angles of squint in patients in
whom the image of the nonfixating eye is not excluded. The screen is provided with a grid pattern,
which indicates horizontal and vertical angles of
squint, as well as with a scale for cyclotorsion. In the
center of the screen, a metal box containing a white
FIGURE l. The tangent scale of Harms for assessment of subjective horizontal, vertical, and cyclorotational angles of
squint (for further explanation, see Methods).
light is attached to serve as a fixation target. The shape
of the fixation light can be changed from circular to
a horizontal streak of light by removing the top cover
of the box. The box can be rotated by remote control
so that the horizontal streak of light can be turned to
any oblique position, the degree of which is indicated
on a scale. The patient is seated 2.5 m from the screen,
and the room is moderately dark. Proper head position is controlled by means of a special projector,
attached to the forehead, that points a dim white light
to the scale.
Beginning with the circular fixation light, a dark
red glass is held in front of the fixating eye, and the
patient is asked to fixate the red light. Because the
dark red filter excludes anything but the fixation light,
there is complete dissociation without any fusion response. The patient is given a green light pointer and
is asked to point at the red fixation light. Because the
fixating eye can see nothing but the red light, the
green light has to be localized by the uncovered eye
to which the white light and the scale pattern are
visible. According to the principle of confusion, the
red foveal image of the fixating eye is centrally superimposed with the foveal image of the nonfixating,
squinting eye. If the patient has central fixation and
normal retinal correspondence, the red light is localized according to the type of squint beside, above, or
under the white fixation light, and the angle of squint
can be read from the scale to which the patient points
with the green light.
The fixation light then is changed to a horizontal
streak measuring 5° of arc at 2.5 m. The red streak
appears oblique if there is subjective cyclodeviation.
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407
Cyclorotational Changes After Inferior Oblique Recession
obliquity was measured for each eye separately. Therefore, the angles of objective cycloposition of right and
left eye had to be added. As demonstrated by Bixenman1 and Herzau,1'1 healthy persons show an average
physiologic excycloposition of 7° per eye (range, 0° to
12°). For a comparison of subjective to objective data,
we subtracted 7° from the objective value of each eye.
Because individual physiologic excyclopositions were
unknown, the preoperative value of objective cycloposition served as a reference for induced changes.
FIGURE 2. Fundus cyciometry in primary position ("gerIn the current study, only the primary position was
ade") on a patient with right eye strabismus sursoadductorevaluated. Concerning the Harms tangent scale, only
ius (physiologic excycloposition not subtracted), (top) Be- fixation with the affected eye was evaluated. Right and
fore surgery (objective excycloposition of 16° OD and 2°
left gaze of fundus cyclometry and fixation with the
OS), (bottom) One day after maximum recession of the right
inferior oblique muscle (objective excycloposition of 6° OD unaffected eye of the Harms tangent scale were omitted in this study to keep the amount of data within
and 4° OS).
reasonable limits.
The patient is asked to rotate the red streak by remote
control until it appears horizontal. The amount of
obliquity is read from the scale. As on routine orthoptic examination, the angles of horizontal, vertical,
and cyclorotatory squint are measured in the nine
diagnostic positions of gaze controlled with the forehead projector with right eye and left eye fixation.
Objective cycloposition was determined by fundus
cyclometry, a novel monocular technique of assessing
real, objective bulbar rotation described in detail elsewhere.12'13 Examinations were performed on right and
left eyes separately in primary position, right gaze, and
left gaze; the nonfixating eye was patched. Correct
head position was assured by the use of a bite bar.
The patient had to look into an infrared scanning
laser ophthalmoscope (Rodenstock Instruments, Ottobrunn, Germany). Within a homogenous field of
dim red laser light, a bright red cross measuring 2° of
arc was presented as a fixation target. Images of the
posterior pole were obtained without pupil dilation
and were transferred to a computer system. After encircling of the optic disk with the computer mouse,
its geometric center was marked by the computer. This
point had to be connected with the fixation mark
indicating the location of the foveola. The angle between this line and the horizontal line, representing
the amount of objective bulbar rotation, was calculated by the computer. Figure 2 illustrates the result
of fundus cyclometry on one of our patients before
and after surgery.
Evaluation
On examination of the subjective cyclodeviation on
the Harms tangent scale, the difference of cyclotorsion between the fixating and the nonfixating eye was
assessed and included the amount of obliquity of both
eyes. In fundus cyclometry, however, the amount of
RESULTS
Double vision in the primary position occurred in 20
of 26 patients before surgery, and surgery cured it in
all of them. Binocular functions were measured using
the random dot stereo test by Lang (Lang II test)
and the striated lens test by Bagolini. Stereopsis was
considered good if Lang test figures with a disparity
of :s400 seconds of arc were recognized. Stereopsis
was reduced markedly before surgery in four patients.
After surgery, only one patient still had poor stereopsis. Similarly, good binocular function was obsen'ed
in 22 patients before and in 25 patients after surgery.
Data on subjective cyclodeviation and objective
cycloposition before and after surgery are listed in
Tables 1 to 4 and are illustrated in Figure 3. They
represent the statistical mean of 26 patients. Table 1
shows means, standard deviations and ranges of subjective cyclodeviation and objective cycloposition before and after surgery. Table 2 lists the mean induced
subjective and objective changes, their standard deviations, and the significances with P, t, and df values.
Statistical significance was calculated using the pairedsamples Hest. Table 3 shows the mean differences,
the standard deviations, and the significances with P,
iy and df values between subjective cyclodeviation and
objective cycloposition before and after surgery. Table
4 lists the mean differences, their standard deviations,
and the significances with P, t, and df values among
subjective and objective surgically induced cyclorotatory changes.
Effect of Diagnostic Occlusion
Diagnostic occlusion had no statistically significant influence on subjective or objective excyclodeviation.
Mean preoperative subjective excyclodeviation was
6.3° ± 6.4° (range, 0° to 22°) before diagnostic occlu-
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Investigative Ophthalmology & Visual Science, February 1997, Vol. 38, No. 2
TABLE i.
Subjective Cyclodeviation and Objective Cycloposition in 26 Patients With
Unilateral Strabismus Sursoadductorius (Inferior Oblique Overfunction) Before and After
Inferior Oblique Muscle Recession
Preoperative (°)
Subjective
Objective
Total
Operated eye
only
Nonoperated
eye only
Postoperative (°)
Without Diagostic
Occlusion
After Diagnostic
Occlusion
6.3 ± 6.4 ex
(0-22 ex)
7.4 ± 5.7 ex
(1 in-22 ex)
1.1 ± 5.0 ex
(6 in-15 ex)
1.3 ± 4.1 ex
(4 in-14 ex)
2.3 ± 4.2 ex
(2 in-15 ex)
5.9 ± 6.5 ex
(2 in-20 ex)
3.0 ± 3.3 ex
(2 in-8 ex)
2.9 ± 4.3 ex
(3 in-12 ex)
6.6 ± 5.9 ex
(4 in-17 ex)
3.3 ± 4.4 ex
(5 in-11 ex)
3.3 ± 4.2 ex
(4 in-10 ex)
1.2 ± 5.3 in
(11 in-12 ex)
2.9 ± 4.2 in
(10 in-10 ex)
1.7 ± 5.1 ex
(10 in-12 ex)
0.7 ± 6.5 in
(13 in-18 ex)
2.9 ± 4.7 in
(13 in-9 ex)
2.2 ± 5.6 ex
(10 in-16 ex)
3.0 ± 5.8 ex
(4 in-19 ex)
0.1 ± 3.2 ex
(7 in-6 ex)
2.9 ± 4.4 ex
(5 in-14 ex)
Day 1
Day 3
4 Montlis
ex = excyclorotation; in = incyclorotation.
Data are mean ± standard deviation (range).
sion and 7.4° ± 5.7° (range, 1° incyclodeviation to
21° excyclodeviation) after diagnostic occlusion; the
change was not considered statistically significant (P
= 0.225). Preoperative objective excycloposition was
5.9° ± 6.4 ° (range, 2° incycloposition to 20° excycloposition) before diagnostic occlusion and 6.6° ± 5.9°
(range, 4° incycloposition to 17° excycloposition) after
diagnostic occlusion; die change was not considered
statistically significant (P = 0.538). Preoperative total
objective excycloposition was nearly equally distributed, with 3° on the affected eye and 2.9° on the fellow
eye before diagnostic occlusion and 3.3° on the affected eye and the fellow eye after diagnostic occlusion.
Effect of Surgery
On the first postoperative day without binocular stimulation, subjective excyclodeviation of 1.1° ± 5° (range,
6° incyclodeviation to 15° excyclodeviation) was measured. Objectively, an incycloposition of 1.2° ± 5.3°
(range, 11° incycloposition to 12° excycloposition) was
found. The surgical incyclorotatory effect was 6.3° ±
3.1° subjectively and 7.8° ± 4.3° objectively. Both
changes were considered statistically significant (P <
0.0001). Objective surgical incyclorotation was 6.2° on
the operated eye and 1.6° on the fellow eye.
After 2 days of binocular stimulation, no statistically significant changes were found compared to the
TABLE 2.
Changes of Subjective Cyclodeviation and Objective
Cycloposition and Their Standard Deviations and Significances of
26 Patients After Inferior Oblique Muscle Recession for Unilateral
Strabismus Sursoadductorius (Inferior Oblique Overfunction)
Postoperative
Preoperative
(after diagnostic occlusion) Day 1
Subjective
Difference (°)
Standard deviation (°)
Significance (P)
t value
rf/"value
Objective
Difference (°)
Standard deviation (°)
Significance (P)
I value
rf/" value
Day 3
4 Months
1.1 ex
±3.4
0.225
1.25
21
6.3 in
±3.1
<0.0001
10.39
25
0.2 ex
±2.1
0.647
0.46
25
1.0 ex
±2.3
0.021
2.47
25
0.7 ex
±4.0
0.538
0.63
22
7.8 in
±4.3
<0.0001
9.19
25
0.5 ex
±4.0
0.528
0.64
25
3.7 ex
±3.8
<0.0001
5.57
25
ex = excyclorotation; in = incyclorotation.
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Cyclorotational Changes After Inferior Oblique Recession
409
TABLE 3.
Differences Between Subjective Cyclodeviation and Objective Cycloposition and
Their Standard Deviations and Significances of 26 Patients After Inferior Oblique Muscle
Recession for Unilateral Strabismus Sursoadductorius (Inferior Oblique Overfunction)
Preoperative
Postoperative
Difference (°)
Standard deviation (°)
Significance (P)
t value
df value
Before Diagnostic
Occlusion
/xjier uiagnosnc
Occlusion
Day 1
Day 3
4 Months
+0.4
±5.1
0.838
0.21
21
+0.8
±5.0
0.424
0.81
25
+2.3
±4.9
0.024
2.39
25
+2.0
±5.0
0.049
2.07
25
-0.7
±4.7
0.442
0.78
25
+ = more subjective than objective excyclodeviation; — = less subjective than objective excyclodeviation.
immediate postoperative positions. The mean surgical
incyclorotatory effect dropped by 0.2° ± 2.1° subjectively and by 0.5° ± 4° objectively; P = 0.647 and P =
0.528, respectively.
sidered statistically significant (P = 0.005 and P <
0.0001, respectively).
Long-term Follow-up
Differences Between Subjective and Objective
Data
Four months after surgery, subjective excyclodeviation
increased to 2.3° ± 4.2° (range, 2° incyclodeviation to
15° excyclodeviation). The increase of 1° was statistically significant (P = 0.021). During the same interval,
a marked reduction of the objective surgical incyclorotatory effect was found. Objective cycloposition
changed from 0.7° incycloposition to 3° excycloposition ± 5.8° (range, 4° incycloposition to 19° excycloposition). The 3.7° change was considered statistically
significant (P< 0.0001). The objective incyclorotatory
effect on the unoperated eye disappeared; it had been
2.9° excycloposition both before and 4 months after
surgery. Thus, surgically induced objective long-term
incyclorotation of the operated eye was 2.9°. Surgically
induced subjective long-term incyclorotation was 4°.
Objective and subjective long-term changes were con-
The differences between subjective cyclodeviation and
objective cycloposition at each time of measurement
are listed in Table 3. Except for days 1 and 3 after
surgery, the values were small and not statistically significant. Before surgery, there was 0.4° more excyclodeviation subjectively than objectively without diagnostic occlusion and 0.8° more excyclodeviation subjectively than objectively after diagnostic occlusion.
The differences were not statistically significant (P =
0.838 and P = 0.424, respectively). After surgery, there
was 2.3° more excyclodeviation subjectively than objectively on day 1 and 2° more excyclodeviation subjectively than objectively on day 3. The differences were
considered statistically significant (P = 0.024 and P =
0.049, respectively). Four months after surgery, there
was 0.7° less excyclorotation subjectively than objec-
TABLE 4.
Differences Between Subjective and Objective Surgically
Induced Cyclorotatory Changes and Their Standard Deviations and
Significances of 26 Patients After Inferior Oblique Muscle
Recession for Unilateral Strabismus Sursoadductorius (Inferior
Oblique Overfunction)
Postoperative
Difference (°)
Standard deviation (°)
Significance (P)
I value
df value
Preoperative (after
diagnostic occlusion)
Day 1
Day 3
4 Months
0.4 +ex
±4.2
0.487
0.71
21
1.5 - i n
±3.8
0.053
2.03
25
0.3 - e x
±4.6
0.736
0.34
25
2.7 - e x
±4.0
0.002
3.51
25
+ex = subjectively more excyclorotatory effect than objectively; —ex = subjectively less
excyclorotatory effect than objectively; —in = subjectively less incyclorotatory effect than objectively.
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410
Investigative Ophthalmology & Visual Science, February 1997, Vol. 38, No. 2
excycloposition ("]
7
•
6
•
'A
• sub|ec'ive cyclodeviolion
O objective cycloposition
5.
5
\
•
6.
\
4 \
•
•
3
2
\
V
\A
\
•
X/'
1 *
^r
/
8.
1 2 incyclopotition [*]
preoperative
i
postoperative
i
without with
diogn. occl.
7.
significant changes of objective and subjective
cyclodeviation.
The immediate surgical incyclorotatory effect
was more pronounced objectively than subjectively.
Short-term binocular stimulation for 2 days after
surgery did not significantly influence subjective
cyclodeviation or objective cycloposition.
After 4 months of binocular stimulation, a reduction of the surgical incyclorotatory effect was
found, and it was more pronounced objectively
than subjectively.
The surgically induced long-term incyclorotatory
effect was more pronounced subjectively than
objectively.
day 1
day 3
4 months
FIGURE 3. Change of subjective cyclodeviation and objective
cycloposition in 26 patients after inferior oblique muscle
recession for unilateral strabismus sursoadductorius (inferior oblique overfunction).
tively; the difference was not considered statistically
significant (P = 0.442).
Differences between subjective and objective surgically induced cyclorotatory changes are listed in Table 4. The 0.4° mean difference after diagnostic occlusion before surgery was not considered statistically significant (P = 0.487). Immediately after surgery, the
in cyclorotatory effect was 1.5° stronger objectively
than subjectively. On the alpha = 0.1 level, the difference was not considered statistically significant {P =
0.053). Two days later, there was a difference of 0.3°,
which was considered statistically significant (P =
0.736). Four months after surgery, the reduction of
the surgical incyclorotatory effect was 2.7° stronger
objectively than subjectively; the difference was statistically significant (P = 0.002).
Summary of Results
The results can be summarized as follows:
1. A significant difference between subjective and
objective cycloposition was seen early after surgery.
2. A significant difference between subjective and
objective cyclorotatory changes was found immediately after surgery and on long-term follow-up.
3. Preoperative objective excycloposition was nearly
equally distributed between the affected and the
unaffected eye.
4. Diagnostic occlusion did not show statistically
DISCUSSION
It was the aim of this study to measure subjective and
objective cyclorotatory changes in patients with strabismus sursoadductorius (inferior oblique overfunction)
undergoing inferior oblique recession. These changes
were induced by interruption of binocularity, by surgery, and by short- and long-term binocular stimulation after surgery. The purpose of these investigations
was to determine motor and sensory elements of
cyclorotatory changes.
For the assessment of subjective cyclodeviation,
we used the tangent scale devised by Harms.10 It is one
of the standard methods in Germany for simultaneous
assessment of horizontal, vertical, and cyclotorsional
angles of squint in the nine positions of gaze8 in patients who do not exclude the image of the nonfixating eye. Examination of objective cycloposition was
achieved by fundus cyclometry, based on measurement of objective bulbar rotation by means of fundus
photography. Fundus cyclometry offers several advantages over fundus photography for the assessment of
cycloposition: There is no need for pupil dilation because of infrared laser light, and, hence, further orthoptic examination is not impaired, which makes it
more convenient for the patient; no photographic material has to be processed, and, therefore, results are
available immediately; and computerized calculation
of the angle of torsion is precise. The method proved
to be reliable and has been discussed in detail elsewhere.12'13
As described by Kertesz and Jones4 and by Kert1
esz, "'' the size and complexity of the fixation target
must be considered because they affect both cyclofusion and objective cycloposition under binocular conditions. In our study, however, the assessment of subjective cyclodeviation was performed under complete
dissociation with a dark red glass, and the measurement of objective cycloposition was made monocularly
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Cyclorotational Changes After Inferior Oblique Recession
with the nonfixating eye patched. For that reason,
there was no fusion, and objective cycloposition was
not affected by the different sizes of the fixation targets. On subjective measurement, space constancy,
which also can affect cyclotorsional measurements,
was interrupted by the dark red glass, which excluded
anything to the fixating eye but the streak of light.
On fundus cyclometry, there was no space constancy
because nothing but the fixation target was visible.
For the same reasons, no visual context could have
influenced cycloposition.
On the assessment of preoperative subjective
cyclodeviation using the Harms tangent scale, the affected eye is situated in primary position when fixating
and in vertical deviation when not fixating, whereas
on fundus cyclometry each eye, is measured in primary
position. Because it is known that a change of vertical
position can affect cyclodeviation, we compared preoperative subjective cyclodeviation on fixation with
the affected eye to that on fixation with the nonaffected eye. No significant differences between cyclodeviations on either fixation were found. We concluded
that vertical deviation to the extent present in our
patients did not significantly affect cyclodeviation.
Thus, comparison of preoperative subjective cyclodeviation to preoperative objective cycloposition and of
preoperative subjective cyclodeviation to postoperative subjective and objective cycloposition was possible. Mean hypertropia of the affected eye in our patients was 6° before surgery and 1° after surgery; horizontal deviation was not present. These results are in
accord with Boergen,9 who reported a mean vertical
change of 5° and no horizontal change in 28 patients
after inferior oblique muscle recession.
When interpreting the data, intraindividual variations in the measurement of cyclodeviation and cycloposition must be considered. Apart from possible
spontaneous torsional eye movements as described by
Roessler,16 Herzau found intraindividual fluctuations
of unilateral objective cycloposition up to 3.5°.6 Kraft
reported intraindividual variations of subjective cyclodeviation up to 70.17 The high levels of standard deviation in this study reflect these variations.
The observation of preoperative equal distribution of objective excycloposition between the affected
and the fellow eye is in accord with Bixenman, who
found that some patients with unilateral superior
oblique palsy have a greater degree of objective excyclotorsion in the normal than in the paretic eye.1
Olivier18 reported 15 of 60 patients with unilateral
superior oblique palsy who had subjective excyclotropia of the nonparetic eye. These patients habitually
fixated with the paretic eye. Olivier interpreted this
phenomenon as ". . . the result of a monocular sensorial adaptation to the cyclodeviation by means of a
411
reordering of the spatial response of retinal elements
along new horizontal and vertical meridians."18
The effect of preoperative diagnostic occlusion on
cyclodeviation was not statistically significant. In some
patients, however, there was a slight increase of excyclodeviation that could be interpreted in terms of
cyclofusional mechanisms under binocular conditions
interrupted by diagnostic occlusion. At this time, we
cannot explain why the surgically induced incyclotorsional effect was greater objectively than subjectively
one day after surgery without binocular stimulation
nor why an objective incyclorotatory effect was found
on the unoperated eye.
The observed long-term reduction of the surgically induced incyclorotatory effect was more pronounced objectively than subjectively. What could be
the cause of postoperative subjective reduction of surgically induced incyclotorsion? Ruttum19 described a
sensory reorientation in patients with congenital and
acquired cyclotropia that prevents awareness of tilting
of the environment. If this compensatory mechanism
is no longer necessary, sensory reorientation could
give rise to sensory excyclotorsion and, thereby, to
subjective weakening of the surgically induced incyclotorsional effect. This suggestion, however, is not plausible because on average there was still subjective excyclodeviation immediately after surgery; there was no
reason for cessation of the compensatory mechanism.
In patients with postoperative subjective overcorrection, this phenomenon could be based on cyclofusional mechanisms described by von Noorden,2 Herzau,1'1
and Boergen.20 If there was no overcorrection, weakening of the objective surgical effect could be interpreted by a cessation or reduction of preoperatively required binocular compensatory innervation, as discussed by Rolling.8 This, however, does not explain the
difference between objective and subjective reduction,
which led to a long-term incyclorotatory effect of 3.6°
objectively compared to 5.1° subjectively (related to
the preoperative examination after diagnostic occlusion). Figure 3 makes us question why objective and
subjective rotational changes behave nearly parallel
up to the third day after surgery but show such a
marked difference after 4 months. Analysis of individual data, such as looking at patients with extreme variations or comparing preoperative compensation of
cyclophoria, did not provide an explanation. The answer appears to be sensory cyclofusion as described by
Herzau6 and von Noorden21; it partially compensates
the postoperative motor weakening of the objective
surgical incyclorotatory effect. In this study, the
amount of sensory cyclofusion equaled the difference
between subjective and objective torsional change.
Results of this study improved our knowledge of
subjective and objective cyclorotatory behavior before
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Investigative Ophthalmology & Visual Science, February 1997, Vol. 38, No. 2
and after surgery, and this knowledge is important for
the management of oblique muscle disorders. Because
long-term weakening of the surgical incyclorotatory
effect after inferior oblique muscle recession has been
confirmed, we advise refraining from early correction
if an immediate postoperative overeffect is present.
Key Words
cyclodeviation, fundus cyclometry, inferior oblique muscle
surgery, objective-subjective, strabismus, torsional changes
Acknowledgments
The authors thank Prof. Dr. G. Rolling, Orthoptic Department, Eye Hospital, Ruprecht-Rarls—University (Heidelberg, Germany) for his support concerning the interpretation of the results.
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