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Fifteen-Year Outcome of Surgery for the Near Angle in Patients With Accommodative Esotropia and a High Accommodative Convergence to Accommodation Ratio
Burton J. Kushner, MD
Arch Ophthalmol. 2001;119:1150-1153.
ABSTRACT
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Objective To determine the 15-year outcome of patients with partly accommodative
esotropia with a high accommodative convergence to accommodation (AC/A) ratio
who underwent surgery based on the angle of esotropia at one-third meter while
wearing full hyperopic correction.
Methods A retrospective chart review to determine the 15-year outcome of 25
patients whose 6-month outcome had been previously reported as part of a prospective,
randomized, masked clinical trial. All patients had partly accommodative esotropia
with a high AC/A ratio and underwent surgery based on their esotropia at one-third
meter while wearing full-distance optical correction.
Results Fifteen years after surgery, 19 of the 22 patients for whom follow-up
data are available had between 0 and less than 10 prism diopters of esotropia.
Only 6 of the 19 needed to continue to wear optical correction to maintain
satisfactory alignment; however, 8 more needed spectacles for visual purposes.
Only 1 patient needed to use a bifocal add to have satisfactory alignment
at one-third meter. All patients showed some degree of sensory fusion, with
4 obtaining 40 seconds of stereopsis and another 8 obtaining between 60 and
200 seconds of stereopsis.
Conclusion Surgery for the near angle obtained with patients wearing their full
hyperopic distance correction provides excellent motor and sensory results
in patients with partly accommodative esotropia with a high AC/A ratio.
INTRODUCTION
HISTORICALLY, the surgical management of partly accommodative esotropia
has been to operate based on the angle of misalignment obtained at 6 m with
the patient wearing his or her full cycloplegic refractive correction.1-2 It has been known for many years, however,
that if patients have a high accommodative convergence to accommodation (AC/A)
ratio and if the near deviation exceeds the distance deviation by more than
10 prism diopters (PD), surgery based on the misalignment at 6 m will result
in an unacceptably high number of surgical undercorrections.1, 3-5
For many years, Parks1 has recommended adding
1 mm to the recession of each medial rectus if a high AC/A ratio is present.
Even using this 1-mm augmentation as recommended by Parks, I experienced a
high number of surgical undercorrections in this patient population and observed
that a large number of these patients needed to continue wearing a bifocal
to control their near deviation after surgery.4
This led me and my colleagues to conduct a prospective, randomized clinical
trial of 2 alternative treatment modalities for the management of patients
with accommodative esotropia with a high AC/A ratio, the results of which
were published in 1987.4 In that study, one
treatment group received medial rectus recessions based on the angle of misalignment
at 6 m while wearing their full cycloplegic spectacle correction. In addition,
the recession was combined with posterior fixation of each medial rectus muscle
12- to 14-mm posterior to the insertion. The other group underwent bilateral
medial rectus recessions based on a formula that was augmented to take into
account the amount by which near deviation exceeded the distance deviation.
The amount of bilateral medial rectus recession was determined using standard
surgical tables based on the size of the deviation obtained at 6 m with the
patient wearing full cycloplegic spectacle correction. That number was then
augmented by adding 1 mm to each medial rectus recession if the near deviation
exceeded the distance by 10 PD, 1.5 mm if the near deviation exceeded the
distance by 15 PD, and 2 mm if the near deviation exceeded the distance by
20 PD. Because my standard surgical formula for medial rectus recessions increases
in increments of 0.5 mm for each 5 PD of deviation, this augmented surgical
formula for treating high–AC/A ratio esotropia turns out, in fact, to
be exactly the same as operating on the near deviation (although I did not
realize it at the time the study was conducted).
A satisfactory outcome in that study (described subsequently5) was defined as less than 10 PD of esotropia 6 months
after surgery; any exotropia was considered unsatisfactory. I found that patients
treated with the augmented surgical formula based on the near deviation had
significantly better results than those treated with medial rectus recessions
combined with posterior fixation. All 25 of the augmented recession group
had satisfactory alignment compared with 17 (80%) of 21 of the patients undergoing
posterior fixation surgery (P = .02,  2 test) at the 6-month postsurgery outcome date. Also, 84% of the augmented
recession group was able to discontinue the use of a bifocal add after surgery
compared with 57% of those who received medial rectus recessions combined
with posterior fixation (P = .04, 2
test). That study was limited to patients who initially had more than 10 PD
of manifest esotropia at 6 m while wearing their full cycloplegic spectacle
correction and excluded patients who were amblyopic at the time of surgery.
Although at the 6-month outcome determination date, 4 of the 25 patients in
the augmented medial rectus recession group were still in need of a bifocal,
most of them were able to tolerate a reduction in the strength of their bifocal
add after surgery. I concluded that this augmented medial rectus recession
surgical formula (in effect operating for the near deviation obtained with
full hyperopic correction in place) was preferable to medial rectus recessions
combined with posterior fixation. The purpose of this study is to give 15-year
follow-up data for the patients who were included in my prior short-term outcome
report and were treated with the augmented medial rectus recession formula.
A 15-year follow-up outcome date was chosen because all 25 patients in that
initial study group would be 16 years or older by 15 years after surgery.
By this age, most of the loss of hyperopia or normalization of the AC/A ratio
that occurs in childhood would have been completed.6-10
SUBJECTS AND METHODS
The subjects were patients in the augmented surgery group from the previously
reported prospective randomized clinical trial.4
Descriptive characteristics of the patients are available in detail in the
previous report. All had undergone surgery for the nonaccommodative component
of a partly accommodative esotropia associated with a high AC/A ratio as previously
defined. This present study design consists of a retrospective chart review.
The outcome determination date for each patient was the first examination
obtained 15 years after surgery (range, 15-17 years). For patients
who were lost to follow-up, information obtained from their last examination
was noted and analyzed separately. In several cases, patients were under the
care of other pediatric ophthalmologists who provided me with the necessary
data. Specific information obtained was the deviation at 6 and one-third meter,
stereopsis (Titmus test), the need of spectacles for maintaining ocular alignment,
the need of spectacles for visual clarity (eg, myopia), presence of simultaneous
perception with the Bagolini lenses, recurrence of amblyopia (all patients
had been free of amblyopia at the time of surgery), and fusion with the Worth
4-dot test. A satisfactory outcome was defined as less than 10 PD of esotropia
as determined by the alternate prism and cover test; an exotropia of any size
was considered unsatisfactory. In addition, any patient in whom hyperopic
correction needed to be reduced for treating a consecutive exotropia was also
considered to have an unsatisfactory outcome, because such patients have been
shown to have poor long-term stability.11 Finally,
any patient undergoing a reoperation for esotropia or exotropia was considered
to have an unsatisfactory outcome.
RESULTS
Of the 25 patients who initially comprised the augmented surgery treatment
group, 18 were still under my care for the 15-year outcome examination. An
additional 4 patients were under the care of other pediatric ophthalmologists
who provided me with the necessary data. Three patients were lost to follow-up.
The 15-year outcome results of the 22 patients for whom data are available
are presented in Table 1. With
respect to motor alignment, the outcome data are presented in several categories,
depending on the patients' need of optical correction. The satisfactory category
1 group consisted of patients who had satisfactory alignment but needed to
continue to wear hyperopic optical correction (spectacles or contact lenses)
to maintain that alignment. All but 1 of the 6 patients in that category had
more than +2.50 diopters (D) of hyperopia before surgery. The satisfactory
category 2 group consisted of patients who did not need to wear optical correction
for maintaining satisfactory motor alignment. They did, however, need to continue
wearing optical correction for visual purposes (to correct myopia, astigmatism,
or anisometropia). Patients in the satisfactory category 3 group had satisfactory
alignment and were visually comfortable without optical correction. Only 1
(5%) of the 22 patients still required a bifocal add of +1.25 D to maintain
satisfactory ocular alignment at a near distance. An additional patient was
found to have a reduced near point of accommodation and continued to wear
a low plus bifocal add (+1.50 D) for visual clarity when reading; however,
his ocular alignment was satisfactory at one-third meter without the bifocal.
Of the 3 patients with unsatisfactory alignment, 1 had a recurrent esotropia
and underwent additional horizontal surgery. This patient was previously described
as having satisfactory alignment at the 6-month outcome date, but developed
an esotropia several years after surgery.4
Another patient had an 8-PD exotropia at 6 and one-third meter, which had
been stable for more than 5 years. The third patient had 4 D of hyperopia
before surgery. By the 6-month outcome date, she met the criteria for a satisfactory
outcome; however, she needed to discontinue use of her hyperopic correction
to have satisfactory alignment. In my initial report,4
I indicated that this patient should not be considered a success because of
concern she was at risk for a late consecutive exotropia.11
In fact, she did show an increasing exotropia, which necessitated additional
horizontal surgery. Another 3 patients have undergone additional surgery to
treat inferior oblique overaction. Three other patients required resumption
of amblyopia treatment some point after surgery; however, none of the patients
were amblyopic by the time of their 15-year outcome evaluation.
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Surgical Results for 22 Patients 15 Years After Surgery
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The 3 patients who were lost to follow-up were last examined by me at
1, 3, and 4 years after surgery, respectively. Two of them had satisfactory
motor alignment when last examined. The third (last examined 4 years after
surgery) had a 6-PD exotropia that had been stable for the previous 2 years.
COMMENT
The study shows that surgery based on the near angle (determined while
wearing full hyperopic correction) is an effective treatment for partly accommodative
esotropia associated with a high AC/A ratio. Although initially after surgery
some patients may still need to continue wearing a bifocal add, the additional
optical correction for near gaze can be gradually decreased during the subsequent
years. Most patients will be able to discontinue the use of a bifocal add
by the end of adolescence. These results are consistent with the reports3, 12-14 of
others who have found success with surgery for the near angle in this population.
In preparing the protocol for my previously published clinical trial
for treating this patient population, I conducted a retrospective chart review
of patients I had operated on between 1974 and 1980. That review resulted
in an interesting observation regarding the response to surgery in patients
with partly accommodative esotropia associated with a high AC/A ratio.4 It appeared that the response of the distance deviation
of patients was inversely related to the size of the AC/A ratio. For example,
if 2 hypothetical patients each had a 20-PD deviation at 6 m, but 1 had a
30-PD deviation at one-third meter and the other a 45-PD deviation, both would
receive the same amount of surgery based on Park's recommendation (the protocol
I had previously been following).1 Surgery
in these 2 hypothetical patients would consist of operating for the distance
angle of 20 PD and adding 1 mm to each medial rectus recession because of
the high AC/A ratio. During my chart review, I observed that the hypothetical
patient with the 45-PD near deviation (and hence the higher AC/A ratio) would
routinely experience a smaller reduction in the distance deviation of 20 PD
than would the other patient with the near deviation of 30 PD. This led me
to base my surgical approach on the size of the AC/A ratio, which is reflected
in the near deviation.
Interestingly, in 6 of the patients in this series, one or both medial
rectus muscles were recessed to a point greater than 10.5 mm from the limbus
(11 mm in 2 patients, 11.5 mm in 3 patients, and 12 mm in 1 patient). None
of these patients developed a consecutive exotropia.
For the present study, I did not use the common outcome criteria for
success as ±10 PD from orthotropia; any exotropia was considered unsuccessful
in this series. I chose that more rigid criterion because that was the one
I used in the short-term outcome report on this group of patients.4-5 Also, it has been shown that a small-angle
exotropia is not as stable an outcome for surgery for esotropia as a small-angle
esotropia.15
It is noteworthy that none of the patients in my series underwent prism
adaptation. Some comments about the role of prism adaptation in this patient
population deserve mention. In a frequently cited study, Kutschke and coworkers16 concluded that prism adaptation for the near angle
in patients with high AC/A ratio esotropia would improve the surgical outcome.
That study, however, compared prism adaptation of the near angle (and surgery
based on that adapted angle in prism responders) with surgery based on the
distance angle with no augmentation for the high AC/A ratio. My experience,
and that of others, suggests that surgery based on the distance angle alone
would be inadequate in treating this patient population.1, 3-5
Perhaps the improved results obtained by Kutschke and coworkers in their prism
adaptation group were merely a result of the fact that they were operating
for the near angle rather than the fact that they were using prism adaptation.
On the other hand, there is something intuitively appealing about the concept
of using prism adaptation for the near angle of misalignment in this patient
population. A reasonable concern is that patients might be overcorrected at
6 m if surgery is based on the near angle, if the near angle substantially
exceeds that of the distance angle. At first glance it seems logical that
prism adaptation for the near angle might help predict which patients are
at risk for developing a consecutive exotropia at distance viewing if surgery
is performed for the near angle. Theoretically, if patients undergoing prism
adaptation for the near angle do not adapt by overcoming the immediate exotropia
that they typically manifest at distance viewing through the prisms, then
they might not be expected to overcome an initial overcorrection at distance
viewing if surgery is performed for the near angle.
As appealing as this concept is, however, some clinical experience contradicts
its validity. Kutschke and coworkers 16 found
that 20% of the patients who underwent prism adaptation for the near angle
were "nonresponders" (they did not overcome the distance exotropia induced
by the prism). These patients would be expected to have a surgical overcorrection
at distance viewing when surgery is performed for the near angle if, in fact,
the response to prism adaptation was predictive of a surgical overcorrection
(based on the aforementioned hypothetical reasoning). Extrapolating from their
data, one would expect a 20% overcorrection rate in this and other series
of patients who received surgery for the near angle and did not undergo prism
adaptation.3, 12-14
In fact, the overcorrection rates in these series were substantially smaller.
Also, the reasoning outlined herein as theoretical justification for the role
of prism adaptation would suggest that patients with high AC/A ratio esotropia
would experience an initial surgical overcorrection at distance viewing if
surgery were performed for the near angle, and then those with good fusion
potential (presumably responders to prism adaptation) would compensate for
it by ultimately controlling that distance exotropia. In fact, patients in
this series routinely did not show an initial overcorrection at distance viewing
even if evaluated immediately on emergence from anesthesia after the strabismus
surgery. The role of prism adaptation for the near angle in patients with
high AC/A ratio accommodative esotropia has yet to be determined.
This study needs to be viewed in light of its limitations. It is important
to stress that all of the patients in this study met strictly defined inclusion
criteria. Patients with amblyopia at the time of surgery, those who underwent
simultaneous oblique muscle surgery, or those who received vertical transposition
of the medial rectus muscles to treat an A or V pattern were excluded. Caution
is urged in extrapolating results from this series to the patient population
that was excluded. Also, all of my patients had a manifest deviation of at
least 10 PD at 6 m while wearing their full hyperopic spectacle correction.
This study did not include patients who had satisfactory ocular alignment
at distance but needed a bifocal add for near alignment. One similarly cannot
extrapolate results from this study to patients who have good ocular alignment
with bifocals but want to stop using those bifocals. Also, none of the patients
in this study who achieved satisfactory ocular alignment did so as a result
of intentionally cutting their hyperopic correction to treat a surgical overcorrection.
Past studies11 have shown that patients treated
in this manner do not show a satisfactory long-term outcome. Finally, there
were 3 patients (12%) in the study who were lost to follow-up. I believe this
represents a relatively small amount of unavailable data for a study with
a 15-year outcome date. Nevertheless, all patients who are lost to follow-up
somewhat diminish the power of the conclusions of any study.
In conclusion, it appears that surgery for the near angle of patients
with a partly accommodative esotropia (as determined while wearing full hyperopic
spectacle correction) has a high likelihood of producing satisfactory ocular
alignment with stability and the discontinuation of the need of a bifocal
add.
AUTHOR INFORMATION
Accepted for publication February 1, 2001.
This study was supported by an unrestricted grant from Research to Prevent
Blindness Inc, New York, NY, and the Wisconsin Lions Foundation, Stevens Point,
to the Department of Ophthalmology and Visual Sciences, University of Wisconsin,
Madison.
Corresponding author: Burton J. Kushner, MD, Department of Ophthalmology
and Visual Sciences, UW Hospital and Clinics, 2870 University Ave, Suite 206,
Madison, WI 53705 (e-mail: bkushner{at}facstaff.wisc.edu).
From the Department of Ophthalmology and Visual Sciences, University
of Wisconsin, Madison.
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