Journal of Pediatric Ophthalmology and Strabismus

Original Article Supplemental Data

Torsional Changes After Vertical Transposition of Horizontal Recti in V-pattern Exotropia Without Oblique Dysfunction

Sara Maher, MD; Dina El-Fayoumi, MD; Ahmed Awadein, MD; Lobna Khazbak, MD

Abstract

Purpose:

To evaluate pattern collapse and torsional changes following vertical transposition of horizontal recti in patients with V-pattern exotropia and no oblique dysfunction.

Methods:

A prospective study was performed on patients who had V-pattern exotropia and no oblique dysfunction. Lateral recti were transposed upward half-tendon width in V-pattern of 25 prism diopters (PD) or less (n = 14) and full-tendon width in V-pattern of greater than 25 PD (n = 10). Amblyopic patients had unilateral lateral rectus recession with upward transposition and medial rectus resection with downward transposition (n = 8). Ductions, versions, pattern strabismus, disc foveal angle, and astigmatic axis were analyzed before and 6 months after surgery.

Results:

In the 32 patients (21 females), the mean age was 8.25 ± 1.23 years. Only amblyopic patients showed preoperative fundus extorsion (mean disc foveal angle = 16.9°, P < .01). Mean pattern collapse was 13.1 ± 3.8 PD with half-tendon transposition, 35.6 ± 13.7 PD with full-tendon transposition, and 13.8 ± 7.9 PD in the unilateral group. Pattern collapse increased gradually so that pattern normalization occurred after 6 months in most patients. There was a statistically significant correlation between the preoperative V-pattern and the magnitude of pattern collapse after surgery (r = 0.80, P < .01). There were no significant changes in the mean disc foveal angle (< 0.5°) or axis of astigmatism (< 0.5°) in all three groups.

Conclusions:

Vertical transposition of horizontal muscles can correct V-pattern exotropia, although the effect might not be immediate. Torsional changes are minimal. Amblyopic patients with V-pattern exotropia showed a preoperative extorsion that did not change after surgery.

[J Pediatr Ophthalmol Strabismus. 2019;56(2):107–115.]

Abstract

Purpose:

To evaluate pattern collapse and torsional changes following vertical transposition of horizontal recti in patients with V-pattern exotropia and no oblique dysfunction.

Methods:

A prospective study was performed on patients who had V-pattern exotropia and no oblique dysfunction. Lateral recti were transposed upward half-tendon width in V-pattern of 25 prism diopters (PD) or less (n = 14) and full-tendon width in V-pattern of greater than 25 PD (n = 10). Amblyopic patients had unilateral lateral rectus recession with upward transposition and medial rectus resection with downward transposition (n = 8). Ductions, versions, pattern strabismus, disc foveal angle, and astigmatic axis were analyzed before and 6 months after surgery.

Results:

In the 32 patients (21 females), the mean age was 8.25 ± 1.23 years. Only amblyopic patients showed preoperative fundus extorsion (mean disc foveal angle = 16.9°, P < .01). Mean pattern collapse was 13.1 ± 3.8 PD with half-tendon transposition, 35.6 ± 13.7 PD with full-tendon transposition, and 13.8 ± 7.9 PD in the unilateral group. Pattern collapse increased gradually so that pattern normalization occurred after 6 months in most patients. There was a statistically significant correlation between the preoperative V-pattern and the magnitude of pattern collapse after surgery (r = 0.80, P < .01). There were no significant changes in the mean disc foveal angle (< 0.5°) or axis of astigmatism (< 0.5°) in all three groups.

Conclusions:

Vertical transposition of horizontal muscles can correct V-pattern exotropia, although the effect might not be immediate. Torsional changes are minimal. Amblyopic patients with V-pattern exotropia showed a preoperative extorsion that did not change after surgery.

[J Pediatr Ophthalmol Strabismus. 2019;56(2):107–115.]

Introduction

Pattern strabismus is defined as a significant difference between the horizontal angle of strabismus in up and down gaze. Pattern strabismus is usually associated with oblique muscle dysfunction, but it can also be caused by abnormal innervation of the horizontal recti or abnormal muscle pulleys or in association with craniofacial abnormalities.1–3

A clinically significant V-pattern exotropia is defined as 15 prism diopters (PD) or greater exotropia in up gaze than in down gaze. V-pattern esotropia is usually associated with inferior oblique overaction, and in such cases weakening of the inferior oblique muscle is usually used to improve the pattern.4 However, in the absence of oblique dysfunction, upward transposition of the lateral recti can be done to correct the V-pattern.5 Half-tendon width transposition is often used in small pattern strabismus, whereas full-tendon width vertical displacement is usually reserved for larger pattern strabismus.6 However, little is known about the exact amount of pattern collapse after such procedures, with no reported prospective studies.

The rationale for vertical transposition is that the strength of a horizontal rectus muscle is decreased when the eye is vertically rotated in the direction of transposition.2 So after upward transposition of the lateral recti, the lateral rectus muscle becomes less effective as an abductor in up gaze and more effective as an abductor in down gaze, resulting in an improvement of V-pattern. Nevertheless, this vertical transposition may induce torsional changes that would worsen the pattern.7 For example, in V-pattern exotropia, upward transposition of the lateral recti may cause extorsion of both globes with a resultant temporal rotation of the superior rectus muscle path and nasal rotation of the inferior rectus muscle path, which might worsen the pattern.

The aim of our study was to calculate the magnitude of pattern correction after half- and full-tendon width vertical transposition of horizontal recti in patients with V-pattern exotropia with no oblique muscle dysfunction, and to determine whether there are induced torsional changes in the fundus or axis of astigmatism that might affect the pattern collapse.

Patients and Methods

The study protocol was approved by Cairo University Research Ethics Committee. The study and data collection conformed to all local laws and were compliant with the principles of the Declaration of Helsinki. A prospective study was performed with patients in Cairo University Hospital who presented with V-pattern exotropia and no oblique muscle dysfunction from August 2015 to March 2017.

Patients with V-pattern exotropia with no oblique dysfunction, in whom the exotropia increased by 15 PD or more in up gaze than in down gaze, were included in the study. Patients with vertical deviation in any position of gaze, superior oblique muscle deficit or underaction, Duane syndrome, Brown syndrome, craniofacial anomalies, or prior eye muscle surgery were excluded from the study. In addition, patients with perceivable tightness of the inferior oblique muscles on exaggerated traction testing8 during surgery were excluded from the study.

A detailed examination was done for all patients during the initial evaluation and at each follow-up visit. Cycloplegic refraction was done using cyclopentolate 1% instilled two times 5 minutes apart, followed by refraction after 45 minutes. Patients were prescribed spectacles prior to surgical intervention if they had hyperopia of greater than 2.00 diopters (D), astigmatism of greater than 1.00 D, or any degree of myopia, and were reevaluated 1 month later. Hypermetropia was partially corrected after reducing 1.00 D from the cycloplegic refraction. Astigmatism and myopia were fully corrected. The ductions and versions were analyzed in all secondary and tertiary positions of gaze. During evaluation of oblique dysfunction, the examiner covered the adducting eye to make sure that the abducting eye was the fixing eye and to allow the adducting eye to manifest any oblique dysfunction if present.

The prism and alternating cover test was used to measure the angle of horizontal misalignment. Measurement of the angle was done for both distance and near, but only the distance angle was used for statistical analysis. The angle of horizontal misalignment was also measured in side gazes and in straight up and down gazes. Measurement was done with the patients wearing their spectacle correction and with the accommodation controlled with appropriate accommodative targets. Measurement of the angle of deviation in up and down gazes was done by tilting the head 25° down and up, respectively, with the patient fixing on a distance target. Degree of head tilt was checked using a goniometer. The amount of pattern strabismus was defined as the difference between the angles of horizontal misalignment in up and down gazes.

The degree of fundus torsion and the corneal astigmatism were evaluated before and 6 months after surgery.

Fundus torsion was evaluated through fundus photography using a TRC-50DX retinal camera (Topcon Medical System, Tokyo, Japan). Fundus photographs were taken through a dilated pupil while ensuring that the patient's head was well aligned with the side marks and with the patient fixing internally at the center of the cross marks. The degree of fundus torsion was measured from the disc foveal angle. The disc foveal angle was calculated from a well-focused single still photograph using IMAGEnet software (Topcon Medical System). Two lines were drawn: one straight line passing through the center of the disc and another line passing between the center of the disc and the fovea. The disc foveal angle was defined as the angle between those two lines.

Corneal astigmatism was studied using Pentacam tomography (Oculus Optikgeräte, Wetzlar, Germany). The magnitude of astigmatism and steep axis of the cornea were automatically calculated by the manufacturer's software from the anterior sagittal curvature map. During capturing of the corneal imaging, the photographer ensured the horizontal alignment of the patients' eyes with the side marks of the chin rest attachment. To ensure there was no missing information during image capturing, only captured images with acceptable quality specification were used.8

An exaggerated traction test was done to assess the tightness of oblique muscles prior to surgery in all patients.9 In all patients, the amount of lateral rectus recession and/or medial rectus resection performed was based on the distance angle of deviation in primary position. Bilateral half-tendon width upward transposition of both lateral recti was done if the pattern was up to 25 PD and full-tendon width upward transposition was done if the pattern was greater than 25 PD. In patients with unilateral amblyopia, unilateral lateral rectus recession with half-tendon width upward transposition and medial rectus resection with half-tendon width downward transposition was done irrespective of the amount of pattern because limited data are available on the effect of full-tendon transposition of both medial and lateral rectus muscles in V-pattern exotropia. All surgeries were done by one surgeon (SM).

In all patients, the lateral rectus muscle was exposed and hooked through a superotemporal fornix approach, whereas the medial rectus muscle was exposed through an inferonasal approach. For lateral rectus muscle recession, the muscle was secured with 6-0 polyglactin (Vicryl; Ethicon, Somerville, NJ) sutures. In half-tendon width transposition, the lower scleral suture was directed to enter the sclera, at the desired amount of recession, posterior to the middle of the original muscle insertion, and directed superiorly parallel to the muscle stump for approximately 4 mm to exit the sclera at the same distance posterior to the upper pole of the muscle stump. The upper scleral suture was directed to enter the sclera approximately 4 to 5 mm superior to the exit site of the lower suture while preserving the spiral of Tillaux and then directed to exit the sclera close to the exit site of the lower suture in a crossing sword fashion.

Full-tendon transposition was done in a similar way, but the lower suture entered the sclera posterior to the upper pole of the muscle insertion and was directed upward for 4 mm and the upper suture was placed to enter the sclera approximately 4 to 5 mm superior to the exit site of the lower suture, while preserving the spiral of Tillaux in both suture paths. For medial rectus resection, the muscle was secured with 6-0 polyglactin sutures just behind the desired amount of resection. Resection was then performed and the muscle was then sutured to the sclera at the original insertion, with both sutures centered to exit the sclera at the lower pole of the original muscle insertion (Figure 1).

Schematic drawing showing lateral recession with half-tendon width upward transposition (top left), lateral rectus recession with full-tendon width upward transposition (top right), and medial rectus resection with half-tendon width downward transposition (bottom).

Figure 1.

Schematic drawing showing lateral recession with half-tendon width upward transposition (top left), lateral rectus recession with full-tendon width upward transposition (top right), and medial rectus resection with half-tendon width downward transposition (bottom).

A successful outcome was defined as esophoria of less than 4 PD to exophoria/tropia of 8 PD or less in the primary position. Pattern collapse was defined as reduction to less than 10 PD difference in deviation between supraversion and infraversion. Any degree of “A” pattern after surgery was considered an overcorrection.

Data at 6 months postoperatively were used for statistical analysis. Patients who did not complete 6 months of follow-up were excluded from the analysis. Comparison between the preoperative and postoperative data was done using the paired t test for continuous variables and the Wilcoxon signed-rank test for scores and ranks. Differences between the three groups were evaluated using analysis of variance for continuous variables and the Kruskal–Wallis test for ranks and scores. Correlation between different variables was done using Pearson's correlation coefficient. Statistical analysis was performed using SPSS for Windows software (version 17; SPSS, Inc., Chicago, IL).

Results

A total of 39 patients with V-pattern and no oblique dysfunction were identified. Six patients were excluded due to prior eye muscle surgery and 1 patient was excluded due to hypertropia of one eye in the primary position. All remaining 32 patients completed 6 months of follow-up after surgery. The mean age at the time of surgery was 8.25 years (range: 3 to 25 years). Fourteen patients underwent bilateral lateral rectus recession with half-tendon upward transposition, 10 patients had bilateral lateral rectus recession with full-tendon upward transposition, and 8 patients had unilateral recession-resection with half-tendon opposite transposition. A summary of the preoperative patient characteristics is shown in Table 1.

Preoperative Characteristics of the Studied Patients

Table 1:

Preoperative Characteristics of the Studied Patients

The mean amount of lateral rectus recession performed was 6.8 ± 0.8 mm (range: 5 to 8.5 mm). The mean amount of medial rectus resection performed in the recession-resection group was 6.5 ± 0.3 mm (range: 6 to 7 mm). None of the patients demonstrated perceivable tightness of the inferior oblique muscle on exaggerated traction testing.

The mean preoperative angle of deviation in the primary position was 32 ± 10 PD (range: 15 to 45 PD), whereas the mean postoperative angle of deviation in the primary position was 2 ± 9 PD (range: 10 PD of exotropia to 25 PD of esotropia).

Orthophoria within 8 PD in the primary position was achieved in 24 patients (75%). The success rate was slightly better in the recession-resection group (P = .075). Six patients had undercorrection with residual exotropia of greater than 8 PD, whereas 2 patients were overcorrected with esotropia of 25 PD. The mean preoperative pattern value was 26 ± 8 PD (range: 15 to 45 PD) and the mean postoperative pattern value was 4 ± 10 PD (range: 25 PD A-pattern to 2 PD V-pattern). The average pattern corrected was 11.7 PD for half-tendon transposition, 35.6 PD for full-tendon transposition, and 14 PD for unilateral recession-resection with opposite transposition (Figures AC, available in the online version of this article).

Top panels show preoperative photographs of a patient with V-pattern exotropia with no oblique dysfunction. Bottom panels show improvement of the V-pattern 6 months after bilateral lateral rectus recession 5 mm with half-tendon upward transposition.

Figure A.

Top panels show preoperative photographs of a patient with V-pattern exotropia with no oblique dysfunction. Bottom panels show improvement of the V-pattern 6 months after bilateral lateral rectus recession 5 mm with half-tendon upward transposition.

Top panels show preoperative photographs of a patient with large V-pattern exotropia with no oblique dysfunction. Bottom panels show improvement of the V-pattern 6 months after bilateral lateral rectus recession 5 mm with full-tendon upward transposition.

Figure B.

Top panels show preoperative photographs of a patient with large V-pattern exotropia with no oblique dysfunction. Bottom panels show improvement of the V-pattern 6 months after bilateral lateral rectus recession 5 mm with full-tendon upward transposition.

Top panels show preoperative photographs of a patient with V-pattern exotropia with no oblique dysfunction. Bottom panels show improvement of the V-pattern 6 months after right lateral rectus recession with half-tendon upward transposition and right medial rectus resection with half-tendon downward transposition.

Figure C.

Top panels show preoperative photographs of a patient with V-pattern exotropia with no oblique dysfunction. Bottom panels show improvement of the V-pattern 6 months after right lateral rectus recession with half-tendon upward transposition and right medial rectus resection with half-tendon downward transposition.

In the half-tendon transposition and unilateral recession-resection groups, normalization of V-pattern appeared early after surgery and remained constant throughout the follow-up period. In patients who had full-tendon transposition, although pattern collapse started to appear in the first few weeks after surgery, normalization of the V-pattern did not occur until several months after surgery (Figure 2).

Line curve showing gradual pattern collapse in the full-tendon transposition group over 6 months of follow-up. Patients with half-tendon transposition and the unilateral recession-resection group showed early and persistent pattern collapse after surgery. PD = prism diopters; BLR = bilateral lateral rectus muscle

Figure 2.

Line curve showing gradual pattern collapse in the full-tendon transposition group over 6 months of follow-up. Patients with half-tendon transposition and the unilateral recession-resection group showed early and persistent pattern collapse after surgery. PD = prism diopters; BLR = bilateral lateral rectus muscle

At the end of the 6 months of follow-up, normalization of the pattern (< 10 PD) was achieved in 24 patients (75%) and 4 patients had residual pattern greater than 10 PD, all of them in the half-tendon transposition group. Four patients had overcorrection of the pattern with consecutive A-pattern, all of them in the full-tendon transposition group (Table 2). There was no statistically significant difference between the pattern normalization rate in the three groups (P = .89). There was a statistically significant correlation between the preoperative V-pattern and the magnitude of pattern collapse after surgery (r = 0.80, P < .01), signifying that the pattern collapse was self-adjusting, with the magnitude of pattern collapse after surgery being smaller in patients with a smaller pattern and greater in patients with a larger pattern (Figure 3).

Operative and Postoperative Characteristics of the Studied Patients

Table 2:

Operative and Postoperative Characteristics of the Studied Patients

Scatter plot showing positive correlation between the preoperative V-pattern and the pattern collapse after surgery. The number of markers in the scatter plot is less than the total number of patients due to overlap because several patients had the same preoperative and postoperative V-pattern. PD = prism diopters

Figure 3.

Scatter plot showing positive correlation between the preoperative V-pattern and the pattern collapse after surgery. The number of markers in the scatter plot is less than the total number of patients due to overlap because several patients had the same preoperative and postoperative V-pattern. PD = prism diopters

Preoperatively, most of the patients who had bilateral lateral rectus recession showed no evidence of fundus extorsion (Figure 4). In contrast, 87.5% of patients who had unilateral recession-resection showed preoperative fundus extorsion with a disc foveal angle of greater than 10° (Figure 5). The mean preoperative disc foveal angle in the unilateral recession-resection group was significantly higher than in the other two groups (P < .01). The fundus extorsion was present in both the amblyopic eye (mean disc foveal angle: 16.3° ± 3.1º) and the fixing eye (mean disc foveal angle: 16.3° ± 3.1º). Postoperatively, there were non-significant changes in the fundus torsion in all three groups (P = .47).

Fundus photography showing no extorsion of both eyes in a patient before surgery (top panels) with little change in the disc foveal angle 6 months after bilateral 6-mm lateral rectus recession with full-tendon upward transposition (bottom panels).

Figure 4.

Fundus photography showing no extorsion of both eyes in a patient before surgery (top panels) with little change in the disc foveal angle 6 months after bilateral 6-mm lateral rectus recession with full-tendon upward transposition (bottom panels).

Fundus photography showing extorsion of both the sound (right) eye and the amblyopic (left) eye in an amblyopic patient before surgery (top panels). The bottom panels show little change in the disc foveal angle 6 months after left lateral rectus recession with half-tendon upward transposition and left medial rectus resection with half-tendon downward transposition.

Figure 5.

Fundus photography showing extorsion of both the sound (right) eye and the amblyopic (left) eye in an amblyopic patient before surgery (top panels). The bottom panels show little change in the disc foveal angle 6 months after left lateral rectus recession with half-tendon upward transposition and left medial rectus resection with half-tendon downward transposition.

There was no statistically significant change in the axis of astigmatism in all three groups postoperatively (Figure 6). Moreover, other than transient horizontal diplopia in the first few weeks after surgery in some patients, none of the patients complained of any torsional diplopia during follow-up.

Anterior sagittal map using Pentacam corneal tomography (Oculus Optikgeräte, Wetzlar, Germany) of both eyes of a patient before surgery (left) and 6 months after bilateral 7-mm lateral rectus recession with full-tendon upward transposition (right) showing no significant change in the axis of astigmatism after surgery.

Figure 6.

Anterior sagittal map using Pentacam corneal tomography (Oculus Optikgeräte, Wetzlar, Germany) of both eyes of a patient before surgery (left) and 6 months after bilateral 7-mm lateral rectus recession with full-tendon upward transposition (right) showing no significant change in the axis of astigmatism after surgery.

There was no statistically significant correlation between the amount of recession and the amount of pattern corrected (r = 0.15, P = .41). In addition, there was no significant correlation between the magnitude of pattern correction and the changes in fundus torsion (r = 0.12, P = .51) or axis of astigmatism (r = 0.11, P = .55).

Discussion

Vertical displacement of the lateral recti alters their scleral attachment relative to the rotation center of the globe, increasing the arc of contact of the transposed muscle in down gaze and decreasing it in up gaze. Thus, the lateral rectus muscles become more effective abductors in down gaze and less effective abductors in up gaze.2 However, the concern about upward displacement of the lateral recti is that it might induce extorsion of both globes. The extorsion might increase the V-pattern as a result of altering the line of action of both superior and inferior recti. Such extorsion might be more evident with full-tendon transposition, thus negating the useful effect of transposition in pattern collapse.5 The current study was designed to study the amount of pattern collapse after vertical displacement of the lateral recti and to evaluate whether there would be any torsional changes that might influence the outcome.

In the current study, the average pattern corrected by bilateral lateral rectus recession with half-tendon transposition was approximately 12 PD, which is close to that reported by Parks and Mitchell10 and Awadein.11 The mean pattern collapse after full-tendon transposition was higher than reported before,12 but the improvement in the V-pattern was gradual so that in most patients there was still a significant V-pattern at 1 month postoperatively. There was a gradual spread of comitance afterward in most patients, with disappearance of the pattern by the end of 6 months.

We opted for strict success criteria to better study the outcome. Any degree of A-pattern was considered a pattern reversal. In addition, we defined pattern normalization as a postoperative V-pattern of less than 10 PD because some patients started with a preoperative V-pattern of only 20 PD; so to minimize the error caused by variability in measurement, the postoperative V-pattern needed to be less than 10 PD to be considered normal.

Our study was prospective with a follow-up of 6 months. Prior studies that evaluated pattern collapse after vertical transposition of lateral recti were retrospective.10–12 In addition, all surgeries were done using the same surgical technique by the same surgeon. The degree of head tilt during measurement of the angle in up and down gaze was checked using a goniometer to ensure precise measurement at each visit.

Torsional changes after vertical offset of the lateral recti are poorly studied in the literature. Most studies focused on the torsional changes after oblique muscle surgery. Studies that addressed the torsional changes after inferior oblique muscle surgery used fundus torsion to evaluate these changes.11,12 Kushner13 was the first to assess the changes in torsion using retinoscopy. He reported that inferior oblique weakening induced a 10° incyclorotation of the astigmatic axis that persisted for at least 6 months after surgery, with no drift of the axis toward the preoperative orientation. Eum and Chun14 used vector analysis to assess the changes in astigmatism following inferior oblique anteriorization. They reported that the induced intorsion was only temporary during the first week after surgery. Only a few retrospective studies evaluated fundus torsion in patients who had vertical offset of the lateral rectus muscles using indirect ophthalmoscopy, and reported no significant fundus torsion in those patients before or after surgery.10–12

Fundus photography is a reproducible and reliable method for evaluation of the ocular torsion.15 It is an objective method that avoids the drawbacks of subjective torsion evaluation, which might not be suitable for children. Moreover, many patients undergoing strabismus surgery do not have bifoveal fusion or diplopia awareness; a change in subjective torsion might not be helpful in assessing whether a torsional change has actually occurred after the operation. In the current study, we used the disc foveal angle as a method to evaluate the torsional status of the eye. The photography and the measurement of the angle were done by an observer who was masked to the study design. In addition, during capturing of the fundus imaging, the photographer ensured the horizontal position of the patients' eyes by using the side marks as a guide.

In addition, torsional changes were evaluated by studying the changes in the axes of astigmatism using the Pentacam. Kushner13 reported changes in the axes of astigmatism following oblique muscle surgery and suggested that these torsional changes can be seen in retinoscopy. Awadein et al.16 were the first to use the Pentacam to study the changes in the axis of astigmatism following inferior oblique myectomy, and they reported that these torsional changes can also be seen in the corneal tomography. In the current study, we used the Pentacam to evaluate the torsional changes following the vertical offset of the lateral recti in conjunction with the changes in the disc foveal angle. Only captured images that had an acceptable quality specification during Pentacam tomography were used to ensure there was no missing information during image capture.

Although our study showed no significant change in the axis of astigmatism following vertical transposition of lateral recti, the refractive and astigmatic changes after extraocular muscle surgery should be taken into consideration. Extraocular muscle surgery might induce a change in corneal curvature secondary to the alterations in muscle tension transmitted via the sclera to the cornea.17–19

Our study showed that torsional changes after vertical offset of the lateral recti are minimal after both half- and full-tendon transposition. The fact that transposition of the lateral recti was combined with recession might have reduced the torsional effect of the transposition. However, we have noted that there were no torsional changes even with small amounts of recession, suggesting that this might not be the reason for the minimal torsional changes.

In the current study, patients with unilateral amblyopia and V-pattern exotropia showed significant fundus torsion in both the amblyopic and the sound eye. Guyton and Weingarten20 reported that patients who had loss of fusion developed sensory torsion that resulted in A- and V-pattern strabismus. He suggested that the muscle length adaptation would cause the torsion to manifest in both the sound and the amblyopic eye.

Limitations of the study include the small sample size, which might be explained by the strict inclusion criteria, and that we excluded patients with any evidence of oblique dysfunction. In addition, no subjective tests were used to evaluate the sensory torsion of the patients due to the relatively young age of the studied group.

Both half- and full-tendon transposition of the lateral rectus muscles are effective in correcting V-pattern exotropia in the absence of oblique dysfunction. The pattern collapse seemed to be related to the preoperative V-pattern, so that the majority of patients had disappearance of the V-pattern irrespective of the preoperative V-pattern value. Pattern collapse was not associated with any significant torsional changes.

References

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Preoperative Characteristics of the Studied Patients

CharacteristicHalf-tendon Transposition (n = 14)Full-tendon Transposition (n = 10)Recession-Resection (n = 8)P
Mean ± SD age (y)6.1 ± 3.24.7 ± 0.818.1 ± 5.7< .001
Females8/14 (57%)8/10 (80%)5/8 (62.5%).497
Mean ± SD angle of horizontal deviation in primary position (PD) (range)27.1 ± 9.1 (15 to 40)29.0 ± 8.4 (15 to 35)41.8 ± 2.6 (45 to 55).005
Mean ± SD angle of deviation in up gaze (PD) (range)37.9 ± 7.8 (25 to 45)44.0 ± 7.7 (30 to 50)50.0 ± 7.0 (40 to 45)< .001
Mean ± SD angle of deviation in down gaze (PD) (range)16.3 ± 6.9 (0 to 25)11.6 ± 10.0 (0 to 20)26.8 ± 7.0 (20 to 35).001
Mean ± SD pattern (PD) (range)21.5 ± 2.3 (20 to 25)32.4 ± 6.8 (27 to 45)23.1 ± 7.0 (15 to 30)< .005
Mean ± SD astigmatic error (D) range)1.60 ± 1.40 (1.00 to 4.00)1.80 ± 1.60 (1.00 to 4.00)1.70 ± 1.50 (1.00 to 3.00).783
Mean ± SD DFA (degrees) (range)7.3 ± 2.8 (4 to 15)7.8 ± 2.7 (5 to 13)16.9 ± 5.4 (6 to 23)< .001

Operative and Postoperative Characteristics of the Studied Patients

CharacteristicHalf-tendon Transposition (n = 14)Full-tendon Transposition (n = 10)Recession-Resection (n = 8)P
Mean ± SD amount of recession/resection (mm) (range)6.1 ± 1.4 (4 to 8)6.2 ± 1.3 (4 to 7.5)8.5 ± 0.2 (7.5 to 8.5)/6.5 ± 0.3 (6 to 7).002
Mean ± SD angle of horizontal deviation in primary position (PD) (range)5.4 ± 4.5 (0 to 10)−3.8 ± 11.4 (−25 to 6)6.3 ± 1.7 (4 to 8).005
Mean ± SD angle of deviation in up gaze (PD) (range)10.0 ± 4.8 (6 to 20)−2.8 ± 17.9 (−35 to 15)13.8 ± 5.2 (10 to 20).005
Mean ± SD angle of deviation in down gaze (PD) (range)1.4 ± 2.4 (0 to 6)0.4 ± 6.3 (−10 to 8)4.5 ± 6.2 (0 to 12).211
Mean ± SD pattern (PD) (range)8.6 ± 3.3 (6 to 14)−3.2 ± 12.2 (−25 to 7)9.3 ± 1.0 (8 to 10).006
Mean ± SD change in pattern (PD) (range)13.1 ± 3.8 (8 to 19)35.6 ± 13.7 (20 to 55)13.8 ± 7.9 (5 to 22)< .001
Orthophoria8 (57.1%)8 (80.0%)8 (100.0%).075
Mean ± SD axis rotation (degrees) (range)1.5 ± 6.79 (−6 to 15)1.17 ± 6.03 (−10 to 12)0.6 ± 2.84 (−3 to 5).892
Mean ± SD postoperative DFA (degrees) (range)7.77 ± 2.2 (4 to 15)8 ± 4.8 (−7 to 13)17 ± 7.8 (5 to 30)< .001
Mean ± SD surgically induced fundus torsion (degrees) (range)0.5 ± 1.91 (−2 to 5)0.125 ± 3.15 (−6 to 3)0.125 ± 4.16 (−5 to 7).882
Normalization of V-pattern10 (71.4%)6 (60.0%)8 (100.0%).138
Authors

From the Faculty of Medicine, Cairo University, Cairo, Egypt.

The authors have no proprietary or financial interest in the materials presented herein.

Correspondence: Ahmed Awadein, MD, 16 Abd El-Hady Street, Manial, Cairo 11451, Egypt. E-mail: ahmedawadein@yahoo.com

Received: October 28, 2018
Accepted: January 07, 2019

10.3928/01913913-20190205-03

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