|Year : 2020 | Volume
| Issue : 2 | Page : 133-138
Comparative study of unilateral lateral rectus hang-back recession versus bilateral rectus hang-back recession for management of small-angle basic intermittent exotropia in Egyptians children
Nermeen M Badawi
Depatement of Ophthalmology, Menoufia University, Shebin Elkom, Menoufia, Egypt
|Date of Submission||24-Dec-2019|
|Date of Decision||29-Jan-2020|
|Date of Acceptance||02-Feb-2020|
|Date of Web Publication||26-Jun-2020|
MD, FRCS Ophth.(Glasgow) Nermeen M Badawi
Compound Lake View, 90th Street, Villa 3/1, New Cairo, Cairo 11835
Source of Support: None, Conflict of Interest: None
Purpose The aim of this study was to evaluate the efficacy of unilateral lateral rectus hang-back recession (ULR) compared with bilateral rectus hang-back recession (BLR) for management of small-angle basic intermittent exotropia in Egyptian children.
Patients and methods The study included 50 patients with basic intermittent exotropia. They were divided into two groups: group A underwent ULR, and group B underwent BLR. All patients underwent a complete ophthalmological examination including measuring the angles of deviation at distant and near. They were followed up at 1 day, 1 week, 1 month, 3 months, 6 months, and 1 year postoperatively.
Results The final postoperative distant angle of deviation was 4.9±4.4 prism diopter (PD) for the ULR group and 3.2±6.9 PD for the BLR group, whereas the final postoperative near angle of deviation was 4.4±2.3 PD for the ULR group and 2.88±8.2 PD for the BLR group, with no statistically significant difference between the two group regarding both angles by the end of the follow-up period (P>0.05).
Conclusion The ULR technique is comparable to the BLR technique regarding the efficacy and long-term angle stability.
Keywords: basic, exotropia, intermittent, recession, unilateral lateral rectus hang-back recession
|How to cite this article:|
Badawi NM. Comparative study of unilateral lateral rectus hang-back recession versus bilateral rectus hang-back recession for management of small-angle basic intermittent exotropia in Egyptians children. Delta J Ophthalmol 2020;21:133-8
|How to cite this URL:|
Badawi NM. Comparative study of unilateral lateral rectus hang-back recession versus bilateral rectus hang-back recession for management of small-angle basic intermittent exotropia in Egyptians children. Delta J Ophthalmol [serial online] 2020 [cited 2020 Oct 30];21:133-8. Available from: http://www.djo.eg.net/text.asp?2020/21/2/133/287465
| Introduction|| |
The one muscle surgery for management of comitant strabismus had been controversial regarding the resultant under-corrections and/or ocular incomitance . Many surgical techniques are used to correct intermittent exotropia (IXT), with bilateral rectus recession being one of the most favored . However, Nelson et al.  suggested that unilateral rectus recession is also a safe and effective management for small and moderate angle exotropia, with their opinion being supported by many other authors ,,,.
In this study, the unilateral lateral rectus hang-back recession (ULR) was compared with bilateral rectus hang-back recession (BLR) for management of small-angle basic IXT in Egyptian children.
| Patients and methods|| |
The study was conducted in accordance with the tenets of the Declaration of Helsinki and was approved by the Ethical Committee of the Faculty of Medicine, Menoufia University. Before surgeries, all legal guardians of the patients were informed about the expected complications. All of them signed an informed consent matching the Helsinki Declaration. All patients’ guardians signed a written informed consent to participate in the study and for publication of data before enrollment in the study.
Fifty patients, with small-angle basic IXT 15–20 prism diopters (PD), were included in this prospective study. They were divided into two groups: group A underwent ULR, and group B underwent BLR. All patients were subjected to complete ophthalmic examination and a full cycloplegic refraction. Anisometropia was defined when there was a between-eyes spherical or cylindrical difference more than 1.5 diopters (D). Stereo-acuity evaluation was performed using Titmus stereo-acuity test (Stereo Optical Co. Inc., Chicago, Illinois, USA) at 33 cm and was defined as good stereopsis with a record less than or equal to 100 of seconds of arc. All values were converted from stereo-acuity seconds of arc to logarithm of second of arc (log arc sec) to facilitate statistical analysis. Visual acuity and best-corrected visual acuity were examined using the illiterate E visual acuity chart.
Amblyopia was diagnosed when there was a between-eye difference of more than two lines or when the best-corrected visual acuity was less than 20/30. In this case, part-time alternate patching was prescribed for at least a month up to 3 months. Those who failed to improve were excluded from the study.
An alternate prism cover test with an accommodative target was used to measure deviations in the nine positions of gaze, for distance at 6 m (D) and for near at 33 cm (N) without (S) and with (C) best optical correction. Deviation was classified as basic intermittent XT, when the difference between the distance and near angle was within 10 PD.
The control of exodeviation was examined by cover test at distance and was classified as good (patient regain fusion without blinking or re-fusion), fair (patient needs to blink or re-fixate), and poor (does not spontaneously regain alignment despite blink or refixation).
Duction and version movements were examined and lateral gaze incomitance was defined with more than 10 PD change from the primary position. Ocular movement limitations were scaled on a five-unit scale from 0 to 4, where 0 represents full or 100% abduction or adduction and 4 represents a failure to abduct or adduct beyond the midline.
Ocular dominance was tested using the 10 prism base down test.
Exclusion criteria were other forms of exotropia (restrictive, paralytic, etc.), previous surgeries abnormal head posture (AHP), oblique muscle dysfunction, patterns (A, V, etc.), nystagmus, ocular structural abnormalities, neurological abnormalities, and developmental delays.
All operations were performed under general anesthesia using the operating microscope. Patients with a dominant eye underwent unilateral lateral rectus recession of the nondominant eye by 7.5 mm for angle of 15 PD and 8.5 mm for angle of 20 PD, using the hang-back technique through a fornix incision. Patients without eye dominance underwent bilateral rectus recession by 4 mm bilaterally for angle of 15 PD and 5 mm for angle of 20 PD, using the hang-back technique through a fornix incision.
Follow-up visits were conducted at 1 day, 1 week, 1 month, 3 months, 6 months, and 1 year postoperatively. Visual acuity was determined by illiterate E chart. AHP, angle of deviation (for distance and near) with satisfaction (success) defined as less than or equal to 10 PD of XT or ET, as well as ocular motility were assessed during the follow-up examinations. Rates of reoperation for residual XT (under-correction) more than or equal to 20 PD or consecutive ET (overcorrection) more than or equal to 20 PD were recorded and scheduled for reoperation after at least 1 month of trials of nonsurgical treatments like alternate patching and over-minus lenses for 1 month after angle stabilization.
All data were tabulated and analyzed. Statistical analysis was done by the correlation t test, Mann–Whitney U test, Friedman test, and Fisher’s exact test. P values less than 0.05 were considered statistically significant.
| Results|| |
The age of the patients in group A ranged between 5.2 and 12.2 years (mean=8.2±3.8 years), whereas in group B, it ranged between 4.6 and 11.5 years (mean=7.9±4.2 years), with no statistically significant difference between the two groups (P>0.05 by Mann–Whitney test).
The preoperative distant angle of deviation was 18.5±1.3 PD in group A and 17.9±1.8 PD in group B, with no statistically significant difference (P>0.05), whereas for near, it was 17.4±2.8 PD in group A and 16.8±4.6 PD in group B, with also no statistically significant difference (P>0.05).
The mean time for the surgical procedure was 11.45±4.33 min in group A and 19.26±4.96 min in group B, with a statistically significant difference (P<0.001).
The average values of the angle of deviation at distance at 1 day, 1 week, 1 month, 3 months, and 6 months postoperatively are shown in [Table 1]. There was a statistically significant decrease of the angle in every postoperative visit in comparison with the preoperative value (P<0.001). Although the BLR group showed an early overcorrection during the 1-day and the 1-week visits, there were no statistically significant differences between both groups in each following postoperative visit.
|Table 1 The average values of the angle of deviation at distance, preoperatively and postoperatively|
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Similar results were found regarding the average values of the angle of deviation at near, at 1 day, 1 week, 1 month, 3 months, and 6 months postoperatively ([Table 2]). There was a statistically significant decrease of the angle in each postoperative visit compared with the preoperative value (P<0.001). Similarly, the BLR group showed an early overcorrection during the 1 day and the 1 week visits; however, there were no statistically significant differences between both groups in each following postoperative visit.
|Table 2 The average values of the angle of deviation at near, preoperatively and postoperatively|
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The postoperative surgical outcome in both groups is demonstrated in [Table 3]. Although the BLR group showed a statistically significant higher number of overcorrected cases during the first week, by the next visits, the results of both groups were comparable to each other with a final success rate (satisfactory results) of 64% in group A and 68% in group B.
The amounts of exo-drifting at the first day, first week, first month, third month, sixth month, and first year, postoperatively were 2.2±0.8, 1.1±0.9, 0.9±0.7, 0.6±1.2, and 1.1±0.9, 0.9±1.3 PD in group A and 3.9±2.8, 2.0±2.5, 1.1±2.1, 0.9±2.8, 1.1±3.1, and 1.1±2.5 PD in group B, with a statistically significant difference between the two groups at the first day and first week (P<0.05), with more exo-drifting in group B. There was no statistically significant difference at 1 and 3 months, postoperatively. However, after 6 months, group A showed more statistically significant exo-drifting than group B.
The lateral gaze incomitance was found in seven (28%) patients in group A and in two (8%) patients in group B at the first postoperative visit, with a statistically significant difference (P<0.05). These results decreased to four (16%) patients in group A and 0 (0%) in group B by the first week, which was also statistically significant (P<0.05). However, by the end of the first month, all cases of lateral gaze incomitance resolved.
The amount of limitation of abduction ranged from 1 to 4 (mean=1.9±2.3) in group A at the first postoperative visit and 0–1 (mean=0.5±0.5) in group B, with a statistically significant difference (P<0.05). At the first week visit, the limitation of abduction in group A decreased to 0.8±1.1, whereas it disappeared in group B (P<0.05). By the end of the first month, no limitation of abduction was detected in both groups.
It was possible to examine stereo-acuity in 49% (28) of the patients in group A and 47% (24) of the patients in group B. Preoperatively its logarithmic value ranged from 1.7 to 2.5 log arc sec (mean=1.9±0.4) in group A, and 1.7–2.6 (mean=1.8±0.5) log arc sec in group B. By the end of the follow-up period, it ranged from 1.6 to 2.9 (2.0±0.7) log arc sec in group A and 1.8 to 2.8 (2.1±0.6) log arc sec in group B, with no statistically significant difference between the two groups (>0.05).
There were no reported AHP or A or V patterns in both groups. Two cases of reoperation were reported in group A for residual XT (20 PD) and were managed by contralateral LR recession, and one case in group B for consecutive ET (25 PD) and was managed by bimedial rectus recession.
| Discussion|| |
Correcting the angle of strabismus by performing surgery on a lesser number of muscles has always been a privilege for any technique. This has its major influence on the anesthesia and operative time. Moreover, it decreases the incidence of many complications, for example, scleral perforation, retinal detachment, and endophthalmitis . It preserves more muscles for any further maneuvers in case of recurrence, lowers overcorrection rates, and decreases the incidence of consecutive esotropia ,,,. However, many concerns have been raised against performing a unilateral recession for correction of exotropia as compared with the more commonly used bilateral rectus recession. Among these concerns is the possibility of lateral gaze incomitance, abduction limitation, and under-correction . The incidence of occurrence of these complications is expected to be minimized with small angles of deviations as less amount of recession is needed.
The technique used for recession in both groups, in this study, was the hang-back recession technique, which is considered as effective as the conventional techniques. It still provides more safety and lower rates of complications, for example, scleral perforation, retinal detachment, and induced astigmatism ,,,,,,.
In the present study, the two techniques (ULR and BLR) for management of small-angle exotropia (15–20 PD) were compared both intraoperatively and postoperatively. As expected, the operative time was statistically significantly less in the ULR group, as operating on one muscle takes less time than operating on two muscles.
Some authors considered the immediate postoperative overcorrection to be a sign for a satisfactory long-term alignment, both for BLR , and ULR . However, it was stated that this is not required in case of ULR .
The results concluded by Wang and Nelson , Spierer and Ben-Simon , and Kim et al. , in their studies on small to moderate exotropia, stated that during the early postoperative period the rate of overcorrection in the BLR was higher than that of the ULR, which usually shows a higher rate of under-correction. However, by the end of their follow-up periods, they stated that both groups showed comparable results regarding success and overcorrection and under-correction rates. In the present study, the BLR group showed a statistically significantly higher incidence of overcorrection (36%) in all follow-up visits during the first month, whereas that of the ULR was 12%. On the contrary, the ULR showed a higher incidence of under-correction (40%) than that of the BLR (20%) during the same period. However, on the following visits, there was no statistically significant difference between the two groups with a final success rate of 64% in ULR and 68% in BLR.
In addition, they stated that the results of both groups were comparable to each other regarding the final angles of deviation ,,. In the current study, the final postoperative distant angle of deviation was 4.9±4.4 PD in the ULR group and 3.2±6.9 PD in the BLR group. The final postoperative near angle of deviation was 4.4±2.3 PD in the ULR group and 2.88±8.2 PD in the BLR group, with no statistically significant difference between the two groups regarding both angles by the end of the follow-up period.
Although the lateral gaze incomitance and limitation of abduction are among the major concerns against ULR, some studies did not face these complications during the follow-up period ,,. However, in the current study, lateral gaze incomitance and limitation of abduction were more remarkable in a statistically significant way in the ULR during the early postoperative period (first day and first week), owing to the larger amount of recession that was performed unilaterally. However, they both decreased during the following visits and disappeared by the end of the first month. Similar results were found by other authors ,, who reported that the incidence of lateral gaze incomitance increased with recessions more than 8 mm. On the contrary, Spierer et al.  confirmed that no incomitance was observed even with large recessions up to 9 mm.
Regarding the angle stability, some authors like Wang and Nelson , Olitsky , and Dadeya and Kamlesh  were interested in examining the postoperative exo-drift following lateral rectus recession and stated that, during the early postoperative period, exo-drift was more noticeable when the lateral recti were recessed bilaterally rather than recessing a unilateral lateral rectus muscle. Similarly, Kushner  suggested that exo-drifting was less likely to occur when operating on one eye (i.e. recession–resection operations) rather than when operating on the two eyes (BLR). In the present study, as well, the BLR showed more exo-drifting during the first month in a statistically significant way, which also disappeared by the end of the first year.
Similar to the results of Kim et al. , there was no statistically significant improvement of stereopsis in both groups postoperatively, and neither there was any statistically significant difference between the two groups either preoperatively or postoperatively.
| Conclusion|| |
The ULR using the hang-back technique is as efficient as the BLR technique in management of small-angle basic IXT.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]