Strabismus, 2013; 21(4): 235–241 ! Informa Healthcare USA, Inc. ISSN: 0927-3972 print / 1744-5132 online DOI: 10.3109/09273972.2013.851260
Strabismus surgery outcomes after scleral buckling procedures for retinal reattachment Jee Ho Chang,
MD
1,2
, Amy K. Hutchinson, MD1, Monica Zhang, and Scott R. Lambert, MD1
1
MD
,
1
Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, and Department of Ophthalmology, Soonchunhyang University Hospital Bucheon, Bucheon, South Korea
ABSTRACT Objective: To investigate the outcomes of strabismus surgery in patients with a prior history of a scleral buckling procedure for retinal reattachment. Methods: We reviewed the medical records of 18 patients who underwent strabismus surgery following a scleral buckling procedure and investigated the effect of multiple variables on postoperative alignment after strabismus surgery including gender, age, surgeon, number of strabismus surgeries, adjustable suture use, previous pars plana vitrectomy, preoperative best-corrected visual acuity, and scleral buckle removal. Outcomes were considered successful if there was 10 prism diopters (PD) residual horizontal and/or 4 PD residual vertical deviations. Statistical analyses were performed using Fisher’s exact test, Mann-Whitney test, and nominal logistic regression. Results: Success using our criteria of motor alignment was achieved in 6 of 18 eyes (33%). A higher rate of success was found in the scleral buckle removal group (success with buckle removal, 62.5%; success without buckle removal, 10.0%; p = 0.04). Nominal logistic regression analysis showed scleral buckle removal was the most significant factor associated with successful surgical alignment (p = 0.03; odds ratio = 16.67). Although the success rate was higher in the adjustable suture group (50% in adjustable group vs 14.3% in non-adjustable group: Fisher’s exact test, p = 0.30), this difference was not statistically significant. No retinal redetachments occurred after scleral buckle removal. Conclusions: These results suggest that scleral buckles can be safely removed in selected patients with strabismus following retinal reattachment surgery and scleral buckle removal may improve ocular alignment following strabismus surgery. Keywords: Scleral buckle, strabismus surgery, retinal detachment
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2
beneath extraocular muscles; 3,5 or the redirection of muscle force vectors either directly or indirectly by the buckle.11,12 When planning the surgical approach for a patient with strabismus after a scleral buckling procedure, the question frequently arises whether to remove a scleral buckle. If the buckle is the obvious cause of the strabismus, the removal of the buckle either before or during strabismus surgery is viewed as helpful by many surgeons.13,14 However, the benefit and safety of scleral buckle removal when it is not the obvious cause of strabismus is more controversial.
INTRODUCTION Strabismus following retinal reattachment surgery may resolve spontaneously,1,2 but in 5% to 25% of cases it can persist on a long-term basis.3,4,5 Strabismus following a scleral buckling procedure may occur on a sensory basis,6 from peribulbar anesthesia myotoxicity7 or mechanical factors related to the implantation of a scleral buckle. These mechanical factors may arise secondary to direct muscle injury; 3,4,5,8 adhesions between muscle, sclera, and fat; 9,10 the bulk effect of scleral buckling elements
Received 20 August 2012; Accepted 18 September 2013; Published online 12 November 2013 Correspondence: Scott R. Lambert, MD, Emory Eye Center, 1365-B Clifton Road, Atlanta, GA 30322. Tel: 404-778-4417. Fax: 404-778-5203. E-mail: [email protected].
235
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236 J. H. Chang et al. Some authors have suggested that the removal of a scleral buckle does not affect the outcome of strabismus surgery,3,5 while others have recommended buckle removal to relieve restriction 4 and even suggested that removal of the scleral buckle alone can improve ocular alignment and consider buckle removal to be the logical first step in correcting the strabismus.1 While a recent small study of 5 patients reported no benefit of scleral explant removal,15 another study reported resolution of diplopia in 4 patients after scleral buckle removal.16 However, neither of these studies evaluated the effect of scleral buckle removal combined with strabismus surgery. We retrospectively reviewed the motor outcomes of strabismus surgery in a cohort of patients who had all previously undergone a scleral buckling procedure to treat retinal detachment.
MATERIALS AND METHODS This retrospective study was approved by the institutional review board at Emory University School of Medicine. The data used for this analysis were treated in accordance with the Health Insurance Portability and Accountability Act (HIPAA) and the tenets of the Declaration of Helsinki. We reviewed the medical records of patients who underwent strabismus surgery following retinal detachment surgery at the Emory Eye Center between 1989 and 2010. Patients were identified from a large database of adult strabismus surgery patients and by searching for adult patients with the ICD-9 code for retinal detachment (361.00-361.09) and strabismus surgery (67311, 67312, 69314, 69316, or 67318) between 1996 and 2010. We excluded patients known to have strabismus prior to retinal reattachment surgery and ocular comorbidities that could have caused restrictive strabismus (eg, thyroid ophthalmopathy, orbital trauma, etc). We also excluded patients who incurred unintended muscle injuries during scleral buckling procedures such as rupture of a muscle or peribulbar anesthetic myotoxicity. Finally, we excluded patients with a follow-up of less than 1 month after the final strabismus surgery. To be included in the series, patients must have undergone a surgical procedure to treat retinal detachment that included the placement of a scleral buckle. If it was deemed possible that removal of the scleral buckle would improve the outcome of strabismus surgery, a retina surgeon was consulted prior to strabismus surgery to assess the patient’s risk of retinal detachment if the scleral buckle was removed. Factors considered to be high risk for retinal detachment included a history of proliferative vitreoretinopathy or a giant retinal tear, multiple operations
required to achieve retinal reattachment, recent retinal operation, and any visible traction on the retina. We extracted the following data from the medical record for each patient: gender, age, strabismus surgeon, type of strabismus surgery or surgeries, the duration between scleral buckling surgery and the first strabismus surgery, the timing of scleral buckle removal relative to strabismus surgery, whether the scleral buckle was partially or completely removed, whether the patient had undergone pars plana vitrectomy, whether an adjustable suture technique was used, preoperative best-corrected visual acuity, preoperative horizontal and vertical ocular alignment, horizontal and vertical ocular alignment at the last follow-up examination, postoperative prism use, and the length of follow-up after strabismus surgery. Ocular alignment was assessed using the alternate prism cover test except in patients with a severe visual deficit. The Krimsky test was used to assess ocular alignment in patients with a severe visual deficit. We did not analyze torsion since it was inconsistently documented. Although the reasons for scleral buckle removal or non-removal were not always documented, when available the reasons are shown in Table 1. For descriptive purpose, esodeviation was assigned a negative value and exodeviation a positive value. For vertical deviation, the right eye was the reference eye. Right hypodeviation was assigned a negative value and right hyperdeviation a positive value. As a single representative of preoperative deviation, preoperative vector magnitude of deviation was used so that horizontal and vertical deviations could be described with one variable. The magnitude of the vector was calculated by taking the square root of the sum of squares of horizontal deviations and vertical deviations.15 We defined strabismus surgery as being successful when the final postoperative horizontal deviation was 10 prism diopters (PD) and the final postoperative vertical deviation was 4 PD. Because pre- and postoperative binocularity was not consistently documented in the medical record, we did not use this as a factor when evaluating the success of strabismus surgery. Likewise, we did not use the presence or absence of diplopia as a factor when evaluating the success of strabismus surgery because best corrected visual acuity was severely reduced in many of the operative eyes so that diplopia was not always a reliable indicator of successful ocular alignment. For the sake of statistical coding, categorizational reduction of information was inevitable. The surgical procedures were especially diverse in terms of horizontal, vertical, and torsional surgeries and the timing of scleral buckle removal. Three features of the surgical technique were selected for analysis: (1) whether the scleral buckle was removed or not; (2) the number of strabismus surgeries performed; Strabismus
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2013 Informa Healthcare USA, Inc.
F
F F
F
F F
M
F
M
F
M
M M M
5
6 7
8
9 10
11
12
13
14
15
16 17 18
36 31 61
59
58
49
56
14
53 58
41
32 62
53
35 67 44 49
1 2 1
1
1
3
1
3
1 3
3
1 2
2
1 1 2 1
During strabismus surgery No removal No removal
3 months before No removal No removal During 2nd strabismus surgery
Time of buckle removal
LMR res, LLR rec RLR rec LSR rec
No removal No removal No removal
During strabismus surgery RIR rec No removal LMR res/LLR rec During 1st strabismus surgery RMR res, RLR rec During strabismus surgery LIR rec, LSR and LSO adhe- During strabismus sion lysis surgery RMR rec During strabismus surgery RMR rec, RLR rec, No removal vertical transposition LMR res, LLR rec No removal
RMR rec
RLR rec, RMR res LLR rec
RSR rec, RIR res RSR rec LSR rec, LIR res RLR rec, RMR res/RLR rec, RMR res, RSO repositioning RLR rec, RMR res
Surgery or surgeries*
Complete
Complete
Complete
Complete
Complete
Partial
Partial
Complete
Complete/ partial SB removal
Risk of redetachment-giant retinal tear N/A N/A N/A
N/A
N/A
N/A
N/A
Patient refusal N/A
Reluctant remove all buckle N/A Lessen damage to muscle, severe fibrotic muscle Due to extrusion
Due to extrusion N/A N/A Displacement of SO tendon
Reason of removal/ no removal
No No No
No
Yes
No Yes Yes
Yes
Yes
Yes
No
Yes Yes
No
No No
Yes
Yes Yes Yes Yes
Yes
Yes
No
Yes
Yes Yes
No
Yes Yes
Yes
No No Yes Yes
20/80 20/20 20/25
20/25
20/50
20/400
CF
20/50
20/200 20/100
20/30
CF 20/100
20/70
20/30 20/200 20/100 CF
35
15 0
50 25
70 20 0
20
40
0 3 20
0
6
25
4 45
16 0 0
20
14
6
0 8
14 8 0 25
2 0
1.5
2.8 2.8 6.7
10 6 6
3.8
21.3
2.5
2.9
1.5 2.4
1.5
2.1 4.7
5.5
4.4 51.0 58.6 16.1
0
2
0
14
0
0 6
0
0 0
15 16
20
0
0 9 20 2
0
0 20 16 8
0 0
0
35 14 25 14
No No No
No
No
Yes
No
No
Yes No
Yes
No No
Yes
Yes No No Yes
No No No
No
Yes
No
No
No
No Yes
No
No No
No
No Yes Yes Yes
Duration of F/U Surgical Prism Vertiz Horiy Vertiz (months) Success Use
Final F/U deviation
25 35
20
10 12 0 14
BCVA of operated eye Horiy PPV Adjust
Preoperative deviation
PPV, history of pars plana vitrectomy; adjust, use of adjustable suture technique; BCVA, best corrected visual acuity; hori, horizontal; verti, vertical; preop, preoperative; F/U, follow-up; SR, superior rectus; IR, inferior rectus; LR, lateral rectus; MR, medial rectus; SO, superior oblique; rec, recession; res, resection; N/A, not available; SB, scleral buckle. *Delineates different surgical intervention. y þ, exotropia; , esotropia. z þ, right hypertropia; , right hypotropia.
F M M M
1 2 3 4
Pt. No. Gender Age Surgeon
TABLE 1. Patient clinical characteristics.
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Scleral buckle removal 237
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238 J. H. Chang et al. and (3) whether the adjustable suture technique was used during strabismus surgery. Two-tailed Fisher’s exact test was used to determine whether there was a significant difference in surgical success as defined when the following factors were analyzed: gender, surgeon performing the strabismus surgery, the number of strabismus surgeries, scleral buckle removal, pars plana vitrectomy, use of adjustable sutures, and poor vision. Poor vision was defined as visual acuity 520/200. The MannWhitney test was used to evaluate the effect of patient’s age and preoperative vector magnitude of deviation on surgical success. Since the scleral buckle removal was found to be significantly related to surgical success from the primary analysis, a subsequent analysis was performed to test whether other variables may be confounding factors. The two-tailed Fisher’s exact test was performed for nominal variables and MannWhitney test was used for continuous variables. Nominal logistic regression was performed for additional statistical analysis of confounding factors since it does not assume a standard distribution of dependent variables. We chose scleral buckle removal as the pivotal variable and paired it with 3 probable variables: surgeon, use of adjustable sutures, and preoperative vector magnitude of deviation. All statistical analysis was performed using SPSS version 16.0 (SPSS Inc., Chicago, Illinois) and P value for significance was set at 0.05.
RESULTS The medical records of 23 patients who had undergone strabismus surgery at our institution following a scleral buckling procedure were reviewed. Two patients were excluded because their strabismus was judged to be secondary to the rupture or loss of an extraocular muscle during the scleral buckling procedure. Another patient was excluded who was believed to have developed strabismus secondary to peribulbar anesthesia myotoxicity prior to the scleral buckling procedure. Finally, two cases were excluded because their follow-up was less than one month. Statistical analyses were performed on the remaining 18 patients. The clinical characteristics of the patients are shown in Table 1. The mean patient age at the time of strabismus surgery was 48 years (range, 14 to 67 years). The median time from scleral buckling surgery to the first strabismus surgery was 14.5 months (range, 8 months to 19 years). The median preoperative best corrected visual acuity of the postretinal detachment eyes was 20/100 (range, 20/20 to counting fingers). All of the operated eyes had worse visual acuity than their fellow eyes. The median best corrected visual acuity of the fellow eyes was 20/20 (range, 15/20 to 20/30).
Their preoperative horizontal deviations ranged from 25 PD esodeviation to 70 PD exodeviation (median, 20 PD exodeviation) and the preoperative vertical deviations from 25 PD right hypodeviation to 35 PD right hyperdeviation (median, 0 PD vertical deviation). Eight patients had both horizontal and vertical deviations. Seven patients only had horizontal deviations and three patients only had vertical deviations. All strabismus surgeries were performed on postretinal detachment surgery eyes only. The following strabismus surgeries were performed as the initial procedure: horizontal rectus recession and resection (n = 6), horizontal rectus recession or resection (n = 5), vertical rectus recession and resection (n = 3), inferior or superior rectus recession (n = 3), and lysis of adhesions to the superior oblique tendon (n = 1). Patients 4 and 10 underwent a second strabismus surgery. An adjustable suture was used in 10 patients. Scleral buckles were removed from 8 patients. The buckle was removed at the time of strabismus surgery in 7 patients and prior to strabismus surgery in one patient. Complete buckle removal was performed on 6 patients and partial removal on two patients. In two patients, extrusion of the scleral buckle prompted its removal. One of the extruded implants (Patient 8) was a hydrogel explant (Miragel, Medical Instruments Research Associates, Waltham, Massachusetts). Reasons cited for not removing the scleral buckle included high risk of redetachment (Patient 16, with giant retinal tear), severe fibrosis around the scleral buckle (Patient 7), and patient refusal (Patients 5 and 9). In one patient (Patient 4), the superior oblique tendon was found to be incarcerated by the encircling band. The type of scleral buckle was not always known since many of the patients had been referred from outside institutions for strabismus surgery. The median postoperative follow-up was 3.4 months (range, 1.5 to 59 months). The overall success rate was 33% (6 of 18 patients). A higher rate of success was found in the scleral buckle removal group (62.5%) versus the group not undergoing buckle removal (10.0%; p = 0.04). Three patients were orthotropic—2 in the group that underwent scleral buckle removal and 1 in the group retaining the scleral buckle. All of the other patients had some residual strabismus (Table 1). Five patients were prescribed prisms postoperatively to treat diplopia—2 in the group that underwent scleral buckle removal and 3 in the group retaining the scleral buckle. Although the success rate was higher in the adjustable suture group (50% in adjustable group versus 14.3% in non-adjustable group: Fisher’s exact test, p = 0.30), this difference was not statistically significant. Three strabismus surgeons performed the strabismus surgeries but there was no significant difference in the rate of success between surgeons Strabismus
Scleral buckle removal 239 TABLE 2. Detailed table of individual variable statistical analyses. Name of variable
Categories
Agey
–
Gender Surgeon
Number of strabismus surgeries SB removal
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Prior PPV Adjustable Poor vision Preop vector magnitude of deviationy
Male Female Surgeon 1 Surgeon 2 Surgeon 3 Once Twice No removal Removal No Yes No Yes 20/200 520/200 –
No success group (n = 12)
Success group (n = 6)
Success rate in each row
p Value
Median = 57 (interquartile range: 33–61) 7 5 7 3 2 11 1 9 3 3 9 7 5 10 2 Median = 20.0 (interquartile range: 18–28)
Median = 49 (interquartile range: 40–53) 2 4 3 1 2 5 1 1 5 2 4 1 5 4 2 Median = 26.2 (interquartile range: 20–45)
–
0.43
22.2% 44.4% 30.0% 25.0% 50.0% 31.3% 50.0% 10.0% 62.5% 33.3% 30.8% 12.5% 50.0% 28.6% 50.0% –
0.62 0.82
1.00 0.04* 1.00 0.15 0.57 0.07
SB, scleral buckle; PPV, pars plana vitrectomy; preop, preoperative. *Denotes statistical significance. For all nominal variables, Fisher’s exact tests were performed. yMann-Whitney tests were performed for age and preoperative vector magnitude of deviation. The number in the cell is median and numbers in parentheses are interquartile range from 25% to 75%.
using the two-tailed Fisher’s exact test (p = 0.82) (Table 2). Statistical tests for differences in the frequency of other variables between the scleral removal and non-removal group did not show a significant difference. With nominal logistic regression analyses, scleral buckle removal was the strongest predictor of surgical success (p = 0.03; odds ratio = 16.67). None of the other variables were statistically significant with this model. However, with scleral buckle in the model, there was a trend for preoperative vector magnitude of deviation to be significant (p = 0.08). There were no retinal redetachments in any of the patients following scleral buckle removal and/or strabismus surgery.
DISCUSSION We found better postoperative ocular alignment in patients who underwent scleral buckle removal either preceding or during strabismus surgery compared to patients in whom the buckle was not removed. Scleral buckle removal may have improved ocular alignment in our patients for a number of reasons: (1) it may have allowed the rectus muscles to attach directly to the sclera; (2) it may have lengthened muscles that were splayed over bulky implants; (3) the careful dissection and lysis of adhesions during removal of the buckle may have lessened muscle restriction; !
2013 Informa Healthcare USA, Inc.
(4) it may have permitted the muscles to move more freely during the adjustment procedure; and (5) it may have freed an oblique tendon or muscle inadvertently incorporated in the scleral buckle. Our overall success rate was relatively low (33%) using the criteria we chose to define success. Some series have defined success using subjective factors such as ‘‘symptomatic vs. non symptomatic’’17 or ‘‘cosmetic improvement’’.18 We used motor alignment as our definition of success. Other series have defined success as binocular vision with or without a prismatic correction or a compensatory head posture.18,15 Ideally, sensory outcomes would have been included in our definition of success, but this was not possible given the inconsistency of the reporting of these findings in the medical record for our retrospective study. Recent studies on retinal redetachment rate following scleral buckle removal report rates from 0% to 8%19,20,17,16 whereas earlier studies reported rates from 14%21 to 47%.22 These differences likely reflect improvements in surgical techniques and patient selection. For example, earlier studies of retinal redetachment often used techniques that are no longer in use (eg, diathermy, scleral dissection, and polyethylene tubing explants)20 and many scleral buckles were removed secondary to infections.22,21 Risk factors for retinal redetachment following removal of a scleral explant include: a shorter interval between the primary retinal detachment repair and
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240 J. H. Chang et al. removal of the buckle; 21 the presence of retinal tears, as opposed to holes; 21 failure to identify retinal breaks at the time of the initial retinal detachment surgery; 20 the presence of vitreous traction,19,22,21 and an increased number of quadrants of retinal detachment prior to retinal reattachment.22 All of the patients in our study were screened by retinal surgeons prior to removal of the scleral buckle and none of the patients who had their scleral buckle removed prior to or in conjunction with strabismus surgery were deemed to be at high risk for retinal redetachment. Similarly, no retinal redetachments have been reported in other studies evaluating scleral buckle removal in conjunction with strabismus surgery.23,1,24 Consultation with a retinal surgeon should be obtained prior to scleral buckle removal to assess the risk of retinal redetachment.24,4 Because of the anatomical changes brought about by scleral buckle surgery, standard tables for strabismus surgery may not apply. For this reason, adjustable sutures may be advantageous.1,25,24,4 Although the success rate was higher in the adjustable suture group (50% in adjustable group versus 14.3% in the non-adjustable group), this difference was not statistically significant. The lack of benefit of adjustable sutures in our study may be related to its small sample size. There are conflicting reports on the effect of decreased vision on the success rate of strabismus surgery after a scleral buckling procedure.6,26 We defined poor vision as 520/200 and did not find a difference in the success rate based on preoperative vision. Our study had a number of limitations. First, the sample size of our study was quite small (n = 18). However, since strabismus surgery following scleral buckling surgery is an uncommon procedure, it would be difficult to perform a large randomized clinical trial of this condition. Indeed, the largest comparable series in the literature only included 20 patients,24 17 patients,23 and 12 patients27 and none of these studies compared the effect of scleral buckle removal versus non-removal on the outcomes of strabismus surgery. A second limitation of our study was its retrospective design. Because the data were collected over420 years and involved 3 different surgeons, important data such as pre- and postoperative binocularity and the presence or absence of diplopia were not consistently documented. A third limitation was the many confounding factors. To identify potential confounders, we evaluated differences in the frequency of other variables between the scleral buckle removal and non-removal groups. We also performed a multiple logistic regression analysis to control for potential confounding variables. In conclusion, scleral buckle was associated with better ocular alignment following strabismus surgery
in our series and none of our patients had retinal redetachment after scleral buckle removal.
ACKNOWLEDGEMENTS Supported in part by an unrestricted grant to the Emory Eye Center from Research to Prevent Blindness, Inc., New York, New York, and NIH Core Grant EY06360.
DECLARATION OF INTEREST No financial conflict of interest in subject matter in the manuscript.
REFERENCES 1. Fison PN, Chignell AH. Diplopia after retinal detachment surgery. Br J Ophthalmol 1987;71:521–525. 2. Mets MB, Wendell ME, Gieser RG. Ocular deviation after retinal detachment surgery. Am J Ophthalmol 1985; 99:667–672. 3. Farr AK, Guyton DL. Strabismus after retinal detachment surgery. Curr Opin Ophthalmol 2000;11:207–210. 4. Rosenbaum AL. Strabismus following retinal detachment surgery. Am Orthopt J 2001;51:47–53. 5. Seaber JH, Buckley EG. Strabismus after retinal detachment surgery: etiology, diagnosis, and treatment. Semin Ophthalmol 1995;10:61–73. 6. Maurino V, Kwan A, Khoo BK, et al. Ocular motility disturbances after surgery for retinal detachment. J AAPOS 1998;2:285–292. 7. Salama H, Farr AK, Guyton DL. Anesthetic myotoxicity as a cause of restrictive strabismus after scleral buckling surgery. Retina 2000;20:478–482. 8. Wu TE, Rosenbaum AL, Demer JL. Severe strabismus after scleral buckling: multiple mechanisms revealed by highresolution magnetic resonance imaging. Ophthalmology 2005;112:327–336. 9. Metz HS. Restrictive factors in strabismus. Surv Ophthalmol 1983;28:71–83. 10. Wright KW. The fat adherence syndrome and strabismus after retina surgery. Ophthalmology 1986;93: 411–415. 11. Kushner BJ. The inferior oblique muscle adherence syndrome. Arch Ophthalmol 2007a;125:1510–1514. 12. Kushner BJ. Superior oblique tendon incarceration syndrome. Arch Ophthalmol 2007b;125:1070–1076. 13. Covert DJ, Wirostko WJ, Lindren KE, et al. Risk factors for scleral buckle removal: a matched, case-control study. Am J Ophthalmol 2008;146:434–439. 14. Kearney JJ, Lahey JM, Borirakchanyavat S, et al. Complications of hydrogel explants used in scleral buckling surgery. Am J Ophthalmol 2004;137:96–100. 15. Wong V, Kasbekar S, Young J, et al. The effect of scleral exoplant removal on strabismus following retinal detachment repair. J AAPOS 2011;15:331–333. 16. Nuzzi G, Rossi S. Buckle removal in retinal detachment surgery: a consecutive case series. Acta Biomed 2008;79: 128–132. Strabismus
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17. James M, O’Doherty M, Beatty S. Buckle-related complications following surgical repair of retinal dialysis. Eye (Lond) 2008;22:485–490. 18. Wolff SM. Strabismus after retinal detachment surgery. Trans Am Ophthalmol Soc 1983;81:182–192. 19. Deokule S, Reginald A, Callear A. Scleral explant removal: the last decade. Eye (Lond) 2003;17:697–700. 20. Deutsch J, Aggarwal RK, Eagling EM. Removal of scleral explant elements: a 10-year retrospective study. Eye (Lond) 1992;6:570–573. 21. Schwartz PL, Pruett RC. Factors influencing retinal redetachment after removal of buckling elements. Arch Ophthalmol 1977;95:804–807. 22. Lindsey PS, Pierce LH, Welch RB. Removal of scleral buckling elements. Causes and complications. Arch Ophthalmol 1983;101:570–573.
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23. Cooper LL, Harrison S, Rosenbaum AL. Ocular torsion as a complication of scleral buckle procedures for retinal detachments. J AAPOS 1998;2:279–284. 24. Munoz M, Rosenbaum AL. Long-term strabismus complications following retinal detachment surgery. J Pediatr Ophthalmol Strabismus 1987;24:309–314. 25. Mallette RA, Kwon JY, Guyton DL. A technique for repairing strabismus after scleral buckling surgery. Am J Ophthalmol 1988;106:364–365. 26. Smiddy WE, Loupe D, Michels RG, et al. Extraocular muscle imbalance after scleral buckling surgery. Ophthlamology 1989;96:1485–1489. 27. Wright LA, Cleary M, Barrie T, Hammer HM. Motility and binocularity outcomes in vitrectomy versus scleral buckling in retinal detachment surgery. Graefes Arch Clin Exp Ophthalmol 1999;237:1028–1032.
Strabismus surgery outcomes after scleral buckling procedures for retinal reattachment Jee Ho Chang,
MD
1,2
, Amy K. Hutchinson, MD1, Monica Zhang, and Scott R. Lambert, MD1
1
MD
,
1
Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, and Department of Ophthalmology, Soonchunhyang University Hospital Bucheon, Bucheon, South Korea
ABSTRACT Objective: To investigate the outcomes of strabismus surgery in patients with a prior history of a scleral buckling procedure for retinal reattachment. Methods: We reviewed the medical records of 18 patients who underwent strabismus surgery following a scleral buckling procedure and investigated the effect of multiple variables on postoperative alignment after strabismus surgery including gender, age, surgeon, number of strabismus surgeries, adjustable suture use, previous pars plana vitrectomy, preoperative best-corrected visual acuity, and scleral buckle removal. Outcomes were considered successful if there was 10 prism diopters (PD) residual horizontal and/or 4 PD residual vertical deviations. Statistical analyses were performed using Fisher’s exact test, Mann-Whitney test, and nominal logistic regression. Results: Success using our criteria of motor alignment was achieved in 6 of 18 eyes (33%). A higher rate of success was found in the scleral buckle removal group (success with buckle removal, 62.5%; success without buckle removal, 10.0%; p = 0.04). Nominal logistic regression analysis showed scleral buckle removal was the most significant factor associated with successful surgical alignment (p = 0.03; odds ratio = 16.67). Although the success rate was higher in the adjustable suture group (50% in adjustable group vs 14.3% in non-adjustable group: Fisher’s exact test, p = 0.30), this difference was not statistically significant. No retinal redetachments occurred after scleral buckle removal. Conclusions: These results suggest that scleral buckles can be safely removed in selected patients with strabismus following retinal reattachment surgery and scleral buckle removal may improve ocular alignment following strabismus surgery. Keywords: Scleral buckle, strabismus surgery, retinal detachment
20 13
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2
beneath extraocular muscles; 3,5 or the redirection of muscle force vectors either directly or indirectly by the buckle.11,12 When planning the surgical approach for a patient with strabismus after a scleral buckling procedure, the question frequently arises whether to remove a scleral buckle. If the buckle is the obvious cause of the strabismus, the removal of the buckle either before or during strabismus surgery is viewed as helpful by many surgeons.13,14 However, the benefit and safety of scleral buckle removal when it is not the obvious cause of strabismus is more controversial.
INTRODUCTION Strabismus following retinal reattachment surgery may resolve spontaneously,1,2 but in 5% to 25% of cases it can persist on a long-term basis.3,4,5 Strabismus following a scleral buckling procedure may occur on a sensory basis,6 from peribulbar anesthesia myotoxicity7 or mechanical factors related to the implantation of a scleral buckle. These mechanical factors may arise secondary to direct muscle injury; 3,4,5,8 adhesions between muscle, sclera, and fat; 9,10 the bulk effect of scleral buckling elements
Received 20 August 2012; Accepted 18 September 2013; Published online 12 November 2013 Correspondence: Scott R. Lambert, MD, Emory Eye Center, 1365-B Clifton Road, Atlanta, GA 30322. Tel: 404-778-4417. Fax: 404-778-5203. E-mail: [email protected].
235
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236 J. H. Chang et al. Some authors have suggested that the removal of a scleral buckle does not affect the outcome of strabismus surgery,3,5 while others have recommended buckle removal to relieve restriction 4 and even suggested that removal of the scleral buckle alone can improve ocular alignment and consider buckle removal to be the logical first step in correcting the strabismus.1 While a recent small study of 5 patients reported no benefit of scleral explant removal,15 another study reported resolution of diplopia in 4 patients after scleral buckle removal.16 However, neither of these studies evaluated the effect of scleral buckle removal combined with strabismus surgery. We retrospectively reviewed the motor outcomes of strabismus surgery in a cohort of patients who had all previously undergone a scleral buckling procedure to treat retinal detachment.
MATERIALS AND METHODS This retrospective study was approved by the institutional review board at Emory University School of Medicine. The data used for this analysis were treated in accordance with the Health Insurance Portability and Accountability Act (HIPAA) and the tenets of the Declaration of Helsinki. We reviewed the medical records of patients who underwent strabismus surgery following retinal detachment surgery at the Emory Eye Center between 1989 and 2010. Patients were identified from a large database of adult strabismus surgery patients and by searching for adult patients with the ICD-9 code for retinal detachment (361.00-361.09) and strabismus surgery (67311, 67312, 69314, 69316, or 67318) between 1996 and 2010. We excluded patients known to have strabismus prior to retinal reattachment surgery and ocular comorbidities that could have caused restrictive strabismus (eg, thyroid ophthalmopathy, orbital trauma, etc). We also excluded patients who incurred unintended muscle injuries during scleral buckling procedures such as rupture of a muscle or peribulbar anesthetic myotoxicity. Finally, we excluded patients with a follow-up of less than 1 month after the final strabismus surgery. To be included in the series, patients must have undergone a surgical procedure to treat retinal detachment that included the placement of a scleral buckle. If it was deemed possible that removal of the scleral buckle would improve the outcome of strabismus surgery, a retina surgeon was consulted prior to strabismus surgery to assess the patient’s risk of retinal detachment if the scleral buckle was removed. Factors considered to be high risk for retinal detachment included a history of proliferative vitreoretinopathy or a giant retinal tear, multiple operations
required to achieve retinal reattachment, recent retinal operation, and any visible traction on the retina. We extracted the following data from the medical record for each patient: gender, age, strabismus surgeon, type of strabismus surgery or surgeries, the duration between scleral buckling surgery and the first strabismus surgery, the timing of scleral buckle removal relative to strabismus surgery, whether the scleral buckle was partially or completely removed, whether the patient had undergone pars plana vitrectomy, whether an adjustable suture technique was used, preoperative best-corrected visual acuity, preoperative horizontal and vertical ocular alignment, horizontal and vertical ocular alignment at the last follow-up examination, postoperative prism use, and the length of follow-up after strabismus surgery. Ocular alignment was assessed using the alternate prism cover test except in patients with a severe visual deficit. The Krimsky test was used to assess ocular alignment in patients with a severe visual deficit. We did not analyze torsion since it was inconsistently documented. Although the reasons for scleral buckle removal or non-removal were not always documented, when available the reasons are shown in Table 1. For descriptive purpose, esodeviation was assigned a negative value and exodeviation a positive value. For vertical deviation, the right eye was the reference eye. Right hypodeviation was assigned a negative value and right hyperdeviation a positive value. As a single representative of preoperative deviation, preoperative vector magnitude of deviation was used so that horizontal and vertical deviations could be described with one variable. The magnitude of the vector was calculated by taking the square root of the sum of squares of horizontal deviations and vertical deviations.15 We defined strabismus surgery as being successful when the final postoperative horizontal deviation was 10 prism diopters (PD) and the final postoperative vertical deviation was 4 PD. Because pre- and postoperative binocularity was not consistently documented in the medical record, we did not use this as a factor when evaluating the success of strabismus surgery. Likewise, we did not use the presence or absence of diplopia as a factor when evaluating the success of strabismus surgery because best corrected visual acuity was severely reduced in many of the operative eyes so that diplopia was not always a reliable indicator of successful ocular alignment. For the sake of statistical coding, categorizational reduction of information was inevitable. The surgical procedures were especially diverse in terms of horizontal, vertical, and torsional surgeries and the timing of scleral buckle removal. Three features of the surgical technique were selected for analysis: (1) whether the scleral buckle was removed or not; (2) the number of strabismus surgeries performed; Strabismus
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F
F F
F
F F
M
F
M
F
M
M M M
5
6 7
8
9 10
11
12
13
14
15
16 17 18
36 31 61
59
58
49
56
14
53 58
41
32 62
53
35 67 44 49
1 2 1
1
1
3
1
3
1 3
3
1 2
2
1 1 2 1
During strabismus surgery No removal No removal
3 months before No removal No removal During 2nd strabismus surgery
Time of buckle removal
LMR res, LLR rec RLR rec LSR rec
No removal No removal No removal
During strabismus surgery RIR rec No removal LMR res/LLR rec During 1st strabismus surgery RMR res, RLR rec During strabismus surgery LIR rec, LSR and LSO adhe- During strabismus sion lysis surgery RMR rec During strabismus surgery RMR rec, RLR rec, No removal vertical transposition LMR res, LLR rec No removal
RMR rec
RLR rec, RMR res LLR rec
RSR rec, RIR res RSR rec LSR rec, LIR res RLR rec, RMR res/RLR rec, RMR res, RSO repositioning RLR rec, RMR res
Surgery or surgeries*
Complete
Complete
Complete
Complete
Complete
Partial
Partial
Complete
Complete/ partial SB removal
Risk of redetachment-giant retinal tear N/A N/A N/A
N/A
N/A
N/A
N/A
Patient refusal N/A
Reluctant remove all buckle N/A Lessen damage to muscle, severe fibrotic muscle Due to extrusion
Due to extrusion N/A N/A Displacement of SO tendon
Reason of removal/ no removal
No No No
No
Yes
No Yes Yes
Yes
Yes
Yes
No
Yes Yes
No
No No
Yes
Yes Yes Yes Yes
Yes
Yes
No
Yes
Yes Yes
No
Yes Yes
Yes
No No Yes Yes
20/80 20/20 20/25
20/25
20/50
20/400
CF
20/50
20/200 20/100
20/30
CF 20/100
20/70
20/30 20/200 20/100 CF
35
15 0
50 25
70 20 0
20
40
0 3 20
0
6
25
4 45
16 0 0
20
14
6
0 8
14 8 0 25
2 0
1.5
2.8 2.8 6.7
10 6 6
3.8
21.3
2.5
2.9
1.5 2.4
1.5
2.1 4.7
5.5
4.4 51.0 58.6 16.1
0
2
0
14
0
0 6
0
0 0
15 16
20
0
0 9 20 2
0
0 20 16 8
0 0
0
35 14 25 14
No No No
No
No
Yes
No
No
Yes No
Yes
No No
Yes
Yes No No Yes
No No No
No
Yes
No
No
No
No Yes
No
No No
No
No Yes Yes Yes
Duration of F/U Surgical Prism Vertiz Horiy Vertiz (months) Success Use
Final F/U deviation
25 35
20
10 12 0 14
BCVA of operated eye Horiy PPV Adjust
Preoperative deviation
PPV, history of pars plana vitrectomy; adjust, use of adjustable suture technique; BCVA, best corrected visual acuity; hori, horizontal; verti, vertical; preop, preoperative; F/U, follow-up; SR, superior rectus; IR, inferior rectus; LR, lateral rectus; MR, medial rectus; SO, superior oblique; rec, recession; res, resection; N/A, not available; SB, scleral buckle. *Delineates different surgical intervention. y þ, exotropia; , esotropia. z þ, right hypertropia; , right hypotropia.
F M M M
1 2 3 4
Pt. No. Gender Age Surgeon
TABLE 1. Patient clinical characteristics.
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Scleral buckle removal 237
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238 J. H. Chang et al. and (3) whether the adjustable suture technique was used during strabismus surgery. Two-tailed Fisher’s exact test was used to determine whether there was a significant difference in surgical success as defined when the following factors were analyzed: gender, surgeon performing the strabismus surgery, the number of strabismus surgeries, scleral buckle removal, pars plana vitrectomy, use of adjustable sutures, and poor vision. Poor vision was defined as visual acuity 520/200. The MannWhitney test was used to evaluate the effect of patient’s age and preoperative vector magnitude of deviation on surgical success. Since the scleral buckle removal was found to be significantly related to surgical success from the primary analysis, a subsequent analysis was performed to test whether other variables may be confounding factors. The two-tailed Fisher’s exact test was performed for nominal variables and MannWhitney test was used for continuous variables. Nominal logistic regression was performed for additional statistical analysis of confounding factors since it does not assume a standard distribution of dependent variables. We chose scleral buckle removal as the pivotal variable and paired it with 3 probable variables: surgeon, use of adjustable sutures, and preoperative vector magnitude of deviation. All statistical analysis was performed using SPSS version 16.0 (SPSS Inc., Chicago, Illinois) and P value for significance was set at 0.05.
RESULTS The medical records of 23 patients who had undergone strabismus surgery at our institution following a scleral buckling procedure were reviewed. Two patients were excluded because their strabismus was judged to be secondary to the rupture or loss of an extraocular muscle during the scleral buckling procedure. Another patient was excluded who was believed to have developed strabismus secondary to peribulbar anesthesia myotoxicity prior to the scleral buckling procedure. Finally, two cases were excluded because their follow-up was less than one month. Statistical analyses were performed on the remaining 18 patients. The clinical characteristics of the patients are shown in Table 1. The mean patient age at the time of strabismus surgery was 48 years (range, 14 to 67 years). The median time from scleral buckling surgery to the first strabismus surgery was 14.5 months (range, 8 months to 19 years). The median preoperative best corrected visual acuity of the postretinal detachment eyes was 20/100 (range, 20/20 to counting fingers). All of the operated eyes had worse visual acuity than their fellow eyes. The median best corrected visual acuity of the fellow eyes was 20/20 (range, 15/20 to 20/30).
Their preoperative horizontal deviations ranged from 25 PD esodeviation to 70 PD exodeviation (median, 20 PD exodeviation) and the preoperative vertical deviations from 25 PD right hypodeviation to 35 PD right hyperdeviation (median, 0 PD vertical deviation). Eight patients had both horizontal and vertical deviations. Seven patients only had horizontal deviations and three patients only had vertical deviations. All strabismus surgeries were performed on postretinal detachment surgery eyes only. The following strabismus surgeries were performed as the initial procedure: horizontal rectus recession and resection (n = 6), horizontal rectus recession or resection (n = 5), vertical rectus recession and resection (n = 3), inferior or superior rectus recession (n = 3), and lysis of adhesions to the superior oblique tendon (n = 1). Patients 4 and 10 underwent a second strabismus surgery. An adjustable suture was used in 10 patients. Scleral buckles were removed from 8 patients. The buckle was removed at the time of strabismus surgery in 7 patients and prior to strabismus surgery in one patient. Complete buckle removal was performed on 6 patients and partial removal on two patients. In two patients, extrusion of the scleral buckle prompted its removal. One of the extruded implants (Patient 8) was a hydrogel explant (Miragel, Medical Instruments Research Associates, Waltham, Massachusetts). Reasons cited for not removing the scleral buckle included high risk of redetachment (Patient 16, with giant retinal tear), severe fibrosis around the scleral buckle (Patient 7), and patient refusal (Patients 5 and 9). In one patient (Patient 4), the superior oblique tendon was found to be incarcerated by the encircling band. The type of scleral buckle was not always known since many of the patients had been referred from outside institutions for strabismus surgery. The median postoperative follow-up was 3.4 months (range, 1.5 to 59 months). The overall success rate was 33% (6 of 18 patients). A higher rate of success was found in the scleral buckle removal group (62.5%) versus the group not undergoing buckle removal (10.0%; p = 0.04). Three patients were orthotropic—2 in the group that underwent scleral buckle removal and 1 in the group retaining the scleral buckle. All of the other patients had some residual strabismus (Table 1). Five patients were prescribed prisms postoperatively to treat diplopia—2 in the group that underwent scleral buckle removal and 3 in the group retaining the scleral buckle. Although the success rate was higher in the adjustable suture group (50% in adjustable group versus 14.3% in non-adjustable group: Fisher’s exact test, p = 0.30), this difference was not statistically significant. Three strabismus surgeons performed the strabismus surgeries but there was no significant difference in the rate of success between surgeons Strabismus
Scleral buckle removal 239 TABLE 2. Detailed table of individual variable statistical analyses. Name of variable
Categories
Agey
–
Gender Surgeon
Number of strabismus surgeries SB removal
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Prior PPV Adjustable Poor vision Preop vector magnitude of deviationy
Male Female Surgeon 1 Surgeon 2 Surgeon 3 Once Twice No removal Removal No Yes No Yes 20/200 520/200 –
No success group (n = 12)
Success group (n = 6)
Success rate in each row
p Value
Median = 57 (interquartile range: 33–61) 7 5 7 3 2 11 1 9 3 3 9 7 5 10 2 Median = 20.0 (interquartile range: 18–28)
Median = 49 (interquartile range: 40–53) 2 4 3 1 2 5 1 1 5 2 4 1 5 4 2 Median = 26.2 (interquartile range: 20–45)
–
0.43
22.2% 44.4% 30.0% 25.0% 50.0% 31.3% 50.0% 10.0% 62.5% 33.3% 30.8% 12.5% 50.0% 28.6% 50.0% –
0.62 0.82
1.00 0.04* 1.00 0.15 0.57 0.07
SB, scleral buckle; PPV, pars plana vitrectomy; preop, preoperative. *Denotes statistical significance. For all nominal variables, Fisher’s exact tests were performed. yMann-Whitney tests were performed for age and preoperative vector magnitude of deviation. The number in the cell is median and numbers in parentheses are interquartile range from 25% to 75%.
using the two-tailed Fisher’s exact test (p = 0.82) (Table 2). Statistical tests for differences in the frequency of other variables between the scleral removal and non-removal group did not show a significant difference. With nominal logistic regression analyses, scleral buckle removal was the strongest predictor of surgical success (p = 0.03; odds ratio = 16.67). None of the other variables were statistically significant with this model. However, with scleral buckle in the model, there was a trend for preoperative vector magnitude of deviation to be significant (p = 0.08). There were no retinal redetachments in any of the patients following scleral buckle removal and/or strabismus surgery.
DISCUSSION We found better postoperative ocular alignment in patients who underwent scleral buckle removal either preceding or during strabismus surgery compared to patients in whom the buckle was not removed. Scleral buckle removal may have improved ocular alignment in our patients for a number of reasons: (1) it may have allowed the rectus muscles to attach directly to the sclera; (2) it may have lengthened muscles that were splayed over bulky implants; (3) the careful dissection and lysis of adhesions during removal of the buckle may have lessened muscle restriction; !
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(4) it may have permitted the muscles to move more freely during the adjustment procedure; and (5) it may have freed an oblique tendon or muscle inadvertently incorporated in the scleral buckle. Our overall success rate was relatively low (33%) using the criteria we chose to define success. Some series have defined success using subjective factors such as ‘‘symptomatic vs. non symptomatic’’17 or ‘‘cosmetic improvement’’.18 We used motor alignment as our definition of success. Other series have defined success as binocular vision with or without a prismatic correction or a compensatory head posture.18,15 Ideally, sensory outcomes would have been included in our definition of success, but this was not possible given the inconsistency of the reporting of these findings in the medical record for our retrospective study. Recent studies on retinal redetachment rate following scleral buckle removal report rates from 0% to 8%19,20,17,16 whereas earlier studies reported rates from 14%21 to 47%.22 These differences likely reflect improvements in surgical techniques and patient selection. For example, earlier studies of retinal redetachment often used techniques that are no longer in use (eg, diathermy, scleral dissection, and polyethylene tubing explants)20 and many scleral buckles were removed secondary to infections.22,21 Risk factors for retinal redetachment following removal of a scleral explant include: a shorter interval between the primary retinal detachment repair and
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240 J. H. Chang et al. removal of the buckle; 21 the presence of retinal tears, as opposed to holes; 21 failure to identify retinal breaks at the time of the initial retinal detachment surgery; 20 the presence of vitreous traction,19,22,21 and an increased number of quadrants of retinal detachment prior to retinal reattachment.22 All of the patients in our study were screened by retinal surgeons prior to removal of the scleral buckle and none of the patients who had their scleral buckle removed prior to or in conjunction with strabismus surgery were deemed to be at high risk for retinal redetachment. Similarly, no retinal redetachments have been reported in other studies evaluating scleral buckle removal in conjunction with strabismus surgery.23,1,24 Consultation with a retinal surgeon should be obtained prior to scleral buckle removal to assess the risk of retinal redetachment.24,4 Because of the anatomical changes brought about by scleral buckle surgery, standard tables for strabismus surgery may not apply. For this reason, adjustable sutures may be advantageous.1,25,24,4 Although the success rate was higher in the adjustable suture group (50% in adjustable group versus 14.3% in the non-adjustable group), this difference was not statistically significant. The lack of benefit of adjustable sutures in our study may be related to its small sample size. There are conflicting reports on the effect of decreased vision on the success rate of strabismus surgery after a scleral buckling procedure.6,26 We defined poor vision as 520/200 and did not find a difference in the success rate based on preoperative vision. Our study had a number of limitations. First, the sample size of our study was quite small (n = 18). However, since strabismus surgery following scleral buckling surgery is an uncommon procedure, it would be difficult to perform a large randomized clinical trial of this condition. Indeed, the largest comparable series in the literature only included 20 patients,24 17 patients,23 and 12 patients27 and none of these studies compared the effect of scleral buckle removal versus non-removal on the outcomes of strabismus surgery. A second limitation of our study was its retrospective design. Because the data were collected over420 years and involved 3 different surgeons, important data such as pre- and postoperative binocularity and the presence or absence of diplopia were not consistently documented. A third limitation was the many confounding factors. To identify potential confounders, we evaluated differences in the frequency of other variables between the scleral buckle removal and non-removal groups. We also performed a multiple logistic regression analysis to control for potential confounding variables. In conclusion, scleral buckle was associated with better ocular alignment following strabismus surgery
in our series and none of our patients had retinal redetachment after scleral buckle removal.
ACKNOWLEDGEMENTS Supported in part by an unrestricted grant to the Emory Eye Center from Research to Prevent Blindness, Inc., New York, New York, and NIH Core Grant EY06360.
DECLARATION OF INTEREST No financial conflict of interest in subject matter in the manuscript.
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23. Cooper LL, Harrison S, Rosenbaum AL. Ocular torsion as a complication of scleral buckle procedures for retinal detachments. J AAPOS 1998;2:279–284. 24. Munoz M, Rosenbaum AL. Long-term strabismus complications following retinal detachment surgery. J Pediatr Ophthalmol Strabismus 1987;24:309–314. 25. Mallette RA, Kwon JY, Guyton DL. A technique for repairing strabismus after scleral buckling surgery. Am J Ophthalmol 1988;106:364–365. 26. Smiddy WE, Loupe D, Michels RG, et al. Extraocular muscle imbalance after scleral buckling surgery. Ophthlamology 1989;96:1485–1489. 27. Wright LA, Cleary M, Barrie T, Hammer HM. Motility and binocularity outcomes in vitrectomy versus scleral buckling in retinal detachment surgery. Graefes Arch Clin Exp Ophthalmol 1999;237:1028–1032.
