- Email: [email protected]
Z-tenotomy of the superior oblique tendon and horizontal rectus muscle surgery for A-pattern horizontal strabismus
Z-tenotomy of the superior oblique tendon and horizontal rectus muscle surgery for A-pattern horizontal strabismus Yonina Ron, MD,*,a,c Moshe Snir, MD,*,a,b,c Ruth Axer-Seigel, MD,b,c and Ronit Friling, MDa,c PURPOSE
METHODS
RESULTS
CONCLUSIONS
Few studies have investigated combined surgeries for horizontal deviation and A pattern caused by superior oblique overaction (SOOA). This study presents our experience with combined surgery and examines the effect of the type of strabismus and prior surgery on outcome. The medical records of patients who underwent combined surgery for horizontal deviation occurring with A-pattern misalignment from 2000 through 2004 were reviewed. The procedure consisted of horizontal extraocular muscle recession or resection with superior oblique Z-tenotomy. The criteria for surgical success were horizontal deviation at primary gaze of ⱕ10⌬, A pattern of ⱕ8⌬, and SOOA of ⱕ1.0. The study group included 28 patients with a mean age of 13.4 years. Thirteen (46.4%) had A-pattern esotropia; 15 (53.6%) had A-pattern exotropia. Fifteen (50%) had undergone previous surgery. The success rate for the whole group was 60.7%. There was no statistically significant difference in success rate between patients with esotropia (53.8%) or exotropia (66.7%) ( p ⫽ 0.48) or between patients in whom the combined procedure was the primary (71.4%) or secondary (50.0%) treatment ( p ⫽ 0.246). Measurements of horizontal strabismus remained stable throughout follow-up in the esotropia group but were unpredictable in the exotropia group. The success rate of combined horizontal deviation/A-pattern surgery is unaffected by type of horizontal deviation or prior surgery. ( J AAPOS 2009;13:27-30)
T
he etiology of A-pattern deviation is not understood. There is some evidence that it is caused by overaction of the superior oblique muscle, apparently as the result of an alteration in central vestibular tone.1 Gobin2 suggests that A-pattern deviation is caused by sagittalization of the trochlea of the superior oblique, that is, a reduction of the angle between the muscle and the visual axis. Several surgical procedures have been described to correct A pattern, all with a success rate of 60% to 90%.3-6 The success rate for horizontal strabismus correction ranges from 60% to 80%, with the outcome being generally better for esotropia correction than for exotropia correction.7
Author affiliations: aPediatric Ophthalmology Unit, Schneider Children’s Medical Center of Israel, Petah Tiqwa, Israel; bDepartment of Ophthalmology Rabin Medical Center, Petah Tiqwa, Israel; and cSackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel *The first two authors Y.R. and M.S. contributed equally to this work. Submitted December 20, 2007. Revision accepted September 12, 2008. Published online December 15, 2008. Reprint requests: Y. Ron, MD, Pediatric Ophthalmology Unit Schneider Children’s Medical Center of Israel, 14 Kaplan Street, Petah Tiqwa 49202, Israel (email: [email protected]). © 2009 Published by Elsevier Inc. on behalf of the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2009/$36.00 ⫹ 0 doi:10.1016/j.jaapos.2008.09.004
Journal of AAPOS
Few studies to date have investigated the value of combined surgical treatment in patients with horizontal deviation and A pattern caused by superior oblique overaction (SOOA).8-12 The results indicate that the horizontal correction is not affected by the presence of A or V pattern and that the outcome of the horizontal strabismus procedure is not influenced by the cyclovertical procedure, or vice versa, even when performed in the same session.8-10 Shuey et al11 described an 84% rate of A-pattern collapse combined with a more than 50% decrease in horizontal misalignment, and Lee and Rosenbaum12 reported a 60% success rate of simultaneous surgery on the horizontal and superior oblique muscles. The aim of the present study was to describe our experience with combined surgery for horizontal deviation and A pattern caused by SOOA. We also investigated the effect of the type of horizontal strabismus (esotropia vs exotropia) and previous strabismus surgery on surgical outcome.
Patients and Methods We reviewed the medical records of all patients who underwent combined surgery for horizontal deviation (esotropia or exotropia) and A pattern misalignment caused by SOOA between January 2000 and December 2004. Other inclusion criteria were as follows: (1) no previous superior oblique muscle surgery; (2) A
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Table 1. Success rates of combined surgery according to subgroups
Esotropia Exotropia Total
First surgery, n (%)
Not first surgery, n (%)
Total, n (%)
5/7 (71.4) 5/7 (71.4) 10/14 (71.4)
2/6 (33.3) 5/8 (62.5) 7/14 (50.0); p ⫽ 0.592
7/13 (53.8), p ⫽ 0.2861 10/15 (66.6), p ⫽ 1.00
pattern of ⱖ10⌬; (3) horizontal deviation of ⱖ10⌬; (4) no ocular abnormality; and (5) follow-up of ⱖ6 months. All patients underwent a thorough neurological examination by a pediatrician to exclude the presence of myasthenia gravis, intracranial vascular problems, or space-occupying lesions. A comprehensive ophthalmic and orthoptic evaluation was performed before and after surgery, including cycloplegic refraction with 2 instillations of cyclopentolate 1% and phenylephrine 2.5% (10 minutes apart). Distance (6 m) and near (0.33 m) deviations in the primary directions were measured with the alternate prism cover test using an accommodative target in all diagnostic positions of gaze, with normal head position and the best optical correction. A pattern was calculated by the difference in alignment between 30° upgaze and 30° downgaze positions. Gross binocular vision was evaluated with a Bagolini test and stereopsis was measured with the Titmus fly test. Both tests were performed in primary position with best corrected visual acuity. SOOA was assessed by version examination. Surgery in all cases consisted of standard horizontal extraocular muscle surgery for esotropia or exotropia as well as Z-tenotomy to reduce SOOA and to collapse the A pattern. Z-tenotomy of the superior oblique is performed by 90% disinsertion of the superior oblique tendon followed by a second incision at a distance of 10 –12 mm in the opposite direction. This procedure lengthens and thins the tendon, thereby weakening its action.13 All operations were performed by the same surgeons (RF or MS). The criteria for surgical success were horizontal deviation at primary gaze (distance and near) of ⱕ10⌬, A pattern of ⱕ8⌬, and SOOA of ⱕ ⫹1.0, where ⫹ 1 is considered minimal overaction, ⫹2 moderate, ⫹3 severe, and ⫹ 4 maximal. The anatomical landmarks used to assess the degree of overaction (⫹1 to ⫹3) were based on the position of the pupil in respect to the lower eyelid margin; ⫹4 was used when the eye was abducted while trying to perform infraversion.
Statistical Analysis Statistical analyses were performed with Pearson’s 2 test. Differences in quantitative variables, such as distance and near deviation and A pattern at diagnosis and before surgery, were analyzed with the t-test. A p-value of 0.05 or less was considered significant.
Results The study group consisted of 28 patients, 12 male and 16 female, of mean age 13.4 ⫾ 10.9 years at the time of surgery (range, 2-46 years). Thirteen patients (46.4%) had A-pattern esotropia and 15 (53.6%) had A-pattern exotropia. Fourteen patients (50%) had undergone previous horizontal strabismus surgery. Mean duration of postopera-
tive follow-up was 32.5 ⫾ 16.9 months (range, 7-63 months for 27 of 28 patients); 1 patient underwent a second surgery after 2 months of follow-up because of a large residual misalignment. For the patients treated for esotropia, mean preoperative distance was 25⌬ ⫾ 6.7⌬ and mean near horizontal deviation was 26.4⌬ ⫾ 9.0⌬. For the patients treated for exotropia, the measurements were 12.6⌬ ⫾ 25.3⌬ for distance and 20.1⌬ ⫾ 16.3⌬ for near. At the last postoperative follow-up visit, the distance and near horizontal deviations in the esotropia group were 4.4⌬ ⫾ 7.3⌬ and 7.3⌬ ⫾ 8.4⌬, respectively, and in the exotropia group, 2.5⌬ ⫾ 9.6⌬ and 2.4⌬ ⫾ 11.6⌬, respectively. Individually, the postoperative horizontal distance and near deviations were within ⫾ 10⌬ in all but 5 patients. The success rate of surgery for horizontal deviation alone was 76.9%, regardless of whether it was performed as the primary or secondary procedure. The mean A pattern before surgery was 24.2⌬ ⫾ 13.8⌬ (range, 10⌬-70⌬). There was no statistically significant difference in preoperative A pattern between patients in whom horizontal deviation surgery was performed as the secondary (22.1⌬ ⫾ 12.7⌬) or primary (26.2⌬ ⫾ 15.0⌬) procedure ( p ⫽ 0.44), and between patients treated for esotropia (mean A pattern: 26.23⌬ ⫾ 12.6⌬) or exotropia (mean A pattern: 22.4⌬ ⫾ 14.9⌬; p ⫽ 0.473). Postoperatively, the mean A pattern was reduced to 2.8⌬ ⫾ 9.8⌬ (range, 0⌬-35⌬), representing a 21.4⌬ (88%) collapse. There was no significant difference in postoperative A pattern between patients undergoing primary or secondary surgery (5.15⌬ ⫾ 10.04⌬ and ⫺0.30⌬ ⫾ 9.07⌬, respectively; p ⫽ 0.193), or by type of horizontal deviation (5.80⌬ ⫾ 11.40⌬ for esotropia and 0.46⌬ ⫾ 8.06⌬ for exotropia; p ⫽ 0.203). The total rate for collapsing the A pattern was 71.4%: 61.5% in the esotropia group and 80.0% in the exotropia group ( p ⫽ 0.843). There was no statistically significant difference in success rate between patients who had had previous strabismus surgery (64.3%) and those who had not (78.6%) ( p ⫽ 0.403). Mean SOOA decreased from ⫹ 1.6 preoperatively to ⫹ 0.33 postoperatively (a reduction of 79.4%). The total surgical success rate, which was defined as horizontal deviation of 10⌬ or less and A pattern of 8⌬ or less, was 60.7% for the whole group. There was no statistical difference in the success rate between the patients with esotropia (53.8%) or exotropia (66.7%) ( p ⫽ 0.480), or between the patients who had or had not undergone prior strabismus horizontal surgery (50.0% and 71.4%, respectively, p ⫽ 0.246) (Table 1).
Journal of AAPOS
Volume 13 Number 1 / February 2009
One difference was found between the esotropia and exotropia groups. In the first 3 postoperative weeks, mean near deviation in the esotropia group measured ⫹ 7.5⌬ and mean distance deviation measured ⫹4.36⌬. These values were almost identical to the final horizontal measurements of ⫹ 7.4⌬ and ⫹ 4.45⌬, respectively. However, in the exotropia group, the near distance value changed from ⫺4.50 ⌬ (minus sign represents exotropia) to ⫹ 7.80⌬, and the near distance value from ⫺3.60⌬ to ⫹ 6.40⌬; this difference was statistically significant ( p ⫽ 0.03). The A pattern, however, was stable throughout follow-up in both groups ( p ⫽ 0.874). Four patients had normal fusion and stereopsis preoperatively, which did not change postoperatively. Two additional patients gained postoperative stereopsis, as measured with the Titmus fly test (one patient improved to 3,000 “the other to 140”). Both were 17 years old at the time of surgery, and both were treated for exotropia. Complications After the combined surgical procedure, 5 of the 28 patients (17.9%) required further surgery for various reasons: right eye hypertropia and dissociated vertical deviation; residual exotropia; residual A-pattern esotropia; consecutive A-pattern esotropia; and residual A pattern exotropia with left hypertropia. One patient had a V pattern of 20⌬ but did not undergo further surgery. Two of the patients undergoing additional surgery developed a large deviation that was noted immediately after surgery; in the others, the deviation developed later.
Discussion In the present single-center retrospective study, the overall success rate for combined horizontal strabismus and A-pattern surgery was 60%. When the patients who underwent combined surgery as the primary procedure were assessed separately, the overall success rate increased to 71%. This value is greater than the 60% reported by Lee and Rosenbaum12 for primary combined surgery. Their criteria for success were similar to ours, except for their definition of horizontal alignment as ⫾ 8⌬ versus ⫾ 10⌬ in the present study. The success rate in the primary-surgery group alone was 21% higher than in the secondarysurgery group. However, the difference did not reach statistical significance, perhaps because of the small sample size or because the previous procedure for horizontal misalignment did not include the superior oblique muscle. Although the patient group in the report of Shuey et al11 was similar to ours, the focus was on A pattern collapse, and the authors did not provide numerical results for horizontal deviation or combined outcome. As for collapsing the A pattern, we reported a success rate of 71.4% whereas other studies reported a slightly greater (85%) rate in combined surgery.11,12 Nevertheless, our result is in line with the 60% to 90% success rates reported for superior oblique weakening procedures
Journal of AAPOS
Ron et al
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alone.3-6 Given that the preoperative A pattern measurements were similar in the patients with or without previous horizontal extraocular muscle surgery, and in the patients with esotropia or exotropia, these results may indicate that the combined procedure is a good alternative to the 2-step approach. The improvement in the superior oblique overaction was similar to that reported by Suh et al14 using an adjustable superior oblique tendon spacer. Our success rate for horizontal deviation surgery alone was almost 80% for the whole group, with no difference between patients undergoing primary or secondary surgery or between patients with esotropia or exotropia. Lipton and Willshaw,7 in a multicenter retrospective study, reported a comparable success rate of 60% to 80%. Several studies have shown that the procedure performed to correct horizontal deviation and the procedure for A pattern caused by SOOA have no influence on each other. Gezer et al8 reported that a favorable or horizontal deviation outcome in patients with exotropia was unaffected by the presence of an A or V pattern, and Jin et al9 reported a negligible effect of bilateral superior oblique tenotomy on the primary horizontal binocular alignment. Exodeviation was the more common misalignment in our series (15 patients), although not statistically significant, in accordance with the findings of Parks15 and Jampolsky.16 The reason why A-pattern exotropia occurs more often than A pattern esotropia is not known. In our series, stereopsis was present in 6 patients: before surgery in 4, postoperatively in 2. Previous reports have shown that stereoacuity may improve after surgery in patients with previous fusion,16 but the mechanism underlying the changes remains unclear. The recovery of stereopsis has been associated with surgical correction of acquired strabismus,17 depending on the duration of the strabismus and the presurgical binocular vision status. Ball et al18 noted that, in some cases, stereoacuity develops postoperatively in the presence of good bilateral visual acuity and excellent postoperative alignment. Our total failure rate was 18%: 5 patients required repeated surgery after the combined procedure, and one showed a significant V pattern postoperatively but refused reoperation. McNeer et al19 reported a surgical complication rate of 50% in patients after bilateral superior oblique tenotomy. Complications included postoperative head tilt and hypertropia. Superior oblique underaction after superior oblique tendon recession was reported by Drummond et al20 in 1 of 10 patients, and by Caldeira21 in 3 of 16 patients. Using a similar design, Lee and Rosenbaum12 found significant unequal weakening effects in 4 patients. Urist22 reported a change to V-pattern deviation in 4 of 10 patients after bilateral superior oblique weakening procedures for A-pattern deviations. The patients treated for exotropia and A pattern showed a statistically significant shift in misalignment measurements. The outcome of surgical correction of exotropia is known to be less predictable and less stable than that of esotropia correction.23-25
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Our assessment of the clinical significance of surgical treatment for esotropia versus exotropia suggested that the combined procedure has equally good results. Comparison of each group separately (Table 1) yielded a higher success rate for the exotropia group, although the number of patients was too small to reach a definitive conclusion. One explanation may be the additive effect of superior oblique weakening on the abduction ability of the eye as the result of its tertiary action. In conclusion, our retrospective study indicates the effectiveness of simultaneous surgical treatment of the horizontal rectus muscles with superior oblique Z tenotomy in patients with combined horizontal misalignment and A pattern due to SOOA. The success rate of the combined surgery was comparable with the rates for each procedure performed separately, suggesting that the combined procedure offers a good alternative to 2 separate procedures. No difference was found between patients with esotropia and exotropia, or between those who underwent primary or secondary horizontal strabismus surgery. References 1. Brodsky MC, Donahue SP. Primary oblique muscle overaction: The brain throws a wild pitch. Arch Ophthalmol 2001;119:1307-14. 2. Gobin MH. Sagittalization of the oblique muscles as a possible cause for the “A”, “V”, and “X” phenomena. Br J Ophthalmol 1968;52: 13-18. 3. Vempali VM, Lee JP. Results of superior oblique posterior tenotomy. J AAPOS 1998;2:147-50. 4. Pollard ZF, Greenberg MF. Results and complications in 66 cases using a silicone tendon expander on overacting superior oblique with A pattern anisotropia. Bonocular Vis Strabismus Q 2000;15:113-20. 5. Sharma P, Khokhar S, Thanikachalam S. Evaluation of superior oblique weakening procedure. J Pediatr Ophthalmol Strabismus 1999;36:189-95. 6. Bardorf CM, Baker JD. The efficacy of superior oblique Z-tendon lengthening for superior oblique overaction. J AAPOS 2003;7:96102. 7. Lipton JR, Willshaw HE. Prospective multicentre study of the accuracy of surgery for horizontal strabismus. Br J Ophthalmol 1995; 79:10-11. 8. Gezer A, Sezen F, Nasri N, Gozum N. Factors influencing the outcome of strabismus surgery in patients with exotropia. J AAPOS 2004;8:56-60.
9. Jin YH, Sung KR, Kook MS. The immediate effect of bilateral superior oblique tenotomy on primary position horizontal binocular alignment. Binocul Vis Strabismus Q 1999;14:33-8. 10. Minguini N, Dantas FJ, Monteiro de Carvalho KM, Moreira-Filho DC. A study to determine: Should conventional amounts of eye muscle surgery for horizontal binocular deviations be changed when oblique muscle weakening procedures are simultaneously performed? Binocular Vis Strabismus Q 2005;20:21-5. 11. Shuey TF Jr, Parks MM, Friendly DS. Results of combined surgery on the superior oblique and horizontal rectus muscles for A-pattern horizontal strabismus. J Pediatr Ophthalmol Strabismus 1992;29: 199-201. 12. Lee SY, Rosenbaum AL. Surgical results of patients with A-pattern horizontal strabismus. J AAPOS 2003;7:251-5. 13. Bardorf CM, Baker JD. The efficacy of superior oblique split Ztendon lengthening for superior oblique overaction. J AAPOS 2003; 7:96-102. 14. Suh DW, Guyton DL, Hunter DG. An adjustable superior oblique tendon spacer with the use of nonabsorbable sutures. J AAPOS 2001;5:164-71. 15. Parks MM. Doyne Memorial Lecture, 1977. The superior oblique tendon. Trans Ophthalmol Soc U K. 1977;97:288-304. 16. Jampolsky AS. Bilateral anomalies of the oblique muscles. Trans Am Acad Ophthalmol Otolaryngol 1957;61:689-98. 17. Fawcett SL, Stager DR Sr, Felius J. Factors influencing stereoacuity outcomes in adults with acquired strabismus. Am J Ophthalmol 2004;138:931-35. 18. Ball A, Drummond GT, Pearce WG. Unexpected stereoacuity following surgical correction of long-standing horizontal strabismus. Can J Ophthalmol 1993;28:217-20. 19. McNeer KW. Untoward effects of superior oblique tenotomy. Ann Ophthalmol. 1972;4:747-50. 20. Drummond GT, Pearce WG, Astle WF. Recession of the superior oblique tendon in A-pattern strabismus. Can J Ophthalmol 1990;25: 301-5. 21. Caldeira JAF. Graduated recession of the superior oblique muscle. Br J Ophthalmol 1975;59:553-9. 22. Urist MJ. Complications following bilateral superior oblique weakening surgical procedures for A-pattern horizontal deviations. Am J Ophthalmol 1970;70:583-7. 23. Kushner BJ, Preslan MW, Morton GV. Treatment of partly accommodative esotropia with a high accommodative convergenceaccommodation ratio. Arch Ophthalmol 1987;105:815-18. 24. Kushner BJ, Morton GV. A randomized comparison of surgical procedures for infantile esotropia. Am J Ophthalmol 1984;95:50-61. 25. Kushner BJ. Exotropic deviations: A functional classification and approach to treatment. Am Orthoptic J. 1988;38:81-93.
Journal of AAPOS
METHODS
RESULTS
CONCLUSIONS
Few studies have investigated combined surgeries for horizontal deviation and A pattern caused by superior oblique overaction (SOOA). This study presents our experience with combined surgery and examines the effect of the type of strabismus and prior surgery on outcome. The medical records of patients who underwent combined surgery for horizontal deviation occurring with A-pattern misalignment from 2000 through 2004 were reviewed. The procedure consisted of horizontal extraocular muscle recession or resection with superior oblique Z-tenotomy. The criteria for surgical success were horizontal deviation at primary gaze of ⱕ10⌬, A pattern of ⱕ8⌬, and SOOA of ⱕ1.0. The study group included 28 patients with a mean age of 13.4 years. Thirteen (46.4%) had A-pattern esotropia; 15 (53.6%) had A-pattern exotropia. Fifteen (50%) had undergone previous surgery. The success rate for the whole group was 60.7%. There was no statistically significant difference in success rate between patients with esotropia (53.8%) or exotropia (66.7%) ( p ⫽ 0.48) or between patients in whom the combined procedure was the primary (71.4%) or secondary (50.0%) treatment ( p ⫽ 0.246). Measurements of horizontal strabismus remained stable throughout follow-up in the esotropia group but were unpredictable in the exotropia group. The success rate of combined horizontal deviation/A-pattern surgery is unaffected by type of horizontal deviation or prior surgery. ( J AAPOS 2009;13:27-30)
T
he etiology of A-pattern deviation is not understood. There is some evidence that it is caused by overaction of the superior oblique muscle, apparently as the result of an alteration in central vestibular tone.1 Gobin2 suggests that A-pattern deviation is caused by sagittalization of the trochlea of the superior oblique, that is, a reduction of the angle between the muscle and the visual axis. Several surgical procedures have been described to correct A pattern, all with a success rate of 60% to 90%.3-6 The success rate for horizontal strabismus correction ranges from 60% to 80%, with the outcome being generally better for esotropia correction than for exotropia correction.7
Author affiliations: aPediatric Ophthalmology Unit, Schneider Children’s Medical Center of Israel, Petah Tiqwa, Israel; bDepartment of Ophthalmology Rabin Medical Center, Petah Tiqwa, Israel; and cSackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel *The first two authors Y.R. and M.S. contributed equally to this work. Submitted December 20, 2007. Revision accepted September 12, 2008. Published online December 15, 2008. Reprint requests: Y. Ron, MD, Pediatric Ophthalmology Unit Schneider Children’s Medical Center of Israel, 14 Kaplan Street, Petah Tiqwa 49202, Israel (email: [email protected]). © 2009 Published by Elsevier Inc. on behalf of the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2009/$36.00 ⫹ 0 doi:10.1016/j.jaapos.2008.09.004
Journal of AAPOS
Few studies to date have investigated the value of combined surgical treatment in patients with horizontal deviation and A pattern caused by superior oblique overaction (SOOA).8-12 The results indicate that the horizontal correction is not affected by the presence of A or V pattern and that the outcome of the horizontal strabismus procedure is not influenced by the cyclovertical procedure, or vice versa, even when performed in the same session.8-10 Shuey et al11 described an 84% rate of A-pattern collapse combined with a more than 50% decrease in horizontal misalignment, and Lee and Rosenbaum12 reported a 60% success rate of simultaneous surgery on the horizontal and superior oblique muscles. The aim of the present study was to describe our experience with combined surgery for horizontal deviation and A pattern caused by SOOA. We also investigated the effect of the type of horizontal strabismus (esotropia vs exotropia) and previous strabismus surgery on surgical outcome.
Patients and Methods We reviewed the medical records of all patients who underwent combined surgery for horizontal deviation (esotropia or exotropia) and A pattern misalignment caused by SOOA between January 2000 and December 2004. Other inclusion criteria were as follows: (1) no previous superior oblique muscle surgery; (2) A
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Volume 13 Number 1 / February 2009
Table 1. Success rates of combined surgery according to subgroups
Esotropia Exotropia Total
First surgery, n (%)
Not first surgery, n (%)
Total, n (%)
5/7 (71.4) 5/7 (71.4) 10/14 (71.4)
2/6 (33.3) 5/8 (62.5) 7/14 (50.0); p ⫽ 0.592
7/13 (53.8), p ⫽ 0.2861 10/15 (66.6), p ⫽ 1.00
pattern of ⱖ10⌬; (3) horizontal deviation of ⱖ10⌬; (4) no ocular abnormality; and (5) follow-up of ⱖ6 months. All patients underwent a thorough neurological examination by a pediatrician to exclude the presence of myasthenia gravis, intracranial vascular problems, or space-occupying lesions. A comprehensive ophthalmic and orthoptic evaluation was performed before and after surgery, including cycloplegic refraction with 2 instillations of cyclopentolate 1% and phenylephrine 2.5% (10 minutes apart). Distance (6 m) and near (0.33 m) deviations in the primary directions were measured with the alternate prism cover test using an accommodative target in all diagnostic positions of gaze, with normal head position and the best optical correction. A pattern was calculated by the difference in alignment between 30° upgaze and 30° downgaze positions. Gross binocular vision was evaluated with a Bagolini test and stereopsis was measured with the Titmus fly test. Both tests were performed in primary position with best corrected visual acuity. SOOA was assessed by version examination. Surgery in all cases consisted of standard horizontal extraocular muscle surgery for esotropia or exotropia as well as Z-tenotomy to reduce SOOA and to collapse the A pattern. Z-tenotomy of the superior oblique is performed by 90% disinsertion of the superior oblique tendon followed by a second incision at a distance of 10 –12 mm in the opposite direction. This procedure lengthens and thins the tendon, thereby weakening its action.13 All operations were performed by the same surgeons (RF or MS). The criteria for surgical success were horizontal deviation at primary gaze (distance and near) of ⱕ10⌬, A pattern of ⱕ8⌬, and SOOA of ⱕ ⫹1.0, where ⫹ 1 is considered minimal overaction, ⫹2 moderate, ⫹3 severe, and ⫹ 4 maximal. The anatomical landmarks used to assess the degree of overaction (⫹1 to ⫹3) were based on the position of the pupil in respect to the lower eyelid margin; ⫹4 was used when the eye was abducted while trying to perform infraversion.
Statistical Analysis Statistical analyses were performed with Pearson’s 2 test. Differences in quantitative variables, such as distance and near deviation and A pattern at diagnosis and before surgery, were analyzed with the t-test. A p-value of 0.05 or less was considered significant.
Results The study group consisted of 28 patients, 12 male and 16 female, of mean age 13.4 ⫾ 10.9 years at the time of surgery (range, 2-46 years). Thirteen patients (46.4%) had A-pattern esotropia and 15 (53.6%) had A-pattern exotropia. Fourteen patients (50%) had undergone previous horizontal strabismus surgery. Mean duration of postopera-
tive follow-up was 32.5 ⫾ 16.9 months (range, 7-63 months for 27 of 28 patients); 1 patient underwent a second surgery after 2 months of follow-up because of a large residual misalignment. For the patients treated for esotropia, mean preoperative distance was 25⌬ ⫾ 6.7⌬ and mean near horizontal deviation was 26.4⌬ ⫾ 9.0⌬. For the patients treated for exotropia, the measurements were 12.6⌬ ⫾ 25.3⌬ for distance and 20.1⌬ ⫾ 16.3⌬ for near. At the last postoperative follow-up visit, the distance and near horizontal deviations in the esotropia group were 4.4⌬ ⫾ 7.3⌬ and 7.3⌬ ⫾ 8.4⌬, respectively, and in the exotropia group, 2.5⌬ ⫾ 9.6⌬ and 2.4⌬ ⫾ 11.6⌬, respectively. Individually, the postoperative horizontal distance and near deviations were within ⫾ 10⌬ in all but 5 patients. The success rate of surgery for horizontal deviation alone was 76.9%, regardless of whether it was performed as the primary or secondary procedure. The mean A pattern before surgery was 24.2⌬ ⫾ 13.8⌬ (range, 10⌬-70⌬). There was no statistically significant difference in preoperative A pattern between patients in whom horizontal deviation surgery was performed as the secondary (22.1⌬ ⫾ 12.7⌬) or primary (26.2⌬ ⫾ 15.0⌬) procedure ( p ⫽ 0.44), and between patients treated for esotropia (mean A pattern: 26.23⌬ ⫾ 12.6⌬) or exotropia (mean A pattern: 22.4⌬ ⫾ 14.9⌬; p ⫽ 0.473). Postoperatively, the mean A pattern was reduced to 2.8⌬ ⫾ 9.8⌬ (range, 0⌬-35⌬), representing a 21.4⌬ (88%) collapse. There was no significant difference in postoperative A pattern between patients undergoing primary or secondary surgery (5.15⌬ ⫾ 10.04⌬ and ⫺0.30⌬ ⫾ 9.07⌬, respectively; p ⫽ 0.193), or by type of horizontal deviation (5.80⌬ ⫾ 11.40⌬ for esotropia and 0.46⌬ ⫾ 8.06⌬ for exotropia; p ⫽ 0.203). The total rate for collapsing the A pattern was 71.4%: 61.5% in the esotropia group and 80.0% in the exotropia group ( p ⫽ 0.843). There was no statistically significant difference in success rate between patients who had had previous strabismus surgery (64.3%) and those who had not (78.6%) ( p ⫽ 0.403). Mean SOOA decreased from ⫹ 1.6 preoperatively to ⫹ 0.33 postoperatively (a reduction of 79.4%). The total surgical success rate, which was defined as horizontal deviation of 10⌬ or less and A pattern of 8⌬ or less, was 60.7% for the whole group. There was no statistical difference in the success rate between the patients with esotropia (53.8%) or exotropia (66.7%) ( p ⫽ 0.480), or between the patients who had or had not undergone prior strabismus horizontal surgery (50.0% and 71.4%, respectively, p ⫽ 0.246) (Table 1).
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Volume 13 Number 1 / February 2009
One difference was found between the esotropia and exotropia groups. In the first 3 postoperative weeks, mean near deviation in the esotropia group measured ⫹ 7.5⌬ and mean distance deviation measured ⫹4.36⌬. These values were almost identical to the final horizontal measurements of ⫹ 7.4⌬ and ⫹ 4.45⌬, respectively. However, in the exotropia group, the near distance value changed from ⫺4.50 ⌬ (minus sign represents exotropia) to ⫹ 7.80⌬, and the near distance value from ⫺3.60⌬ to ⫹ 6.40⌬; this difference was statistically significant ( p ⫽ 0.03). The A pattern, however, was stable throughout follow-up in both groups ( p ⫽ 0.874). Four patients had normal fusion and stereopsis preoperatively, which did not change postoperatively. Two additional patients gained postoperative stereopsis, as measured with the Titmus fly test (one patient improved to 3,000 “the other to 140”). Both were 17 years old at the time of surgery, and both were treated for exotropia. Complications After the combined surgical procedure, 5 of the 28 patients (17.9%) required further surgery for various reasons: right eye hypertropia and dissociated vertical deviation; residual exotropia; residual A-pattern esotropia; consecutive A-pattern esotropia; and residual A pattern exotropia with left hypertropia. One patient had a V pattern of 20⌬ but did not undergo further surgery. Two of the patients undergoing additional surgery developed a large deviation that was noted immediately after surgery; in the others, the deviation developed later.
Discussion In the present single-center retrospective study, the overall success rate for combined horizontal strabismus and A-pattern surgery was 60%. When the patients who underwent combined surgery as the primary procedure were assessed separately, the overall success rate increased to 71%. This value is greater than the 60% reported by Lee and Rosenbaum12 for primary combined surgery. Their criteria for success were similar to ours, except for their definition of horizontal alignment as ⫾ 8⌬ versus ⫾ 10⌬ in the present study. The success rate in the primary-surgery group alone was 21% higher than in the secondarysurgery group. However, the difference did not reach statistical significance, perhaps because of the small sample size or because the previous procedure for horizontal misalignment did not include the superior oblique muscle. Although the patient group in the report of Shuey et al11 was similar to ours, the focus was on A pattern collapse, and the authors did not provide numerical results for horizontal deviation or combined outcome. As for collapsing the A pattern, we reported a success rate of 71.4% whereas other studies reported a slightly greater (85%) rate in combined surgery.11,12 Nevertheless, our result is in line with the 60% to 90% success rates reported for superior oblique weakening procedures
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alone.3-6 Given that the preoperative A pattern measurements were similar in the patients with or without previous horizontal extraocular muscle surgery, and in the patients with esotropia or exotropia, these results may indicate that the combined procedure is a good alternative to the 2-step approach. The improvement in the superior oblique overaction was similar to that reported by Suh et al14 using an adjustable superior oblique tendon spacer. Our success rate for horizontal deviation surgery alone was almost 80% for the whole group, with no difference between patients undergoing primary or secondary surgery or between patients with esotropia or exotropia. Lipton and Willshaw,7 in a multicenter retrospective study, reported a comparable success rate of 60% to 80%. Several studies have shown that the procedure performed to correct horizontal deviation and the procedure for A pattern caused by SOOA have no influence on each other. Gezer et al8 reported that a favorable or horizontal deviation outcome in patients with exotropia was unaffected by the presence of an A or V pattern, and Jin et al9 reported a negligible effect of bilateral superior oblique tenotomy on the primary horizontal binocular alignment. Exodeviation was the more common misalignment in our series (15 patients), although not statistically significant, in accordance with the findings of Parks15 and Jampolsky.16 The reason why A-pattern exotropia occurs more often than A pattern esotropia is not known. In our series, stereopsis was present in 6 patients: before surgery in 4, postoperatively in 2. Previous reports have shown that stereoacuity may improve after surgery in patients with previous fusion,16 but the mechanism underlying the changes remains unclear. The recovery of stereopsis has been associated with surgical correction of acquired strabismus,17 depending on the duration of the strabismus and the presurgical binocular vision status. Ball et al18 noted that, in some cases, stereoacuity develops postoperatively in the presence of good bilateral visual acuity and excellent postoperative alignment. Our total failure rate was 18%: 5 patients required repeated surgery after the combined procedure, and one showed a significant V pattern postoperatively but refused reoperation. McNeer et al19 reported a surgical complication rate of 50% in patients after bilateral superior oblique tenotomy. Complications included postoperative head tilt and hypertropia. Superior oblique underaction after superior oblique tendon recession was reported by Drummond et al20 in 1 of 10 patients, and by Caldeira21 in 3 of 16 patients. Using a similar design, Lee and Rosenbaum12 found significant unequal weakening effects in 4 patients. Urist22 reported a change to V-pattern deviation in 4 of 10 patients after bilateral superior oblique weakening procedures for A-pattern deviations. The patients treated for exotropia and A pattern showed a statistically significant shift in misalignment measurements. The outcome of surgical correction of exotropia is known to be less predictable and less stable than that of esotropia correction.23-25
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Our assessment of the clinical significance of surgical treatment for esotropia versus exotropia suggested that the combined procedure has equally good results. Comparison of each group separately (Table 1) yielded a higher success rate for the exotropia group, although the number of patients was too small to reach a definitive conclusion. One explanation may be the additive effect of superior oblique weakening on the abduction ability of the eye as the result of its tertiary action. In conclusion, our retrospective study indicates the effectiveness of simultaneous surgical treatment of the horizontal rectus muscles with superior oblique Z tenotomy in patients with combined horizontal misalignment and A pattern due to SOOA. The success rate of the combined surgery was comparable with the rates for each procedure performed separately, suggesting that the combined procedure offers a good alternative to 2 separate procedures. No difference was found between patients with esotropia and exotropia, or between those who underwent primary or secondary horizontal strabismus surgery. References 1. Brodsky MC, Donahue SP. Primary oblique muscle overaction: The brain throws a wild pitch. Arch Ophthalmol 2001;119:1307-14. 2. Gobin MH. Sagittalization of the oblique muscles as a possible cause for the “A”, “V”, and “X” phenomena. Br J Ophthalmol 1968;52: 13-18. 3. Vempali VM, Lee JP. Results of superior oblique posterior tenotomy. J AAPOS 1998;2:147-50. 4. Pollard ZF, Greenberg MF. Results and complications in 66 cases using a silicone tendon expander on overacting superior oblique with A pattern anisotropia. Bonocular Vis Strabismus Q 2000;15:113-20. 5. Sharma P, Khokhar S, Thanikachalam S. Evaluation of superior oblique weakening procedure. J Pediatr Ophthalmol Strabismus 1999;36:189-95. 6. Bardorf CM, Baker JD. The efficacy of superior oblique Z-tendon lengthening for superior oblique overaction. J AAPOS 2003;7:96102. 7. Lipton JR, Willshaw HE. Prospective multicentre study of the accuracy of surgery for horizontal strabismus. Br J Ophthalmol 1995; 79:10-11. 8. Gezer A, Sezen F, Nasri N, Gozum N. Factors influencing the outcome of strabismus surgery in patients with exotropia. J AAPOS 2004;8:56-60.
9. Jin YH, Sung KR, Kook MS. The immediate effect of bilateral superior oblique tenotomy on primary position horizontal binocular alignment. Binocul Vis Strabismus Q 1999;14:33-8. 10. Minguini N, Dantas FJ, Monteiro de Carvalho KM, Moreira-Filho DC. A study to determine: Should conventional amounts of eye muscle surgery for horizontal binocular deviations be changed when oblique muscle weakening procedures are simultaneously performed? Binocular Vis Strabismus Q 2005;20:21-5. 11. Shuey TF Jr, Parks MM, Friendly DS. Results of combined surgery on the superior oblique and horizontal rectus muscles for A-pattern horizontal strabismus. J Pediatr Ophthalmol Strabismus 1992;29: 199-201. 12. Lee SY, Rosenbaum AL. Surgical results of patients with A-pattern horizontal strabismus. J AAPOS 2003;7:251-5. 13. Bardorf CM, Baker JD. The efficacy of superior oblique split Ztendon lengthening for superior oblique overaction. J AAPOS 2003; 7:96-102. 14. Suh DW, Guyton DL, Hunter DG. An adjustable superior oblique tendon spacer with the use of nonabsorbable sutures. J AAPOS 2001;5:164-71. 15. Parks MM. Doyne Memorial Lecture, 1977. The superior oblique tendon. Trans Ophthalmol Soc U K. 1977;97:288-304. 16. Jampolsky AS. Bilateral anomalies of the oblique muscles. Trans Am Acad Ophthalmol Otolaryngol 1957;61:689-98. 17. Fawcett SL, Stager DR Sr, Felius J. Factors influencing stereoacuity outcomes in adults with acquired strabismus. Am J Ophthalmol 2004;138:931-35. 18. Ball A, Drummond GT, Pearce WG. Unexpected stereoacuity following surgical correction of long-standing horizontal strabismus. Can J Ophthalmol 1993;28:217-20. 19. McNeer KW. Untoward effects of superior oblique tenotomy. Ann Ophthalmol. 1972;4:747-50. 20. Drummond GT, Pearce WG, Astle WF. Recession of the superior oblique tendon in A-pattern strabismus. Can J Ophthalmol 1990;25: 301-5. 21. Caldeira JAF. Graduated recession of the superior oblique muscle. Br J Ophthalmol 1975;59:553-9. 22. Urist MJ. Complications following bilateral superior oblique weakening surgical procedures for A-pattern horizontal deviations. Am J Ophthalmol 1970;70:583-7. 23. Kushner BJ, Preslan MW, Morton GV. Treatment of partly accommodative esotropia with a high accommodative convergenceaccommodation ratio. Arch Ophthalmol 1987;105:815-18. 24. Kushner BJ, Morton GV. A randomized comparison of surgical procedures for infantile esotropia. Am J Ophthalmol 1984;95:50-61. 25. Kushner BJ. Exotropic deviations: A functional classification and approach to treatment. Am Orthoptic J. 1988;38:81-93.
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