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Unilateral inferior oblique anterior transposition for dissociated vertical deviation
Unilateral Inferior Oblique Anterior Transposition for Dissociated Vertical Deviation Erick D. Bothun, MD,a and C. Gail Summers, MD,a,b Purpose: This study analyzes the outcomes after unilateral inferior oblique anterior transposition (IOAT) for manifest dissociated vertical deviation (DVD). Methods: A retrospective chart review was conducted for all patients who had unilateral or markedly asymmetric DVD, ipsilateral overaction of the inferior oblique muscle, lack of alternating fixation, and underwent unilateral IOAT surgery between March 1997 and March 2001. In each case, the bunched inferior oblique muscle was anteriorly transposed to the lateral edge of the insertion of the inferior rectus muscle. The primary outcome variable was change in DVD. Secondary outcome variables included inferior oblique muscle action, graded from ⫺4 to ⫹4, and vertical deviation in primary gaze. Results: Ten consecutive patients met the inclusion criteria. Median age at the time of surgery was 14 years (range, 2 to 41 years.) Mean follow-up was 25 months (range, 6 to 60 months). Ipsilateral DVD in primary position decreased from a mean of 20.2 prism diopters (PD) (range, 14 to 33 PD) to 3.7 PD (range, 0 to 9 PD) (t test, P ⬍ .001). Nine (90%) of the patients had an excellent postoperative result (residual DVD of 0 to 4 PD) and one (10%) had a good result (5 to 9 PD). Inferior oblique overaction was eliminated in all patients. Mean inferior oblique muscle action decreased from ⫹2.4 to ⫺1.3. Three patients developed a transient or permanent 4 to 5 PD postoperative ipsilateral hypotropia in primary position. Dissociated vertical deviation in the fellow eye did not develop, or if present preoperatively, did not increase. Conclusions: Unilateral IOAT is an effective treatment for unilateral or markedly asymmetric DVD in patients with a strong, contralateral fixation preference. This surgery reduces inferior oblique overaction but may cause an ipsilateral hypotropia. (J AAPOS 2004;8:259-263) ultiple approaches to the surgical management of dissociated vertical deviation (DVD) have been described. In the past, both recessing and placing posterior fixation sutures on the superior rectus muscle and resections of the inferior rectus muscle have been used.1,2 Bilateral superior rectus muscle recessions and inferior rectus muscle resections have the advantage of being graded according to the amount of DVD.3 More recently, bilateral inferior oblique anterior transpositions (IOAT) have been found to be effective, especially in the setting of inferior oblique overaction.4 –7 Although the etiology of DVD is not well understood, it is often considered to be a bilateral condition.8 Many
M
From the Departments of Ophthalmologya and Pediatrics,b University of Minnesota, Minneapolis, MN. Supported, in part, by an unrestricted grant from Research to Prevent Blindness, Inc., New York, NY. Presented, in part, as a poster at the Annual Meeting of the Twenty-Eighth Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Seattle, Washington, March 2002. Submitted December 2, 2002. Revision accepted January 9, 2004. Reprint requests; Erick D. Bothun, MD, Department of Ophthalmology, MMC 493, 420 Delaware Street SE, Minneapolis, Minnesota 55455-0501; e-mail: [email protected] Copyright © 2004 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2004/$35.00 ⫹ 0 doi:10.1016/j.jaapos.2004.01.016
Journal of AAPOS
approach correction of markedly asymmetric DVD with bilateral surgery. Good outcomes are reported using both bilateral superior rectus muscle recessions and IOAT for asymmetric DVD.4,5 Asymmetric placement of the inferior oblique muscles has been studied and is recommended by some authors.3,9 Unilateral surgical treatment has been used in the unusual setting of unilateral or markedly asymmetric DVD.3–5 However, a switch to fixation with the operative eye could result in manifest DVD in the fellow eye or a large secondary vertical deviation.10,11 Asymmetry of the palpebral fissures, ocular ischemia in the setting of concurrent rectus muscle surgery, and postoperative hypotropias are occasionally concerns with unilateral superior rectus muscle surgery. Because these potential problems rarely occur, unilateral superior rectus muscle recession has been described as an effective treatment for unilateral DVD, resulting in a residual deviation of less than 5 prism diopters (PD) in 77% of cases.12 A less commonly performed procedure for unilateral DVD is unilateral IOAT. Some have suggested that unilateral IOAT be avoided to reduce the incidence of a postoperative hypotropia.6,10,13,14 Successful outcomes have been reported with unilateral IOAT in studies with small sample sizes when inferior oblique overaction coexists with unilateral or asymmetric DVD.4,5,13,15–17 We have used unilateral June 2004
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IOAT for unilateral or asymmetric DVD, and performed a retrospective review of the charts of consecutive patients to assess the efficacy of this procedure.
SUBJECTS AND METHODS After obtaining Institutional Review Board approval, we reviewed the charts of all patients who underwent unilateral IOAT for manifest DVD at the University of Minnesota between March 1997 and March 2001. Patients were excluded if they underwent simultaneous surgery on another vertically acting muscle or if unilateral IOAT surgery was not performed for DVD. The following data were recorded from the chart review: patient age, diagnosis, preoperative visual acuity, and strabismus measurements (including vertical deviation due to DVD) and versions. Strabismus measurements were performed by an unmasked examiner experienced in measurement of motility and assessment of versions. We used maximum preoperative and postoperative measurements of DVD, measured by prism under cover test,4 in this study. An estimate of DVD by Krimsky light reflex evaluation was performed on one patient with light perception vision. Dissociated vertical deviation was considered to be manifest if the vertical deviation in the nonfixating eye was spontaneously apparent. Difference in preoperative and postoperative measurements was evaluated using a standard t test. Inferior oblique muscle action was graded with versions on a scale from ⫺4 to ⫹4, with 0 being normal action.18 Alignment in primary gaze was made using best refractive correction. All patients received preoperative correction of refractive error, and optical change in fixation was not used in the assessment of success. We did not specifically evaluate the development of a Y or V pattern, limitation to elevation in abduction, or the effect of unilateral IOAT on palpebral fissure in this study. All patients undergoing unilateral IOAT for manifest DVD were included in this retrospective study. Unilateral IOAT was selected due to concurrent inferior oblique overaction in the setting of unilateral or markedly asymmetric DVD and a strong, contralateral fixation preference. Patients who either alternated fixation or lacked ipsilateral inferior oblique muscle overaction were not considered suitable candidates for unilateral IOAT. In each case, the inferior oblique muscle was isolated to its insertion through an inferior-temporal cul-de-sac incision, clamped with a small, straight hemostat as close as possible to the scleral insertion, and disinserted between the insertion and the hemostat. Then 6 – 0 polyglactin suture (Ethicon, Somerville, NJ) was used to secure the muscle in a bunched fashion19 after a locking bite had been placed. The inferior oblique muscle was transposed to the lateral edge of the insertion of the inferior rectus muscle using one scleral pass. This prevented lateral splaying of the posterior fibers. The position of the transposed muscle was not graded according to the amount of DVD, and
resection of the inferior oblique was not performed. All procedures were performed by one surgeon (C.G.S). Postoperative DVD was graded in which excellent results referred to residual DVD of less than or equal to 4 PD, good results were 5 to 9 PD, fair results were 10 to 14 PD, and poor results were ⬎14 PD.12
RESULTS Ten consecutive patients underwent unilateral IOAT for manifest DVD (Table 1). None of these patients met the exclusion criteria. The median age at the time of surgery was 14 years (range, 2 to 41 years). The underlying diagnoses were congenital esotropia (3 patients), congenital cataracts (3), exotropia (2), and macular pathology (2). Six patients had previous strabismus repair (three of whom had previously undergone bilateral superior rectus muscle recessions for DVD [Patients no. 1, no. 8, no. 9]). All patients had preoperative inferior oblique overaction (mean, 2.4; range, ⫹1 to ⫹4). Four patients had concurrent horizontal muscle strabismus repair at the time of the inferior oblique anterior transposition. Mean follow-up was 25 months (range, 6 to 60 months). No patient underwent further surgical treatment of DVD. Preoperative vision ranged from 20/20 to light perception in the operated eye, and all patients never fixated with the operated eye either preoperatively or postoperatively. Visual acuity difference of more than one line was found in 70% of the patients. A history of treatment for amblyopia was noted in 60% of patients. Dissociated vertical deviation in primary position decreased from a preoperative mean of 20.2 PD (range, 14 to 33 PD) to 3.2 PD (range, 0 to 9 PD) (P ⬍ .001) (Figure 1). Nine (90%) of the patients had an excellent postoperative result (residual DVD of 0 to 4 PD) and one (10%) had a good result (9 PD) (Figure 2). Three patients had undergone previous bilateral superior rectus muscle recessions ranging from 6 to 10 mm for either previously symmetric or asymmetric DVD. Each of these patients had results classified as excellent after IOAT, although one (Patient no. 8) developed a 4 PD consecutive hypotropia. Mean inferior oblique overaction decreased from ⫹2.5 (range, ⫹1 to ⫹4) to ⫺1.3 (range, 0 to ⫺3). Three patients developed transient or permanent 4 to 5 PD postoperative ipsilateral hypotropias in primary position, including one patient who had marked inferior oblique underaction (⫺3). One of these three (Patient no. 2) developed the hypotropia two years postoperatively. A second showed resolution of the hypotropia three years postoperatively. None of these patients underwent additional surgery. Although there were no subjective concerns reported postoperatively, three of the ten patients developed ipsilateral ⫺2 to ⫺3 limitation to elevation after surgery. Only one of these patients had previously undergone a bilateral superior rectus muscle recession. Four patients had latent DVD preoperatively in the fellow eye (mean, 5 PD; range, 3 to 10 PD) and it did not change after contralateral
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TABLE 1. Pre- and postoperative patient information with DVD and IOOA
Patient No.
Eye
Age at Surgery (Years)
1
OS
15
2
OS
12
3
OS
41
4
OS
11
5
OS
2
6
OD
14
7
OS
6
8
OS
17
9
OD
17
10
OS
4
Best Preop VA 20/30 20/30 20/20 20/30 20/20 20/80 20/20 20/125 20/25 20/40 LP 20/20 20/25 20/70 20/20 20/25 20/20 20/20 20/25 20/50
Preop DVD (PD)
Postop DVD at Last Visit (PD)
Inferior Oblique Function Pre/Post
Postop Hypotropia* (PD)
Followup (Months)
Myopia/XT s/p BSRc (6 mm) Cong Cat OU
14
0
⫹2/⫺1
0
36
18
0
⫹3/⫺2
5
60
Cong XT
17
9
⫹3/0
0
10
Cong Cat OS
33
0
⫹2/⫺1
4†
41
Cong ET
25
4
⫹4/⫺1
0
21
Cong Cat OD
16
4
⫹2/⫺1
0
9
Toxo OS
18
4
⫹2/0
0
25
Cong ET s/p BSRc (10 mm) Cong XT s/p BSRc (6.5 mm) Coloboma OU
20
0
⫹2/⫺3
4
6
18
0
⫹1/⫺2
0
22
25
3
⫹3/⫺2
0
20
Diagnosis
*Primary position; †transient; VA: visual acuity, OD: right eye, OS: left eye; OU: both eyes; XT: exotropia; ET: esotropia; Cong: congenital; Cat: cataract; Toxo: toxoplasmosis; s/p BSRc: status post bilateral superior rectus muscle recession; DVD: dissociated-vertical deviation; IOOA: inferior oblique overaction.
FIG 1. Change in manifest dissociated vertical deviation (DVD).
IOAT. None of the other six patients developed DVD in the fellow eye postoperatively. Although most of our patients had decreased visual acuity in the operated eye, none of our patients reported vertical and/or torsional diplopia postoperatively.20
DISCUSSION Inferior oblique anterior transposition has emerged as an effective surgery for inferior oblique overaction (IOOA), DVD, and other vertical deviations over the past two decades. In 1981, Elliot and Nankin described anteriorization of the inferior oblique muscle to further reduce inferior oblique overaction.21 Stager et al showed that the
FIG 2. Postoperative vertical deviation. Black box: residual dissociated vertical deviation (grey box: new hypotropia; *:grading scheme by Schwartz et al12; PD: prism diopter.
neurofibrovascular bundle of the inferior oblique muscle effectively changes the muscle from an elevator to an antielevator after anterior transposition.22 In an effort to titrate the IOAT, several have studied transposing the inferior oblique muscle to positions anterior to the inferior rectus muscle.4,5,14,23 With increasing use of IOAT, adverse outcomes have been reported, including postoperative hypotropia4,10,14,17,24,25 and antielevation syndrome.24,26 Further work has shown that the antielevation syndrome is less likely when temporal splaying of the
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posterior fibers is avoided and the inferior oblique muscle is not transposed beyond the inferior rectus muscle insertion.26,27 Lastly, an increase in amount of spontaneous expression of DVD in the fellow eye can occur after unilateral IOAT.15 Our study focused on patients managed with unilateral IOAT for manifest DVD with marked asymmetry on prism under cover testing, IOOA, and a strong, contralateral fixation preference. In contrast to previous studies of unilateral IOAT4,5,16,17 we bunched the inferior oblique muscle reinsertion and uniformly transposed it to a position adjacent to the lateral edge of the insertion of the inferior rectus muscle. We found that unilateral IOAT effectively reduces the amount of DVD, using the outcome grading scheme developed by Schwartz et al.12 All of our patients had good to excellent results (residual DVD ⱕ 9 PD). In addition, IOOA was reduced. Three patients developed a postoperative hypotropia ranging from 4 to 5 PD. Our results compare favorably with other reports of unilateral surgery for asymmetric DVD. In a study of 57 patients treated with unilateral superior rectus muscle recession for the DVD, 93% of patients had an excellent or good result (residual DVD ⱕ 9 PD).12 In that study, 21% of patients developed a hypotropia and 10% developed increased DVD in the fellow eye. Our results also compare favorably to the few existing reports of unilateral IOAT for unilateral or asymmetric DVD. In 1989, Kratz et al reported excellent outcomes in two patients with DVD and IOOA at 6 and 9 months following unilateral graded IOAT with splayed placement.5 In 1993, Burke et al used unilateral IOAT in 12 patients with DVD.4 All had reduced IOOA but only five had residual DVD ⬍ 5 PD at last follow-up (1 to 4.9 years). Unlike our study, these authors did not secure the muscle in a bunched fashion to avoid the temporal splaying of posterior fibers or uniformly transpose the inferior oblique muscle to the lateral insertion of the inferior rectus muscle. Occasionally unilateral IOAT has been reported in studies of bilateral inferior oblique muscle surgery. Although the sample size of unilateral IOAT is often small, the results are grouped in the bilateral surgical outcomes, or follow-up is short, one can find evidence of excellent outcomes when the data are carefully inspected.5,13,15–17,28 IOAT has inherent limitations. Burke et al suggested that patients with DVD ⬎ 15 PD have poor outcomes.4 This was not confirmed in our study that included nine patients with DVD measuring 17 to 33 PD. Postoperative development or unmasking of contralateral DVD, diplopia, or fixation switch did not occur in our study. It is possible that selecting patients with poor binocularity for the procedure limits these complications. Information regarding the use of unilateral IOAT in the setting of equal visual acuity remains limited. Although three patients in our study had near equal visual acuity, each demonstrated a strong fixation preference preoperatively. In addition,
Journal of AAPOS Volume 8 Number 3 June 2004
these three patients had undergone previous bilateral superior rectus muscle recession for bilateral DVD. It is possible that their previous surgery protected them against the development of a hyperdeviation in the fellow eye after unilateral IOAT. Although concern has been raised over the risk of postoperative hypotropias after unilateral IOAT, most studies report this outcome infrequently.4,10,14,17,24,25 Three patients in our study developed a transient or permanent postoperative ipsilateral hypotropia measuring 4 to 5 PD. Whether masked by spectacles or not cosmetically apparent, no patient expressed concern about this issue. This may be because hypotropias are generally considered less noticeable than hypertropias and this would be expected in these patients with a strong contralateral fixation preference. Reports have shown a much lower rate of postoperative hypotropias following unilateral IOAT compared with unilateral superior rectus muscle recession.4,12 Strengths of this study include uniform placement of the bunched inferior oblique muscle adjacent to the lateral edge of the insertion of the inferior rectus muscle. It has been suggested that this surgical technique best avoids an antielevation syndrome.26,29 Although our retrospective study was not able to fully address this adverse outcome, no patient expressed subjective concerns about this sign even though it was documented in three of the ten patients. The number of patients undergoing unilateral IOAT is larger than most other reports, and one surgeon performed all surgeries. The authors recognize that the sample size is small, due to the uncommon scenario for consideration of unilateral IOAT. Follow-up period in this study was variable and was less than a year in three cases. Delayed development of increasingly manifest DVD after IOAT4 makes longer term assessment important. Although one patient developed a small ipsilateral hypotropia two years after surgery, a delayed postoperative increase in DVD was not seen in our other patients. An ideal study would have randomly assigned treatment to unilateral IOAT or superior rectus muscle recession and evaluated outcomes after a specified time of follow-up. In conclusion, based on the results of this retrospective study, we recommend that unilateral inferior oblique anterior transposition be considered for unilateral or markedly asymmetric DVD and IOOA in patients with a strong, contralateral fixation preference, even if a previous superior rectus muscle recession has been performed. Although a small hypotropia can develop with the technique used, the deviation does not appear clinically significant. Statistical analysis by research scientist Ann Holleschau, University of Minnesota, Minneapolis, MN.
References 1. von Noorden GK. Posterior fixation suture in strabismus surgery. In: Symposium on strabismus: Trans New Orleans Academy of Ophthalmology. St. Louis: CV Mosby; 1978. pp. 307-20. 2. Spraque JB, Moore S, Eggers H, Knapp P. Dissociated vertical
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3.
4.
5.
6. 7. 8. 9.
10.
11.
12.
13.
14.
15.
deviation: treatment with the Faden operation of cuppers. Arch Ophthalmol 1980;98:465-8. Magoon E, Cruciger M, Jampolsky A. Dissociated vertical deviation: an asymmetric condition treated with bilateral superior rectus recession. J Pediatr Ophthalmol Strabismus 1982;19:152-6. Burke JP, Scott WE, Kutschke PJ. Anterior transposition of the inferior oblique muscle for dissociated vertical deviation. Ophthalmology 1993;100:245-50. Kratz RE, Rogers GL, Bremer DL, Leguire LE. Anterior tendon displacement of the inferior oblique for DVD. J Pediatr Ophthalmol Strabismus 1989;26:212-7. Mims JL III, Wood RC. Bilateral anterior transposition of inferior obliques. Arch Ophthalmol 1989;107:41-4. Sargent RA. Surgical correction of dissociated hyperdeviations. Am Orthopt J 1976;26:89-99. Guyton DL. Dissociated vertical deviation: etiology, mechanism, and associated phenomena. J AAPOS 2000;4:131-44. Guemes A, Wright KW. Effect of graded anterior transposition on the inferior oblique muscle on versions and vertical deviations in primary position. J AAPOS 1998;2:201-6. Bremer DL, Rogers GL, Quick LD. Primary-position hypotropia after anterior transposition of the inferior oblique. Arch Ophthalmol 1986;104:229-32. Mallette RA, Repka MX, Guyton DL. Superior rectus suspensionrecession for dissociated vertical deviation: a report of 59 operations. Binocular Vision 1987;2:209-15. Schwartz T, Scott W. Unilateral superior rectus recession for the treatment of dissociated vertical deviation. J Pediatr Ophthalmol Strabismus 1991;28:219-22. Quinn AG, Kraft SP, Day C, Taylor RS, Levin AV. A prospective evaluation of anterior transposition of the inferior oblique muscle, with and without resection, in the treatment of dissociated vertical deviation. J AAPOS 2000;4:348-53. Ziffer AF, Isenberg SJ, Elliot RL, Apt L. The effect of anterior transposition of the inferior oblique muscle. Am J Ophthalmol 1993; 116:224-7. Bacal DA, Nelson LB. Anterior transposition of the inferior oblique muscle for both dissociated vertical deviation and/or inferior oblique
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16. 17.
18. 19. 20.
21. 22.
23.
24.
25. 26. 27.
28.
29.
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overaction: results of 94 procedures in 55 patients. Binoc Vis Eye Muscle Surgery Quarterly 1992;7:219-25. Seawright AA, Gole GA. Results of anterior transposition of the inferior oblique. Austral N Zealand J Ophthalmol 1996;24:339-45. Black BC. Results of anterior transposition of the inferior oblique muscle in incomitant dissociated vertical deviation. J AAPOS 1997; 1:83-7. Doughty DD, Lennarson LW, Scott WE. A geographic portrayal of versions. Perspect Ophthalmol 1978;2:55-9. Apt L, Call B. Inferior oblique muscle recession. Am J Ophthalmol 1978;85:95-100. Santiago AP, Isenberg SJ, Apt L, Roh YB. The effect of anterior transposition of the inferior oblique muscle on ocular torsion. J AAPOS 1997;1:191-6. Elliot RL, Nankin SJ. Anterior transposition of the inferior oblique. J Pediatr Ophthalmol Strabismus 1981;18:35-8. Stager DR, Weakley DR, Stager D. Anterior transposition of the inferior oblique. Anatomic assessment of the neurovascular bundle. Arch Ophthalmol 1992;110:360-2. Engman JH, Egbert JE, Summers CG, Young TL. Efficacy of inferior oblique anterior transposition placement grading for dissociated vertical deviation. Ophthalmology 2001;108:2045-50. Elliot RL, Parks MM. A comparison of inferior oblique muscle weakening by anterior transposition or denervation-extirpation. Binocular Vision & Eye Muscle Surgery Qtrly Fall 1992;7:205-10. Mims JL III. Benefits of bilateral anterior transposition of the inferior obliques. Arch Ophthalmol 1986;104:800-2. Kushner BJ. Restriction of elevation in abduction after inferior oblique anteriorization. J AAPOS 1997;1:56-61. Mims JL, Wood RC. Antielevation syndrome after bilateral anterior transposition of the inferior oblique muscles: incidence and prevention. J AAPOS 1999;3:333-6. Milot J, Tremblay C, Ouellette C. Anterior transposition of the inferior oblique for dissociated vertical deviation with inferior oblique overaction. Can J Ophthalmol 1994;29:284-7. Kushner BJ. Torsion as a contributing cause of the anti-elevation syndrome. J AAPOS 2001;5:172-7.
M
From the Departments of Ophthalmologya and Pediatrics,b University of Minnesota, Minneapolis, MN. Supported, in part, by an unrestricted grant from Research to Prevent Blindness, Inc., New York, NY. Presented, in part, as a poster at the Annual Meeting of the Twenty-Eighth Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Seattle, Washington, March 2002. Submitted December 2, 2002. Revision accepted January 9, 2004. Reprint requests; Erick D. Bothun, MD, Department of Ophthalmology, MMC 493, 420 Delaware Street SE, Minneapolis, Minnesota 55455-0501; e-mail: [email protected] Copyright © 2004 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2004/$35.00 ⫹ 0 doi:10.1016/j.jaapos.2004.01.016
Journal of AAPOS
approach correction of markedly asymmetric DVD with bilateral surgery. Good outcomes are reported using both bilateral superior rectus muscle recessions and IOAT for asymmetric DVD.4,5 Asymmetric placement of the inferior oblique muscles has been studied and is recommended by some authors.3,9 Unilateral surgical treatment has been used in the unusual setting of unilateral or markedly asymmetric DVD.3–5 However, a switch to fixation with the operative eye could result in manifest DVD in the fellow eye or a large secondary vertical deviation.10,11 Asymmetry of the palpebral fissures, ocular ischemia in the setting of concurrent rectus muscle surgery, and postoperative hypotropias are occasionally concerns with unilateral superior rectus muscle surgery. Because these potential problems rarely occur, unilateral superior rectus muscle recession has been described as an effective treatment for unilateral DVD, resulting in a residual deviation of less than 5 prism diopters (PD) in 77% of cases.12 A less commonly performed procedure for unilateral DVD is unilateral IOAT. Some have suggested that unilateral IOAT be avoided to reduce the incidence of a postoperative hypotropia.6,10,13,14 Successful outcomes have been reported with unilateral IOAT in studies with small sample sizes when inferior oblique overaction coexists with unilateral or asymmetric DVD.4,5,13,15–17 We have used unilateral June 2004
259
260
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Bothun and Summers
IOAT for unilateral or asymmetric DVD, and performed a retrospective review of the charts of consecutive patients to assess the efficacy of this procedure.
SUBJECTS AND METHODS After obtaining Institutional Review Board approval, we reviewed the charts of all patients who underwent unilateral IOAT for manifest DVD at the University of Minnesota between March 1997 and March 2001. Patients were excluded if they underwent simultaneous surgery on another vertically acting muscle or if unilateral IOAT surgery was not performed for DVD. The following data were recorded from the chart review: patient age, diagnosis, preoperative visual acuity, and strabismus measurements (including vertical deviation due to DVD) and versions. Strabismus measurements were performed by an unmasked examiner experienced in measurement of motility and assessment of versions. We used maximum preoperative and postoperative measurements of DVD, measured by prism under cover test,4 in this study. An estimate of DVD by Krimsky light reflex evaluation was performed on one patient with light perception vision. Dissociated vertical deviation was considered to be manifest if the vertical deviation in the nonfixating eye was spontaneously apparent. Difference in preoperative and postoperative measurements was evaluated using a standard t test. Inferior oblique muscle action was graded with versions on a scale from ⫺4 to ⫹4, with 0 being normal action.18 Alignment in primary gaze was made using best refractive correction. All patients received preoperative correction of refractive error, and optical change in fixation was not used in the assessment of success. We did not specifically evaluate the development of a Y or V pattern, limitation to elevation in abduction, or the effect of unilateral IOAT on palpebral fissure in this study. All patients undergoing unilateral IOAT for manifest DVD were included in this retrospective study. Unilateral IOAT was selected due to concurrent inferior oblique overaction in the setting of unilateral or markedly asymmetric DVD and a strong, contralateral fixation preference. Patients who either alternated fixation or lacked ipsilateral inferior oblique muscle overaction were not considered suitable candidates for unilateral IOAT. In each case, the inferior oblique muscle was isolated to its insertion through an inferior-temporal cul-de-sac incision, clamped with a small, straight hemostat as close as possible to the scleral insertion, and disinserted between the insertion and the hemostat. Then 6 – 0 polyglactin suture (Ethicon, Somerville, NJ) was used to secure the muscle in a bunched fashion19 after a locking bite had been placed. The inferior oblique muscle was transposed to the lateral edge of the insertion of the inferior rectus muscle using one scleral pass. This prevented lateral splaying of the posterior fibers. The position of the transposed muscle was not graded according to the amount of DVD, and
resection of the inferior oblique was not performed. All procedures were performed by one surgeon (C.G.S). Postoperative DVD was graded in which excellent results referred to residual DVD of less than or equal to 4 PD, good results were 5 to 9 PD, fair results were 10 to 14 PD, and poor results were ⬎14 PD.12
RESULTS Ten consecutive patients underwent unilateral IOAT for manifest DVD (Table 1). None of these patients met the exclusion criteria. The median age at the time of surgery was 14 years (range, 2 to 41 years). The underlying diagnoses were congenital esotropia (3 patients), congenital cataracts (3), exotropia (2), and macular pathology (2). Six patients had previous strabismus repair (three of whom had previously undergone bilateral superior rectus muscle recessions for DVD [Patients no. 1, no. 8, no. 9]). All patients had preoperative inferior oblique overaction (mean, 2.4; range, ⫹1 to ⫹4). Four patients had concurrent horizontal muscle strabismus repair at the time of the inferior oblique anterior transposition. Mean follow-up was 25 months (range, 6 to 60 months). No patient underwent further surgical treatment of DVD. Preoperative vision ranged from 20/20 to light perception in the operated eye, and all patients never fixated with the operated eye either preoperatively or postoperatively. Visual acuity difference of more than one line was found in 70% of the patients. A history of treatment for amblyopia was noted in 60% of patients. Dissociated vertical deviation in primary position decreased from a preoperative mean of 20.2 PD (range, 14 to 33 PD) to 3.2 PD (range, 0 to 9 PD) (P ⬍ .001) (Figure 1). Nine (90%) of the patients had an excellent postoperative result (residual DVD of 0 to 4 PD) and one (10%) had a good result (9 PD) (Figure 2). Three patients had undergone previous bilateral superior rectus muscle recessions ranging from 6 to 10 mm for either previously symmetric or asymmetric DVD. Each of these patients had results classified as excellent after IOAT, although one (Patient no. 8) developed a 4 PD consecutive hypotropia. Mean inferior oblique overaction decreased from ⫹2.5 (range, ⫹1 to ⫹4) to ⫺1.3 (range, 0 to ⫺3). Three patients developed transient or permanent 4 to 5 PD postoperative ipsilateral hypotropias in primary position, including one patient who had marked inferior oblique underaction (⫺3). One of these three (Patient no. 2) developed the hypotropia two years postoperatively. A second showed resolution of the hypotropia three years postoperatively. None of these patients underwent additional surgery. Although there were no subjective concerns reported postoperatively, three of the ten patients developed ipsilateral ⫺2 to ⫺3 limitation to elevation after surgery. Only one of these patients had previously undergone a bilateral superior rectus muscle recession. Four patients had latent DVD preoperatively in the fellow eye (mean, 5 PD; range, 3 to 10 PD) and it did not change after contralateral
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TABLE 1. Pre- and postoperative patient information with DVD and IOOA
Patient No.
Eye
Age at Surgery (Years)
1
OS
15
2
OS
12
3
OS
41
4
OS
11
5
OS
2
6
OD
14
7
OS
6
8
OS
17
9
OD
17
10
OS
4
Best Preop VA 20/30 20/30 20/20 20/30 20/20 20/80 20/20 20/125 20/25 20/40 LP 20/20 20/25 20/70 20/20 20/25 20/20 20/20 20/25 20/50
Preop DVD (PD)
Postop DVD at Last Visit (PD)
Inferior Oblique Function Pre/Post
Postop Hypotropia* (PD)
Followup (Months)
Myopia/XT s/p BSRc (6 mm) Cong Cat OU
14
0
⫹2/⫺1
0
36
18
0
⫹3/⫺2
5
60
Cong XT
17
9
⫹3/0
0
10
Cong Cat OS
33
0
⫹2/⫺1
4†
41
Cong ET
25
4
⫹4/⫺1
0
21
Cong Cat OD
16
4
⫹2/⫺1
0
9
Toxo OS
18
4
⫹2/0
0
25
Cong ET s/p BSRc (10 mm) Cong XT s/p BSRc (6.5 mm) Coloboma OU
20
0
⫹2/⫺3
4
6
18
0
⫹1/⫺2
0
22
25
3
⫹3/⫺2
0
20
Diagnosis
*Primary position; †transient; VA: visual acuity, OD: right eye, OS: left eye; OU: both eyes; XT: exotropia; ET: esotropia; Cong: congenital; Cat: cataract; Toxo: toxoplasmosis; s/p BSRc: status post bilateral superior rectus muscle recession; DVD: dissociated-vertical deviation; IOOA: inferior oblique overaction.
FIG 1. Change in manifest dissociated vertical deviation (DVD).
IOAT. None of the other six patients developed DVD in the fellow eye postoperatively. Although most of our patients had decreased visual acuity in the operated eye, none of our patients reported vertical and/or torsional diplopia postoperatively.20
DISCUSSION Inferior oblique anterior transposition has emerged as an effective surgery for inferior oblique overaction (IOOA), DVD, and other vertical deviations over the past two decades. In 1981, Elliot and Nankin described anteriorization of the inferior oblique muscle to further reduce inferior oblique overaction.21 Stager et al showed that the
FIG 2. Postoperative vertical deviation. Black box: residual dissociated vertical deviation (grey box: new hypotropia; *:grading scheme by Schwartz et al12; PD: prism diopter.
neurofibrovascular bundle of the inferior oblique muscle effectively changes the muscle from an elevator to an antielevator after anterior transposition.22 In an effort to titrate the IOAT, several have studied transposing the inferior oblique muscle to positions anterior to the inferior rectus muscle.4,5,14,23 With increasing use of IOAT, adverse outcomes have been reported, including postoperative hypotropia4,10,14,17,24,25 and antielevation syndrome.24,26 Further work has shown that the antielevation syndrome is less likely when temporal splaying of the
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posterior fibers is avoided and the inferior oblique muscle is not transposed beyond the inferior rectus muscle insertion.26,27 Lastly, an increase in amount of spontaneous expression of DVD in the fellow eye can occur after unilateral IOAT.15 Our study focused on patients managed with unilateral IOAT for manifest DVD with marked asymmetry on prism under cover testing, IOOA, and a strong, contralateral fixation preference. In contrast to previous studies of unilateral IOAT4,5,16,17 we bunched the inferior oblique muscle reinsertion and uniformly transposed it to a position adjacent to the lateral edge of the insertion of the inferior rectus muscle. We found that unilateral IOAT effectively reduces the amount of DVD, using the outcome grading scheme developed by Schwartz et al.12 All of our patients had good to excellent results (residual DVD ⱕ 9 PD). In addition, IOOA was reduced. Three patients developed a postoperative hypotropia ranging from 4 to 5 PD. Our results compare favorably with other reports of unilateral surgery for asymmetric DVD. In a study of 57 patients treated with unilateral superior rectus muscle recession for the DVD, 93% of patients had an excellent or good result (residual DVD ⱕ 9 PD).12 In that study, 21% of patients developed a hypotropia and 10% developed increased DVD in the fellow eye. Our results also compare favorably to the few existing reports of unilateral IOAT for unilateral or asymmetric DVD. In 1989, Kratz et al reported excellent outcomes in two patients with DVD and IOOA at 6 and 9 months following unilateral graded IOAT with splayed placement.5 In 1993, Burke et al used unilateral IOAT in 12 patients with DVD.4 All had reduced IOOA but only five had residual DVD ⬍ 5 PD at last follow-up (1 to 4.9 years). Unlike our study, these authors did not secure the muscle in a bunched fashion to avoid the temporal splaying of posterior fibers or uniformly transpose the inferior oblique muscle to the lateral insertion of the inferior rectus muscle. Occasionally unilateral IOAT has been reported in studies of bilateral inferior oblique muscle surgery. Although the sample size of unilateral IOAT is often small, the results are grouped in the bilateral surgical outcomes, or follow-up is short, one can find evidence of excellent outcomes when the data are carefully inspected.5,13,15–17,28 IOAT has inherent limitations. Burke et al suggested that patients with DVD ⬎ 15 PD have poor outcomes.4 This was not confirmed in our study that included nine patients with DVD measuring 17 to 33 PD. Postoperative development or unmasking of contralateral DVD, diplopia, or fixation switch did not occur in our study. It is possible that selecting patients with poor binocularity for the procedure limits these complications. Information regarding the use of unilateral IOAT in the setting of equal visual acuity remains limited. Although three patients in our study had near equal visual acuity, each demonstrated a strong fixation preference preoperatively. In addition,
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these three patients had undergone previous bilateral superior rectus muscle recession for bilateral DVD. It is possible that their previous surgery protected them against the development of a hyperdeviation in the fellow eye after unilateral IOAT. Although concern has been raised over the risk of postoperative hypotropias after unilateral IOAT, most studies report this outcome infrequently.4,10,14,17,24,25 Three patients in our study developed a transient or permanent postoperative ipsilateral hypotropia measuring 4 to 5 PD. Whether masked by spectacles or not cosmetically apparent, no patient expressed concern about this issue. This may be because hypotropias are generally considered less noticeable than hypertropias and this would be expected in these patients with a strong contralateral fixation preference. Reports have shown a much lower rate of postoperative hypotropias following unilateral IOAT compared with unilateral superior rectus muscle recession.4,12 Strengths of this study include uniform placement of the bunched inferior oblique muscle adjacent to the lateral edge of the insertion of the inferior rectus muscle. It has been suggested that this surgical technique best avoids an antielevation syndrome.26,29 Although our retrospective study was not able to fully address this adverse outcome, no patient expressed subjective concerns about this sign even though it was documented in three of the ten patients. The number of patients undergoing unilateral IOAT is larger than most other reports, and one surgeon performed all surgeries. The authors recognize that the sample size is small, due to the uncommon scenario for consideration of unilateral IOAT. Follow-up period in this study was variable and was less than a year in three cases. Delayed development of increasingly manifest DVD after IOAT4 makes longer term assessment important. Although one patient developed a small ipsilateral hypotropia two years after surgery, a delayed postoperative increase in DVD was not seen in our other patients. An ideal study would have randomly assigned treatment to unilateral IOAT or superior rectus muscle recession and evaluated outcomes after a specified time of follow-up. In conclusion, based on the results of this retrospective study, we recommend that unilateral inferior oblique anterior transposition be considered for unilateral or markedly asymmetric DVD and IOOA in patients with a strong, contralateral fixation preference, even if a previous superior rectus muscle recession has been performed. Although a small hypotropia can develop with the technique used, the deviation does not appear clinically significant. Statistical analysis by research scientist Ann Holleschau, University of Minnesota, Minneapolis, MN.
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