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Show ORIGINAL CONTRIBUTION Binocular Vertical Rectus Muscle Recession For Comitant Vertical Strabismus Oliver Bergamin, MD, Maria Gabriela Wirth, MD, and Klara Landau, MD Background: Binocular vertical rectus muscle re-cession has not been formally evaluated in the correction of comitant vertical strabismus. Methods: Eight patients with stable comitant verti-cal strabismus for at least 6 months were included. All underwent recession of the superior rectus muscle of the hypertropic eye combined with an equal or nearly equal recession of the inferior rectus muscle in the hypotropic eye. On the day before surgery, on one of the first three postoperative days, and at one year postoperatively, ocular alignment in vertical and horizontal gaze directions were measured with simultaneous and alternate cover test at a viewing distance of 5 meters, and with the two dimensional Hess screen test. The field of single binocular vision was determined with a Goldmann perimeter. The Lang stereopsis chart was presented at the last follow-up visit. Results: All patients were orthotropic at the last postoperative follow-up visit. In primary gaze, the degree of vertical and horizontal phoria diminished significantly. Normal alignment was achieved in nearly all gaze directions and stereopsis was reestablished. The field of single binocular vision enlarged after the surgery. Conclusions: Binocular vertical rectus muscle re-cession is an effective surgical approach for patients with comitant vertical ocular misalignment. (J Neuro-Ophthalmol 2008;28:296-301) The correction of vertical ocular misalignment poses a special challenge. There is less fusional amplitude in vertical than in horizontal misalignment because vertical misalignment is minimally influenced by vergence and other mechanisms of fusion. Vertical eye misalignment is Department of Ophthalmology, University Hospital of Zurich, Zurich, Switzerland. Address correspondence to Klara Landau, MD, Department of Ophthalmology, Zurich University Hospital, CH-8091, Zurich, Switzerland; E-mail: klara.landau@usz.ch often incomitant. However, spread of comitance may develop even in paretic or restrictive vertical strabismic forms when the innervation pattern of the unaffected muscles is adjusted to compensate for the impaired component of the ocular motor plant (1). Although prisms provide symptomatic improvement, especially in misalignments of up to 10 prism-diopters (2), larger comitant vertical misalignments are usually managed by vertical extraocular muscle surgery. In this study we examine 8 patients whose comitant vertical misalignment was treated by recession of the superior rectus muscle of the hypertropic eye combined with an equal or nearly equal recession of the inferior rectus muscle in the hypotropic eye (binocular vertical rectus muscle recession). METHODS Subjects Between December 1991 and August 2002, all patients with nonrestrictive comitant or nearly comitant vertical strabismus were treated with binocular vertical rectus muscle recession at the Orthoptic Unit of the Department of Ophthalmology, Zurich University Hospital. Eleven subjects (1.04%) were recruited consecutively out of the 1,065 patients who had strabismus surgery during the study time period. Institutional review board/ethics committee approval was not required for this retrospective study. Three patients were excluded either because the preoperative vertical incomitance between 15° right and 15° left gaze was >10° using the Hess screen test, the difference in recession between the right and the left eye was > 1 mm, or a horizontal extraocular muscle was also operated upon. The remaining 8 patients included 3 men and 5 women, with a mean age of 34 years and a range of 9- 56 years. The underlying diagnosis and the side of the hypertropic eye are shown in Table 1. Preoperatively all patients reported intermittent or constant double vision. Detection of stereoacuity with or without prism correction provided evidence of normal retinal correspondence. Forced duction testing revealed no limitation of passive ocular motility in either eye. 296 J Neuro-Ophthalmol, Vol. 28, No. 4, 2008 Binocular Vertical Rectus Muscle Recession for Comitant Vertical Strabismus J Neuro-Ophthalmol, Vol. 28, No. 4, 2008 TABLE 1. Clinical features of 8 patients with comitant vertical strabismus Case 1 2 3 4 56 7 8 Diagnosis Old right orbital floor fracture Long-standing thyroid orbitopathy Long-standing thyroid orbitopathy Old right orbital floor fracture Old left orbital floor fracture Old traumatic brain injury, skew deviation? Old acquired left trochlear nerve palsy Congenital left trochlear nerve palsy Preoperative Vertical Misalignment with Alternate Cover Test Left HT 12 PD Right HT 25 PD Right HT 14 PD Right HT 25 PD Left HT 14 PD Left HT 12 PD Left HT 20 PD Left HT 16 PD Recession (mm) of Superior Rectus 3 4 3 3 2.5 2 2.5 3 Inferior Rectus of Fellow Eye 3 4 3.5 3.5 2 2.5 3 2 HT, hypertropia; PD, prism-diopters. Data Analysis Ocular misalignment was measured in prism-diopters with the simultaneous and alternate prism and cover test for distance fixation. The degree of misalignment was also determined in 15° left, straight ahead 15° right gaze, 15° upgaze, and 15° downgaze directions using the Hess screen test. Data were predominantly obtained on the day before surgery (pre-OP), at one of the first 3 postoperative days (post-OP), and at various times after surgery (1-year follow-up), (range 3-17 months, median 12 months follow-up). The field of single binocular vision (diplopia-free zone) was determined with Goldmann stimulus size 5 (1.68° diameter) on the Goldmann perimeter (Haag-Streit, Bern, Switzerland). The patients pressed a button when a stimulus that was moved toward the center of the bowl appeared single instead of double. The fields of single binocular vision were all copied on paper with the same weight. To determine the size of the diplopia-free zone, this area was cut with scissors and weighed on a Mettler Toledo PG 503-S Delta Range scale, scaled in milligrams. The weight was calibrated with circular fields of radius 10, 20, 30, 40, 50, and 60°. No fields of single binocular vision were obtained from Case 3 and 6. In Case 7, this test was only performed at the post-OP and the 1-year follow-up visit. At the preoperative visit of Case 7, diplopia was present in all gaze directions, and therefore the value was set to zero. To investigate the change in torsional alignment sepa-rately from the horizontal and vertical components of mis-alignment, Case 5 was measured with dual magnetic search coils in different gaze directions before and after surgery (3,4). Binocular Vertical Rectus Muscle Recession Procedure Equal or nearly equal recession of the superior rectus muscle of the hypertropic eye and of the inferior rectus muscle of the fellow eye was performed in the same operation. According to Parks (5), 3 or 4 mm of binocular vertical rectus muscle recession can correct 15-25 prism-diopters of vertical misalignment. The recessions were individualized but did not exceed 4 mm. For more information on the amount of binocular vertical rectus muscle recession refer to Table 1. All patients were operated by the senior author (K.L.) except Case 8 who was operated by M.G.W. In 5 patients, who had a slightly greater vertical misalignment in right or left gaze, the recession performed on the vertical rectus on the side with the greater degree of misalignment exceeded by 0.5 mm that performed on the fellow eye (Cases 3-7). In Case 8, the difference in recessions was 1 mm. RESULTS Figure 1 depicts the change in vertical and horizontal ocular misalignment of the 8 patients who were measured with the simultaneous prism and cover test at distance. Figure 1A shows the pre-OP and post-OP measurements, and Figure 1B depicts the post-OP and 1-year follow-up measurements. Preoperatively, 6 of the 8 patients presented with constant vertical misalignment. Two patients had intermittent diplopia with intermittent vertical misalignment (Case 4 and 8). Postoperatively, all patients were orthotropic and did not experience vertical diplopia. Stereopsis was present in all patients at the last examination (average stereopsis 275 sec-angle; range 200-600 sec-angle using the Lang stereopsis chart). In 4 of the 8 patients, prism alternate cover testing showed vertical orthophoria at the post-OP visit at a viewing distance of 5 m. Four patients had residual hyperphoria of less than 5 prism-diopters (mean vertical misalignment from zero: 17.3 prism-diopters at pre-OP vs 0.75 prism-diopter 297 J Neuro-Ophthalmol, Vol. 28, No. 4, 2008 Bergamin et al FIG. 1. Horizontal and vertical change of misalignment (open circles, start point; arrowhead, end point) of 8 patients with comitant vertical strabismus between the preoperative visit and the days after binocular vertical rectus muscle recession (A, C, E) and between the postoperative days and the 1-year follow-up (B, D, F). Measurements were made with the simultaneous prism cover test at distance (A, B; for clarification, horizontal data were displaced by 0.2 prism-diopter in A and B, respectively), with the alternate prism cover test (C, D), and with the two-dimensional Hess screen test (E, F). at post-OP) (Fig. 1C). This stayed stable for the first year (mean 0.63 prism-diopter at follow-up visit) (Fig. 1D). The horizontal phoria diminished immediately after binocular vertical rectus muscle recession (mean horizontal mis-alignment from zero: 3.62 prism-diopters at pre-OP vs 3.13 prism-diopters at post-OP) (Fig. 1D) and showed further reduction at the first-year postoperative visit (mean 0.63 prism-diopter at follow-up) (Fig. 1D). This reduction in horizontal phoria between the preoperative and the 1-year follow-up visit was significant (P = 0.016). The vertical phoria measured with the two-dimensional Hess screen test at a viewing distance of 0.3 m was also much improved (mean vertical misalignment from zero: 19.1° at pre-OP vs 3.94° at post-OP) (Fig. 1E). The alignment was stable at the 1-year follow-up visit (mean 1.69) (Fig. 1F), except for Case 5, initially the most undercorrected patient, who improved to nearly orthopho-ria. The reduction in vertical phoria between the pre-operative and the 1-year follow-up visit was significant (P = 0.0017). Also, the horizontal phoria improved in the days after binocular vertical rectus muscle recession (mean misalignment from zero: 7.50° at pre-OP vs 4.75° at post- OP) (Fig. 1E) and between the postoperative and the 1-year follow-up visit (mean 3.25° at follow-up) (Fig. 1F). The reduction in horizontal phoria between the preoperative and the 1-year follow-up visit was also statistically significant (P = 0.018). Figure 2 shows the Hess screen test of Case 5 preoperatively (Fig. 2A) and at the 1-year follow-up visit (Fig. 2B). The level of the thick black bar indicates the amount of left hyperdeviation and shows that this was comitant in left gaze, straight ahead (filled arrows), and right gaze. Also, the left hyperdeviation was comitant in the vertical gaze direction (empty arrows at 15° downgaze). Figure 3A-C depicts the vertical misalignment in 15° left, straight ahead, and 15° right gaze for all 8 subjects and, as in Figure 3, is shown by the thick black horizontal bar at the preoperative visit (Fig. 3A), at post-OP (Fig. 3B), and at the 1-year follow-up visit (Fig. 3C). To determine whether vertical comitance changed after binocular vertical rectus muscle recession, regression lines between the gaze directions for each patient were fitted. The absolute values of the slopes of the regression lines did not vary much between the pre-OP and postoperative visit. There was also no large change between the postoperative measurement and the 1-year follow-up visit. Vertical misalignment was also measured in 15° upgaze, straight ahead, and 15° downgaze at the preoperative (Fig. 3D), post-OP (Fig. 3E), and the 1-year follow-up visit (Fig. 3F). Preoperatively, the incomitance was never greater than 5°. Directly after surgery, there was a transient incomitance present in 2 of the 8 patients that resolved without further intervention at the 1-year follow-up visit. The field of single binocular vision of Case 5 is shown preoperatively in Figure 4A and at the 1-year follow-up visit (Fig. 4B). The area of fusion is enlarged for the entire study group after surgery (see median value in Fig. 4C, solid line). The size of the diplopia-free zone increased between the post-OP and the 1-year follow-up visit, with considerable variety among individual patients. This enlargement was not significant. Fusion requires minimal horizontal, vertical, and torsional misalignment in each gaze direction. Using dual 298 q 2008 Lippincott Williams & Wilkins Binocular Vertical Rectus Muscle Recession for Comitant Vertical Strabismus J Neuro-Ophthalmol, Vol. 28, No. 4, 2008 FIG. 2. Hess screen test of Case 5 preoperatively (A) and 1 year after binocular vertical rectus muscle recession (B). The thick black bar marks the comitant left hyperdeviation, the filled arrowheads mark zero misalignment, and the empty arrows show the left hyperdeviation at 15° downgaze (reading position). scleral search coils, all three components of eye direction within the 20° gaze field were simultaneously measured in Case 5. To clarify the torsional misalignment at different gaze directions, a three-dimensional Hess screen test (4) is presented. Fracture of the left orbital floor and orbital floor reconstruction 3 years before the strabismus surgery had caused this patient's comitant vertical strabismus. Figure 5 depicts and numerically describes the misalignment of all three ocular rotation axes preoperatively (Fig. 5A, C) and 2 months after a 2.5-mm recession of the left superior rectus muscle and 2-mm recession of the right inferior rectus muscle (Fig. 5B, D). A slightly greater hyperphoria in right gaze compared with left gaze preoperatively (from left [L]/right [R] 13.1° to L/R 17.1°, difference 4°) (Fig. 5C) was successfully diminished with slightly unequal (0.5 mm) recession of the vertical rectus muscles (from L/R 1.1° to L/R 2.5°, difference 1.4°) (Fig. 5D). Preop-erative torsional misalignment was minimal. There was incyclo misalignment in left gaze and excyclo misalign-ment in right gaze. This pattern changed postoperatively to excyclotorsional misalignment in upgaze and incyclotor-sional misalignment in downgaze. DISCUSSION The present study demonstrates that binocular vertical rectus muscle recession is effective in correcting comitant vertical strabismus in patients with normal retinal correspondence. Although introduced by Parks (5), this surgical option has not received attention (6). Recession of the superior rectus muscle in the hypertropic eye and recession of the inferior rectus muscle in the fellow Vertical gaze direction FIG. 3. Vertical misalignment of the 8 patients in left, straight ahead, and right gaze at the preoperative (A), postoperative (B), and 1-year follow-up visits (C) after binocular vertical rectus muscle recession. Vertical misalignment in 15° upgaze, straight ahead, and 15° downgaze at the preoperative (D), postoperative (E), and 1-year follow-up visits (F). 299 J Neuro-Ophthalmol, Vol. 28, No. 4, 2008 Bergamin et al FIG. 4. Field of single binocular vision for Case 5 before (A) and 1 year after binocular vertical rectus muscle recession (B). C. Summary of all patients at the day before operation (pre-OP), within 3 days after binocular vertical rectus muscle recession (post-OP), and at the 1-year follow-up. The diplopia-free zone enlarged slightly between the two first visits and further until the first year (dashed line, each single patient; solid line, median of the patients). eye did not induce incomitance across the 15° vertical and horizontal field of gaze (Fig. 3) and consequently reestablished stereopsis. In addition, when fusion was active after binocular vertical rectus muscle recession (Fig. 1A-B), even horizontal phorias normalized signifi-cantly (Fig. 1C-F). With the reduction in misalignment after binocular vertical rectus muscle recession, the field of binocular fusion enlarged minimally after the operation and more so by the time of the 1-year follow-up visit (Fig. 4). Binocular vertical rectus muscle recession is a straightforward approach to treating patients with comitant vertical strabismus. By performing equal or nearly equal recessions of the superior rectus muscle in the hypertropic eye and the inferior rectus muscle in the fellow eye, an overall and symmetrical improvement in alignment is achieved. Although we did not perform alternate and prism cover testing in convergent downgaze, patients did not report diplopia postoperatively in the reading position. The summation of both muscle recessions did not induce incomitance over a wide horizontal gaze range because one rectus muscle performs its vertical action most effectively in right gaze and the other in left gaze (5). To reduce or eliminate vertical incomitant strabismus, a combined adjustable recession and posterior fixation suture of the same vertical rectus muscle is effective and therefore appropriate (7). In these patients, unilateral vertical rectus muscle recession with or without adjustable sutures can also be applied (8). However, when larger comitant vertical misalignment needs to be corrected a unilateral combined procedure such as recession of the superior rectus muscle and resection of the inferior rectus muscle in the hypertropic right eye would probably lead to a vertical overcorrection in right gaze and a vertical undercorrection in left gaze. Moreover, if only the superior rectus muscle in the hypertropic eye were recessed one would weaken not only its primary action as an elevator, but also its function as an incyclo rotator. That would cause excyclo rotation in the treated eye. If the inferior rectus muscle in the same eye were additionally resected an even larger excyclo rotation would result. Our patients' mis-alignment showed balance in the torsional axis before and after the operation. This held true also in the two patients with fourth cranial nerve palsy as the initial cause of the misalignment. As stereovision was reestablished in our study patients, we may conclude that binocular vertical rectus muscle recessions symmetrically weaken the incyclo rotator in one eye and the excyclo rotator in the fellow eye. In Case 5, who was investigated with dual search coils, torsional misalignment of no more than 3° was measured. In this patient with an old orbital floor fracture this small amount of comitant torsional misalignment could be fused. However, if a larger torsional misalignment had been present, the surgeon may have considered an alternative approach. In our series, neither ptosis nor lid retraction was induced perhaps because the recessions were small. This study does not claim that binocular vertical rectus muscle recession is superior to unilateral vertical muscle recession with or without the use of adjustable sutures. However, it does establish the efficacy of this surgical approach. Given that only 8 patients could be recruited in a 10-year period the incidence of comitant vertical strabismus in a single center is likely to be too small to allow comparison of different types of surgical treatment. Acknowledgments We thank the orthoptists at the Department of Ophthalmology, supervised by Brigitte Barlocher, who performed the pre- and postoperative measurements, as well as Hanna Obzina for recording the search coil 300 q 2008 Lippincott Williams & Wilkins Binocular Vertical Rectus Muscle Recession for Comitant Vertical Strabismus J Neuro-Ophthalmol, Vol. 28, No. 4, 2008 FIG. 5. Dual search coil recordings of Case 5 with the right eye viewing and the left eye covered preoperatively (A, C) and 2 months after binocular vertical rectus muscle recession (B, D). This figure reads like the original two-dimensional Hess screen test, as seen from the subject's view, with left gaze positions on the left side of the graph. The pattern of torsional misalignment changed between the two measurements. Arrows show the amount of horizontal/vertical misalignment, the sectors, the amount of torsional misalignment: 1 clock-hour deviating from the 12 o'clock position indicates the number of degrees of torsional mis-alignment (see also ref. 4). Eso, esophoria; Exo, exophoria; L/R, left hyperphoria; R/L, right hyperphoria; Incyc, incyclo misalignment; excyc, excyclo misalignment. measurements. We also thank Dominik Straumann and Michael C. Brodsky for their helpful comments on the manuscript. REFERENCES 1. Jampolsky A. Management of vertical strabismus. Trans New Orleans Acad Ophthalmol 1986;34:141-71. 2. Scott WE, Werner DB, Lennarson L. Evaluation of Jensen procedures by saccades and diplopic fields. Arch Ophthalmol 1979;97:1886-9. 3. Robinson DA. A method of measuring eye movement using a scleral search coil in a magnetic field. IEEE Trans Biomed Eng 1963;10:137-45. 4. Bergamin O, Zee DS, Roberts DC, et al. Three-dimensional Hess screen test with binocular dual search coils in a three-field magnetic system. Invest Ophthalmol Vis Sci 2001;42:660-7. 5. Parks MM. Concomitant vertical deviations, In: Parks MM, ed., Ocular Motility and Strabismus. Hagerstown, MD: Harper & Row; 1975:15:133. 6. de Faber JT, Kingma-Wilschut C, Grootendorst R. Comitant strabismus. Curr Opin Ophthalmol 1999;10:305-9. 7. Hoover DL. Results of a combined adjustable recession and posterior fixation suture of the same vertical rectus muscle for incomitant vertical strabismus. J AAPOS 1998;2:336-9. 8. Helveston EM, Ellis FD. Adjustable sutures for horizontal and vertical strabismus. Am Orthopt J 1978;28:18-23. 301 [VBstrabismus] |
