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Pigmented retinopathy in Hallermann-Streiff syndrome
Volume 11 Number 1 February 2007
plication following strabismus surgery. Good visual outcomes may occur more frequently than previously reported. Genotype-phenotype correlations seen in a cohort of British patients with Leber’s congenital amaurosis. Robert H. Henderson, Naushin Waseem, Andrew R. Webster, Isabelle Russell-Eggitt, David Taylor, Anthony T. Moore Introduction: The purpose of this study was to investigate the relationship between genotype and phenotype in a large cohort of patients with Leber’s Congenital Amaurosis (LCA). A trial of gene therapy in a subset of patients with LCA due to mutations in the RPE65 gene is planned and it is essential that patients with mutations in this gene and others are identified and the phenotypes are carefully refined. Methods: Patients were recruited from two main centers (Moorfields Eye Hospital and Great Ormond Street Hospital, London, UK). Where possible, all patients underwent a full ophthalmic examination including refraction, Goldman visual fields, optical coherence tomography, fundus autofluorescence, and digital fundus photography. DNA aliquots were sent for analysis using the LCA chip (Asper Bio), which identifies previously published mutations in eight known genes. Direct sequencing of three genes, RPE65, RDH12 and CRB1, was carried out. Results: Eighty-six probands from 75 families were recruited. Phenotypic information was obtained in 70 subjects. A definitive molecular genetic diagnosis was obtained in 16/62 (26%) families: 9 patients were identified with mutations in RPE65; 2 in RPGRIP1, 2 in GUCY2D; 1 in AIPL1; and 9 with mutations in CRB1; no patients with LCA were found to have mutations in RDH12. There is a characteristic phenotype recognizable in both RPE65 and CRB1 patients. Conclusions: Identification of causative mutations remains a challenge but use of the LCA chip and careful assessment of the phenotype can improve the efficiency of genotyping strategies. RDH12 is not a cause of LCA in our cohort of patients. Distance Worth 4-Dot testing with variable target size: A quantitative assessment of control in intermittent exotropia. Sandra Holgado, Namita Kashyap, Sharon F. Freedman Introduction/Purpose: Patients with intermittent exotropia X(T ) have shown diminished distance stereoacuity; this measure has been used for pre- and postoperative sensory evaluation of X(T ). Using the distance Worth 4-Dot ( W4D) test on the M&S system (M&S Technologies, Inc., Park Ridge, IL), one may vary the size of the target, and thereby, the subtended visual angle. We wished to evaluate subjects with X(T ) using this variable distance W4D test. Methods: Prospective clinical series of children/adults with X(T ), including complete sensory motor assessment, and distance W4D testing with the M&S system (varying the target size from 3.0 to 0.3° in 11 possible gradations, and recording either fusion or suppression/alternate fixation at each step). Results: Included were normals (n ⫽ 8), and subjects with X(T ), n ⫽ 19, mean deviation ⫽ 21⌬. All subjects with X(T ) were intermittent at both distance and near and were tested with distance W4D as the first sensory test of the examination. Vision was better than 20/40 in both eyes of each subject. The mean break-point of fusion for the distance W4D was 0.54° for Normals versus 1.6° for subjects with X(T ), p ⫽ 0.008. Subjects with X(T ) were divided into four groups based upon control of their deviation (scale 1-4, with 1 ⫽ excellent and 4 ⫽ poor). Mean break-point for groups 1/2/3/4 was 0.75/1.4/3.0/2.1°, respectively. Discussion/Conclusions: Preoperative evaluation of
Journal of AAPOS
Abstracts
91
X(T ) includes subjective assessment of clinical control by the examiner. The distance W4D M&S test provides an additional, quantitative tool for sensory evaluation of X(T ). Application of this test to X(T ) both pre- and then postoperatively may further validate its usefulness. Improvement of distance stereoacuity in intermittent exotropia following surgery. Jonathan M. Holmes, David A. Leske, Sarah R. Hatt, Brian G. Mohney Purpose: Distance stereoacuity has been reported as a useful measure in assessing severity and outcome in intermittent exotropia (IXT ). The methods for assessing distance stereoacuity are evolving; the BVAT BVS system is no longer available, but the Frisby-Davis Distance (FD2) and Distance Randot (DR) tests have recently been introduced. Initial studies suggest that patients with IXT often demonstrate distance stereoacuity on FD2 but not on the DR test. We evaluated the change in pre- to postoperative distance stereoacuity measured by these tests. Methods: Fourteen patients with IXT undergoing surgery were enrolled prospectively (distance exotropia ranging from 16⌬ to 60⌬). All patients were successfully aligned postoperatively (⬍10⌬ exophoria, and ⬍4⌬ esotropia, at distance). Distance stereoacuity was evaluated with the FD2 and DR tests preoperatively and 6 weeks (4 to 9 weeks) postoperatively. We compared pre- and postoperative stereoacuity thresholds. Results: Preoperatively, four patients had normal stereoacuity (⬍60 arcsec) by FD2 and one of these by DR. When preoperative distance stereoacuity was subnormal (n ⫽ 10 [71%] by FD2 and n ⫽ 13 [93%] by DR), postoperative stereoacuity improved, from a median of nil to 200 arcsec with the DR ( p ⫽ 0.02), and a median of 80 to 40 arcsec with the FD2 ( p ⫽ 0.004). Conclusions: In successfully aligned IXT patients, there was significant improvement of distance stereoacuity when measured using the new DR and FD2 tests. The new DR and FD2 tests may be useful outcome measures in future clinical trials of interventions for intermittent exotropia. Pigmented retinopathy in Hallermann-Streiff syndrome. Denise A. Hug, Srinivas Iyengar, Greg I. Ostrow Purpose: To report a retinopathy seen in patients with Hallermann-Streiff syndrome and to review the indications for surgical intervention or further diagnostic evaluation. Design: Observational case series and review of the literature. Methods: Case 1: The ophthalmology service was consulted to evaluate a 1-monthold infant recently diagnosed with Hallermann-Streiff syndrome. Ophthalmic evaluation showed visually significant cataracts in both eyes. Case 2: A 3-month-old infant presented to the pediatric ophthalmology clinic with parental concerns regarding eye movement and white opacities. On examination, she had several findings consistent with a diagnosis of Hallerman-Streiff syndrome, in addition to the distinct bird-beak facies and visually significant bilateral cataracts. Results: Both patients underwent bilateral lensectomies and were found to show remarkably similar pigmented and atrophic lesions in the retina. The pigmented lesions were in the midperiphery of the retina and the atrophic RPE lesions were confined to the peripapillary region. RetCam photography was used to document these findings. Conclusions: Hallermann-Streiff syndrome, also known as oculomandibulofacial dyscephaly, is a rare genetic disorder with variable visual prognosis that may present undiagnosed to the ophthalmologist. Cataract surgery, warranted for lenticular opacities likely to be visually significant, may be complicated by respiratory difficulty and various structural abnormalities of the eye, not limited to
92
Abstracts
microphthalmos and posterior synechiae. We describe a previously unreported posterior segment finding that appears to be common in both of our patients. This retinopathy may be associated with other cases of Hallerman-Streiff and may also play a role in visual prognosis. A novel computerized visual acuity test in children. JeongMin Hwang, Young Joo Shin, In Bum Lee, Won Ryang Wee, Jin Hak Lee Purpose: To investigate the efficacy of a novel computerized visual acuity test for children—the Seoul National University (SNU ) visual acuity test. Methods: Sixty-three children from 1 to 5 years old were included. In a dark room, the children gazed at and followed a circular dot with 50% contrast moving at a fixed velocity of 10 pixels/s on a computer monitor. Eye movement was captured using an Osprey camera ( Viewcast, USA) and was expressed as coordinates on a graph. Movements of eye and dot were overlapped on a graph and analyzed. Minimal dot diameters visualized were compared with Teller visual acuity. Results: Average Teller visual acuity was 14.50 cycles/degree and average SNU visual acuity was 2.68 pixels. Teller visual acuity and SNU visual acuity were significantly correlated ( p ⫽ 0.009). LogMAR visual acuity converted from Teller visual acuity and SNU visual acuity were also significantly correlated ( p ⫽ 0.019). Conclusions: The devised SNU visual acuity test was found to be significantly correlated with Teller visual acuity and the authors believe that it could be used clinically in children. Unilateral medial rectus recession for moderate angle esotropia. Magdalene D. Israel, Anupam Deka Aim: Unilateral medial rectus recession is a predictable method for surgical correction of small-angle esotropia. This approach limits surgery to one eye, leaves the other muscles untouched, and requires less surgical time. A retrospective study on 19 patients with unilateral medial rectus recession of 6.0 mm for moderate-angle esotropia (30-35⌬) was analyzed. Method: Retrospective data were collected for all the children who underwent unilateral medial rectus recession for esotropia of 30 to 35⌬ between June 2004 and April 2006. The postoperative deviations and ocular motility were noted at follow-up (6 weeks to 24 months). Results: Unilateral medial rectus recessions were performed on 19 children with esotropia of which 47.5% were acquired esotropia. The mean age was 9 years, with a preponderance of males (57.89%). Ten children (52.63%) were amblyopic, with visual acuity between 6/60 and 6/18. Sixteen of the children (84.21%) were straight postoperatively. Only three patients (15.78%) had greater than 12⌬; none were exotropic and there was no restriction of adduction. Conclusion: Unilateral medial rectus recession is a safe and predictable procedure and should be considered as an alternative approach in the management of moderate angle esotropia. Eye movements are commutative. Robert S. Jampel Purpose: To provide evidence that all eye movements are commutative and to use that evidence to establish a coherent theory of ocular kinematics. Methods: Fixation targets and two miniature video cameras, one to record eye movements and the other to record head movements, were suspended from a head band. The apparatus ( VOG) keeps the eyes stable in the orbits during head yaw, pitch, and tilt while allowing the head to move freely. It was also used for tracking eye movements with the head held stationary. Ocular orientation was determined from downloaded
Volume 11 Number 1 February 2007
video clips by superimposing serial frames. Results: Video frame analysis reveals that all eye movements are commutative. The eye has one fixed axis within its substance, which serves eye movements to and from the midsagittal orbital plane. Brow-up and chin-down eye movements occur around an axis fixed in the orbit. Oblique movements consist of alternating arcs of great and small circles. The vertical extraocular muscles act synergistically when the head is held stationary producing slope and reciprocally during head tilt producing transient torsional movements. Conclusions: The globe rotates around two axes when the eye is stationary and one axis when the head tilts. The orientation of the eye can be calculated using the formula for the derivative of an ellipse. The results suggest a coherent theory of ocular movement: The function of the extraocular muscles is to maintain the fixation plane of each eye in equilibrium with the brain and coplanar with the fixation plane of the other eye in all gaze directions and head positions. Explaining the large hypertropia in superior oblique palsy: Magnetic resonance imaging shows relative adaptive changes in the size and contractility of inferior rectus. Li Jiang, Joseph L. Demer Introduction: Biomechanical modeling consistently indicates that superior oblique muscle weakness alone cannot explain the large hypertropia observed in superior oblique muscle palsy. We used magnetic resonance imaging (MRI) to investigate if any adaptive changes in inferior oblique muscle may contribute. Methods: We used surface coils to obtain high-resolution, coronal MRI in central gaze, supraduction, and infraduction in six patients with unilateral superior oblique muscle palsy and 17 orthotropic controls. Patients had 18.5 ⫾ 10.9⌬ central gaze hypertropia. We determined maximum inferior oblique muscle cross-sections, and contractility from cross-section changes from supraduction to infraduction. Patients then underwent ipsilesional inferior oblique muscle weakening and contralesional inferior oblique muscle recession. Results: All patients exhibited ipsilesional superior oblique muscle atrophy and subnormal contractility. Mean ipsilesional and contralesional inferior oblique muscle cross-sections were 27.6 ⫾ 3.0 and 33.0 ⫾ 4.2 mm2, while mean contractilities were 8.0 ⫾ 4.8 and 10.0 ⫾ 4.9 mm2, respectively. Both ipsilesional inferior oblique muscle cross-sections and contractilities were significantly less than contralesional inferior oblique muscle ( p ⬍ 0.05), but neither contractilities differ significantly from normal controls ( p ⬎ 0.1). All patients achieved excellent postoperative alignment. Discussion: Relative reductions in ipsilesional inferior oblique muscle size and contractility to superior oblique muscle palsy are probably neurally mediated changes that augment substantially the relatively small hypertropia due to superior oblique muscle weakness. There may be increased contralesional inferior oblique muscle force, decreased ipsilesional inferior oblique muscle force, or both. Relatively decreased ipsilesional inferior oblique muscle size and contractility may explain the surgical success of contralesional inferior oblique muscle recession. Conclusions: In superior oblique muscle palsy, the ipsilesional inferior oblique muscle exhibits reduced size and contractility relative to the contralesional inferior oblique muscle, reflecting likely neural adaptations increasing hypertropia. Contralesional inferior oblique muscle weakening is a physiologic therapy.
Journal of AAPOS
plication following strabismus surgery. Good visual outcomes may occur more frequently than previously reported. Genotype-phenotype correlations seen in a cohort of British patients with Leber’s congenital amaurosis. Robert H. Henderson, Naushin Waseem, Andrew R. Webster, Isabelle Russell-Eggitt, David Taylor, Anthony T. Moore Introduction: The purpose of this study was to investigate the relationship between genotype and phenotype in a large cohort of patients with Leber’s Congenital Amaurosis (LCA). A trial of gene therapy in a subset of patients with LCA due to mutations in the RPE65 gene is planned and it is essential that patients with mutations in this gene and others are identified and the phenotypes are carefully refined. Methods: Patients were recruited from two main centers (Moorfields Eye Hospital and Great Ormond Street Hospital, London, UK). Where possible, all patients underwent a full ophthalmic examination including refraction, Goldman visual fields, optical coherence tomography, fundus autofluorescence, and digital fundus photography. DNA aliquots were sent for analysis using the LCA chip (Asper Bio), which identifies previously published mutations in eight known genes. Direct sequencing of three genes, RPE65, RDH12 and CRB1, was carried out. Results: Eighty-six probands from 75 families were recruited. Phenotypic information was obtained in 70 subjects. A definitive molecular genetic diagnosis was obtained in 16/62 (26%) families: 9 patients were identified with mutations in RPE65; 2 in RPGRIP1, 2 in GUCY2D; 1 in AIPL1; and 9 with mutations in CRB1; no patients with LCA were found to have mutations in RDH12. There is a characteristic phenotype recognizable in both RPE65 and CRB1 patients. Conclusions: Identification of causative mutations remains a challenge but use of the LCA chip and careful assessment of the phenotype can improve the efficiency of genotyping strategies. RDH12 is not a cause of LCA in our cohort of patients. Distance Worth 4-Dot testing with variable target size: A quantitative assessment of control in intermittent exotropia. Sandra Holgado, Namita Kashyap, Sharon F. Freedman Introduction/Purpose: Patients with intermittent exotropia X(T ) have shown diminished distance stereoacuity; this measure has been used for pre- and postoperative sensory evaluation of X(T ). Using the distance Worth 4-Dot ( W4D) test on the M&S system (M&S Technologies, Inc., Park Ridge, IL), one may vary the size of the target, and thereby, the subtended visual angle. We wished to evaluate subjects with X(T ) using this variable distance W4D test. Methods: Prospective clinical series of children/adults with X(T ), including complete sensory motor assessment, and distance W4D testing with the M&S system (varying the target size from 3.0 to 0.3° in 11 possible gradations, and recording either fusion or suppression/alternate fixation at each step). Results: Included were normals (n ⫽ 8), and subjects with X(T ), n ⫽ 19, mean deviation ⫽ 21⌬. All subjects with X(T ) were intermittent at both distance and near and were tested with distance W4D as the first sensory test of the examination. Vision was better than 20/40 in both eyes of each subject. The mean break-point of fusion for the distance W4D was 0.54° for Normals versus 1.6° for subjects with X(T ), p ⫽ 0.008. Subjects with X(T ) were divided into four groups based upon control of their deviation (scale 1-4, with 1 ⫽ excellent and 4 ⫽ poor). Mean break-point for groups 1/2/3/4 was 0.75/1.4/3.0/2.1°, respectively. Discussion/Conclusions: Preoperative evaluation of
Journal of AAPOS
Abstracts
91
X(T ) includes subjective assessment of clinical control by the examiner. The distance W4D M&S test provides an additional, quantitative tool for sensory evaluation of X(T ). Application of this test to X(T ) both pre- and then postoperatively may further validate its usefulness. Improvement of distance stereoacuity in intermittent exotropia following surgery. Jonathan M. Holmes, David A. Leske, Sarah R. Hatt, Brian G. Mohney Purpose: Distance stereoacuity has been reported as a useful measure in assessing severity and outcome in intermittent exotropia (IXT ). The methods for assessing distance stereoacuity are evolving; the BVAT BVS system is no longer available, but the Frisby-Davis Distance (FD2) and Distance Randot (DR) tests have recently been introduced. Initial studies suggest that patients with IXT often demonstrate distance stereoacuity on FD2 but not on the DR test. We evaluated the change in pre- to postoperative distance stereoacuity measured by these tests. Methods: Fourteen patients with IXT undergoing surgery were enrolled prospectively (distance exotropia ranging from 16⌬ to 60⌬). All patients were successfully aligned postoperatively (⬍10⌬ exophoria, and ⬍4⌬ esotropia, at distance). Distance stereoacuity was evaluated with the FD2 and DR tests preoperatively and 6 weeks (4 to 9 weeks) postoperatively. We compared pre- and postoperative stereoacuity thresholds. Results: Preoperatively, four patients had normal stereoacuity (⬍60 arcsec) by FD2 and one of these by DR. When preoperative distance stereoacuity was subnormal (n ⫽ 10 [71%] by FD2 and n ⫽ 13 [93%] by DR), postoperative stereoacuity improved, from a median of nil to 200 arcsec with the DR ( p ⫽ 0.02), and a median of 80 to 40 arcsec with the FD2 ( p ⫽ 0.004). Conclusions: In successfully aligned IXT patients, there was significant improvement of distance stereoacuity when measured using the new DR and FD2 tests. The new DR and FD2 tests may be useful outcome measures in future clinical trials of interventions for intermittent exotropia. Pigmented retinopathy in Hallermann-Streiff syndrome. Denise A. Hug, Srinivas Iyengar, Greg I. Ostrow Purpose: To report a retinopathy seen in patients with Hallermann-Streiff syndrome and to review the indications for surgical intervention or further diagnostic evaluation. Design: Observational case series and review of the literature. Methods: Case 1: The ophthalmology service was consulted to evaluate a 1-monthold infant recently diagnosed with Hallermann-Streiff syndrome. Ophthalmic evaluation showed visually significant cataracts in both eyes. Case 2: A 3-month-old infant presented to the pediatric ophthalmology clinic with parental concerns regarding eye movement and white opacities. On examination, she had several findings consistent with a diagnosis of Hallerman-Streiff syndrome, in addition to the distinct bird-beak facies and visually significant bilateral cataracts. Results: Both patients underwent bilateral lensectomies and were found to show remarkably similar pigmented and atrophic lesions in the retina. The pigmented lesions were in the midperiphery of the retina and the atrophic RPE lesions were confined to the peripapillary region. RetCam photography was used to document these findings. Conclusions: Hallermann-Streiff syndrome, also known as oculomandibulofacial dyscephaly, is a rare genetic disorder with variable visual prognosis that may present undiagnosed to the ophthalmologist. Cataract surgery, warranted for lenticular opacities likely to be visually significant, may be complicated by respiratory difficulty and various structural abnormalities of the eye, not limited to
92
Abstracts
microphthalmos and posterior synechiae. We describe a previously unreported posterior segment finding that appears to be common in both of our patients. This retinopathy may be associated with other cases of Hallerman-Streiff and may also play a role in visual prognosis. A novel computerized visual acuity test in children. JeongMin Hwang, Young Joo Shin, In Bum Lee, Won Ryang Wee, Jin Hak Lee Purpose: To investigate the efficacy of a novel computerized visual acuity test for children—the Seoul National University (SNU ) visual acuity test. Methods: Sixty-three children from 1 to 5 years old were included. In a dark room, the children gazed at and followed a circular dot with 50% contrast moving at a fixed velocity of 10 pixels/s on a computer monitor. Eye movement was captured using an Osprey camera ( Viewcast, USA) and was expressed as coordinates on a graph. Movements of eye and dot were overlapped on a graph and analyzed. Minimal dot diameters visualized were compared with Teller visual acuity. Results: Average Teller visual acuity was 14.50 cycles/degree and average SNU visual acuity was 2.68 pixels. Teller visual acuity and SNU visual acuity were significantly correlated ( p ⫽ 0.009). LogMAR visual acuity converted from Teller visual acuity and SNU visual acuity were also significantly correlated ( p ⫽ 0.019). Conclusions: The devised SNU visual acuity test was found to be significantly correlated with Teller visual acuity and the authors believe that it could be used clinically in children. Unilateral medial rectus recession for moderate angle esotropia. Magdalene D. Israel, Anupam Deka Aim: Unilateral medial rectus recession is a predictable method for surgical correction of small-angle esotropia. This approach limits surgery to one eye, leaves the other muscles untouched, and requires less surgical time. A retrospective study on 19 patients with unilateral medial rectus recession of 6.0 mm for moderate-angle esotropia (30-35⌬) was analyzed. Method: Retrospective data were collected for all the children who underwent unilateral medial rectus recession for esotropia of 30 to 35⌬ between June 2004 and April 2006. The postoperative deviations and ocular motility were noted at follow-up (6 weeks to 24 months). Results: Unilateral medial rectus recessions were performed on 19 children with esotropia of which 47.5% were acquired esotropia. The mean age was 9 years, with a preponderance of males (57.89%). Ten children (52.63%) were amblyopic, with visual acuity between 6/60 and 6/18. Sixteen of the children (84.21%) were straight postoperatively. Only three patients (15.78%) had greater than 12⌬; none were exotropic and there was no restriction of adduction. Conclusion: Unilateral medial rectus recession is a safe and predictable procedure and should be considered as an alternative approach in the management of moderate angle esotropia. Eye movements are commutative. Robert S. Jampel Purpose: To provide evidence that all eye movements are commutative and to use that evidence to establish a coherent theory of ocular kinematics. Methods: Fixation targets and two miniature video cameras, one to record eye movements and the other to record head movements, were suspended from a head band. The apparatus ( VOG) keeps the eyes stable in the orbits during head yaw, pitch, and tilt while allowing the head to move freely. It was also used for tracking eye movements with the head held stationary. Ocular orientation was determined from downloaded
Volume 11 Number 1 February 2007
video clips by superimposing serial frames. Results: Video frame analysis reveals that all eye movements are commutative. The eye has one fixed axis within its substance, which serves eye movements to and from the midsagittal orbital plane. Brow-up and chin-down eye movements occur around an axis fixed in the orbit. Oblique movements consist of alternating arcs of great and small circles. The vertical extraocular muscles act synergistically when the head is held stationary producing slope and reciprocally during head tilt producing transient torsional movements. Conclusions: The globe rotates around two axes when the eye is stationary and one axis when the head tilts. The orientation of the eye can be calculated using the formula for the derivative of an ellipse. The results suggest a coherent theory of ocular movement: The function of the extraocular muscles is to maintain the fixation plane of each eye in equilibrium with the brain and coplanar with the fixation plane of the other eye in all gaze directions and head positions. Explaining the large hypertropia in superior oblique palsy: Magnetic resonance imaging shows relative adaptive changes in the size and contractility of inferior rectus. Li Jiang, Joseph L. Demer Introduction: Biomechanical modeling consistently indicates that superior oblique muscle weakness alone cannot explain the large hypertropia observed in superior oblique muscle palsy. We used magnetic resonance imaging (MRI) to investigate if any adaptive changes in inferior oblique muscle may contribute. Methods: We used surface coils to obtain high-resolution, coronal MRI in central gaze, supraduction, and infraduction in six patients with unilateral superior oblique muscle palsy and 17 orthotropic controls. Patients had 18.5 ⫾ 10.9⌬ central gaze hypertropia. We determined maximum inferior oblique muscle cross-sections, and contractility from cross-section changes from supraduction to infraduction. Patients then underwent ipsilesional inferior oblique muscle weakening and contralesional inferior oblique muscle recession. Results: All patients exhibited ipsilesional superior oblique muscle atrophy and subnormal contractility. Mean ipsilesional and contralesional inferior oblique muscle cross-sections were 27.6 ⫾ 3.0 and 33.0 ⫾ 4.2 mm2, while mean contractilities were 8.0 ⫾ 4.8 and 10.0 ⫾ 4.9 mm2, respectively. Both ipsilesional inferior oblique muscle cross-sections and contractilities were significantly less than contralesional inferior oblique muscle ( p ⬍ 0.05), but neither contractilities differ significantly from normal controls ( p ⬎ 0.1). All patients achieved excellent postoperative alignment. Discussion: Relative reductions in ipsilesional inferior oblique muscle size and contractility to superior oblique muscle palsy are probably neurally mediated changes that augment substantially the relatively small hypertropia due to superior oblique muscle weakness. There may be increased contralesional inferior oblique muscle force, decreased ipsilesional inferior oblique muscle force, or both. Relatively decreased ipsilesional inferior oblique muscle size and contractility may explain the surgical success of contralesional inferior oblique muscle recession. Conclusions: In superior oblique muscle palsy, the ipsilesional inferior oblique muscle exhibits reduced size and contractility relative to the contralesional inferior oblique muscle, reflecting likely neural adaptations increasing hypertropia. Contralesional inferior oblique muscle weakening is a physiologic therapy.
Journal of AAPOS