Long-Term Patient-Reported Outcomes of Visual Field Defects and Compensatory Mechanisms in Patients After Cerebral Hemispherectomy

Background: In cases of intractable epilepsy resistant to drug therapy, hemispherectomy is often the only treatment option to mitigate seizures; however, the true long-term subjective visual outcomes are relatively unexplored. In this study, we sought to determine and characterize patient-reported visual function years after hemispherectomy. Methods: This was an observational study conducted on a large cohort of children with seizure disorder treated with cerebral hemispherectomy. An online survey was sent to parents with questions to assess subjective visual function with a variety of questions from presence of visual field defects after hemispherectomy, to improvement over time, compensatory mechanisms used, and development of strabismus. Results: This survey was emailed to 248 parents of previously evaluated children who agreed to be re-surveyed, 48 (20%) of which responded. The average age at hemispherectomy was approximately 5 (±4) years, and the average time after hemispherectomy was 7 (±5) years. Thirty-nine patients (81%) were seizure-free after 1 surgery and 85% (n = 41) were seizure-free after ≥1 surgeries. Thirty-four (71%) experienced a visual field defect after surgery, but 25 (52%) experienced subjective improvement over time. Thirty-eight (79%) used compensatory mechanisms, such as head tilting, with 16 (33%) patients experiencing subjective improvement over time. Twenty-seven (56%) patients experienced a decrease in visual acuity after surgery with 12 (25%) experiencing subjective improvement over time. Conclusion: In a large cohort examining patient-reported visual outcomes years after hemispherectomy, most patients experienced strabismus and/or visual field defects. However, more than half reported improvements and compensatory mechanisms (exotropic strabismus and ipsilateral esotropic strabismus) over time, presumably to enhance visual field function. By exploring subjective visual and cognitive function, this paper uniquely characterizes patient-reported improvements over time, and provides motivation for larger longitudinal studies using more quantitative measures of visual function and improvement after hemispherectomy.

Clinical Research: Epidemiology Meets Neuro-Ophthalmology Section Editors: Heather E. Moss, MD, PhD Stacy L. Pineles, MD Long-Term Patient-Reported Outcomes of Visual Field Defects and Compensatory Mechanisms in Patients After Cerebral Hemispherectomy Elana A. Meer, BA, Monica F. Chen, BA, Monika Jones, JD, Gary W. Mathern, MD, Stacy L. Pineles, MD, MS Background: In cases of intractable epilepsy resistant to drug therapy, hemispherectomy is often the only treatment option to mitigate seizures; however, the true long-term subjective visual outcomes are relatively unexplored. In this study, we sought to determine and characterize patientreported visual function years after hemispherectomy. Methods: This was an observational study conducted on a large cohort of children with seizure disorder treated with cerebral hemispherectomy. An online survey was sent to parents with questions to assess subjective visual function with a variety of questions from presence of visual field defects after hemispherectomy, to improvement over time, compensatory mechanisms used, and development of strabismus. Results: This survey was emailed to 248 parents of previously evaluated children who agreed to be Perelman School of Medicine (EAM), University of Pennsylvania, Philadelphia, Pennsylvania; University of California Los Angeles School of Medicine (MFC), Los Angeles, California; CEO (MJ), Brain Recovery Project Childhood Epilepsy Surgery Foundation, Los Angeles, California; Brain Research Institute (GWM), University of California Los Angeles School of Medicine, Los Angeles, California; Neurological Surgery and Pediatric Neurological Surgery (GWM), Santa Monica UCLA Medical Center, Ronald Reagan UCLA Medical Center, Los Angeles, California; and Department of Ophthalmology (SLP), Stein Eye Institute, University of California Los Angeles, California. Unrestricted Funds, Research to Prevent Blindness (S.L.P.); G. W. Mathern was partly supported as the Davies/Crandall endowed chair for epilepsy research at UCLA. re-surveyed, 48 (20%) of which responded. The average age at hemispherectomy was approximately 5 (±4) years, and the average time after hemispherectomy was 7 (±5) years. Thirty-nine patients (81%) were seizure-free after 1 surgery and 85% (n = 41) were seizure-free after $1 surgeries. Thirty-four (71%) experienced a visual field defect after surgery, but 25 (52%) experienced subjective improvement over time. Thirty-eight (79%) used compensatory mechanisms, such as head tilting, with 16 (33%) patients experiencing subjective improvement over time. Twenty-seven (56%) patients experienced a decrease in visual acuity after surgery with 12 (25%) experiencing subjective improvement over time. Conclusion: In a large cohort examining patient-reported visual outcomes years after hemispherectomy, most patients experienced strabismus and/or visual field defects. However, more than half reported improvements and compensatory mechanisms (exotropic strabismus and ipsilateral esotropic strabismus) over time, presumably to enhance visual field function. By exploring subjective visual and cognitive function, this paper uniquely characterizes patient-reported improvements over time, and provides motivation for larger longitudinal studies using more quantitative measures of visual function and improvement after hemispherectomy. Journal of Neuro-Ophthalmology 2021;41:147–153 doi: 10.1097/WNO.0000000000000998 © 2020 by North American Neuro-Ophthalmology Society The authors report no conflicts of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www. jneuro-ophthalmology.com). We have confirmed that we have read the Journal’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines. Ethical Publication Statement: We confirm that we have read the Journal’s psition on issues involved in ethical publication and affirm that this report is consistent with those guidelines. Address correspondence to Stacy Pineles, MD, MS, Department of Ophthalmology, Jerome and Joan Snyder Chair in Ophthalmology, Stein Eye Institute, UCLA, 200 Stein Plaza, Los Angeles, CA; E-mail: [e-mail] Meer et al: J Neuro-Ophthalmol 2021; 41: 147-153 INTRODUCTION F or over 50 years, hemispherectomy procedures have been performed to treat intractable epilepsy due to etiologies such as perinatal stroke, malformations of cortical development, Rasmussen encephalitis, and Sturge–Weber syndrome (1). An umbrella term for any of the multiple neurosurgical procedures in which a cerebral hemisphere is removed, disconnected, or disabled, hemispherectomy has 147 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Research: Epidemiology Meets Neuro-Ophthalmology demonstrated success in cases of seizure disorders in which the source of epilepsy is localized to one cerebral hemisphere. However, these procedures often result in substantial visual field defects, such as homonymous hemianopia, in which the contralateral visual field is lost on the same side of both eyes. In a recent systemic review, it was found that 5 years after hemispherectomy surgery, 71% of children were seizure-free (2); however, the optimal timing of surgery, depending on age of presentation and effect of underlying pathology, is still very unclear. Furthermore, although the immature brain may be expected to compensate for impaired function if surgery is performed early (3), there has been little definitive research to determine the long-term functional effects of resulting visual field defects (4). Previous studies have explored the visual field defect and compensatory mechanisms over time; however, the functional visual outcome after cerebral hemispherectomy is still unclear (5). Unfortunately, such studies are limited by many factors, including long-term follow-up on visual function. For example, Devlin et al (6) demonstrated that, as expected, visual fields were either unchanged if already impaired or worse following surgery; however, postoperative follow-up was limited. Koenraads et al (7) sought to determine the visual outcome and prevalence of compensatory mechanisms in children after hemispherectomy by retrospectively reviewing postoperative ophthalmic examination of visual fixation, visual acuity, visual fields, optic discs, head posturing, ocular alignment, and cognitive development. All children assessed with visual field assessment had a homonymous hemianopia. Some children developed a contralateral exotropia, which the authors opined may be a compensatory mechanism that expanded the visual field, but did not address whether the exotropia was instead a result of oculomotor impairments from the surgery. In addition, the cohort median follow-up time was 2.3 years, not nearly long enough time to fully evaluate the childrens’ development, visual field defects, or outcomes after hemispherectomy. Furthermore, visual field defects specifically were not assessed over time in the context of other demographic factors. Hemispherectomy procedures may be the only option to attempt to allow children with intractable epilepsy to grow and develop to lead relatively stable lives (5). However, without clear research demonstrating how visual fixation, acuity, and fields may be affected by the surgery over time, the possible functional strategies children may develop to compensate for the homonymous hemianopsia, and the potential factors that may ameliorate the progression, it is challenging to holistically counsel parents of children who will undergo hemispherectomy. Furthermore, given the dearth of longitudinal studies, it is difficult to provide parents with timelines of compensatory improvement, or characteristics of improvement along the course of the child’s development. 148 The aim of this study was to examine how the impact of postoperative visual field defects subjectively changed over time with use of compensatory mechanisms, and how contributing factors such as age of surgery, gender, etiology of epilepsy, age of onset of epilepsy and duration, and improvement of epilepsy/outcome of surgery may affect this. This study uses subjective measures of visual field defect improvement based on parental experience and observation, and builds on previous studies by inquiring about compensatory mechanisms that optimize visual field function. METHODS The study protocol was certified as exempt by the Institutional Review Board of the University of California of Los Angeles (IRB 17-000725-AM-00002). The Brain Recovery Project: Childhood Epilepsy Surgery Foundation, a U.S.-based nonprofit organization which works with families of children impacted by epilepsy surgery, initially sent out an e-mail to its members containing a description of the study, an invitation to participate, and the survey link to the parents of children who had a cerebral hemispherectomy and agreed to be contacted for studies in a past study. In this follow-up study, a survey was sent to all parents who agreed to participate again. A copy of the survey questions can be found in Supplemental Digital Content (See Table E1, http://links.lww.com/WNO/ A404). Demographic information, including age, sex, age of onset of epilepsy, cause of epilepsy, age when patient had a hemispherectomy, and side of hemispherectomy, was collected, and information regarding timeline of improvements, general cognitive development, activity level, diet, and visual and physical therapy, incorporating key components of pedsQL QOL tools for visual impairment such as physical and cognitive functioning. Visual function was assessed by the presence of peripheral field defects, compensatory mechanisms (i.e., ocular misalignment and anomalous head posture), and visual acuity. Whenever possible, visual representations were used on the survey to ensure that survey-takers could understand the questions. RESULTS This survey was emailed to 248 parents of children who had a cerebral hemispherectomy, were evaluated in a previous study, and agreed to be surveyed again. Fourty-eight of these patients responded to the current survey. The demographics of the patients are shown in Table 1. Twenty-one (44%) of the patients were boys. The average age at hemispherectomy was approximately 5 (±4 SD) years, and on average, the time since hemispherectomy was approximately 7 (±5 SD) years. Of the patients, 81% (n = 39) were seizure-free after one surgery and 85% Meer et al: J Neuro-Ophthalmol 2021; 41: 147-153 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Research: Epidemiology Meets Neuro-Ophthalmology TABLE 1. Characteristics of Patients Demographics, Post HH Seizures, Defects, Improvements, and lifestyle factors Demographics Male Female Annual income Age at hemispherectomy Time since hemispherectomy Seizure free Seizure-free after 1 surgery Seizure-free after 1 + surgery Child taking antiseizure medications? Visual field defects after surgery and improvements over time Initial Visual field defect after surgery (not including patients who had a VF defect before surgery) No improvements in VF defects over time Little improvement in VF defects over time (25%) Moderate VF improvement (50% better) Complete VF improvement (100% better) Other (unknown VF improvement or being well-compensated or compensated for) Compensatory mechanisms for VF defects Head tilted/turned to the right Squinting Head tilted/turned to the left No compensatory mechanisms Situations or conditions that improve or negatively affect VF defect No Light/Darkness Crowds/Congested/new environments Purposeful placement of items in visual field Fatigue/illness Reading Timeline of improvement None/NA Immediate to 1 month 6–8 months 1 year 2–3 years Continuous How did VF improvements first manifest None/NA Less scanning for an item/improved object tracking, manipulation, and visual attention Improvement in exotropia/esotropia Less physical collisions Improvement in reading Decrease in visual acuity after surgery Yes No Improvement in visual acuity over time No n/a ,25% Around 50% Around 100% Other (eg still being assessed) Meer et al: J Neuro-Ophthalmol 2021; 41: 147-153 Avg Max min Std Dev 44% (n = 21) 56% (n = 27) 102,821 5 7 300,000 13 24 20,000 0.125 0.33 64,479 4 5.62 81% (n = 39) 85% (n = 41) 46% (n = 22) 71% (n = 34) 48% (n = 23) 21% (n = 10) 6% (n = 3) 2% (n = 1) 13% (n = 6) 29% 2% 40% 21% (n (n (n (n = = = = 14) 2) 19) 10) 56% (n = 27) 8% (n = 4) 19% (n = 9) 6% (n = 3) 4% (n = 2) 6% (n = 3) 67% (n = 32) 4% (n = 2) 8% (n = 4) 4% (n = 2) 10% (n = 5) 6% (n = 3) 65% (n = 31) 13% (n = 6) 10% (n = 5) 8% (n = 4) 4% (n = 2) 56% (n = 27) 44% (n = 21) 27% (n = 13) 44% (n = 21) 15% (n = 7) 6% (n = 3) 4% (n = 2) 4% (n = 2) 149 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Research: Epidemiology Meets Neuro-Ophthalmology (Continued ) Avg Strabismus after surgery Right esotropia Left esotropia R/L alternating esotropia Right exotropia Left exotropia R/L alternating exotropia No Eso/Exotropia mostly corrected by surgery Situations or conditions improve or negatively strabismus No N/a fatigue/illness Bright lights Strabismus surgery Viewing stationary objects helps Prism glasses/eye patching helps Improvement in visual acuity over time No n/a ,25% Around 50% Around 100% Improvement only after surgery Cognitive development Learning difficulties Reading difficulties Behavioral problems Attentional deficits Memory deficits Psychiatric conditions Good cognitive development Global deficits/Disabilities Unknown (eg too young to tell) General activity level after surgery 30 min–1 hour/d –3 to 4 times/wk 21 time/wk 22 times/mo 21 time/mo No activity Vision/Physical therapy Visual therapy (eg eye patching, tracking activities) Physical therapy (e.g., aqua therapy, bike riding, swimming, baseball, running, stretching) No (n = 41) were seizure-free after one or more surgeries. Of the seizure-free individuals, 29% (n = 12) were taking antiseizure medications at the time of the survey. Thirty-four (71%) of them reported an initial visual field defect after surgery, 25 of whom (74% of those with initial defects) reported some sort of subjective improvement in visual field defects over time. The VF improvements were also characterized to be first manifested as less scanning for an item/ improved object location, improvement in exotropia/ esotropia, less physical collisions, and improvement in reading. In addition, all of the patients with visual field defects 150 Max min Std Dev 8% (n = 4) 2% (n = 1) 4% (n = 2) 19% (n = 9) 23% (n = 11) 4% (n = 2) 29% (n = 14) 10% (n = 5) 25% 27% 27% 2% 8% 4% 6% (n (n (n (n (n (n (n = = = = = = = 12) 13) 13) 1) 4) 2) 3) 23% (n = 11) 35% (n = 17) 10% (n = 5) 6% (n = 3) 13% (n = 6) 13% (n = 6) 69% (n = 33) 50% (n = 24) 40% (n = 19) 48% (n = 23) 40% (n = 19) 8% (n = 4) 10% (n = 5) 13% (n = 6) 6% (n = 3) 46% (n = 22) 31% (n = 15) 10% (n = 5) 2% (n = 1) 0% (n = 0) 15% (n = 7) 48% (n = 23) 79% (n = 38) 2% (n = 1) used at least one compensatory mechanism, such as head tilting and squinting to accommodate such visual field defects, according to their parents. Twenty-eight (58%) of the patients used compensatory head tilting, and 54% (n = 15) of those patients tilted their head to the contralateral side of the surgery. Of individuals with visual field defects, 44% (n = 21) found conditions were exacerbated by certain factors, with most children negatively affected by crowds/ congestion, light/darkness, and fatigue/illness. Sixteen (33%) reported improvement over time with 4% (n = 2) seeing improvements immediately, 8% (n = 4) from 6 to 8 Meer et al: J Neuro-Ophthalmol 2021; 41: 147-153 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Research: Epidemiology Meets Neuro-Ophthalmology months later, 4% (n = 2) by 1 year, 10% (n = 5) by 2 to 3 years, and 6% continuously (n = 3). Twenty-seven (56%) patients reported a decrease in visual acuity after surgery with 44% (n = 12) of those patients experiencing some level of improvement over time. Seventy-one percent of patients reported strabismus after surgery (n = 34) with 59% (n = 20) experiencing some level of improvement over time. Twenty (63%) of the patients reported exotropia. Of these patients 50% (n = 10 out of 20) demonstrated exotropia contralateral to the side of hemispherectomy. Seven (15%) patients demonstrated esotropia, and of these patients, 29% (n = 2) developed esotropia ipsilateral to the side of hemispherectomy, which is believed to be compensatory. Cognitive development was also assessed; 69% (n = 33) of patients reported learning difficulties, 50% (n = 24) reported reading difficulties, 40% (n = 19) reported behavioral problems, 48% (n = 23) reported attentional deficits, 40% (n = 19) reported memory deficits, 8% (n = 4) reported psychiatric conditions, and 13% (n = 6) reported global deficits/disabilities. Of note, only 13% of patients (n = 6) reported good cognitive development. Of the patients, 48% (n = 23) received some sort of vision therapy (e.g., eye patching, tracking activities), and 79% (n = 38) received physical therapy (e.g., aqua therapy, bike riding, swimming, baseball, running, stretching). Ninety-one percent of the patients with improvements in visual field,,visual acuity, and/or strabismus over time also received “vision therapy,” although the type of therapy was not specified. Diet and general level of activity were also assessed; however, no distinguishing correlations between these variables and improvement in visual defect, acuity, or alignment were found. In a multivariate regression analysis, greater age at hemispherectomy was found to almost significantly predict strabismus (P = 0.055) (Table 2). In addition, the contribution of surgery, gender, socioeconomics, vision therapy, and physical activity to perceived visual field/visual acuity improvements over time was explored. Lower age at surgery was associated with greater subjective visual field defect improvements (P = 0.045), and parental reported vision therapy predicted greater subjective visual field defect improvements (P = 0.00269) (Table 2). None of the factors of age, gender, socioeconomics, vision therapy, activity, strabismus, visual field defect, visual field improvement, and strabismus improvement consistently predicted any of the components of cognitive development explored. We also sought to explore whether those who were seizure-free reported differences in subjective observations of visual outcomes by parents. Of the individuals who were seizure-free and taking antiseizure medications (n = 22), 45% had subjective VF defects (n = 10), 23% (n = 5) had strabismus, 9% (n = 2) had visual field improvements, and 23% (n = 5) had strabismus improvements. Of the individuals who were seizure-free and not taking meds (n = 26), 69% (n = 18) had VF defects, 65% (n = 17) had Meer et al: J Neuro-Ophthalmol 2021; 41: 147-153 strabismus, 31% (n = 8) had VF improvements, and 27% (n = 7) had strabismus improvements. However, differences between the groups in relation to VF defects (P = 0.313), strabismus (P = 0.353), VF improvements (P = 0.405), and strabismus improvements (P = 0.373) were nonsignificant. DISCUSSION This study represents one of the largest cohorts to date looking at patient-reported visual outcomes years after cerebral hemispherectomy. Although the visual fields and strabismus were not directly measured in this study, the results of this study speak to the evolution of subjective visual field defects and strabismus over time. In this study, most patients reported strabismus and/or visual field defects. However, more than half of each cohort reported subjective improvements over time according to a survey of their parents. More than half developed compensatory mechanisms (exotropic strabismus and ipsilateral esotropic strabismus) presumably to enhance function visual field. Most patients were seizure-free after surgery, and less than one third of those patients were concurrently taking antiseizure medications. Of individuals with visual field defects, 52% reported subjective improvements over time, most by 5 years after hemispherectomy, manifesting as decreased physical collisions, improved object tracking etc. Of individuals with strabismus, more than half achieved improvements over time. The results also characterized the development of improvements, and certain logical yet previously unexplored conditions (fatigue, illness, bright lights, crowds, and mobile objects) were found to exacerbate defects. As of yet, the global cognitive developments of individuals who received hemispherectomies have been relatively unexplored. The results that only 12.5% of patients reported good cognitive development, with the rest citing some level of learning difficulties, reading difficulties, behavioral problems, attention deficits, memory deficits, and psychiatric conditions are particularly concerning. Although hemispherectomies may be the only treatment option for unilateral intractable epilepsy (5), it is important to consider that patients may not only experience visual field defects and strabismus, but also potentially debilitating cognitive development defects that may greatly affect quality of life. Although it is impossible to distinguish whether these diagnoses were present before the hemispherectomy or are part of the natural history of the childrens’ underlying diseases in this study, these results speak to the importance of considering prophylactic cognitive development and behavioral therapy to attempt to mitigate these difficulties in our patients lives whether or not they undergo hemispherectomy. These data also suggest that visual therapy should be further explored as a method to facilitate visual field defect and strabismus improvements. In this study, parental-reported therapies (consisting of eye-patching/ 151 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Research: Epidemiology Meets Neuro-Ophthalmology TABLE 2. Multivariable Regression Analysis of Predictors on Strabismus, Strabismus and Visual Field Defect Improvements, and Cognitive Development Endpoint Strabismus Strabismus improvements Visual field defect improvements Cognitive development Predictors/Factors Estimate P Age Age Gender Socioeconomics Vision therapy Physical activity Age Gender Socioeconomics Vision therapy Physical activity Age Gender Socioeconomics Vision therapy Physical activity Strabismus Visual field defect Visual field defect improvement Strabismus improvement 22.26 1.51 20.078 20.125 21.46 0.218 22.064 20.552 20.448 3.17 21.41 20.671 20.780 20.569 1.2432 0.683 0.780 21.32 0.924 0.499 0.055832 0.138 0.9379 0.901 0.151 0.829 0.045* 0.583 0.656 0.00269* 0.166 0.506 0.439 0.572 0.220 0.498 0.439 0.194 0.360 0.62 *P value , 0.05. visual tracking activities, prism glasses, etc.) were found to significantly predict subjective parent-reported visual field defect improvement. However, without actual visual field testing, it is impossible to note whether there was true objective improvement in the visual field of any of these patients. Furthermore, patient-reported improvement may be biased by parents’ expectations of outcomes after hemispherectomy and therapy. These findings are in line with previous studies, which although limited by low statistical power and time to follow-up, have demonstrated similar outcomes. Devlin et al showed that at postoperative follow-up after hemispherectomies, 52% of children were seizure-free, 9% reported rare seizures, 30% showed a greater than 75% reduction in seizures, and only 9% showed less than a 75% reduction in seizures or no improvement at all, slightly lower than the result in this study that 85.42% of patients were seizure-free after hemispherectomy (6). However, postoperative follow-up studies on visual field defects in particular were lacking. Similarly, Koenraads et al (7)sought to determine the visual outcome and prevalence of compensatory mechanisms in children who had undergone hemispherectomy by retrospectively reviewing postoperative ophthalmic examination of visual fixation, visual acuity, visual fields, optic discs, head posturing, ocular alignment, and cognitive development. The results of this study of patient-reported outcomes were consistent with Koenraads et al (7) who found anomalous head posturing and constant or intermittent XT contralateral to the side of hemispherectomy in 53% and 38% of the children, respectively. The results of this study are also consistent with previous studies 152 that have found homonymous hemianopia in most posthemispherectomy children (6); however, our study does not just focus on long-term seizure-free rates, but instead aims to define parent-reported visual and cognitive outcomes (8,9). It is important to note that although previous studies have evaluated hemispherectomy outcomes, typically studies have been limited to retrospectively viewed follow-ups of only few years. Conversely, although reliant on subjective reports, in this study, the average time since hemispherectomy in this population was 7 years, allowing us unique insight into global development after the surgery. Of note, Handley et al (10) uniquely chronicle visual function 20 years after childhood hemispherectomy for intractable epilepsy, and demonstrate that adults after hemispherectomy in childhood may have better visual function in the eye ipsilateral to the side of hemispherectomy over time, with evidence of reorganization to accommodate for postoperative hemispherectomy, similarly suggested by patientreported visual improvements in this study; however, Handlet et al was limited by a small cohort of 6 patients. One major limitation of this study is the method of data retrieval. Although the survey study allowed us to follow the largest cohort size of hemispherectomy patients explored over a period of approximately 5 years to date, it is limited by subjective reports, potential ambiguity of responses, and lack of formal ophthalmic evaluations including visual fixation, visual acuity, visual fields, optic discs, ocular alignment, retinal nerve fiber layers, etc. In addition, patient-reported outcomes may be further influenced by parental counseling and expectations of postoperative recovery. However, previous studies looking at compensatory mechanisms have Meer et al: J Neuro-Ophthalmol 2021; 41: 147-153 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Research: Epidemiology Meets Neuro-Ophthalmology primarily been retrospective, lacking detailed descriptions of abnormal head posture and ocular alignment and have suffered from small sample size and inadequate time to follow-up. Furthermore, subjective measures have been shown to classify visual disability, and have been proven to correlate with objective visual performance in a variety of ophthalmologic studies ranging from visual field size in brain lesioned patients to ocular torsion and macular degeneration (11–13). Therefore, although limited in its clinical description of particular visual changes after hemispherectomy, this study is impactful in its ability to characterize abnormal head posture and ocular alignment in a large cohort of patients as characterized by their families over a significant period of time. The longitudinal nature of this study allowed us to uniquely characterize patient-reported improvements over time, and suggest that future studies further investigate the role of vision therapy on improving visual field defects. In addition, these longitudinal data suggest that cognitive developments, which are as of yet unexplored, should be considered in management of hemispherectomy patients. Finally, these data should provide motivation for a larger longitudinal study in which patients are examined by ophthalmologists and neurologists to fully ascertain changes in their visual function using qualitative and quantitative measures. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: E. A. Meer, M. F. Chen, M. Jones, G. W. Mathern, and S. L. Pineles; b. Acquisition of data: E. A. Meer, M. F. Chen, and M. Jones; c. Analysis and interpretation of data: E. A. Meer, M. F. Chen, M. Jones, G. W. Mathern, and S. L. Pineles. Category 2: a. Drafting the manuscript: E. A. Meer; b. Revising it for intellectual content: E. A. Meer, M. F. Chen, M. Jones, G. W. Mathern, and S. L. Pineles. Category 3: a. Final approval of the completed manuscript: E. A. Meer, M. F. Chen, M. Jones, G. W. Mathern, and S. L. Pineles. Meer et al: J Neuro-Ophthalmol 2021; 41: 147-153 REFERENCES 1. Lee YJ, Kim EH, Yum MS, Lee JK, Hong S, Ko TS. Long-term outcomes of hemispheric disconnection in pediatric patients with intractable epilepsy. J Clin Neurol. 2014;10:101–107. 2. Cao K, Liu M, Wang C, Liu Q, Yang K, Tao L, Guo X. Five-year long-term prognosis of epileptic children after hemispheric surgery: a systematic review and meta-analysis. Medicine (Baltimore). 2016;95:e3743. 3. Sugano H, Arai H. Epilepsy surgery for pediatric epilepsy: optimal timing of surgical intervention. Neurol Med Chir (Tokyo). 2015;55:399–406. 4. Mosch S, Max J, Tranel D. A matched lesion analysis of childhood versus adult-onset brain injury due to unilateral stroke. Cog Behav Neurol. 2005;18:5–17. 5. Griessenauer CJ, Salam S, Hendrix P, Patel DM, Tubbs RS, Blount JP, Winkler PA. Hemispherectomy for treatment of refractory epilepsy in the pediatric age group: a systematic review. J Neurosurg Pediatr. 2015;15:34–44. 6. Devlin AM, Cross JH, Harkness W, Chong WK, Harding B, Vargha-Khadem F, Neville BG. Clinical outcomes of hemispherectomy for epilepsy in childhood and adolescence. Brain. 2003;126:556–566. 7. Koenraads Y, van der Linden DC, van Schooneveld MM, Imhof SM, Gosselaar PH, Porro GL, Braun KP. Visual function and compensatory mechanisms for hemianopia after hemispherectomy in children. Epilepsia. 2014;55:909–917. 8. Moosa AN, Gupta A, Jehi L, Marashly A, Cosmo G, Lachhwani D, Wyllie E, Kotagal P, Bingaman W. Longitudinal seizure outcome and prognostic predictors after hemispherectomy in 170 children. Neurology. 2013;80:253–260. 9. Moosa AN, Jehi L, Marashly A, Cosmo G, Lachhwani D, Wyllie E, Kotagal P, Bingaman W, Gupta A,. Long-term functional outcomes and their predictors after hemispherectomy in 115 children. Epilepsia. 2013;54:1771–1779. 10. Handley SE, Vargha-Khadem F, Bowman RJ, Liasis A. Visual function 20 years after childhood hemispherectomy for intractable epilepsy. Am J Ophthalmol. 2017;177:81–89. 11. Dean S, Mathers JM, Calvert M, Kyte DG, Conroy D, Folkard A, Southworth S, Murray P, Denniston AK. The patient is speaking: discovering the patient voice in ophthalmology. Br J Ophthalmol. 2017;101:700–708. 12. Poggel DA, Muller-Oehring EM, Kasten E, Buzenthal U, Sabel BA. Topographical patterns of visual field recovery: changes of objective and subjective visual field size in brain-lesioned patients. J Vis. 2002;2:64. 13. Kajla G, Rohatgi J, Dhaliwal U. Use of subjective and objective criteria to categorise visual disability. Indian J Ophthalmol. 2014;62:400–406. 153 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.