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Show ORIGINAL CONTRIBUTION Exotropia and Face Turn in Children With Homonymous Hemianopia Sean P. Donahue, MD, PhD and Alden K. Haun, MD Abstract: Four children developed homonymous hemianopia, exotropia with the deviating eye pointing in the direction of the field defect, and a face turn toward the side of the defect following complete third cranial nerve palsy after brain tumor resection, an in utero middle cerebral artery infarction, nonaccidental head trauma, and a hemispherectomy for an intractable seizure disorder. We present evidence that the exotropia and face turn are part of an adaptive mechanism to increase the useful visual field. (/ Neuro- Ophthalmol 2007; 27: 304- 307) any children who develop homonymous hemianopia during infancy also develop an anomalous head posture thought to be a compensatory mechanism to increase the available visual field ( 1). In reporting on a series of 10 patients with early- onset homonymous hemianopia and an anomalous face turn ipsilateral to the hemifield defect, Paysee and Coats ( 1) proposed that this posturing occurs in an effort to maximize visual function by using saccades into the non- seeing hemifield. There have been reports of patients with congenital or early- onset homonymous hemianopia developing an exotropia ( 2,3). Hoyt and Good ( 4) have queried whether the exotropia is compensatory or simply an epiphenomenon due to the associated infantile neurologic disease often found in these patients. We have studied four patients who developed homonymous hemianopia early in life. All had anomalous head posturing and an ipsilateral exotropia. In one patient with acquired third cranial nerve palsy and a homonymous Departments of Ophthalmology and Visual Sciences ( SPD, AKH), Pediatrics ( SPD), and Neurology ( SPD), Vanderbilt University School of Medicine, Nashville, Tennessee. This work was supported in part by a grant from Research to Prevent Blindness ( RPB), New York, NY, to the Vanderbilt University Department of Ophthalmology. Address correspondence to Sean P. Donahue, MD, PhD, Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, 8000 Medical Center East, Nashville, TN 37232- 8808; E- mail: sean. donahue@ vanderbilt. edu hemianopia, the exotropia persisted despite full restoration of ocular motility. A second patient developed exotropia and a face turn after a hemispherectomy that produced a homonymous hemianopia. We present evidence that the development of exotropia in patients with anomalous head posturing and a homonymous hemianopia is an adaptive mechanism that serves to further expand the usable visual field. CASE REPORTS Case 1 A 4M>- year- old boy had a right thalamic- temporal pilocytic astrocytoma resected at the age of 3M> years. The tumor involved the right optic tract. After tumor resection, he was noted to have a complete right third cranial nerve palsy with ptosis, ophthalmoplegia, and a dilated, poorly reactive right pupil. He developed hydrocephalus, partial complex seizures, and a left hemiplegia. He was treated with carboplatin and vincristine. When he was examined by the pediatric ophthalmology service 8 weeks after tumor resection, he had best-corrected distance visual acuities of 20/ 40 in the right eye and 20/ 50 in the left eye. Visual acuity in the right eye was markedly decreased at near, suggesting poor accommodation from the third cranial nerve dysfunction. There was a 1 mm asymmetry in lid function with a narrower right palpebral fissure but no frank ptosis and no anisocoria. There was a 45 prism- diopter exotropia with a mild deficit of supraduction, infraduction, and adduction of the right eye. Ophthalmoscopy revealed optic disc pallor bilaterally and mild incyclotorsion of the right eye. Neurologic examination showed a left hemiparesis. The patient could not cooperate for confrontation visual field testing on this visit. Over the next 2 months the right third cranial nerve palsy resolved completely, but the large-angle exotropia remained and became comitant. The patient developed a left face turn and began to fixate with the previously paretic right eye ( Fig. 1). The patient was noted to have a dense left homonymous hemianopia on confrontation visual field testing. He has been followed for more than 2 years without a change in his examination or recurrence of tumor. 304 J Neuro- Ophthalmol, Vol. 27, No. 4, 2007 Homonymous Hemianopia J Neuro- Ophthalmol, Vol. 27, No. 4, 2007 FIG. 1. Case 1. The patient has a left face turn, right eye ( previously paretic eye) fixation, and exotropia. Case 2 A 7'/ 2- year- old girl with a history of an in utero right middle cerebral artery stroke and left hemiparesis presented with the parents noticing that " her eyes were turning out." Her primary physician and parents both reported that her strabismus was long- standing. Best- corrected visual acuity was 20/ 20 in both eyes. She had a 20 prism- diopter left exotropia, a left face turn, and a left homonymous inferior quadrantanopic defect on automated perimetry ( Fig. 2). A right- beating nystagmus was present in all positions of gaze. It did not change on side gaze, and there was no null position in right gaze. On neurologic examination, a left hemiparesis was found. Follow- up MRI revealed no new lesions, and FIG. 2. Case 2. Humphrey visual field testing shows a left homonymous quadrantanopia. the carbamazepine level at the time of presentation was normal. At age 13, 5 years after having constant exotropia, the patient desired strabismus surgery because she was being teased by her schoolmates. The patient and her mother were both advised of the potential functional benefit of her exotropia. Nevertheless, she chose to proceed, and underwent a resect- recess procedure on her non- fixating left eye. Her vision was initially overcorrected to esotropia, but within 6 months she had developed a recurrent exotropia of 10- 15 prism diopters, which has remained stable over 3 years of follow- up. Her anomalous head position has persisted. Case 3 An 11- month- old girl had undergone a hemispher-ectomy at age 5 months for uncontrolled seizures. An MRI scan had demonstrated cortical neuronal migration abnormalities. The child's parents reported that she had developed an exotropia shortly after the hemispherectomy and preferred to fixate with her left eye. She had a right face turn that her parents had noticed shortly after surgery. Examination at age 11 months demonstrated central, steady, and maintained fixation in each eye although there was a fixation preference for the left eye. She had a 20 prism-diopter comitant exotropia with full versions although detailed alignment measurements could not be performed. Confrontation visual field testing demonstrated a right homonymous hemianopia. The remainder of the examination was normal. When last examined at age 3M> years, she continued to manifest a left eye fixation preference, no significant amblyopia, full versions, a comitant exotropia, a right face turn, and a dense right homonymous hemianopia. Case 4 A 7- month- old girl with a history of severe head trauma due to child abuse at age 5 months was referred to the pediatric ophthalmology service for evaluation of her visual status. She could fix and follow bilaterally and had full ocular motility with a well- controlled esophoria. The pupillary, anterior segment, and dilated funduscopic examinations were normal. Confrontation visual field testing showed a left homonymous hemianopia. Neurologic evaluation showed a left hemiplegia. On examination 7 months later, she had developed an intermittent 20 prism- diopter comitant left exotropia. A left face turn was first noted 6 months later. She has since been followed through the age of 2M> years and has maintained a comitant, poorly controlled, intermittent exotropia with a fixation preference for the right eye, a left homonymous hemianopia, and a left face turn. 305 J Neuro- Ophthalmol, Vol. 27, No. 4, 2007 Donahue and Haun DISCUSSION Children often develop anomalous head postures to compensate for visual or ocular motility impairments. Children with congenital nystagmus may develop a face turn to maintain their eyes in a null position. Patients with superior oblique palsy, Duane syndrome, and other paralytic and restrictive strabismus syndromes also typically have abnormal head postures. The development of a face turn ipsilateral to a visual field defect has been described as a functional adaptation to early onset homonymous hemianopia ( 2,3). Zangemeister et al ( 5) hypothesized that this adaptive mechanism allows the use of large saccades to expand the useful peripheral visual field. In this situation, the patients adopt an ocular motor strategy of a large overshooting saccade into the blind hemifield followed by scanning back through the blind field. The face turn rotates the seeing field toward midline. Similar findings of anomalous head position with homonymous hemianopia were reported by Paysee and Coates ( 1), but only 1 of their 10 patients was exotropic. Our four patients were collected consecutively and prospectively as they presented to the pediatric ophthalmology service. All four had previously acquired homonymous hemianopia early in life and developed ipsilateral exotropia ( fixation preference for the contralateral eye) and a face turn toward the visual field defect. In two patients ( Cases 1 and 4), the exotropia and face turn developed as other related neurologic problems ( third cranial nerve palsy and head trauma) resolved, suggesting that the exotropia and face turn were both compensatory. In our Case 3, the exotropia and face turn became manifest after a surgical procedure that produced a homonymous hemianopia. The exotropic eye of all four of our patients was on the side of the hemianopia, and, in addition, the child with the third cranial nerve palsy switched fixation to the paretic eye as his face turn developed. It is unlikely that all of these events would have occurred by chance alone, suggesting that the exotropia enhances visual function. We believe that the development of an ipsilateral exotropia in patients with anomalous head posturing toward an ipsilateral homonymous hemianopia serves to expand the usable visual field ( Fig. 3). The anomalous retinal correspondence created by the exotropia enlarges the available visual field, as the visual field defect becomes reduced because the exotropic eye is on the side of the homonymous hemianopia. As suggested by Zangemeister et al ( 5) and Paysee and Coates ( 1), large- amplitude saccades may also play a role in visual field expansion, as these saccades into the blind hemifield are a method of " scanning" the visual periphery. The best evidence for an expanded visual field would be to perform visual field testing under binocular conditions. The youth of three of our patients prevented us from doing this in a formal quantitative manner. However, functional enlargement of binocular visual fields in the exotropia- hemianopia syndrome has been previously reported ( 2,3,8). An incomitant exotropia or a symmetric nystagmus with a null position could have produced the face turn we observed. However, only one of our patients had nystagmus ( and no identifiable null position), and all four had lateral gaze comitance. B Visual Field Defect Effective Visual Field FIG. 3. Schematic explanation for visual field expansion with exotropia and face turn in patient with homonymous hemianopia. A. Patient with a right homonymous hemianopia. B. If the eye ipsilateral to the field defect is exotropic, the seeing field expands across the midline. C. A face turn toward the field defect increases the area of effective field when adaptive saccades are made. 306 © 2007 Lippincott Williams & Wilkins Homonymous Hemianopia J Neuro- Ophthalmol, Vol. 27, No. 4, 2007 The outward shift of the hemianopic border and reduction of the quantitative defect created by the exotropia requires the deviated eye's localization of the image to have harmonious anomalous retinal correspondence ( 6). An alternative would be normal retinal correspondence with alternating suppression, but this would not produce an increase in usable visual field. The exotropia in two of our patients was intermittent, and in Case 2 was associated with 200 arc- seconds of stereopsis. Perhaps expansion of the visual field is not required when attention is directed centrally and is superseded in that instance by the need for high- grade stereopsis. However, the exotropia would become manifest when the patient is searching the environment and needs an expanded field rather than central binocularity. In commenting on a case of exotropia and hemianopia ( 7), Hoyt and Good ( 4) proposed that an exotropia in patients with hemianopia may be an epiphenomenon and not compensatory because of the association of exotropia with infantile neurologic disease. Similar comments have been made by Good et al ( 8) However, our Cases 1, 3, and 4 suggest that the exotropia is adaptive. Case 1 showed complete resolution of all the ocular motility defects associated with third cranial nerve palsy except for the exotropia, which became constant, and he switched his fixation to the previously paretic right eye. The exotropia and field defect seen in Case 3 developed after the hemispherectomy that produced the homonymous hemianopia. Case 4 developed an exotropia from an earlier esophoria, and it developed months after the visual field defect occurred. The recurrence of the exotropia after strabismus surgery ( Case 2) is so common that it cannot be attributed to the homonymous hemianopia. Other reports have used confrontation visual field tests to document the visual field defect. We believe that our Case 2 is the first to have formal quantitative perimetry. The defect is particularly dense, but notably incomplete, especially superiorly. The extent and congruency of the homonymous defect required to produce the hemianopia-exotropia- face turn syndrome, however, remain unresolved and await further evaluation of additional patients. In summary, we have observed four patients with early- onset homonymous visual field defects who have an ipsilateral exotropia and an ipsilateral anomalous face turn. None had an incomitant strabismus or nystagmus with a null point. All have remained stable through years of follow- up. We believe that the face turn and the exotropia are both functionally beneficial to increase the usable visual field. 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