Maldevelopment of convergence eye movements in macaque monkeys with small- and large-angle infantile esotropia

PURPOSE: To describe symmetric convergence eye movements evoked by disparity and/or accommodative cues in esotropic macaque monkeys, with the goal of determining whether these animals have the vergence deficits found in humans with esotropia. METHODS: Physical far and near targets were used to evoke large (approximately 8 degrees) symmetric convergence eye movements in four adult macaque monkeys (two with strabismus, two normal), using positive-feedback rewards. One strabismic monkey had infantile-onset, small-angle esotropia (small-eso approximately 2 degrees) induced by alternating occlusion from birth to age 9 months. The other strabismic monkey had naturally occurring, large-angle (approximately 25 degrees) infantile-onset esotropia (large-eso). Visual acuity was normal in each eye as measured by spatial sweep visually evoked potentials (VEPs). Eye movements were recorded using magnetic search coils. RESULTS: When viewing binocularly, both normal monkeys exhibited accurate, stereotyped symmetric convergence movements that achieved 87% to 96% of the required change in vergence angle by the end of the initial movement. In contrast, the small-eso monkey's convergence response when viewing binocularly was variable, strikingly asymmetric, usually accompanied by a disjunctive saccade, and subnormal, achieving only 56% of required vergence. The convergence response of the large-eso monkey was also asymmetric and weak, achieving 18% of the required vergence and employing conjugate saccades to refixate the near target. Monocular viewing (i.e., accommodative vergence) caused substantial reductions in both convergence amplitudes and velocities in the normal monkeys, but had a minor effect on the vergence behavior of the strabismic animals. CONCLUSIONS: Monkeys with small- and large-angle infantile esotropia have striking maldevelopments of binocular (disparity-driven) convergence and use accommodative vergence and saccades to refixate near targets. Their vergence behavior resembles that in esotropic humans. The maldevelopment may be explained in large part by the paucity of binocular connections recently described in the visual cortex of esotropic macaques.     

Suppression of metabolic activity caused by infantile strabismus and strabismic amblyopia in striate visual cortex of macaque monkeys.

INTRODUCTION: Suppression is a major sensorial abnormality in humans and monkeys with infantile strabismus. We previously reported evidence of metabolic suppression in the visual cortex of strabismic macaques, using the mitochondrial enzyme cytochrome oxidase as an anatomic label. The purpose of this study was to further elucidate alterations in cortical metabolic activity, with or without amblyopia. MATERIALS AND METHODS: Six macaque monkeys were used in the experiments (four strabismic and two control). Three of the strabismic monkeys had naturally occurring, infantile strabismus (two esotropic, one exotropic). The fourth strabismic monkey had infantile microesotropia induced by alternating monocular occlusion in the first months of life. Ocular motor behaviors and visual acuity were tested after infancy in each animal, and development of stereopsis was recorded during infancy in one strabismic and one control monkey. Ocular dominance columns (ODCs) of the striate visual cortex (area V1) were labeled using cytochrome oxidase (CO) histochemistry alone, or CO in conjunction with an anterograde tracer ([H 3 ]proline or WGA-HRP) injected into one eye. RESULTS: Each of the strabismic monkeys showed inequalities of metabolic activity in ODCs of opposite ocularity, visible as rows of lighter CO staining, corresponding to ODCs of lower metabolic activity, alternating with rows of darker CO staining, corresponding to ODCs of higher metabolic activity. In monkeys who had infantile strabismus and unilateral amblyopia, lower metabolic activity was found in (suppressed) ODCs driven by the nondominant eye in each hemisphere. In monkeys who had infantile esotropia and alternating fixation (no amblyopia), metabolic activity was lower in ODCs driven by the ipsilateral eye in each hemisphere. The suppression included a monocular core zone at the center of ODCs and binocular border zones at the boundaries of ODCs. This suppression was not evident in the monocular lamina of the LGN, indicating an intracortical rather than subcortical mechanism. CONCLUSION: Suppression of metabolic activity in ODCs of V1 differs depending upon whether infantile strabismus is alternating or occurs in conjunction with unilateral amblyopia. Our findings reinforce the principle that unrepaired strabismus promotes abnormal competition in V1, observable as interocular suppression of ODCs.     

Early versus delayed repair of infantile strabismus in macaque monkeys: I. ocular motor effects.

INTRODUCTION: The appropriate age for surgical correction of esotropic strabismus in human infants is controversial; some clinicians advocate surgery before age 6 months, and others recommend observation and surgery at older ages. Infantile (congenital) esotropia in humans and monkeys is known to be accompanied by a constellation of eye movement abnormalities caused by maldevelopment of cerebral visual motor pathways. The purpose of this study was to determine how early versus delayed correction of strabismus influences development and/or maldevelopment of these eye movement pathways. METHODS: Optical strabismus was created in infant macaques by fitting them with prism goggles on day 1 of life. The early correction group (2 experimental and 1 control) wore the goggles for a period of 3 weeks (the equivalent of 3 months before surgical repair in humans). The delayed correction group (3 experimental and 1 control) wore the goggles for a period of 3 or 6 months (the equivalent of 12 or 24 months before surgical repair in humans). Several months after the goggles were removed, the monkeys were trained to perform visual fixation, smooth pursuit, and optokinetic nystagmus (OKN) tasks for a juice reward. Eye movements were recorded using binocular search coils. The performance of the early versus delayed infant monkey groups was also compared with that of a group of adult monkeys who had unrepaired, naturally occurring infantile esotropia. RESULTS: Early correction monkeys developed normal eye movements and exhibited ocular motor behaviors that were indistinguishable from normal control animals. They regained normal binocular eye alignment and showed stable fixation (no latent nystagmus). Monocular horizontal smooth pursuit and large field OKN were symmetric. In contrast, delayed correction monkeys showed persistent esotropia, latent fixation nystagmus, dissociated vertical deviation, and pursuit/OKN asymmetry. Animals who had the longest delay in correction of the optical strabismus exhibited eye movement abnormalities as severe as those of adult animals with uncorrected, natural esotropia. CONCLUSIONS: Early correction of strabismus in primates prevents maldevelopment of eye movements driven by cerebral motor pathways. Our results provide additional evidence that early strabismus correction may be beneficial for brain development in human infants.     

Horizontal rectus muscle anatomy in naturally and artificially strabismic monkeys

PURPOSE: Structural abnormalities of extraocular muscles (EOMs) or their pulleys are associated with some forms of human strabismus. This experiment was conducted to investigate whether such abnormalities are associated with artificial or naturally occurring strabismus in monkeys. METHODS: Binocular alignment and grating visual acuities were determined in 10 monkeys representing various species using search coil recording and direct observations. Four animals were orthotropic, two had naturally occurring "A"-pattern esotropia, two had concomitant and one had "V"-pattern esotropia artificially induced by alternating or unilateral occlusion in infancy, and one had "A"-pattern exotropia artificially induced by prism wear. After euthanasia, 16 orbits were examined by high-resolution magnetic resonance imaging (MRI) in the quasi-coronal plane. Paths and sizes of horizontal rectus EOMs were analyzed quantitatively in a standardized coordinate system. Whole orbits were then serially sectioned en bloc in the quasi-coronal plane, stained for connective tissue, and compared with MRI. Nerve and EOM features were analyzed quantitatively. RESULTS: Quantitative analysis of MRI revealed no significant differences in horizontal rectus EOM sizes or paths among orthotropic or naturally or artificially strabismic monkeys. Histologic examination demonstrated no differences in EOM size, structure, or innervation among the three groups, and no differences in connective tissues in the pulley system. The accessory lateral rectus (ALR) EOM was present in all specimens, but was small, inconsistently located, and sparsely innervated. Characteristics of the ALR did not correlate with strabismus. CONCLUSIONS: Major structural abnormalities of horizontal rectus EOMs and associated pulleys are unrelated to natural or artificial horizontal strabismus in the monkeys studied. The ALR is unlikely to contribute to horizontal strabismus in primates. However, these findings do not exclude a possible role of pulley abnormalities in disorders such as cyclovertical strabismus.     

Duration of binocular decorrelation predicts the severity of latent (fusion maldevelopment) nystagmus in strabismic macaque monkeys

PURPOSE: Infantile esotropia is linked strongly to latent fixation nystagmus (LN) in human infants, but many features of this comorbidity are unknown. The purpose of this study was to determine how the duration of early-onset strabismus (or timeliness of repair) affects the prevalence of LN in a primate model. METHODS: Optical strabismus was created in infant macaques by fitting them with prism goggles on day 1 of life. The goggles were removed after 3 (n = 2), 12 (n = 1) or 24 weeks (n = 3), emulating surgical repair of strabismus in humans at 3, 12, and 24 months of age, respectively. Eye movements were recorded by using binocular search coils. RESULTS: Each animal in the 12- and 24-week groups exhibited LN and manifest LN, normal spatial vision (no amblyopia), and constant esotropia. The 3-week duration monkeys had stable fixation (no LN) and normal alignment indistinguishable from control animals. In affected monkeys, the longer the duration of binocular decorrelation, the greater the LN: mean slow-phase eye velocity (SPEV) in the 24-week animals was three times greater than that in the 12-week monkey (P = 0.03); mean LN intensity in the 24-week monkeys was three times greater than that in the 12-week monkey (P = 0.03). CONCLUSIONS: Binocular decorrelation in primates during an early period of fusion development causes permanent gaze instability when the duration exceeds the equivalent of 3 months in humans. These findings support the conclusion that early correction of infantile strabismus promotes normal development of cerebral gaze-holding pathways.     

Early Versus Delayed Correction of Infantile Strabismus in Macaque Monkeys: Effects on Long-Term Eye Alignment

Purpose: To determine how the duration of infantile strabismus influences the eventual eye alignment. Methods: Six infant macaques were fitted with prisms, which were removed after 3 weeks (wks.), 3 months (mos.), or 6 mos. Two control monkeys wore plano lenses. Eye alignment was measured using search coils. Results: Longer duration of infantile strabismus is correlated with a more severe misalignment. The strabismus in the 6-mos. group was 96% greater than that in the 3-mos. group, which, in turn, was 25 times greater than that in the 3-wks group (p < 0.05). Conclusions: Longer duration of infantile strabismus causes larger-angle esotropia. Early correction of infantile strabismus is supported.     

Comparison of latent nystagmus and nasotemporal asymmetries of optokinetic nystagmus in adult humans and macaque monkeys who have infantile strabismus

To determine whether macaque monkeys with infantile strabismus have latent nystagmus and directional asymmetries of horizontal optokinetic nystagmus (OKN) similar to those of humans with infantile strabismus, the authors recorded eye movements under conditions of monocular viewing. The presence of latent fixation nystagmus was tested by requiring the subjects to steadily fixate a stationary target subtending less than I deg of visual arc. OKN was tested using high-contrast, vertically-oriented moving stripes that filled 80 deg of the visual field. A macaque monkey who had infantile strabismus induced by alternating occlusion from birth showed latent nystagmus highly similar to that recorded in an adult human subject with infantile strabismus. The strabismic monkey also had asymmetric OKN similar to that of the strabismic human, favoring nasally-directed stimulus motion when viewing with either eye. Neither nystagmus nor an OKN asymmetry was observed in a normal macaque or in humans who had normal binocular vision. The findings of latent nystagmus and OKN asymmetries in the strabismic monkey support the notion that monkeys who have infantile-onset strabismus are an appropriate ocular motor model of human infantile strabismus.     

Effect of infantile strabismus on visuomotor development in the squirrel monkey (Saimiri sciureus): Optokinetic nystagmus,motion VEP and spatial sweep VEP

PURPOSE. To determine whether squirrel monkeys made artificially strabismic in infancy had ocular fixation abnormalities, directional asymmetries of horizontal optokinetic nystagmus (OKN) and asymmetries of motion visually evoked potentials (MVEPs) similar to those of humans with infantile strabismus. METHODS. Esotropia was produced in a newborn squirrel monkey by surgical tenotomy of both lateral rectus muscles. The alignment and eye rotations of the monkey were examined longitudinally and VEP testing was performed at the age of one year. Visual acuity was measured using spatial frequency sweep VEPs (SSVEP) in response to grating stimulation. OKN was tested under conditions of monocular viewing using full-visual-field, vertically oriented, moving stripes. MVEPs in response to horizontal motion were recorded with the animal sedated to reduce the possibility of eye movement artifact. RESULTS. The artificially strabismic squirrel monkey displayed a constant, comitant esotropic strabismus accompanied by latent nystagmus. Monocular SSVEP acuity was subnormal in one eye, consistent with mild monocular strabismic amblyopia. The monkey demonstrated asymmetric OKN favoring nasally-directed stimulus motion when viewing with either eye. Monocular MVEPs were also characterized by a horizontal asymmetry with a directional bias inverted 180 degrees between the right and the left eyes. The eye movements and MVEP asymmetries were similar to those observed in strabismic macaque monkeys and humans with early-onset strabismus. Neither the OKN asymmetry nor the MVEP asymmetry was evident in a normal squirrel or normal macaque monkey. CONCLUSION. The artificially strabismic squirrel monkey is an appropriate eye movement and VEP model for the study of neural mechanisms in human infantile strabismus.     

Rhombencephalosynapsis associated with infantile strabismus

INTRODUCTION: Malformations of the cerebellum have been well-known to coexist with abnormalities of the oculomotor system. Rhombencephalosynapsis (RES) is a rare malformation of the cerebellum of unknown etiology in which the vermis is hypoplastic and the two cerebellar hemispheres are fused. The type of oculomotor disorders associated with RES is not well documented in the literature. Here, two cases are presented. CASE 1: A 15-year-old girl presented with large-angle infantile esotropia and inferior oblique overaction. Slow (3 to 4 cps) rhythmic anteroposterior oscillation movement of the head was observed while walking and left-sided postural tremor was present. CASE 2: An 8-month-old baby girl presented with facial dysmorphism, right esotropia, anisometropia, motor delay and truncal ataxia. Cranial MRI demonstrated RES in both patients. CONCLUSION: The clinical findings in two children presenting with infantile esotropia and RES may suggest a role of the vermis in ocular alignment. Head nodding in a child with strabismus can be observed only when walking and its presence should prompt neuroimaging.     

Multiple Short Daily Periods of Normal Binocular Vision Preserve Stereopsis in Strabismus

PurposeInfantile strabismus impedes the development of stereopsis. In optically strabismic monkeys, 2 continuous hours of normal binocular vision per day has been shown to preserve near-normal stereopsis. In this study, we investigated whether, as in learning, multiple shorter periods of intervention would further boost performance.MethodsTo simulate infantile esotropia, infant monkeys were reared with 30 prism diopters base-in starting at 4 weeks of age. Daily periods of normal binocular vision were provided by replacing prisms with plano lenses. Altogether, 14 monkeys were prism reared: 2 with continuous prism, 2 with 2 continuous hours of normal binocular vision per day, 6 with 2 noncontinuous hours, and 4 with 1 noncontinuous hour of binocular vision each day. Seven normally reared monkeys provided control data. Behavioral methods were employed to measure spatial contrast sensitivity, eye alignment, and stereopsis.ResultsOne monkey reared with continuous prism had poor stereopsis, and the other had no stereopsis. Ten of the 12 monkeys reared with periods of normal binocular vision had stereopsis, and those with longer and more continuous periods of binocular vision had stereopsis approaching that of normally reared monkeys.ConclusionsDuring early development, multiple short periods of binocular vision were effective in preserving clinically significant stereopsis in monkeys. These results suggest that by providing relatively short multiple daily intervention periods, stereopsis may be preserved in strabismic human children.     

Visual recognition time in strabismus: small-angle versus large-angle deviation.

PURPOSE: To measure the possible differences in monocular detection time of a threshold visual acuity stimulus (recognition time [RT]) between patients with small-angle and large-angle strabismus. METHODS: Ten patients with free alternating esotropia were tested (10 to 18 years old): five with small-angle esotropia (< or = 7 degrees), five with large-angle esotropia (15 degrees to 20 degrees). Six age-matched normal subjects served as controls. The RT of the threshold stimulus was measured in both eyes sequentially for stimuli presented in the center of a computer monitor (RT 1). Moreover, we measured the time necessary for identifying the same threshold visual acuity stimulus generated on the computer screen in the moment in which fixation is taken up by one eye after occlusion of the second eye (RT 2). Using the same setting, RT was also measured monocularly in all strabismic and normal subjects who were originally looking at a luminous fixation point positioned horizontally at 6.5 and 15 degrees from the center of the monitor (RT 3). RESULTS: The multivariate analysis of variance for repeated measures indicated that there was no statistical difference in RT 1 between groups. The mean RT 2 was significantly longer (p<0.001) in large-angle strabismic eyes when compared with that of normal control eyes. The mean RT 2 in small-angle strabismic eyes did not differ significantly from that of normal eyes. Finally, RT 3 (both at 6.5 degrees and 15 degrees of eccentricity) did not show any significant difference in the three different study groups. CONCLUSIONS: The authors hypothesized that alternating strabismus patients may have a significant advantage in maintaining a small-angle deviation, as a large-angle deviation would require longer RT in the moment the deviated eye takes up fixation. It can be speculated that the extension of re-fixation movement, obviously shorter in small-angle strabismus patients, is the main factor responsible for longer RT occurring in large-angle strabismus patients.     

Binocular vision with primary microstrabismus

PURPOSE. Patients with primary microstrabismus have a high degree of binocularity, which suggests that their ocular misalignment may have a sensory rather than an oculomotor origin, as in large-angle strabismus. The purpose of these experiments was to determine whether microstrabismic subjects have sensory abnormalities that could give rise to a small angle of strabismus. METHODS. The binocular disparity response functions for sensory and motor processes were compared in seven orthotropic subjects and six strabismic subjects (four with primary microstrabismus and two with infantile esotropia). Binocularity was assessed by disparity vergence (central and peripheral stimuli) and depth discrimination (relative and absolute disparities) measures. Motor and sensory disparity response functions were both determined by psychophysical methods: vergence responses by dichoptic nonius alignment and sensory responses by forced-choice depth discrimination. RESULTS. All the strabismic subjects demonstrated normal retinal correspondence with peripheral binocular stimuli and anomalous retinal correspondence with central fusion stimuli. The microstrabismic subjects' disparity vergence responses with peripheral fusion stimuli were centered on disparities relative to their angle of strabismus. However, with central fusion stimuli, the disparity vergence responses were relative to the subjective angle of strabismus. The microstrabismic subjects' stereoacuities were substantially reduced, but their discrimination responses did not show an asymmetry indicative of an unrepresented population of disparity-selective mechanisms. CONCLUSIONS. The data do not support a sensory abnormality as the primary cause of microstrabismus. The results are not compatible with an oculomotor adaptation to an inherent anomalous correspondence or with a strabismus caused by an absence of a class of disparity-selective mechanisms. Thus, just as in large-angle strabismus, the anomalous retinal correspondence and defective stereopsis of microstrabismus appear to be consequences of abnormal visual experience caused by an interocular deviation.     

Risk factors for the development of accommodative esotropia following treatment for infantile esotropia.

PURPOSE: One aim of the study was to determine whether accommodative esotropia after surgical alignment in infantile esotropia occurs because a pre-existing accommodative component is unmasked at the time of surgery or whether it occurs as a sequela of infantile esotropia. A second aim of the present study was to examine risk factors for accommodative esotropia after surgery for infantile esotropia. METHODS: A total of 80 consecutive patients who were enrolled in a prospective study of infantile esotropia had been followed for more than 4 years and had achieved orthoposition were included. Twelve potential risk factors were examined: age at onset, initial esodeviation, initial refractive error, age at alignment, delay in alignment, presurgical glasses, amblyopia, additional surgical procedures, unstable alignment, increase in hypermetropia, peripheral fusion, and stereopsis. Mantel-Haenszel odds ratios were computed for each factor and were corrected to relative risks. RESULTS: Overall, 48 of 80 children (60%) developed accommodative esotropia at a mean age of 33 months. Increasing hypermetropia, delay in alignment, and poor stereopsis posed significant risks for accommodative esotropia. The remaining 9 factors were not associated with increased risk for accommodative esotropia. CONCLUSIONS: Accommodative esotropia is unlikely to be a pre-existing condition in most cases because the mean age of onset was 23 months postoperative and the prevalence of preoperative hypermetropia greater than +3.00 D was low. Both delay in alignment and stereopsis risk factors may reflect compromised binocular sensory status that allows accommodative esotropia to occur at low to moderate levels of hypermetropia. Identification of children treated for infantile esotropia who are at risk for accommodative esotropia may allow for prevention or early treatment.     

Effects of extraocular muscle tenotomy on congenital nystagmus in macaque monkeys.

INTRODUCTION: Extraocular muscle tenotomy has been reported to damp congenital nystagmus in an achiasmatic sheepdog. We performed extraocular muscle tenotomy to evaluate its effects on congenital nystagmus in primates. METHODS: Magnetic search coil eye movement recordings were used to document the presence of horizontal congenital nystagmus in 2 adult macaque monkeys that also had naturally occurring infantile strabismus. Extraocular muscle tenotomy was performed by operating on all 4 horizontal recti, surgically detaching the muscles from the globe and suturing them back to their original insertions without resection or recession. Eye movement recordings were repeated 4 months after the procedure, comparing the waveform, amplitude, retinal slip velocity, and intensity (frequency x amplitude) of the nystagmus before and after tenotomy. Visual acuity was also measured before and after surgery in 1 animal. RESULTS: Preoperatively, a disconjugate, pendular nystagmus was evident in 1 monkey, and the other had a conjugate pendular-jerk nystagmus damped by convergence. After tenotomy, nystagmus mean amplitude decreased 18% to 52% in 1 monkey but increased 14% in the other (t test, P <.002). Retinal slip velocity and nystagmus intensity increased in both monkeys. After tenotomy, mean velocity increased 22% to 218%, while mean intensity increased 40% to 208% (t test, P <.002). Visual acuity measured after tenotomy decreased an average of 20% ( approximately 2.0 cycles per degree) in each eye. Tenotomy had no noteworthy effects on eye alignment or other aspects of visual behavior other than the congenital nystagmus. CONCLUSION: Nystagmus velocity and intensity increased after extraocular muscle tenotomy in 2 monkeys. Further studies are required to establish the clinical value of this procedure as a treatment for various subtypes of congenital nystagmus in humans.     

Strabismus and binocular function in children with Down syndrome. A population-based, longitudinal study

PURPOSE: We have performed a population-based, longitudinal study on strabismus in children with Down syndrome. The aims of the study were to examine the frequency and type of strabismus, the age at onset, and the binocular potential. METHODS: An unselected population of 60 children with Down syndrome born 1988-1999 was followed with repeated examinations. Mean follow-up time was 55+/-23 months (range 24--115). The alignment of the eyes was examined using Hirschberg corneal reflex test and cover test for near fixation. To evaluate binocular function, Titmus House Fly Test and Lang's stereo test were used. RESULTS: Twenty-five patients (42%) had strabismus (21 esotropias, two exodeviations and two vertical deviations). Only one case of infantile esotropia was found, the other esotropias were acquired forms. The mean age at "onset" (e.g. when strabismus was first noticed) was 54+/-35 months. In the acquired esotropia group (n=20), 15 (75%) were associated with hypermetropia (mean spherical equivalent +4.3+/-1.7 D). Seventeen of the strabismic patients had an accommodation weakness. Eleven of the strabismus patients gave a clearly positive response to one or both stereotests. CONCLUSIONS: The majority of the Down syndrome children with strabismus have an acquired esotropia and hence a potential for binocularity. Hypermetropia and accommodation weakness are probably important factors in esotropia in Down syndrome patients.     

Infantile esotropia in very low birth weight (VLBW) children

VLBW children are known to have a high frequency of early onset strabismus, which is related to the high prevalence of pre- and perinatal cerebral disturbances reported in these children. It is unknown if the early onset strabismus in VLBW children has the characteristics of infantile esotropia. If so, then (acquired) cerebral damage may play an important role in the origin of this type of strabismus. For this reason, the charts of 265 VLBW children were retrospectively reviewed. Strabismus was present in 55 (20.7%) children. Mean follow-up was 75 weeks, with 29.8% of the children having a follow-up of less then 6 months. Only 5 children (1.9%) with characteristics of infantile esotropia could be identified. Another 8 children (3.0%) possibly had infantile esotropia, but follow-up had been too infrequent during the first year of life to determine the time of onset of strabismus precisely. The other 42 children with strabismus all had ophthalmological disorders (i.e. ROP, optic nerve atrophy, cortical blindness) explaining early disruption of binocular visual development. Therefore, VLBW children are at risk for early onset strabismus. However, infantile esotropia is not typical for VLBW children and may be an indication that early acquired cerebral damage does not play an important role in the pathogenesis of infantile esotropia.     

Early versus late alignment of infantile esotropia

Fifty-two children with infantile esotropia had surgery for their esotropia between two and seven years of age. Another 49 had similar surgery before the age of two years. Of these 101 operated children, the esotropia in 70 patients was aligned to within 10 prism diopters. The patients with successful alignment were reviewed to study the effect of early versus late surgical intervention of their deviation, i.e. before and after two years of age. The motor and sensory states of the selected patients were analysed before and after surgical correction. The choice and number of surgical procedures employed are discussed. It appears that patients two years and older when strabismus was surgically corrected have a good chance of alignment, but less chance of attaining binocularity. In many cases there was a V-pat-tern esotropia, requiring surgery on the overacting inferior oblique muscles. In comparison, the younger group with earlier surgery appeared to show a better chance of attaining binocularity and fewer patients had significant V-pattern requiring surgery on the inferior oblique muscles.     

Proceedings of the 8th Annual Meeting of the Bielschowsky Gesellschaft,Regensburg, Germany,July 6th to 8th 2001

Fifty-two children with infantile esotropia had surgery for their esotropia between two and seven years of age. Another 49 had similar surgery before the age of two years. Of these 101 operated children, the esotropia in 70 patients was aligned to within 10 prism diopters. The patients with successful alignment were reviewed to study the effect of early versus late surgical intervention of their deviation, i.e. before and after two years of age. The motor and sensory states of the selected patients were analysed before and after surgical correction. The choice and number of surgical procedures employed are discussed. It appears that patients two years and older when strabismus was surgically corrected have a good chance of alignment, but less chance of attaining binocularity. In many cases there was a V-pat-tern esotropia, requiring surgery on the overacting inferior oblique muscles. In comparison, the younger group with earlier surgery appeared to show a better chance of attaining binocularity and fewer patients had significant V-pattern requiring surgery on the inferior oblique muscles.     

Comitant horizontal strabismus: an Asian perspective

AIM: Recent studies suggest that Asian strabismus patterns are different from those in the West. This study aims to determine the profile of children with comitant horizontal strabismus in Singapore. METHOD: 682 children aged 相似文献