Optical Coherence Tomography in Optic Nerve Hypoplasia: Correlation With Optic Disc Diameter, Nerve Fiber Layer Thickness, and Visual Function.

BACKGROUND: The correlation between optic disc diameters (DDs) with average retinal nerve fiber layer thickness (RNFLT) and visual function in children with optic nerve hypoplasia (ONH) having nystagmus is unknown. METHODS: Data were obtained from a retrospective review of 28 children (mean age: 9.4 years; ±5.1). Optic DD was defined as the maximal horizontal opening of Bruch membrane with spectral optical coherence tomography combined with a confocal laser ophthalmoscope. Average RNFLT was obtained from circumpapillary b-scans. RNFLT was also remeasured at eccentricities that were proportionate with DD to rule out potential sampling artifacts. Visual function was assessed by visual acuity at last follow-up and by visual evoked potentials (VEP) in 11 patients. The eye with the larger DD, which had better visual acuity, was analyzed to exclude potential effects of amblyopia. RESULTS: DD was correlated with average RNFLT (r = 0.61), visual acuity (r = 0.32), and VEPs (r = 0.66). The relationship between RNFLT and DD was as follows: average RNFLT (µm) = 0.074 * DD (µm) - 18.8. RNFLT also correlated with the ratio of horizontal optic DD to macula-disc-margin distance (DD:DM; r = 0.59). RNFLT measured at eccentricities proportionate with DD showed progressive decrease in thickness only for DDs <1,100 µm. All patients with DD <1,000 µm had subnormal visual acuity, whereas those with DD <1,200 µm had subnormal VEPs. CONCLUSIONS: DD correlates with average RNFLT and with visual function in children with ONH. Using OCT imaging, DD can be obtained in children with nystagmus and provides objective information.

Clinical Outcomes in Children With Orbital Cellulitis and Radiographic Globe Tenting.

PURPOSE: Axial displacement of the globe with tenting centered on the optic nerve-globe junction is a predictor of visual loss in adults. The purpose of this study was to determine the visual outcomes of children with orbital cellulitis and globe tenting. METHODS: The records of 46 consecutive children with orbital cellulitis at a single tertiary children's hospital were reviewed retrospectively. Initial and final visual acuities were available for 34 of 46 patients (74%). Globe tenting was defined by an angle of 130° or less at the optic nerve-globe junction as derived from sagittal CT or MRI. Visual acuities of 4 children with globe tenting (mean age, 10.3 ± 3.3 years) were compared with those of 30 children without globe tenting (mean age, 10.8 ± 3.5 years). Final logarithm of the minimum angle of resolution visual acuities were analyzed. RESULTS: The mean posterior globe angle was 124.5° ± 8.0° in patients with globe tenting, compared with 145.6° ± 7.4° in the affected eye of the patients without globe tenting (p = 0.002). Final visual acuity was logarithm of the minimum angle of resolution = 0 following treatment in patients with globe tenting and logarithm of the minimum angle of resolution = 0.02 in patients without tenting (p = 0.70). DISCUSSION: We propose that the increased elastic compliance of the optic nerve sheath and sclera in children may contribute to better visual outcomes. CONCLUSIONS: Pediatric orbital cellulitis with globe tenting may not lead to devastating vision loss as previously seen in adults.

The relationship of nystagmus waveform on the VEP response in infantile nystagmus syndrome: a small case series.

PURPOSE: The relationship between eye movements and the visual evoked potential (VEP) response was examined in two subjects with infantile nystagmus syndrome (INS). Changes in VEP amplitude were compared between periods of foveation versus periods of high-frequency nystagmus. An analysis is proposed that improves extraction of the checkerboard reversal VEP signal from subjects with INS. METHODS: INS subjects were 2 healthy children (12-13 years old) with 20/40 or better corrected acuity. Optical coherence tomography confirmed the optic nerves, retina, and fovea were within normal variation. VEPs were recorded to checkerboard reversal and to onset/offset of horizontal gratings while simultaneously recording the electrooculogram (EOG). VEP epochs underwent Fourier analysis, and epochs were examined for phase consistency with the mean. Foveation periods were compared to video-oculography recordings from a separate session. RESULTS: Optic nerve misrouting, such as crossed VEP asymmetry seen in albinism, or ipsilateral VEP asymmetry seen in achiasma, was not detected in either subject. By averaging only epochs in which EOG epochs showed foveation, VEP amplitude could be increased ≥59%. Averaging the VEP only on epochs with consistent phase at Oz increased VEP amplitude by ≥twofold; subsequent EOG epochs after this analysis mostly contained foveation periods or minimal EOG activity. Latency varied <14 ms across all analyses. CONCLUSIONS: The checkerboard reversal VEP signal is dependent on foveation periods in subjects with INS despite good visual acuity. Reduction in VEP amplitude due to retinal image motion induces noise and/or lack of phase locking in the VEP epochs. Selective averaging of epochs based on phase consistency improves the extraction of a VEP signal, likely when retinal image motion is minimized.

VEP analysis methods in children with optic nerve hypoplasia: relationship to visual acuity and optic disc diameter.

PURPOSE: Assessing vision in young children with optic nerve hypoplasia (ONH) is challenging due to multi-directional infantile nystagmus, the range of optic nerve loss, and cognitive delay. This study examined visual evoked potential (VEP) responses and averaging techniques in children with ONH. The assumption is that EEG epochs with inconsistent temporal phase would be associated with nystagmus, signal reduction due to axon loss, and visual inattention. METHODS: A retrospective chart review was performed on 44 children (average age 2.2 years; SD 1.9). Optic disc diameter was estimated by ophthalmoscopy. Visual function was measured under binocular viewing and then compared to the eye with the larger optic disc to exclude secondary amblyopia. Visual acuity was measured by Teller cards or by recognition optotypes, and both measures were converted into log minimum angle of resolution (logMAR). VEPs were recorded to onset/offset of horizontal gratings and to reversing checkerboards. Signal-to-noise ratios (SNRs) were estimated from phase consistency across epochs in the Fourier domain. VEPs were also averaged after (1) correction of epochs for phase shifts across a limited bandwidth, or (2) selection of only epochs showing phase consistency. RESULTS: Optic disc diameter, logMAR, VEP amplitudes, and VEP SNR were all significantly inter-correlated. Optic disc diameter correlated best with VEP SNR (Spearman rho = 0.82; p < 0.001). Age-corrected logMAR correlated with optic disc diameter and VEP SNR (Spearman rho = -0.695 and 0.70, respectively; p < 0.001). VEP latency poorly correlated with optic disc diameter or logMAR. Correction of phase shifts or selection of epochs based on phase consistency significantly increased VEP amplitude and SNR for children with optic disc diameters <1000 microns. Correction of phase inconsistency did not improve the correlation of VEP parameters with optic disc diameter or with logMAR. CONCLUSIONS: In ONH, the size of the optic nerve is correlated with VEP SNR and logMAR. The results imply a direct relationship between the reduction in optic nerve axons and generalized reduction in visual function. Our calculation of VEP SNR provides objective assessment of optic nerve function that is independent of subjective scoring of VEP peaks.

Congenital eyelid ptosis: onset and prevalence of amblyopia, associations with systemic disorders, and treatment outcomes.

OBJECTIVES: To determine the age at onset of amblyopia, the response to occlusion therapy, and the association with systemic disorders in children with congenital eyelid ptosis. STUDY DESIGN: Retrospective chart review of children seen at Seattle Children's Hospital with moderate or severe congenital ptosis. Assessments were longitudinal visual acuity development using objective methods, definition of ptosis severity by eyelid margin to pupillary light reflex distance (margin reflex distance [MRD]), age at amblyopia diagnosis, correlation between amblyopia and MRD, and associated systemic disorders. RESULTS: Eighty-four children with moderate-to-severe congenital ptosis met inclusion criteria; the mean longitudinal follow-up was 49.1 months. Fifteen (18%) of these children had amblyopia, of which 9 had deprivation amblyopia (mean age 17.3 months ± 11.2) and 6 had anisometropic or strabismic amblyopia (mean age 60 months ± 11.8). Eleven (73%) of the children with amblyopia were successfully treated with occlusion therapy. Amblyopia was not correlated with MRD. A systemic disorder was identified in 29 (35%) of the children, the most common being genetic, chromosomal, or neurologic conditions. Patients with systemic disorders and developmental delay have significantly lower visual acuity bilaterally compared with patients without systemic disorders (P ≤ .003). CONCLUSIONS: Using longitudinal and objective visual acuity assessments, the incidence of amblyopia was 18% in children with moderate to severe congenital ptosis. Visual deprivation was the predominant risk factor that was reliably distinguished by its earlier onset in young children. The best indicator of amblyopia in children is visual acuity rather than MRD measurements. Systemic disorders are frequent in children with moderate to severe congenital ptosis.

Waveform variance and latency jitter of the visual evoked potential in childhood.

PURPOSE: Recording the visual evoked potential (VEP) in young children is challenging due to movement artifacts with variable fixation or attention. This study examined the effects of latency jitter, noise, and waveform consistency on the averaging of the VEP across childhood age. METHODS: Stimuli were contrast-reversing (1.4 Hz) checkerboards of 163 arc minutes and pattern-onset-offset of 0.5 cycle/degree horizontal sine-wave gratings. Subjects were 79 normal children (0.3-16 years age; mean 6.9). Results were compared to recordings of EEG noise only (noise controls). Epochs underwent four averaging methods: (1) latency jitter correction using cross-correlation, (2) correction of phase shifts across a limited bandwidth in the Fourier domain, (3) selection of epochs based on consistency in the time domain, and (4) selection of epochs based on phase consistency in the Fourier domain. Signal-to-noise ratios (SNR) were estimated in both the time and Fourier domains. RESULTS: Compared to standard averaging, all methods improved the amplitude of the primary peak (P100) while generating mild changes in latency. All methods also increased amplitudes of residual peaks in noise controls. In VEPs with an adequate SNR, selective averaging in the Fourier domain provided the greatest improvement in amplitude (61 % increase; p < 0.0001) without prolongation in latency. Correction of latency jitter did not consistently improve amplitude but caused latency prolongation in 24 % of subjects. There was no age-related effect of any averaging method for either stimulus. CONCLUSIONS: Since latency jitter correction does not improve VEP amplitude more than selective averaging, recording artifacts in children are dominated by random phase components rather than inducing latency jitter.

Anatomic features and function of the macula and outcome of surgical tenotomy and reattachment in achiasma.

OBJECTIVE: To examine the anatomic features and function of the macula in achiasma and to compare visual acuity, eye movements, foveation, and eye velocity before and after tenotomy and reattachment (T&R) surgery. DESIGN: Case series. PARTICIPANTS: Two children with isolated achiasma. METHODS: Ophthalmologic examinations, brain magnetic resonance imaging, full-field and multifocal electroretinography (ERG), visual evoked potentials (VEPs), spectral-domain optical coherence tomography (OCT), eye-movement recordings, and unilateral T&R in 1 patient. MAIN OUTCOME MEASURES: Visual acuity before and after surgery, macular anatomic features and function, and eye velocity before and after T&R surgery in 1 patient. RESULTS: Magnetic resonance imaging and VEP confirmed absence of decussation of retinofugal fibers in both patients. Visual acuity was 20/100 and 20/200. The anatomic features and function of the fovea and macula were normal by OCT and multifocal ERG. After T&R, there was a marked reduction in horizontal eye velocity and monocular visual acuity improved to 20/80. CONCLUSIONS: The finding that the macula is normal in achiasma suggests that reduced acuity is the result of retinal image motion from nystagmus. Two-muscle T&R reduces horizontal retinal image motion and can improve visual acuity in achiasma or patients with infantile nystagmus.

Longitudinal measures of visual function, tumor volume, and prediction of visual outcomes after treatment of optic pathway gliomas.

PURPOSE: To examine longitudinal changes in visual acuity, tumor volume, and visual evoked potentials (VEP) before and after treatment in children with optic pathway gliomas. DESIGN: Retrospective cohort study. PARTICIPANTS: Twenty-one patients (0.7-9 years of age). METHODS: Patients initially were treated either by chemotherapy (n = 18) or radiotherapy (n = 3). Patients were followed up with serial magnetic resonance imaging, age-corrected visual acuity measurements in logarithm of the minimum angle of resolution (logMAR) units, and pattern VEP. Longitudinal visual outcome data were obtained on average for 9 years (range, 4-16 years). Tumor volumes before and after treatment were estimated in 15 patients. Multivariate regression was used to predict visual outcomes. MAIN OUTCOME MEASURES: Visual acuity, relative tumor volumes, and VEP. RESULTS: Before treatment, 81% of patients had reduced visual acuity and 81% had optic nerve pallor, whereas all had a reduced VEP in 1 or both eyes. After initial treatment, tumor volume decreased in 53%, stabilized in 27%, and progressively increased in 20%. Treatment arrested the rapid decline in visual acuity loss and stabilized visual acuity for 4 to 5 years. The rate of visual acuity decline was not correlated with tumor shrinkage. Sixty-two percent of patients required additional treatment with either chemotherapy or radiation because of tumor growth or progressive loss of visual function. Visual acuity at last examination was stable or improved in 33% of patients, but on average declined 0.4 logMAR units. Visual acuity was 20/200 or better in 1 eye of 62% of patients. The rate of visual acuity decline was predicted weakly by tumor volume at presentation (R(2) = 0.19; P<0.009). Visual acuity at last examination was predicted best by visual acuity and tumor volume at presentation (R(2) = 0.66; P<0.001). CONCLUSIONS: Systemic chemotherapy arrested the decline in visual acuity and stabilized vision on average for 5 years. At presentation, VEPs were a more sensitive indicator of optic pathway damage than visual acuity or optic nerve appearance. Although tumor reduction or stabilization was achieved in 80% of patients, pre-existing visual damage, indexed by objective measures of tumor volume and visual function, limited visual outcomes. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

A reduced visual pathway response in infantile nystagmus syndrome.

PURPOSE: To investigate visual cortical responses in children with infantile nystagmus syndrome (INS) and the potential contribution of foveation periods. METHODS: The medical records of children with INS who had visual evoked potential (VEP) recordings to reversing checkerboards and onset of horizontal gratings were reviewed retrospectively. VEP recordings underwent objective selective averaging for extraction of brief periods having consistent amplitude and timing with the stimulus presentation. VEP amplitude, latency, and signal-to-noise ratios (SNR) were compared to results from published age-matched controls under the same conditions. Relative foveation in INS subjects was determined from the proportion of time a video-oculography recording met eye position and velocity criteria. RESULTS: A total of 26 children met inclusion criteria. Selective averaging increased VEP amplitude and SNR in INS by 270%-420% compared to standard averaging (P < 0.0001). The INS change in VEP response was greater for reversing checkerboard stimulation than horizontal-grating onset and was significantly greater than that in controls (P < 0.001). Latency was not changed by selective averaging. Relative foveation was correlated with increasing VEP amplitude (P = 0.02) and number of trials chosen for selective averaging (P < 0.01). After selective averaging, relative foveation correlated with VEP amplitude to reversing checkerboards only (P = 0.007). CONCLUSIONS: Nystagmus likely causes a reduced visual cortical response in children with INS. A significantly larger response can be extracted from brief periods during nystagmus eye movements, supporting the hypothesis that the INS visual system generates a larger cortical signal during brief foveation periods.

Cerebral Visual Impairment Characterized by Abnormal Visual Orienting Behavior With Preserved Visual Cortical Activation.

Purpose: Children with cerebral visual impairment (CVI) often have abnormal visual orienting behaviors due to impaired or damaged visual cortex. Alternatively, visual-cortical function is intact but visual information is not transformed downstream into an appropriate oculomotor output (visuomotor dysfunction). We examined visual, anatomic, and oculomotor assessments to distinguish visuomotor dysfunction from CVI associated with severely reduced visual-cortical response. Methods: We reviewed the medical records from children with CVI having abnormal visual orienting behaviors, normal ocular examinations, and born near term. Relevant data were visual evoked potentials (VEPs), Teller card acuity, eye movements recorded by video-oculography (VOG), and neuroimaging (magnetic resonance imaging [MRI]) including diffusion tensor imaging (DTI) tractography. Results: Thirty subjects had visuomotor dysfunction based on a normal VEP; of these 33% had a normal MRI and 67% had white matter abnormalities associated with metabolic disease and/or decreased volume of brain parenchyma. VOG recordings showed smooth pursuit gains were uniformly reduced and saccades were dysmetric but followed the main sequence. Ten subjects had severe CVI based on VEPs at noise levels; visual acuities and MRI findings overlapped those of the visuomotor dysfunction group. Developmental delay, seizures, microcephaly, and hypotonia were common across all groups. All subjects with an abnormal conventional MRI had abnormal metrics on DTI tractography from the occipital lobe. Conclusions: A subset of patients with CVI have abnormal visual orienting behaviors despite a normal VEP (visuomotor dysfunction). A majority have abnormal white matter metrics on tractography suggesting a downstream defect in sensorimotor transformation. Clinically, visuomotor dysfunction is indistinguishable from severe CVI.

Matching Misaligned Spectralis OCTs to a Reference Scan in Pediatric Glaucoma with Poor Fixation and Nystagmus.

Purpose: Poor fixation or nystagmus in children causes misalignment errors when measuring circumpapillary retinal nerve fiber layer (cpRNFL) thickness by simultaneous scanning laser ophthalmoscope imaging/optical coherence tomography (SLO/OCT). We investigated a method to assess cpRNFL from misaligned SLO/OCT scans. Methods: Heidelberg Spectralis SLO/OCT scans from a single clinical examination were retrospectively analyzed when automated eye tracking was unreliable. Retinal layer thickness was measured at overlapping match locations between a reference and misaligned scans based on the position data from simultaneously acquired SLO images. Three layers were segmented: cpRNFL, internal limiting membrane to outer nuclear layer (ILM-ONL), and total retinal thickness (TR). Accuracy was defined as the difference in thickness between the reference and misaligned scans at their match locations after correction for scan angle. Results: Thirty-five subjects, evaluated for glaucomatous nerve loss, met inclusion criteria. Group-averaged accuracy was -2.7, 1.4, and 0.3 µm for cpRNFL, ILM-ONL, and TR thickness, respectively. Across all layers, interobserver intraclass correlation coefficients ranged from 0.97 to 0.63 and the maximum Bland-Altman 95% limits of agreement were -21.6 to 20.7 µm. Variability was greatest for cpRNFL thickness and least for TR thickness. Increased variability was associated with lower signal-to-noise ratio but not with image-motion indices of shear, rotation, and scale. Conclusions: Retinal layer thickness can be compared to a reference cpRNFL OCT scan when poor fixation and nystagmus causes misalignment errors. The analysis can be performed post hoc using multiple misaligned scans from standard SLO/OCT protocols. Translational Relevance: Our method allows for assessment of cpRNFL in children who fail eye tracking.

Optical coherence tomography findings in Cohen syndrome.

Cohen syndrome is a rare disease that causes myopia and retinal degeneration in the setting of developmental delay and characteristic craniofacial features. We report optical coherence tomography (OCT) abnormalities in 4 patients with Cohen syndrome, 2 of whom have longitudinal follow-up. All subjects had schisis-like changes, with cystoid spaces in the inner retina as well as diffuse outer retinal atrophy sparing the subfoveal region. Ophthalmologic findings in 1 patient led to the work-up that resulted in a diagnosis of Cohen syndrome, suggesting that characteristic retinal abnormalities visualized by fundus examination and OCT may represent distinguishing features of this syndrome.

Reappraisal of astigmatism induced by periocular capillary hemangioma and treatment with intralesional corticosteroid injection.

OBJECTIVE: To document refractive status and visual acuity before and after intralesional corticosteroid injection in children with astigmatism induced by periocular capillary hemangioma (PCH). DESIGN: Retrospective, interocular comparison, interventional case series. PARTICIPANTS: Thirteen infants with anisometropic astigmatism of at least 1.50 diopters (D) induced by PCH. INTERVENTION: All infants had one or more intralesional corticosteroid injections of a PCH between 2 and 10 months of age. Injections of 0.3 to 1.0 ml of a 50:50 mixture of triamcinolone (40 mg/ml) and dexamethasone phosphate (4 mg/ml) were given at a single site under deep sedation. MAIN OUTCOME MEASURES: Refraction and acuity using Teller acuity cards before and after injection. RESULTS: In affected eyes, mean astigmatisms were 3.75 D (pretreatment) and 1.25 D (posttreatment), and mean spherical errors were 0.75 D (pretreatment) and 1.50 D (posttreatment). Reduction in astigmatism was observed within 1 to 14 months after the injection. Despite reciprocal changes in astigmatism and spherical error, the amount of anisometropia (spherical equivalent) remained constant. Amblyopia was not observed before treatment and was observed in only 2 of 13 children after treatment. Complications were limited to adrenal suppression with transient reductions of linear growth and localized eyelid necrosis. CONCLUSIONS: Intralesional corticosteroid injections given in infancy (between 2 and 10 months) resulted in a 63% reduction in the mean amount of astigmatism induced by PCH. The reciprocal changes of astigmatism and spherical error without changes in anisometropia suggest that the treatment effect was due to restoration of the spherical shape of the cornea. Before 3 years of age, visual immaturity exceeded the optical blur related to astigmatism induced by PCH. Therefore, astigmatism, not anisometropia or amblyopia, is the immediate indication for treatment of PCH with intralesional corticosteroids. Injection of corticosteroid at a single site minimizes the potential for severe ocular complications owing to tissue pressure and tumor volume considerations.

Does eye velocity due to infantile nystagmus deprive visual acuity development?

PURPOSE: To use eye movement recordings of young children to determine whether eye velocity from infantile nystagmus (IN) deprives the developing visual system of normal visual acuity. METHODS: The video-oculography recordings and visual acuity measurements (including Teller cards) of 15 children ≤6.0 years of age with IN without visual sensory disease (idiopathic IN) were reviewed retrospectively. Eye velocity that would limit visual acuity development was predicted from both empirical adult data adjusted for age and a temporal limitation model using published photoreceptor density data with age. Foveal alignment onto a target was measured in 5 subjects using confocal retinal imaging. RESULTS: All subjects had periods (85-2440 ms) during which eye velocity was below the limit that would reduce age-appropriate visual acuity. The percentage of time eye velocity was below the limit varied by 4%-54% across all eye movement recordings. Eye movement metrics (eye position variability, average eye velocity, maximum duration of foveation, and the nystagmus optimal foveation fraction) correlated poorly with age or with age-corrected visual acuity (r2 < 0.27 for each metric). Longitudinal visual acuity development overlapped between subjects with different nystagmus waveforms. CONCLUSIONS: Eye velocity was not predicted to completely deprive visual acuity development in subjects with idiopathic IN. Nystagmus may decrease visual acuity development in children with idiopathic IN by interfering with visual-cortical development in the context of increased visual noise due to image motion with imprecise foveation.

Acuity development in infantile nystagmus.

PURPOSE: To compare development of acuity in patients with isolated infantile nystagmus and infantile nystagmus associated with a visual sensory defect. METHODS: Visual acuities in 57 children (1 month to 4 years of age) with infantile nystagmus were assessed by using Teller acuity cards oriented vertically during binocular viewing. Twenty-two had isolated infantile nystagmus, 21 had albinism, 7 had aniridia, and 7 had mild or moderate bilateral optic nerve hypoplasia (BONH). Longitudinal acuity was measured in 40 of these patients (mean 1.8, 2.3, 3.1, and 3.3, measurements per patient group, respectively). The rate of acuity development across the study groups was quantified by linear regression of log acuity versus log age and compared to published normative data. RESULTS: The rate of acuity development was similar across all groups and paralleled the normative data. The slope of log grating acuity versus log age (+/-SEM) was normal, 0.73; isolated infantile nystagmus, 0.80 +/- 0.11; albinism, 0.80 +/- 0.11; aniridia, 0.87 +/- 0.16; and BONH, 0.79 +/- 0.18. The slopes were not significantly different (ANCOVA, F(4,142) = 0.21, P = 0.93). Compared with published binocular normative data, mean acuity adjusted for age was reduced by 1.2 octaves in isolated infantile nystagmus and by 1.7 to 2.5 octaves in nystagmus with associated sensory defect. CONCLUSIONS: The rate of acuity development in infantile nystagmus is largely independent of the gaze-holding instability or an associated visual sensory defect. Reduction of mean acuity in albinism, aniridia, and BONH is due to the visual sensory defect and exceeds the acuity reduction observed in isolated infantile nystagmus.

Hypertropia associated with superolateral translation of the superior rectus muscle pulley in unilateral coronal synostosis.

OBJECTIVE: To explore the mechanisms underlying the hypertropia associated with unilateral coronal synostosis. METHODS: In 13 patients with unilateral coronal synostosis, we measured gaze-dependent binocular alignment before and after strabismus surgery, assessed the superior rectus muscle (SRM) pulley using computed tomography, and simulated posterior displacement of the trochlea and superolateral displacement of the SRM pulley. RESULTS: All the patients had an ipsilateral hypertropia in primary gaze (3-30 diopters) that increased in contralateral gaze and decreased in ipsilateral gaze and that simulated an inferior oblique muscle overaction. Strabismus surgery fully or partially corrected the hypertropia in only 7 of 11 patients. High-resolution computed tomography demonstrated that the pulley of the SRM relative to the inferior rectus muscle was translated 0 to 11.0 mm laterally and up to 2.7 mm vertically. Lateral translation (up to 10 mm) alone or combined with vertical translation (up to 5 mm) of the SRM pulley in the simulated model produced a hypertropia with lateral incomitance. Posterior translation (15 mm) of the trochlea did not induce a significant hypertropia. CONCLUSION: Superolateral translation of the SRM pulley creates an imbalance of muscle pulling forces that better accounts for the hypertropia than posterior displacement of the trochlea.

Topographical retinal function in oculocutaneous albinism.

PURPOSE: Macular hypoplasia is the major ocular finding in albinism because it underlies reduced acuity and congenital nystagmus. Anatomic studies have shown a lack of foveal differentiation. However, functional anatomy of the macula in albinism is not known. DESIGN: Observational case reports. METHODS: We measured the topology of the retinal response in two patients with oculocutaneous albinism by using simultaneous fundus monitoring and multifocal electroretinographs (ERGs). Stimuli consisted of a 103-hexagon array centered on the macula. Recording conditions eliminated nystagmus artifact. RESULTS: ERG amplitudes were reduced only in the central 5 to 10 degrees compared with adult norms. When the response was scaled by stimulation area, multifocal ERG amplitudes were constant across all retinal eccentricities. CONCLUSIONS: The results suggest a homogeneous density of cone photoreceptors across the central retina in albinism, consistent with anatomic studies showing arrest of postnatal macular development. Further normative data are needed to fully quantify macular development in young children.

Congenital and compensated vestibular dysfunction in childhood: an overlooked entity.

We report five children with previously unrecognized vestibular dysfunction detected by clinical examination and confirmed by quantitative vestibular testing. Patient 1 presented with fluctuating visual acuity and intermittent nystagmus. Patient 2 had congenital hearing loss associated with imbalance, delayed motor development, and cyclic vomiting. Patient 3 had neurotrophic keratitis with an intermittent head tilt, imbalance, and motor delays. Patient 4 showed ataxia and eye movement abnormalities following traumatic brain injury and had reading difficulties. Patient 5 had episodic vertigo and eye movement abnormalities from infancy. Clinical vestibular testing emphasized spontaneous nystagmus, rapid head thrust, and assessment of post-rotatory nystagmus. Quantitative vestibular testing included the sinusoidal chair rotation and velocity step tests, measurement of dynamic visual acuity, post-head-shake nystagmus, and computerized platform posturography. Pediatric neurologists encounter children with congenital and compensated vestibular dysfunction, which can be recognized on the basis of relevant history and clinical abnormalities of the ocular-ocular reflex.

Comparison of pattern visual-evoked potentials to perimetry in the detection of visual loss in children with optic pathway gliomas.

PURPOSE: We sought to compare visual evoked potentials (VEPs) with standard visual field testing in children with visual pathway gliomas. METHODS: Fifteen of 40 children with visual pathway gliomas verified on magnetic resonance imaging scan who cooperated with Goldmann visual field (GVF) and 3-channel VEPs were studied. GVFs were obtained in 25 eyes with adequate vision. VEP amplitudes, latencies, and signal-to-noise ratios (SNRs) were compared with control subjects. Four of the patients (5 eyes) also had Humphrey visual field testing. RESULTS: Twenty-two of 25 eyes had a field defect, 15 eyes showed a relative or absolute hemianopia, 7 eyes showed a central or generalized depression, and 3 eyes were normal. In hemianopic eyes, 87% showed a depression (GVF) or reduced sensitivity (Humphrey field) in the opposite hemifield. VEP amplitudes and SNRs, normally largest at the midline electrode, were significantly reduced in all eyes with visual field loss. By comparison, lateral electrodes showed significantly lower amplitudes and SNRs in patients and controls. Interhemispheric VEP asymmetry (>2:1 ratio) was seen in 67% of patients with hemianopia and 53% of controls. CONCLUSIONS: Reduction of amplitude and SNR at the midline VEP electrode was a sensitive indicator of visual field loss. Interhemispheric VEP asymmetry was not reliable in detection of a hemianopic field defect. VEPs can be a reliable and objective alternative for the detection of visual loss due to optic pathway glioma in children who are intolerant to visual field testing. We recommend the test protocol include pattern-onset and check reversal stimuli of at least one high and one low spatial frequency.

Infantile Nystagmus and Abnormalities of Conjugate Eye Movements in Down Syndrome.

PURPOSE: Subjects with Down syndrome (DS) have an anatomical defect within the cerebellum that may impact downstream oculomotor areas. This study characterized gaze holding and gains for smooth pursuit, saccades, and optokinetic nystagmus (OKN) in DS children with infantile nystagmus (IN). METHODS: Clinical data of 18 DS children with IN were reviewed retrospectively. Subjects with constant strabismus were excluded to remove any contribution of latent nystagmus. Gaze-holding, horizontal and vertical saccades to target steps, horizontal smooth pursuit of drifting targets, OKN in response to vertically or horizontally-oriented square wave gratings drifted at 15°/s, 30°/s, and 45°/s were recorded using binocular video-oculography. Seven subjects had additional optical coherence tomography imaging. RESULTS: Infantile nystagmus was associated with one or more gaze-holding instabilities (GHI) in each subject. The majority of subjects had a combination of conjugate horizontal jerk with constant or exponential slow-phase velocity, asymmetric or symmetric, and either monocular or binocular pendular nystagmus. Six of seven subjects had mild (Grade 0-1) persistence of retinal layers overlying the fovea, similar to that reported in DS children without nystagmus. All subjects had abnormal gains across one or more stimulus conditions (horizontal smooth pursuit, saccades, or OKN). Saccade velocities followed the main sequence. CONCLUSIONS: Down syndrome subjects with IN show a wide range of GHI and abnormalities of conjugate eye movements. We propose that these ocular motor abnormalities result from functional abnormalities of the cerebellum and/or downstream oculomotor circuits, perhaps due to extensive miswiring.