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Biomedical subjects

Avery H Weiss

Publications and source records attributed to Avery H Weiss.

12 recordsLinked to original sources
PubMed2006

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.

Child↗
PubMed2006

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.

Albinism, Oculocutaneous↗
PubMed2006

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.

Adolescent↗
PubMed2006

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.

Adolescent↗
PubMed2004

Ophthalmoplegic migraine.

Ophthalmoplegic migraine is a rare presentation of migraine complicated by an isolated oculomotor paresis. Vasodilation of extracranial vessels is believed to underlie the headache, and vasoconstriction to account for the ophthalmoplegia. Whether the vascular insult involves the central or peripheral portions of the oculomotor nerve is still uncertain. We describe a child who presented with ophthalmoplegic migraine and was demonstrated to have a deficiency of the near triad documented by eye movement and pupillary recordings. Voluntary conjugate eye movements--saccades, smooth pursuit, and optokinetic nystagmus--were normal. Vergence amplitudes appropriate to fixation distance were elicited for Snellen optotypes but not to a point source of light. Concurrent measures of pupillary diameter failed to reveal significant modulation to either stimulus. Brain magnetic resonance imaging scan was normal, and there was no contrast enhancement of the oculomotor nerve at its exit from the midbrain. Both the oculomotor paresis and concurrent presence of a deficiency of the near triad localized the vascular insult to the oculomotor nerve complex in the brainstem.

Child↗
PubMed2004

Spatial-frequency-dependent changes in cortical activation before and after patching in amblyopic children.

PURPOSE: To examine the cortical response under transient stimulus conditions in amblyopic children before and after eye patching. To determine whether improvement in acuity is associated with spatial-frequency-dependent changes in specific peaks of the cortical response. METHODS: Visual evoked potentials (VEPs) to check reversal (163-18 arc min) and onset of sine wave gratings (0.5-4 cyc/deg) were measured in 24 amblyopic children (<7 years of age) before eye patching. VEPs were repeated in nine subjects with 20/40 or better acuity after patching. Age, severity of amblyopia, and VEP amplitudes of positive peak (P)100, P1, and negative peak (N)2 were analyzed by multivariate statistics. RESULTS: Before patching, the amblyopic eye showed decreasing amplitude with increasing spatial frequencies (P < 0.05) when compared with the nonamblyopic eye. Reduced amplitudes occurred at frequencies well below acuity. Latencies were mildly prolonged. After patching, amplitudes increased in the amblyopic eye across all spatial frequencies (ANCOVA; P < 0.0001 for each peak). However, a spatial-frequency-dependent increase in amplitude was significant only for a late negative peak (N2). The patched eye showed no significant changes. CONCLUSIONS: Recovery of acuity after eye patching is associated with an overall increase in cortical activation across a wide range of spatial frequencies below the acuity threshold. A spatial-frequency-dependent increase in a late negative peak suggests that the cortical generator of this peak demonstrates plasticity of acuity recovery.

Amblyopia↗
PubMed2003

Imaging a child's fundus without dilation using a handheld confocal scanning laser ophthalmoscope.

Images of the fundus were acquired in children without pupil dilation using a prototype handheld confocal scanning laser ophthalmoscope (SLO). A 780-nm laser beam imaged a 20 degrees x 20 degrees area of the fundus while a 645-nm beam scanned a fixation target. Scorable images of the optic nerve, macula, and vessels were obtained in 67 (72%) of 93 eyes from pediatric patients with nystagmus, amblyopia, media opacities, or optic nerve or macular abnormalities. Images were obtained in all eyes of pediatric and adult controls. Unsuccessful imaging was associated with media opacities, high refractive error, and poor cooperation. Disadvantages of the SLO were the inability to detect optic nerve pallor or consistently image the periphery. Advantages of the SLO were seen in children with nystagmus, photophobia, eccentric fixation, cone dystrophy, and mild papilledema.

Adolescent↗
PubMed2003

Acuity, ophthalmoscopy, and visually evoked potentials in the prediction of visual outcome in infants with bilateral optic nerve hypoplasia.

PURPOSE: To determine whether Teller Acuity Cards, transient visually evoked potentials (VEPs), and optic disc size estimated from ophthalmoscopy were predictive of acuity outcome in infants and young children with bilateral optic nerve hypoplasia (ONH). METHODS: Twenty-eight infants (mean age, 7 months) with bilateral ONH underwent clinical assessment, including ophthalmoscopy. All but a few of these patients underwent neuroimaging studies, analysis of transient VEPs to multiple stimuli, and repeated acuity assessment. Acuity outcome was assessed, on average, 28 months later. RESULTS: Acuity outcome was significantly correlated with the estimated optic disc diameter, initial acuity, and VEP signal-to-noise ratios (r = 0.80, 0.71, 0.69, respectively; all P <.001). Multiple regression analysis showed that the initial acuity and estimated optic disc diameter accounted for 73% of the variation in acuity outcome. VEPs to white-black gratings segregated infants by 6 months of age, whose acuity outcome was better or worse than 5.6 cycles/degree (20/100). CONCLUSIONS: Acuity outcome was predicted in infants with bilateral ONH with a linear equation using initial acuity and estimated optic disc diameter. Additionally, analysis of VEPs may segregate infants with a good visual outcome from those with a poor visual outcome. Longer follow-up will be necessary to determine final Snellen acuity.

Child, Preschool↗
PubMed2003

ERGs, cone-isolating VEPs and analytical techniques in children with cone dysfunction syndromes.

Photoreceptor and post-receptoral function in children with congenital and acquired cone disorders was measured by full-field electroretinogram (ERG) and transient visual evoked potentials (VEPs). Subjects were five rod monochromats (RM), five with cone dystrophy (CD), and 30 controls. Patients were diagnosed by clinical findings, ERGs, and standard color vision tests. VEP stimuli were check reversals and color grating onsets that stimulated each photoreceptor type (L-, M-, or S-cones) or post-receptoral pathways (L-M, white/black). VEP signal-to-noise ratios (S/N) were calculated by Fourier analysis of VEP epochs. All RM patients showed extinguished cone ERGs. A near normal S-cone VEP was recorded from a blue-cone rod monochromat without any signal from the L- or M-cone stimuli. Two other RM patients were classified as incomplete RM based on a low-level VEP signal from either L- or M-cone stimuli. CD patients had mildly to severely reduced ERGs and VEPs were abnormal to all cone-isolating stimuli. The VEP S/N ratio was not significantly correlated with the amount of rod contrast in the color stimuli. Color VEPs provide an objective assessment of macular cone function in children with cone dysfunction syndromes that is more sensitive to residual central cone function than standard full-field ERGs. VEP techniques may be useful in the early detection of cone loss in children, especially in children who do not tolerate ERG testing.

Adolescent↗
PubMed2002

Does soccer ball heading cause retinal bleeding?

OBJECTIVES: To define forces of youth soccer ball heading (headers) and determine whether heading causes retinal hemorrhage. SETTING: Regional Children's Hospital, youth soccer camp. PATIENTS: Male and female soccer players, 13 to 16 years old, who regularly head soccer balls. MEASUREMENTS: Dilated retinal examination, after 2-week header diary, and accelerometer measurement of heading a lofted soccer ball. RESULTS: Twenty-one youth soccer players, averaging 79 headers in the prior 2 weeks, and 3 players who did not submit header diaries lacked retinal hemorrhage. Thirty control subjects also lacked retinal hemorrhage. Seven subjects heading the ball experienced linear cranial accelerations of 3.7 +/- 1.3g. Rotational accelerations were negligible. CONCLUSIONS: Headers, not associated with globe impact, are unlikely to cause retinal hemorrhage. Correctly executed headers did not cause significant rotational acceleration of the head, but incorrectly executed headers might.

Acceleration↗
PubMed2002

Trapdoor fracture of the orbit in a pediatric population.

Orbital-floor blowout fractures of the trapdoor variety, first described by Soll and Poley, have also appeared in the French and Japanese literature. The trapdoor fracture is described as a pure orbital-floor fracture, linear in form and hinged medially, which allows herniation of orbital contents through the fracture and then entraps these herniated contents. A review of the orbital-floor fracture literature reveals a high incidence of persistent diplopia associated with ocular-muscle entrapment, which may later necessitate corrective surgery of extraocular muscles. Recent publications in the ophthalmologic literature have stressed the importance of early surgical intervention. This article reports a retrospective series of 19 pediatric patients (age range, 5 to 16 years) who presented to two institutions. All patients had radiographic confirmation of a trapdoor fracture. Physical examination demonstrated a high association between these fractures and restricted ocular motility (17 of the 19 patients). In the cases with trapdoor fracture and restricted ocular movement, early intervention was associated with better postoperative function. It is thus recommended that the symptomatic trapdoor orbit fracture be considered an urgent indication for surgical intervention. Practitioners therefore must have a high index of suspicion for these injuries. Prompt diagnosis is critical to maximize clinical outcome.

Adolescent↗