Biomedical subjects
Publications and source records attributed to T D France.
A computer-assisted mathematical model of ocular movement has been developed. The model is binocular in operation and allows variation of multiple parameters including: muscle insertions, innervations, length and contractures as well as passive tissue forces. The model can be used in interpretation of clinical findings, such as fourth nerve palsies with contracture of the antagonist inferior oblique.
We recorded electrophysiological responses, both electroretinograms (ERGs) and visual evoked responses (VER), at 4 and 21 months of age in a child with hydranencephaly. As expected, the ERG was normal. Despite the apparent absence of most of the cerebral cortex, a VER was present at both visits. The child's visual performance definitely improved both subjectively and electrophysiologically. The VER contained multiple early components in contrast to previous reports, where only a slow, monophasic response was detected.
Neuronal ceroid-lipofuscinosis is manifested by visual and intellectual deterioration and seizures. Autofluorescent lipopigments are found in neural and many nonneural tissues, with characteristic staining and ultrastructural properties. Presumptive diagnosis can usually be made on the basis of history, physical examination, and electrodiagnostic tests, but in the absence of a specific biochemical defect, histologic confirmation is essential. A 6-year-old boy with the clinical appearance of the juvenile form of the disease had sea-blue histiocytes in the bone marrow, and curvilinear profiles in ultrastructural inclusions in skin biopsy tissue, cultured skin fibroblasts, and bone marrow cells.
A previously apparently undescribed "syndrome" is reported in which megalocornea and iris anomalies are accompanied by minor facial and skeletal anomalies, severe mental retardation, hypotonia, and seizures. The condition was found in 3 siblings of one family and in 4 sporadic cases; it is thought to be recessively inherited.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Careful evaluation of all parameters of ocular function are required to delineate the cause of lack of visual responses in children. Any visual fixation, no matter how fleeting, is a sign of intact visual pathways. If no sign of ocular pathology can be found on the routine exam of the visually inattentive child, electrophysiologic testing may be necessary to confirm the presence of abnormality of the visual pathways. In the child with a generalized CNS disorder, the lack of visual response may be due to his inability to respond to visual information (perceptual blindness) rather than to organic pathology in the occipital cortex (cortical blindness).
Strabismus was present in 40% of patients with cataracts/dislocated lenses at the time of initial diagnosis and continued to present an obstacle to complete rehabilitation with 86% of the congenital patients and 61% of the acquired patients found to have strabismus at their latest post therapy visits. The type of horizontal deviation found at the initial examinations was distributed equally between esotropia and exotropia in the unilateral congenital cataracts patients. However, all of our patients with strabismus and bilateral congenital cataracts were esotropic. The acquired group was heavily weighted toward the exodeviations at the time of the initial examination and during treatment showed an even greater percentage of exotropia. Visual acuity results in the various groups followed perhaps the expected trends with the poorest results in the unilateral congenital cataract patients. Those patients in the acquired groups have better visual results with 56% of the traumatic and 83% of the non-traumatic eyes achieving vision of 20/70 or better. Despite the high incidence of strabismus present in these patients, we feel this should in no way be a deterent to the decision to initiate therapy as it does not seem to relate to visual acuity results. The overall good visual results in these patients justifies the approach of early surgery, adequate correction, and vigorous occlusion.
Explore the source record for details and available documents.
Since commonly used clinical methods of measuring binocular function require subjective responses, this testing has been limited to more cooperative children, usually older than 2 years of age. Recently, we have begun using a clinically practical, visually evoked cortical potential (VECP) method to detect the presence of binocular neurons in infants and young children. We studied 14 children, ages 4 to 44 months, with infantile esotropia. Nine had surgical correction for esotropia by the age of 2 years. Twenty-five normal infants ages 6 weeks to 22 months served as controls. Most normal infants showed the development of the "beat" by 2 months of age. The "sum" VECP was not consistently present until age 6 months. Four of the five esotropic infants less than 1 year of age, demonstrated neither a "sum" nor "beat" response. All nine patients with corrective surgery performed before 2 years of age developed a significant sum response and three developed a beat. Five patients had not had surgery until after 2 years of age. Two developed a sum and one a beat, but none had both beat and sum responses. The results suggest that there is a loss of nonlinear binocular response in esotropic children not corrected before the age of 2 years and that these responses can be restored after early treatment even if not present at the time of surgery.
This study examines the relationship between clinically assessed binocular sensory status and binocular visual evoked potentials (BVEPs) in 11 patients with monofixation syndrome (MFS) and in 12 patients with absent binocular fusion (ABF). BVEPs were elicited using a two-sinusoid "beat" technique. The luminances of red/green anaglyphic circular fields were modulated independently at temporal rates of 6 and 8 Hz. This stimulus elicits a BVEP at 14 Hz in children with normal stereoscopic vision. In this study, we found that this BVEP also is present in patients with MFS, whereas it is near background noise levels in patients with ABF. These results demonstrate the presence of functional binocular cortical mechanisms in patients with MFS. The findings are consistent with the hypothesis that elicitation of this class of BVEPs requires gross sensory fusion, but not fine stereoscopic vision.
PURPOSE: Color vision testing in young children typically is precluded by the motor and cognitive skills required by standard tests; yet this information can be useful for diagnosis and counseling in many conditions. The purpose of this study is to evaluate a visual evoked potential (VEP) method for assessing red-green color vision anomalies in pediatric patients. METHOD: The relative chromatic luminance (C = R/R + G) of a rapidly reversing red-green checkerboard was varied across a wide range within a short viewing period (10 sec). Swept-parameter VEP methods were used to measure the cortical response to the range of C presented. RESULTS: Individuals with normal color vision exhibit a VEP response that exceeds noise levels across all values of C, often with an amplitude minima near the photopic equiluminant point (C = 0.5). Results from children with established protan and deutan color vision anomalies show loss of VEP amplitude and phase at values of C consistent with the respective color defect. A patient with achromatopsia showed a generalized depression of VEP response across all values of C tested. CONCLUSION: Color sweep VEP techniques appear promising for the clinical assessment of color status in pediatric patients.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Seventeen cases of unilateral aphakia secondary to acquired cataracts and dislocated lenses were presented. Final visual acuity was 20/70 or better in 12 of our 17 patients. Binocular single vision has been maintained in four cases. Ten patients had a posttherapy tropia. Early surgery and treatment particularly in the young child is stressed in order to maintain normal binocular single vision. Where once traumatized eyes were felt to be "sick" eyes and better left alone, current surgical and therapeutic methods make restoration of vision and binocularity a reasonable goal.
Explore the source record for details and available documents.