Lawrence E. Leguire

Screening for Vision Problems, Including Usher's Syndrome, Among Hearing Impaired Students

The purpose of this article is to emphasize the importance of screening for vision problems and for Ushers Syndrome among hearing impaired students, and to provide an outline of a vision screening program in central Ohio. The screening program utilizes a dilated ophthalmological exam and an electro-retinogram (ERG), recorded with EEG skin electrodes, for the detection of vision problems and particularly Ushers Syndrome. The program also involves an interagency network of school, health care and support personnel to meet the needs and follow-up care of students identified with vision problems. The initial vision screening of 210 hearing impaired students, from residential and public school programs, revealed that 44 percent have significant vision problems, and that approximately 1 to 2 percent have Ushers Syndrome.

Instruction Dependent Activation during Optokinetic Nystagmus (OKN) Stimulation: An FMRI Study at 3 T

Modifying experimental conditions of optokinetic nystagmus (OKN) result in different outcomes and may not optimally translate into clinical testing. The purpose of this study was to assess the influence of subject instruction on the anatomical correlates of OKN. The instructions were to voluntarily look or stare at the same moving grating with fixed contrast and spatial and temporal frequencies. Look and stare OKN were generated under identical stimulus ON conditions (vertical sine wave grating of 1.14c/deg drifting right to left at 11.4c/s with binocular viewing). FMRI was undertaken utilizing a 3.0T GE system and the BOLD technique. Subjects included 6 normal adults ranging in age from 18 to 54 years with normal visual acuity (20/20 or better) and normal stereoacuity (40s of arc or better). The results reveal that look OKN generated significantly more cortical FMRI activation than stare OKN. Look OKN areas included the culmen, parahippocampal, lingual, middle temporal gyri, inferior and superior parietal lobules and precuneus, all of which were unilaterally activated in the left hemisphere. The middle occipital gyrus was unilaterally activated in the right hemisphere while the cuneus was bilaterally activated. These results show that the activation sites for OKN studies are dependent on subject instruction which influence the type of OKN generated. Specifically, voluntary look OKN involved more brain sites than stare OKN. In so doing, we illustrate the importance of subject instruction and recommend that FMRI investigators of OKN be cognizant of these effects. The anatomical correlates of the look versus stare are discussed.

Using FMRI and FNIRS for localization and monitoring of visual cortex activities

The purpose of this study was to design a near infrared spectroscopy (NIRS) sensor head to continuously monitor visual cortex activation. Visual cortex activation regions as a result of eye movements were localized using functional magnetic resonance imaging (FMRI). Once the region was determined we placed the NIRS sensor head on that region and emulated the same task performed in the FMRI experiment. The eye movement chosen for our current validation study was saccades. One subject was instructed to move their eyes in a saccadic fashion for 30 seconds then fixate for 30 seconds. We were able to see changes in oxyhemoglobin and deoxyhemoglin using the NIRS design. These preliminary results suggest that NIRS can be used as a monitoring tool, guided by FMRI in patients who may have visual disorders.

Contrast Sensitivity Functions in Normal Children With the Vistech Method

The Vistech Contrast Sensitivity Function tester (VCTS 6500-1) for distance was evaluated to determine the minimum age of children who could complete the test and to determine changes in the CSF as a function of age. A total of 72 normal children between the ages of 24 and 84 months were tested twice with each eye. The results revealed that no child below 36 months of age could complete the test and by 48 months of age 50% could complete the test. By 60 months all children could complete the test. It was also found that age increased the CSF increased equally at all spatial frequencies. A comparison between the eyes of the CSFs revealed a highly statistically significant correlation of 0.78, which showed that the eyes were very similar. Test-retest correlations (0.78) also were highly statistically significant, which demonstrated that the test was very reliable. The results are discussed within the context of screening young children for visual disorders and the evaluation of patching therapy for amblyopia.

Relationship among fMRI, contrast sensitivity and visual acuity

The purpose of this study was to ascertain whether visual acuity or contrast sensitivity function (CSF) is proportional to visual cortical function based on fMRI volume and level of activation or Z-score. Forced choice procedures were utilized to measure the monocular log minimal angle of resolution (logMAR) visual acuity and CSF. The CSF data were collapsed into a single index by the use of weighted mean contrast sensitivity (WMCS), being defined as the mean of the products of each spatial frequency multiplied by its corresponding contrast sensitivity. fMRI data had been obtained with a 1.5 T GE Signa scanner with visual stimuli including 1.0 and 2.0 c/deg vertical sinusoidal gratings. Subjects consisted of eight normal adults and five amblyopic patients, with the amblyopic subjects added to gauge whether the outcome was due to a restricted range of scores or the small number of study participants. In normal subjects, the fMRI volume and level of activation exhibited no statistically significant correlation with visual acuity at P<0.05. Statistically significant correlations were obtained between WMCS and fMRI volume (R=0.765, P=0.027) and fMRI level of activation (R=0.645, P=0.007), with right eye stimulation using the 1.0 c/deg grating. On the whole, statistically significant correlations between WMCS and fMRI parameters were maintained when subject age was held constant and when data from the five amblyopic subjects were included to expand the range of values and increase the number of data sets for analysis. fMRI volume and Z-score were more closely associated with the CSF, as defined by WMCS, than visual acuity. The results suggest that the CSF reflects the underlying visual cortical cells responsible for fMRI volume and the level of activation.

Systemic immunostimulation after retinal laser treatment in retinitis pigmentosa

Systemic immunostimulation followed an experimental treatment trial of scatter argon laser photocoagulation directed to the retina of one eye of 10 patients with heredo-degenerative retinitis pigmentosa (RP). Significantly increased RP lymphocyte CD25, CD26, and CD4/CD26 activation epitope expressions over prelaser values and controls were found with a normalization of soluble interleukin-2 receptor secretion after laser treatment. Serum interferon-gamma was low both pre- and postlaser. Interestingly, when a panel of viral antibodies was tested, only those to rubella virus were elevated in the early postlaser period. The character of RP immunostimulation after laser-induced inflammation could be consistent with an antigenic stimulus from laser-released retinal proteins which might be of autoimmune or latent infectious origin. Enhanced immune responses may be a common but unrecognized sequellae of retinal laser.

Screening of School-aged Hearing Impaired Children

Three hundred sixty hearing-impaired students were screened for visual problems, including Ushers syndrome, with a complete ophthalmologic exam and electroretinography (ERG). Over 25% were found to have a significant refractive error, and approximately 32% had one or more pathologic findings. Overall, 43% either had a significant refractive error or pathologic finding. The incidence of Ushers syndrome was estimated to be between 1.1% and 1.9% in the hearing impaired student population. The results emphasize the need for a complete ophthalmologic examination, and possible ERG testing, in the hearing impaired student population.

Immune alterations associated with T lymphocyte activation and regulation in retinitis pigmentosa patients

Altered immunoregulation, suggested previously in the heredo-familial retinal degeneration, retinitis pigmentosa (RP), led us to examine cell-mediated immune responses in 58 RP patients who expressed either recessive or dominant inheritance. Increased absolute numbers of activated T-cells, quantitated by flow cytometry using the Ta1 epitope, were found in the peripheral blood of 60% of these RP patients. The unusual finding was equally distributed between dominant (16 of 25) and recessive (19 of 33) types of RP, suggesting an immune process present in both patterns of heredity. Additional altered lymphocyte immunoregulation was suggested in all RP by lymphocyte responses to stimulants modified by indomethacin or histamine in vitro. Although no clear association could be found between Tal expression and demographic factors including age, sex, years with RP symptoms, or percentage of life with RP disease, the significantly altered immunoregulatory responses in RP may be related to the pathogenesis of RP.

Influence of levodopa/carbidopa on body temperature in children

Abstract In a multidisciplinary study of the efficacy and tolerability of levodopa/carbidopa in a pediatric population, oral body temperature was measured during two 7-week longitudinal dosing studies. In study 1, 15 children received 0.55/0.14 mg/kg of body weight of levodopa/carbidopa three times daily; in study 2, 13 children received 1.02/0.25 mg/kg. Eight children participated in both studies, and follow-up measurements of body temperature were obtained 4 to 6 weeks after the termination of dosing. The results revealed that, from baseline to the end of the 7-week dosing regimen, mean oral body temperature was unchanged in the 0.55/0.14 mg/kg group but significantly (F = 5.06, P

Persistently altered T cell immunity in high school students with the congenital rubella syndrome and profound hearing loss

Because there are frequent progressive and autoimmune complications in children born with the congenital rubella syndrome, we evaluated immunoregulation in eight profoundly deaf adolescents with congenital rubella syndrome who lived in a state school. Serum antiviral antibodies, expressions of peripheral lymphocyte epitopes and serum soluble interleukin 2 receptor (IL-2R) content were compared with those of 16 classmates with profound hearing loss of unknown cause and of 24 age-matched, hearing students from this area. Both deaf groups showed activated but impaired T lymphocyte function compared with normals. Rubella virus alteration of T cell function was suggested in congenital rubella syndrome students by elevated numbers of both CD4+ helper and CD25+ IL-2R cells with unusually low released soluble IL-2R content. In contrast in deaf classmates elevated CD25+ and CD16+ natural killer cell groups and soluble IL-2R content with low numbers of CD4+ helper cells and CD4+ populations were of unknown etiology. Defective immunoregulation of the congenitally deaf to pathogens inherent in their environment may lead to autoimmune and other complications.