Biomedical subjects

Janet P Szlyk

Publications and source records attributed to Janet P Szlyk.

At least 19 recordsLinked to original sources

PubMed2006

Multifocal ERG findings in carriers of X-linked retinoschisis.

PURPOSE: To determine whether retinal dysfunction in obligate carriers of X-linked retinoschisis (XLRS) could be observed in local electroretinographic responses obtained with the multifocal electroretinogram (mfERG). METHODS: Nine obligate carriers of XLRS (mean age, 46.2 years) were examined for the study. Examination of each carrier included an ocular examination and mfERG testing. For the mfERG, we used a 103-scaled hexagonal stimulus array that subtended a retinal area of approximately 40 degrees in diameter. The amplitudes and implicit times in each location for the mfERG were compared with the corresponding values determined for a group of 34 normally-sighted, age-similar control subjects. RESULTS: Mapping of 103 local electroretinographic response amplitudes and implicit times within a central 40 degrees area with the mfERG showed regions of reduced mfERG amplitudes and delayed implicit times in two of nine carriers. CONCLUSIONS: The mfERG demonstrated areas of retinal dysfunction in two carriers of XLRS. When present, retinal dysfunction was evident in the presence of a normal-appearing fundus. Multifocal ERG testing can be useful for identifying some carriers of XLRS.

Adult↗

PubMed2006

Perifoveal function in patients with North Carolina macular dystrophy: the importance of accounting for fixation locus.

PURPOSE: To quantify the extent of visual function losses in patients with North Carolina Macular Dystrophy (NCMD) and to demonstrate the importance of accounting for eccentric fixation when making comparisons with normal data. METHODS: Five patients with NCMD who were from a single family were examined. Multifocal electroretinograms (mfERGs) and psychophysical assessments of acuity and luminance visual field sensitivities were measured throughout the central retina. Comparisons of responses from equivalent retinal areas were accomplished by shifting normal templates to be centered at the locus of fixation for each patient. RESULTS: Losses of psychophysically measured visual function in patients with NCMD extend to areas adjacent to the locations of visible lesions. The multifocal ERG amplitude was reduced only within the area of visible lesion. Multifocal ERG implicit times were delayed throughout the entire central retinal area assessed. CONCLUSIONS: ERG timing is a sensitive assay of retinal function, and our results indicate that NCMD has a widespread effect at the level of the mid and outer retina. The findings also demonstrated that it is necessary to account for fixation locus and to ensure that equivalent retinal areas are compared when testing patients with macular disease who have eccentric fixation.

Adult↗

PubMed2006

Measuring outcomes of vision rehabilitation with the Veterans Affairs Low Vision Visual Functioning Questionnaire.

PURPOSE: To evaluate the sensitivity to change, in patients who undergo vision rehabilitation, of the Veteran Affairs (VA) Low Vision Visual Functioning Questionnaire (LV VFQ-48), which was designed to measure the difficulty visually impaired persons have in performing daily activities and to evaluate vision rehabilitation outcomes. METHODS: Before and after rehabilitation, the VA LV VFQ-48 was administered by telephone interview to subjects from five sites in the VA and private sector. Visual acuity of these subjects ranged from near normal to total blindness. RESULTS: The VA LV VFQ exhibited significant differential item functioning (DIF) for 7 of 48 items (two mobility tasks, four reading tasks, and one distance-vision task). However, the DIF was small relative to baseline changes in item difficulty for all items. Therefore, the data were reanalyzed with the constraint that item difficulties do not change with rehabilitation, which assigns all changes to the person measure. Subjects in the inpatient Blind Rehabilitation Center (BRC) program showed the largest changes in person measures after vision rehabilitation (effect size = 1.9; t-test P < 0.0001). The subjects in the outpatient programs exhibited smaller changes in person measures after rehabilitation (effect size = 0.29; t-test P < 0.01). There was no significant change in person measures for the control group (test-retest before rehabilitation). CONCLUSIONS: In addition to being a valid and reliable measure of visual ability, the VA LV VFQ-48 is a sensitive measure of changes that occur in visual ability as a result of vision rehabilitation. Patients' self-reports of the difficulty they experience performing daily activities measured with this instrument can be used to compute a single number, the person measure that can serve as an outcome measure in clinical studies. The VA LV VFQ-48 can be used to compare programs that offer different levels of intervention and serve patients across the continuum of vision loss.

Activities of Daily Living↗

PubMed2005

The effect of occlusive patching on visually-directed tasks.

PURPOSE: Occlusive patching is used to treat a variety of ocular conditions. A paucity of literature exists regarding the effects of occlusion on functional tasks and driving performance. We investigated the immediate effects of occlusive patching on a variety of visually dependent tasks as well as driving performance on a simulator. METHODS: Thirty normally sighted subjects were examined in a prospective randomized manner. All subjects underwent a complete medical history and eye examination. All subjects performed a variety of near tasks and drove a driving simulator with and without patching. The tasks included traditional clinical depth tests, tests of visual memory, scanning, and tracking, and gross and fine-motor abilities. All subjects filled out a questionnaire relating to their perception of the effects of patching on functional tasks and driving ability. RESULTS: Visual memory, scanning, tracking, and perceptual constancy were unaffected by patching. However, there were significant differences between the patched and unpatched conditions for four of five of the three-dimensional visual coordination tasks. Eight of 19 (42%) of the fine-motor tasks and 4 of 9 gross-motor tasks (44%) showed significant differences between the patched and unpatched conditions. A greater frequency of out of lane events and more abrupt braking profiles were seen when subjects drove monocularly rather than binocularly. CONCLUSIONS: Sudden occlusion immediately changes perceptual ability by decreasing visual field and eliminating stereoacuity. This has important implications for the performance of everyday tasks.

Adolescent↗

PubMed2005

Comprehensive functional vision assessment of patients with North Carolina macular dystrophy (MCDR1).

PURPOSE: Previous studies indicated abnormal development of fixation toward the optic nerve head in patients with the inherited retinal disease North Carolina macular dystrophy (NCMD). The implication of this development on functional vision and structural characteristics has not been described. METHODS: The anatomical characteristics of five NCMD-affected individuals were assessed by measuring the retinal thickness of the macula using optical coherence tomography. The underlying physiologic health of the retina was assessed using the multifocal ERG. Psychophysical assessment of remaining vision in the affected areas was done with a new microperimetry system that measures functional visual acuity at 27 discrete locations and the Humphrey visual field analyzer. RESULTS: All patients had better areas of visual sensitivity toward the nasal macula. Follow-up examination showed no changes in the clinical appearance of the retina. Visual acuities ranged from -0.10 logMAR (Snellen equivalent, approximately 20/16) to 0.50 logMAR (Snellen equivalent, approximately 20/63) in the better eye. No significant changes in visual acuity were found over time. Local multifocal electroretinogram deficits were found in all patients. Patients with grade 2 or 3 disease had large patches of decreased amplitudes and delayed implicit times. Results of the anatomical, electrophysiological, and psychophysical tests were consistent. CONCLUSION: The electrophysiological and psychophysical deficits found in patients with more severe disease were consistent with an abnormal development of fixation from the anatomical fovea toward the optic nerve head with the placement of the lesion temporal to fixation (into the nasal visual field).

Adult↗

PubMed2005

Driving performance of glaucoma patients correlates with peripheral visual field loss.

PURPOSE: To identify clinical vision measures that are associated with the driving performance of glaucoma patients who have visual field loss and visual acuity better than 20/100 and to compare the driving performance of glaucoma patients with the driving performance of a group of age- and sex-equivalent individuals without eye disease. PATIENTS: Forty patients with glaucoma and 17 normally sighted control subjects participated in this study. METHODS: Clinical vision data, consisting of visual acuity, letter contrast sensitivity, and visual fields, were collected. Driving performance was assessed by (1) an interactive driving simulator that measured 7 indices of performance (including number of accidents) and (2) the self-reported accident involvement for the past 5 years. MAIN OUTCOME MEASURES: Driving simulator performance and real-world, self-reported accident involvement. RESULTS: The number of accidents as measured on the driving simulator in the glaucoma group was significantly correlated with three Goldmann visual field measures: combined horizontal extent (rho = -0.47, P = 0.01), total horizontal extent (rho = -0.49, P = 0.007), and total peripheral extent (rho = -0.55, P = 0.002). There were no statistically significant correlations between the driving performance of the glaucoma group and the visual acuity or contrast sensitivity measures. When compared with the control group, a significantly greater proportion of the glaucoma group reported having at least one real-world accident within the past 5 years (Fisher exact test, P = 0.005). CONCLUSIONS: Visual field reduced to less than 100 degrees of horizontal extent may place patients with peripheral field loss at greater accident risk. A higher incidence of real-world and simulator accidents was found for the group with glaucoma.

Adult↗

PubMed2005

Use of prisms for navigation and driving in hemianopic patients.

PURPOSE: (1) To compare the outcomes of orientation and mobility and driving training with Fresnel prisms and the Gottlieb Visual Field Awareness System for patients with homonymous hemianopsia, and (2) To determine whether the patients continue to use the optical enhancement devices at a 2-year follow-up point. METHODS: Patients with homonymous hemianopsia were provided with a rehabilitation program where they were fitted with prism lenses and trained to use them for navigation and driving. Telephone interviews were used to obtain information about device usage 2 years following the completion of the training program. RESULTS: Patients' performance was compared with a test-retest criterion in the visual skills areas of recognition, mobility, peripheral detection, scanning, tracking, and visual memory. Patients with hemianopic loss showed improvements in all of the visual skills categories, ranging from the highest improvements of 26% of tasks improved in the mobility category to 13% in the recognition category. The majority of the hemianopic patients reported using the devices at the 2-year follow-up interview. CONCLUSIONS: The patients with homonymous hemianopsia showed improvements in visual functioning using prism lenses, although these improvements were smaller than those found in previous studies with central or bilateral peripheral vision loss groups who were trained to use other optical enhancement devices for navigation and driving using a similar curriculum. However, given the evidence of increased risk of accidents for patients with peripheral vision loss, the safety of peripheral enhancement devices for driving must be thoroughly evaluated before their impact on public safety is known.

Adult↗

PubMed2005

Eye-movement training for reading in patients with age-related macular degeneration.

PURPOSE: To determine whether training oculomotor control, without direct practice in reading sentences, could increase reading speed in patients with age-related macular degeneration (AMD). METHODS: Sixteen patients with AMD participated in the study (age range, 65-87 years; mean, 77). The training program consisted of a series of exercises that were designed to allow the patients to practice eye movements. At the beginning of training, the subjects practiced small horizontal saccades in response to cognitively easy stimuli (e.g., dots). The training then progressed to practicing larger eye movements and then to practicing saccades with single letters, pairs of letters, and three-letter words. Reading of sentences was practiced in only one exercise, during the last session of the 8-week training. RESULTS: The difference between average reading speeds before and after training was 24.7 wpm (difference between medians, 17.9 wpm). The increase in speed was statistically significant (Wilcoxon signed rank test = 124.0, P < 0.001). There was no significant relationship between change in maximum reading speed and ETDRS (Early Treatment Diabetic Retinopathy Study) acuity (r = -0.14, P = 0.76) or between change in maximum reading speed and age (r = 0.25, P = 0.45). CONCLUSIONS: The results indicate that a training curriculum that concentrates on eye-movement control can increase reading speed in patients with AMD. This finding is especially interesting, because the training involved little direct practice in reading sentences but instead concentrated on having subjects practice control of eye positions and eye movements.

Aged↗

PubMed2004

Psychometric properties of the Veterans Affairs Low-Vision Visual Functioning Questionnaire.

PURPOSE: To describe psychometric properties of a self-report questionnaire, the Veterans Affairs (VA) Low-Vision Visual Functioning Questionnaire (LV VFQ-48), which was designed to measure the difficulty visually impaired persons have performing daily activities and to evaluate low-vision outcomes. METHODS: The VA LV VFQ-48 was administered by telephone interview to subjects with visual acuity ranging from near normal to total blindness at five sites in the VA and private sector. Rasch analysis with the Andrich rating scale model was applied to difficulty ratings from 367 subjects, to evaluate measurement properties of the instrument. RESULTS: High intercenter correlations for item measure estimates (intraclass correlation coefficient [ICC]=0.97) justified pooling the data from these sites. The person measure fit statistics (mean square residuals) confirm that the data fit the assumptions of the model. The item measure fit statistics indicate that responses to 19% of the items were confounded by factors other than visual ability. The separation reliabilities for pooled data (0.94 for persons and 0.98 for items) demonstrate that the estimated measures discriminate persons and items well along the visual ability dimension. ICCs for test-retest data (0.98 for items and 0.84 for persons) confirm temporal stability. Subjects used the rating categories in the same way at all five centers. Ratings of slight and moderate difficulty were used interchangeably, suggesting that the instrument could be modified to a 4-point scale including not difficult, slightly/moderately difficult, extremely difficult, and impossible. Fifty additional subjects were administered the questionnaire with a 4-point scale to confirm that the scale was used in the same way when there were four rather than five difficulty ratings. CONCLUSIONS: The VA LV VFQ-48 is valid and reliable and has the range and precision necessary to measure visual ability of low-vision patients with moderate to severe vision loss across diverse clinical settings.

Activities of Daily Living↗

PubMed2004

Relationship of retinal structural and clinical vision parameters to driving performance of diabetic retinopathy patients.

This study identifies clinical vision measures or retinal structural measures associated with the driving performance of diabetic retinopathy patients. Twenty-five licensed drivers with diabetic retinopathy (median age, 53 years; range, 34-72 years) completed clinical tests (visual acuity, letter contrast sensitivity, and Humphrey 30-2 visual fields) and structural examinations (retinal thickness analysis and fundus photograph grading of retinopathy and laser scarring). Driving performance was assessed with an interactive driving simulator and a driving history questionnaire. Increased retinal thickness was significantly correlated with a higher frequency of simulator accidents and near accidents. Laser scar grades significantly correlated with steeper brake-response slopes, increased brake-pressure standard deviation (SD), and longer response times. Subjects with focal laser scars had significantly higher average brake-pedal pressure and brake-pressure SD than subjects without focal laser scars. Retinal thickness and laser scarring correlated with driving simulator performance in subjects with diabetic retinopathy.

Accidents, Traffic↗

PubMed2004

Multidimensional visual field maps: relationships among local psychophysical and local electrophysiological measures.

Multidimensional psychophysical and electrophysical maps of the central retina are essential for assessing the functioning of the diseased retina. In this study, grating acuity, contrast sensitivity, duration for letter identification, multifocal electroretinograms, and Humphrey visual field thresholds were measured at equivalent positions throughout the central 20 degrees. We found that the rates of sensitivity loss were not equivalent for all psychophysical measures. The rate of loss in the duration required for letter identification as a function of eccentricity was the steepest, followed by acuity and contrast sensitivity. The rate of loss in luminance sensitivity as measured in the Humphrey visual field was the shallowest. The pattern of losses also varied across meridians. Specifically, the rate of loss as a function of eccentricity was highest in the vertical meridian and lowest in the horizontal meridian. These maps and the correlations among measures as a function of retinal position serve as a baseline so that we can examine disease effects throughout the retina. In addition, the development of vision rehabilitation programs focused on eccentric viewing training should consider the differential sensitivities of the peripheral retina.

Adult↗

PubMed2004

Use of Rasch person-item map in exploratory data analysis: a clinical perspective.

The National Institutes of Health (NIH) includes visual impairment in the 10 most prevalent causes of disability in America. As rehabilitation programs have the potential to restore independence and improve the quality of life for affected persons, NIH research priorities include evaluating their effectiveness. This paper demonstrates a clinical perspective on the use of the Rasch person-item map to evaluate the range and precision of a new vision function questionnaire in early analysis (prior to full sample). A self-report questionnaire was developed to measure the difficulty that persons with different levels of vision loss have performing daily activities. This 48-item Veterans Affairs Low-Vision Visual Functioning Questionnaire (VA LV VFQ-48) was administered to 117 low-vision patients. Preliminary analysis indicates that the questionnaire items are applicable to persons of differing abilities. The Rasch person-item map demonstrates that the field-test version of the VA LV VFQ-48 has good range and is well centered with respect to the person measure distribution. Construct validity and reliability are also demonstrated.

Adult↗

PubMed2003

Could empathy be a predictor of hypnotic ability?

This study examined whether trait empathy is related to hypnotic ability and absorption. Sixty-four graduate students and mental health professionals completed the Harvard Group Scale of Hypnotic Susceptibility, Form A; the Davis Interpersonal Reactivity Index; and the Tellegen Absorption Scale as measures of hypnotic ability, empathy, and absorption. Correlation analysis determined that statistically significant relationships exist between empathy and hypnotic ability (r = .41); empathy and absorption (r = .43); and absorption and hypnotic ability (r = .31). The results also indicate that empathy and absorption are both predictors of hypnotic ability, although absorption does not appear to contribute a statistically significant amount of the explained variance in hypnotizability that is independent of empathy. It may be that the conceptual ground shared by both empathy and absorption is what predicts hypnotic ability.

Adult↗

PubMed2003

Multifocal electroretinography as a function of age: the importance of normative values for older adults.

PURPOSE: To determine the influence of age on local electroretinographic responses in humans. METHODS: Multifocal electroretinograms (mfERGs) were obtained from 62 normally sighted subjects ranging in age from 21 to 81 years. A stimulus array of 103 scaled hexagons was used to measure electrical signals within a retinal area approximately 46 degrees in diameter. Commonly reported mfERG methods were used to quantify the responses: peak-to-peak amplitudes and implicit times, scalar product amplitude, and amplitude and time scales derived from the algorithm of Hood and Li, published in 1997. RESULTS: Regression analysis showed significant linear relationships of amplitude and timing measures with age. The rates of losses were 10.5% per decade for peak-to-peak amplitude, 11.7% per decade for scalar product amplitude, and 9.5% per decade for a-scale. The rate of amplitude reduction was highest in the central 3 degrees. Age had less influence on implicit time measures. The rates of timing losses were 1.4% per decade for the N1 component and 1.0% per decade for both the P1 component and the t-scale measure. Using predicted interval ranges, the age was calculated at which 50% of the expected values would fall below the lower 95% prediction interval band of younger subjects. CONCLUSIONS: The age-associated mfERG alterations are presented to emphasize the importance of appropriate normative data in interpretation of mfERGs.

Adult↗

PubMed2003

Comparison of contrast sensitivity, visual acuity, and Humphrey visual field testing in patients with glaucoma.

BACKGROUND: Despite their normal or near-normal Snellen visual acuity, patients with glaucoma often complain of "poor" vision. OBJECTIVE: To investigate the relationship between large-letter contrast sensitivity, high-contrast visual acuity, and visual field defects in patients with glaucoma who have 20/40 or better visual acuity. DESIGN: Prospective, cross-sectional case series. PATIENTS AND METHODS: We evaluated 250 eyes of 144 subjects from the Glaucoma Service at the University of Illinois at Chicago College of Medicine. Subjects with a diagnosis of glaucoma, suspected glaucoma, or ocular hypertension who met the 20/40 or better vision requirement were recruited. Visual acuity was measured using the rear-illuminated Lighthouse Visual Acuity Chart at 4 m. Contrast sensitivity was measured using the Pelli-Robson Chart in a front-illuminated box with even luminance across the chart. Visual fields of the patients were measured using the 24-2 full-threshold program on the Humphrey Visual Field Analyzer. RESULTS: A significant correlation (r = 0.57, P < 0.001, n = 127) was found between the visual field mean deviations and the contrast sensitivity scores. The correlation (r = -0.322, P < 0.001, n = 127) was less between the visual field mean deviation and the log MAR visual acuity values, as was the correlation between the contrast sensitivity scores and log MAR visual acuity values (r = -0.370, P < 0.001, n = 127). In the subgroup of patients with chronic open-angle glaucoma, the correlation between the mean visual field deviation and the contrast sensitivity score was higher at 0.689 (P < or = 0.001, n = 62). CONCLUSIONS: Reduced contrast sensitivity is significantly correlated with visual field losses in patients with glaucoma and a visual acuity of 20/40 or better. The study data support the conclusion that, compared with visual acuity, the disease process preferentially affects contrast sensitivity. In our previous work, contrast sensitivity was shown to be more related than visual acuity to real-world function in patients with early glaucomatous changes.

Contrast Sensitivity↗

PubMed2002

Sequential multifocal electroretinogram findings in a case of Purtscher-like retinopathy.

PURPOSE: To report the multifocal electroretinographic findings of a patient with pancreatitis-associated Purtscher-like retinopathy. DESIGN: Observational case report. METHODS: A 20-year-old man with a history of alcohol abuse and acute pancreatitis underwent multifocal electroretinography (mfERG; 103-scaled hexagons, 8-minute recording time) at 1 week, 4 weeks, and 6 months after the onset of the retinopathy. RESULTS: At 1 week, the patient had extensive cotton- wool spots in the posterior pole bilaterally, and visual acuity was significantly reduced. Both the A-waves and B-waves of the mfERG were depressed in the corresponding areas. At 4 weeks, neither visual acuity nor mfERG showed improvement, although the cotton-wool spots had resolved. Interestingly, at 6 months, visual acuity had improved significantly in the left eye, consistent with increased ratios of mfERG responses for the central area. CONCLUSION: There was no selective reduction of b-waves of the mfERG as anticipated in isolated inner retinal pathology. In this case, both the A-waves and B-waves were reduced, suggesting damage to both outer and inner retinal layers.

Acute Disease↗

PubMed2002

Detection using the multifocal electroretinogram of mosaic retinal dysfunction in carriers of X-linked retinitis pigmentosa.

PURPOSE: To examine whether a mosaic pattern of retinal dysfunction in obligate carriers of X-linked retinitis pigmentosa (XLRP) could be observed in local electroretinographic responses obtained with the multifocal electroretinogram (mfERG). DESIGN: Prospective observational case series. PARTICIPANTS: Five obligate carriers of XLRP (mean age, 53.2 years) were recruited into the study. METHODS: Examination of each subject included a complete ocular examination, Humphrey visual field, standard full-field electroretinogram (ERG), and mfERG testing. For the mfERG, we used a 103-scaled hexagonal stimulus array that subtended a retinal area of approximately 40 in diameter. The amplitudes and implicit times in each location for the mfERG was compared with the corresponding value determined for a group of normally sighted, age-corrected control subjects. MAIN OUTCOME MEASURES: Mapping of 103 local electroretinographic response amplitudes and implicit times within the central 40 with the multifocal electroretinogram. RESULTS: Localized regions of reduced mfERG amplitudes and/or delayed implicit times were found in four of five carriers. In one of these four carriers, a mosaic pattern of mfERG dysfunction was present even in the absence of any clinically apparent retinal changes, retinal sensitivity losses on Humphrey field testing, or abnormal full-field cone ERG responses. However, one carrier with a typical tapetal-like reflex demonstrated no deficit on any functional tests. CONCLUSIONS: The mfERG demonstrated patchy areas of retinal dysfunction in some carriers of XLRP. This mosaic pattern of dysfunction may be observed in some patients with a normal-appearing fundus, normal psychophysical thresholds, and normal amplitude and implicit time full-field ERG cone responses.

Adult↗

PubMed2002

Localized retinal dysfunction in central serous chorioretinopathy as measured using the multifocal electroretinogram.

PURPOSE: To determine the extent of electrophysiologic dysfunction in patients with central serous chorioretinopathy (CSC). DESIGN: Prospective observational case series. PARTICIPANTS: Six patients with unilateral CSC (mean age, 40 years) were recruited into the study. METHODS: Six patients with CSC underwent multifocal electroretinogram (mfERG) testing on both their clinically affected and opposite uninvolved eyes using the VERIS System, with a stimulus array of 103 scaled hexagons. The first positive peak responses were analyzed within six concentric ring annuli centered on the fovea. Amplitudes and implicit times were compared with those of an age-similar control group. MAIN OUTCOME MEASURES: Local electroretinographic response amplitudes and implicit times within the central 40 degrees with the mfERG. RESULTS: All the clinically uninvolved eyes showed mfERG amplitudes and implicit times within the normal range throughout the central 40 degrees of the retina. All six eyes with CSC showed reduced amplitudes and/or delayed implicit times that were limited to the regions of the macula in which clinical changes associated with CSC were apparent. CONCLUSIONS: We observed electroretinographic changes only in the clinically affected eyes, and these were limited to regions with ophthalmoscopically apparent fundus changes. Our findings do not support the conclusion that functional impairment, as measured by the mfERG, in eyes with CSC extends beyond clinically observed fundus changes. We did not observe abnormal mfERG responses in the clinically normal eyes of such patients.

Adult↗