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Biomedical subjects

R P Garzia

Publications and source records attributed to R P Garzia.

18 recordsLinked to original sources
PubMed1998

Vision and attention. II: Is visual attention a mechanism through which a deficient magnocellular pathway might cause reading disability?

Recent research in reading disability has discovered that at least some reading-disabled subjects have deficits in their magnocellular (M) visual pathways. However, the mechanism by which M pathway deficits affect reading has not been addressed. Abnormal attention has long been known to be associated with reading-disabled individuals, and new research in visual attention has determined that transient visual attention is dominated by M-stream inputs. The purpose of this study was to determine whether visual attention might be the mechanism through which a faulty M pathway could produce visual deficits in reading-disabled subjects. Spatiotemporal attentional response functions were measured using the Line Motion Illusion and compared in normal and disabled readers. Specific abnormalities in the visual attention mechanisms of disabled readers were found which might suggest mechanisms by which reading could be affected by a deficient M stream.

Adult↗
PubMed1993

A defective visual pathway in children with reading disability.

BACKGROUND: The possibility that reading disability in children is associated with visual problems is in dispute. We sought to test the existence of this association by using electrophysiologic techniques to measure the processing of visual information in the magnicellular and parvicellular visual pathways of the brain. METHODS: Visual evoked potentials were measured with scalp electrodes in children 8 to 11 years old who were normal readers and in those with reading disability. The potentials were measured for targets with low (0.5 cycle per degree of visual angle) and high (4.5 cycles per degree) spatial frequency, surrounded by either a steady background or a uniform-field flickering 12 times per second. A flickering field normally reduces the amplitude and increases the latency of a transient potential evoked by a low-spatial-frequency target, which preferentially excites the magnicellular visual pathway, but has little effect on the response to a high-spatial-frequency target. RESULTS: With a steady background, the latencies of the early components (N1 and P1) of the visual evoked potentials were longer in the reading-disabled children than in the normal readers when the low-spatial-frequency target was used, but not when the high-spatial-frequency target was used. In normal readers, the flickering background increased the latency and reduced the amplitude of the early components, whereas in the reading-disabled children only the amplitude was affected. No differences were observed in either group with the high-spatial-frequency target. CONCLUSIONS: The pattern of results suggests that the response of the magnicellular visual pathway is slowed in reading-disabled children, who do not, however, have a general slowing of the visual response. The possibility that there is a cause-and-effect relation between these findings and reading disability will require further study.

Child↗
PubMed1990

Experimental evidence for a transient system deficit in specific reading disability.

This paper summarizes the experimental evidence for a transient system deficit in specific reading disability. Differences have been found between controlled readers and specifically disabled readers in measurements of visible persistence, pattern contrast sensitivity and temporal or flicker contrast sensitivity. This transient system deficit was found in approximately 75% of the specifically reading disabled subjects tested. A further series of experiments failed to demonstrate differences in sustained system function between the two groups. Evidence is also presented which suggests that the visual system deficit precedes the reading disability. Possible mechanisms of the impact of a transient system deficit on reading are discussed.

Afterimage↗
PubMed1990

Visual function and reading disability: an optometric viewpoint.

Recent research has identified a low-level transient visual system deficit in patients with reading disability. This deficit has been shown to have consequences on higher level perceptual and cognitive functions, including reading. This new information provides optometrists with a theoretical framework to expand the understanding of the relationship between vision and reading. In this paper, traditional concepts are described and an extensive literature review is provided. The impact of these processing deficits on reading performance is discussed based on metacontrast masking and foveal-parafoveal sequential attention models of reading. Clinical implications of transient system function in other clinical entities are also provided.

Attention↗
PubMed1990

A new visual-verbal saccade test: the development eye movement test (DEM).

The use of presently available clinical oculomotor tests of a visual-verbal format are limited because they do not evaluate automaticity of number naming. There is a significant relationship between automaticity of number naming and reading performance. Presented is a new oculomotor test that has a specific method to factor out the consequences of automaticity on oculomotor performance. Normative data for children age 6-13 years is provided, in addition to reliability and validity information. Clinical utilization of this test for diagnosis and management in visually related learning problems is offered.

Adolescent↗
PubMed1990

Practice profile of University of Missouri-St. Louis optometry graduates.

The results of a survey of the University of Missouri-St. Louis School of Optometry graduates are presented. The practice mode selected and relocation throughout the country is examined for the school's first four graduating classes. Approximately two-thirds of the graduates remained in the state with more than half in proximity of the school. Of these, one-third to one-half maintain "commercial" affiliations.

Demography↗
PubMed1989

Effects of nearpoint visual stress on psycholinguistic processing in reading.

To date, there have been few studies to evaluate directly the relationship between binocular visual stress and reading performance. This study employed the cloze procedure to demonstrate the effects of nearpoint stress on performance and efficiency in reading comprehension. Using 19 third year optometry students as subjects, binocular stress was simulated by -2.00 D lenses. Performance, as determined by the time to complete the task, was significantly reduced (p less than .03), but no significant differences in accuracy scores were measured.

Adult↗
PubMed1988

The effect of volition on the horizontal forced-vergence fixation disparity curve.

An anomalous horizontal forced-vergence fixation disparity curve in the shape of the letters V or U is presented. This phenomenon is associated with an increase in eso fixation disparity with base-out prism. This response is shown to be related to instructional set. Intrusion of voluntary vergence is suggested as the most likely basis for this effect.

Accommodation, Ocular↗
PubMed1988

Astigmatism at nearpoint: adventitious, purposeful, and environmental influences.

Previous studies indicate that a number of individuals display significant differences between astigmatism measured at farpoint and nearpoint. Adventitious effects, purposeful lenticular changes and adaptations in response to environmental forces are reviewed as possible sources of this astigmatic variability.

Accommodation, Ocular↗
PubMed1987

Efficacy of vision therapy in amblyopia: a literature review.

In this paper the major optometric, ophthalmologic, and orthoptic literature on the efficacy of vision therapy for amblyopia has been surveyed. Over the past four decades there are many examples of the successful treatment of amblyopia in the form of well documented individual case reports or large sample studies. Although occlusion of the dominant eye has been applied universally, there are some instances of the successful use of minimal occlusion combined with extensive visual-motor therapy. Overall, the results of the literature review strongly support the use of active vision therapy as an integral part of the clinical treatment of amblyopia.

Amblyopia↗
PubMed1986

Effect of nearpoint stress on the horizontal forced vergence fixation disparity curve.

The effect of nearpoint stress on the forced vergence fixation disparity curve was investigated directly. Data gathered from asymptomatic subjects with normal binocular vision showed that fixation disparity was not influenced by 25 min of continuous reading. Further investigation using symptomatic subjects with large fixation disparities or steep forced vergence curves showed that the nearpoint reading task had a significant effect on the curves of these subjects. Clinical implications and a possible physiological substrate are presented.

Adolescent↗
PubMed1983

Use of an ophthalmoscope for objective refraction of noncooperative patients.

Refractive ophthalmoscopy was performed on 16 subjects aged 5 to 27 years. Subjective refractions were performed on both eyes of the subjects followed by an ophthalmoscopic determination performed under cycloplegia by the authors. A 0.94 correlation was found between the subjectively determined "dry" refractive error and the refractive error determined ophthalmoscopically under cycloplegia by both examiners. The results of the two procedures differed by 1 D or less 82% of the time. The results indicate that refractive ophthalmoscopy is an alternative method for objectively determining refractive error in non-cooperative patients with poor fixational stability.

Adolescent↗
PubMed1983

The bead test: a critical appraisal.

An evaluation of the visual acuity levels obtained with the candy bead test (Bock) was performed. White beads (1 mm) were placed on a white felt background under controlled illumination. Ten subjects were required to localize randomly placed beads through increased degrees of induced optical blur. The visual acuity was then measured at the blur level yielding 60% accuracy in localization. The results indicate a range of visual acuity from 6/45 to 6/60 (20/150 to 20/200). These findings are significantly worse than the levels of acuity [6/18 to 6/24 (20/60 to 20/80)] found by other authors. Therefore, our findings raise concerns and indicate caution in the clinical interpretation of the bead test.

Amblyopia↗
PubMed1983

The impact of automatic digit naming ability on a clinical test of eye movement functioning.

One of the primary reasons for the clinical measurement of eye movements in children is probing the relationship of oculomotor functioning with reading. The purpose of this study was to investigate the relationship between a subjective clinical test of lateral eye movements (KD Saccade Test) using a visual-verbal response format with the ability to name numbers automatically in the absence of eye movements in a first and second grade population. The results support the hypothesis that the eye movement skills measured with subjective visual-verbal formats as described in this study are deficits in automaticity of number knowledge ability and not oculomotor dysfunctions in some children.

Child↗
PubMed1982

Accommodative facility: a study of young adults.

46 young adult men and women (mean age 19.7) were evaluated with a clinical test of binocular accommodative facility utilizing +1.00/-1.00 and +2.00/2.00 lenses. All of the subjects passed a clinical screening of binocular functioning. There were no significant differences between men and women in the number of cycles completed with either lens power and, no differences were found when the responses to both lens pairs were compared. The results are discussed as well as the clinical application of accommodative facility testing.

Accommodation, Ocular↗