Static Visual Acuity (SVA) has been called into question for some time as a measure of overall visual system function and as a predictor of performance on real-life tasks requiring vision (i.e., operating an automobile). Specifically, it has been pointed out that the targets employed in most SVA testing (high contrast, stationary letters) are an insufficient analog to actual targets encountered in everyday activities, which are often in motion and/or of less-than-perfect contrast. In addition, the size-threshold methodology typically used to measure SVA is incongruent with current theories of a multi-channel visual system. Dynamic Visual Acuity (DVA) and Contrast Sensitivity have been suggested as alternatives to SVA, but while each mitigates specific weaknesses of the SVA measure, neither addresses the shortcomings completely. Traditional DVA measures employ moving targets, but these targets are usually of perfect contrast and a size-threshold methodology is used to specify acuity levels. Contrast Sensitivity employs a contrast-threshold methodology and allows measurement of specific visual channels, but stationary targets are utilized. The present study combined the DVA and Contrast Sensitivity measures in an effort to retain the unique qualities of each while addressing their shortcomings, resulting in a more detailed picture of the human visual system and functioning than has yet been possible. By measuring contrast sensitivity to targets at a set of spatial frequencies spanning the human "window of visibility" and under conditions of motion representative of that encountered in everyday activities, it was hoped that a more powerful predictor of actual visual performance would be created. In addition, normative data was established for two separate age populations, in the hopes of learning more about specific changes that occur to the visual system during the aging process. Indeed, several effects and interactions among the three main variables (spatial frequency, velocity, age) were uncovered, which appears to indicate that the new test may provide more information about the visual system than DVA or contrast sensitivity by themselves. The ramifications of this effort to human factors and visual performance research are discussed along with recommendations for the continuation and application of this line of research.

Dynamic Visual Acuity (DVA) in the visual periphery has not been extensively studied. DVA is a measure of an observer's ability to resolve critical details in a target when there is relative motion between the target and the observer. This dissertation examined static and dynamic acuity in the 25-55 deg region of retinal eccentricity under a variety of conditions. Functionally, this region of the visual field is just beyond the "blind spot," but not yet in the "far" visual periphery of 60-90 deg of eccentricity. Traditionally, DVA research has been confined to the assessment of DVA for the foveal (or "central") visual system. However, the peripheral (or "ambient") visual system provides very important information content for the visual and neuro-vestibular systems. This peripheral visual information content is also used to create a sense of ego motion (termed "vection"), and for alerting the visual system to targets entering or leaving the field of view. Past findings involving visual acuity in the peripheral retina have demonstrated that peripheral acuity performance has components related to the notion of "attention" as well. This is particularly true if the peripheral vision research results are to be applied to visually and attentionally complex and/or dynamic real-world environments. In this experiment, the 25-55 deg eccentric region of the retina was tested for DVA in 50 observers. This study used a mixed four-factor research design with Eccentricity (25, 35, 45, 50, 55 deg) as a between-subjects factor. Tracking Difficulty (monitor only, easiest, moderate, most difficult tracking levels), Landolt C Target Velocities (0.0, 4.88, 14.62, and 24.40 deg/s), and Target Direction ("F/R:" fixed or random direction of target appearance) were used as within-subjects factors. A computer presented the Landolt C ring targets under the stated conditions in a random fashion. Acuity was determined for each trial by a modified descending method-of-limits approach with the Landolt C ring target gap widths utilized as the determinant for the acuity measure. The Tracking Task was designated as the primary task, with the secondary task being to indirectly observe the orientation (up, down, right, left) of the Landolt C rings being presented under the various conditions of Target Velocity and Target Direction in the retinal periphery. The resulting Analysis of Variance (ANOVA) revealed significant differences (p < 0.05) for each of the main effects of Eccentricity, Tracking Task Difficulty, Velocity, and Target Direction (F/R). Only two of the two-way interactions were found to be significant (p < 0.05)-- those of Tracking Difficulty x Target Velocity and Target Velocity x Target Direction interactions. The results are discussed in terms of the psychophysical, attention, and "tunnel vision" like models of peripheral visual performance, along with other related human factors literature in the domain of "situation awareness" that are relevant to this general problem area. The results of a separate follow-on mini-study are discussed using a Two-way Contingency Table analysis across all of the treatment conditions when verbal intrusion was embedded in the previously described experimental conditions. This mini-study revealed a significant association (p < 0.05) with not seeing the peripheral targets as accurately when intrusion was present, versus when there was no verbal intrusion. This effect was more pronounced at the highest velocities (14.62 and 24.40 deg/s) as compared with the slower ones (0 and 4.88 deg/s) in terms of the strength of the association, as assessed by a Kappa test statistic. Taken all together, and with consideration given to the relatable scientific literature, these results indicate that the more "busy" a person is with cognitive, visual, or motor-skills tasks, the more likely an individual will show degradation in static or dynamic peripheral visual acuity tasks. Peripheral vision often serves as a "warning" or "status" sensory modality for what is occurring in the local task environment, separate from the foveal visual system. Future research is suggested given the sensitivity of the peripheral visual system to these factors, particularly with regard to how factors involving the notion of attention may affect such "peripheral visual awareness" issues. These issues in turn may play an important role from a human factors and safety perspective in a variety of person-rated vehicular domains. Specific areas that are highlighted for future research in the domain of attention and "peripheral visual awareness" include the low-altitude high-performance flying realm, the flying environment more generally, and in other dynamic multi-task vehicular environments such as that encountered while simultaneously driving and using a car cellular phone. / Ph. D.

The vestibular system senses head motion and facilitates gaze stabilization, allowing for clear vision during movement. The vestibulo-ocular reflex (VOR) causes the eyes to move opposite head motion, thus maintaining focus on a target. Consequently, uncompensated loss of vestibular function leads to reduced VOR function resulting in dizziness, nausea, and visual disturbance. Different testing methods have been developed to measure VOR loss. These tests generally require bulky, expensive equipment, and must be performed by a trained examiner. A newly developed digital form of the dynamic visual acuity (DVA) test requires less equipment, is cost-effective, and may be performed at home making it more accessible. The purpose of this study was to determine the validity and test-retest reliability of the digital DVA test and provide normative data for healthy adults. Fifteen adults – 10 female and 5 male (mean age = 22.0 ± 3.1, range: 19-31 years) – completed the study. Exclusion criteria included age older than 49 years, history of vestibular or neurological disorders, and history of significant head injury. Subjects were screened for normal vestibular function using video head impulse testing. The study consisted of two visits, 3-15 days apart. Participants underwent DVA testing with both the validated NeuroCom (InVision software) system and newly developed digital DVA during the initial visit and the digital DVA during the second visit. The digital DVA system consists of a laptop computer paired with a head/eye tracker (Tobii Eye Tracker 5) and Health in Motion software (Blue Marble Health Company). Outcome measures of interest were the difference between static and dynamic visual acuity measured in LogMAR (DVA loss) for rightward and leftward head movement. Pearson Product-Moment bivariate correlations were used to determine validity of the digital DVA outcomes compared to NeuroCom outcomes. Intraclass correlation coefficients (ICCs) were calculated to determine test-retest reliability of the digital DVA. Pearson correlation coefficients for validity were r = 0.025 and r = -0.015 for left and right DVA loss, respectively. ICCs for test-retest reliability were r = 0.366 and r = 0.313 for left and right DVA loss, respectively. Mean values across both sessions for left and right DVA loss measured by digital DVA were 0.26 ± 0.13 and 0.26 ± 0.11, respectively. Correlations between the digital DVA and standard computerized DVA were poor indicating the need for further development of the current digital system/software. Test-retest reliability for the digital DVA system in its current state was also poor. Tobii sensor used in the software is limited by a 200 ms delay in reporting head motion to the software. Future development of a digital DVA may need to consider other sensors. The current digital DVA will not replace the computerized system; however, it may provide important information for clinicians who do not have access to computerized DVA.

Patients with non-compensated vestibular dysfunction frequently complain of the ability to maintain dynamic visual acuity during activities which require the movement of the head. When this occurs the patient is experiencing oscillopsia, which is the symptom resulting from a non-functional vestibulo-ocular reflex (VOR). To measure the presence of oscillopsia, tests of dynamic visual acuity (DVA) may be used. A recent test of DVA has been reported which is administered while patients are walking on a treadmill. Although this test has been shown to be useful in evaluating DVA in patients, there are several disadvantages to treadmill use. These include physical space, cost and accessibility. Additionally, walking at the required treadmill speed to produce sufficient head movement may pose difficulties and be medically contraindicated for patients with certain health risks. The purpose of this study was to evaluate a different method to measure DVA in patients which would not require the use of the treadmill, but instead utilize a volitional head movement to reveal oscillopsia. In this study, patients performed the DVA test in two conditions: (1) walking on a treadmill, and (2) seated on a chair volitionally moving the head. In this study, DVA was tested in both conditions with 15 adults with normal vestibular function, and 16 adults with vestibular impairment. Results revealed that both methods, treadmill walking and volitional head movement, appeared equivalent for measuring DVA in normal subjects and vestibular impaired subjects. The lack of finding a significant main effect of method, and interactions that include method, supports the equivalence of volitional head movement to a treadmill approach for the measurement of DVA.

Hypothesis: The purpose of this study was to determine reliability of computerized dynamic visual acuity (DVA) testing and to determine reference values for younger and older adults. Background: A primary function of the vestibular system is to maintain gaze stability during head motion. The DVA test quantifies gaze stabilization with the head moving versus stationary. Commercially available computerized systems allow clinicians to incorporate DVA into their assessment; however, information regarding reliability and normative values of these systems is sparse. Methods: Forty-six healthy adults, grouped by age, with normal vestibular function were recruited. Each participant completed computerized DVA testing including static visual acuity, minimum perception time, and DVA using the NeuroCom inVision System. Testing was performed by two examiners in the same session and then repeated at a follow-up session 3 to 14 days later. Intraclass correlation coefficients (ICCs) were used to determine inter-rater and test–retest reliability. Results: ICCs for inter-rater reliability ranged from 0.323 to 0.937 and from 0.434 to 0.909 for horizontal and vertical head movements, respectively. ICCs for test–retest reliability ranged from 0.154 to 0.856 and from 0.377 to 0.9062 for horizontal and vertical head movements, respectively. Overall, raw scores (left/right DVA and up/down DVA) were more reliable than DVA loss scores. Conclusion: Reliability of a commercially available DVA system has poor-to-fair reliability for DVA loss scores. The use of a convergence paradigm and not incorporating the forced choice paradigm may contribute to poor reliability.

Professional research project (Au.D.)--University of South Florida, 2002. / Title from PDF of title page. / Document formatted into pages; contains 24 pages. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Patients with non-compensated vestibular dysfunction frequently complain of the ability to maintain dynamic visual acuity during activities which require the movement of the head. When this occurs the patient is experiencing oscillopsia, which is the symptom resulting from a non-functional vestibulo-ocular reflex (VOR). To measure the presence of oscillopsia, tests of dynamic visual acuity (DVA) may be used.A recent test of DVA has been reported which is administered while patients are walking on a treadmill. Although this test has been shown to be useful in evaluating DVA in patients, there are several disadvantages to treadmill use. These include physical space, cost and accessibility. Additionally, walking at the required treadmill speed to produce sufficient head movement may pose difficulties and be medically contraindicated for patients with certain health risks. The purpose of this study was to evaluate a different method to measure DVA in patients which would not require the use of the treadmill, but instead utilize a volitional head movement to reveal oscillopsia. In this study, patients performed the DVA test in two conditions: (1) walking on a treadmill, and (2) seated on a chair volitionally moving the head.In this study, DVA was tested in both conditions with 15 adults with normal vestibular function, and 16 adults with vestibular impairment. Results revealed that both methods, treadmill walking and volitional head movement, appeared equivalent for measuring DVA in normal subjects and vestibular impaired subjects. The lack of finding a significant main effect of method, and interactions that include method, supports the equivalence of volitional head movement to a treadmill approach for the measurement of DVA. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

The vestibular system senses head motion and facilitates gaze stabilization, allowing for clear vision during movement. The vestibulo-ocular reflex (VOR) causes the eyes to move opposite head motion, thus maintaining focus on a target. Consequently, uncompensated loss of vestibular function leads to reduced VOR function resulting in dizziness, nausea, and visual disturbance. Different testing methods have been developed to measure VOR loss. These tests generally require bulky, expensive equipment, and must be performed by a trained examiner. A newly developed digital form of the dynamic visual acuity (DVA) test requires less equipment, is cost-effective, and may be performed at home making it more accessible. The purpose of this study was to determine the validity and test-retest reliability of the digital DVA test and provide normative data for healthy adults. Fifteen adults – 10 female and 5 male (mean age = 22.0 ± 3.1, range: 19-31 years) – completed the study. Exclusion criteria included age older than 49 years, history of vestibular or neurological disorders, and history of significant head injury. Subjects were screened for normal vestibular function using video head impulse testing. The study consisted of two visits, 3-15 days apart. Participants underwent DVA testing with both the validated NeuroCom (InVision software) system and newly developed digital DVA during the initial visit and the digital DVA during the second visit. The digital DVA system consists of a laptop computer paired with a head/eye tracker (Tobii Eye Tracker 5) and Health in Motion software (Blue Marble Health Company). Outcome measures of interest were the difference between static and dynamic visual acuity measured in LogMAR (DVA loss) for rightward and leftward head movement. Pearson Product-Moment bivariate correlations were used to determine validity of the digital DVA outcomes compared to NeuroCom outcomes. Intraclass correlation coefficients (ICCs) were calculated to determine test-retest reliability of the digital DVA. Pearson correlation coefficients for validity were r = 0.025 and r = -0.015 for left and right DVA loss, respectively. ICCs for test-retest reliability were r = 0.366 and r = 0.313 for left and right DVA loss, respectively. Mean values across both sessions for left and right DVA loss measured by digital DVA were 0.26 ± 0.13 and 0.26 ± 0.11, respectively. Correlations between the digital DVA and standard computerized DVA were poor indicating the need for further development of the current digital system/software. Test-retest reliability for the digital DVA system in its current state was also poor. Tobii sensor used in the software is limited by a 200 ms delay in reporting head motion to the software. Future development of a digital DVA may need to consider other sensors. The current digital DVA will not replace the computerized system; however, it may provide important information for clinicians who do not have access to computerized DVA.

Abstract available through Journal of Neurologic Physical Therapy.

In this study we examined dynamic visual acuity as a functional testing of the vestibulo- ocular reflex. Two groups were examined: 22 healthy seniors and 22 healthy young people as controls. We used two types of situations for testing: while walking on a treadmill at a speed of 2, 4 and 5 kmph, and with a subject's head passively moved in yaw and pitch plane. Visual acuity was measured with optotype charts (for the walking test it was a standard Snellen optotype chart at 6 m distance, for the test of head moves it was a Jaeger chart at 30 cm distance). The values obtained in these ways we related to values of a subject's static visual acuity, measured in the same conditions, just before the dynamic situations were examined. We found significant difference of dynamic visual acuity in senior group within each condition tested. We also found a significant decline as for difference of dynamic visual acuity in the senior group compared to young subjects - in the walking test at 4 and 5 kmph and in both head-moving conditions. These results indicate age-related impairment in function of vestibulo-ocular reflex. Based on our results, the test of passive head moves appears to be more suitable for ordinary clinical examination of dynamic visual acuity.

The loss of central vision subsequent to macular disease is often extremely debilitating. People with central field loss (CFL) must use other peripheral areas of the retina in order to see; areas with inferior resolution capacity, which are also affected by off-axis optical errors. The overall aim of the work encompassed by this thesis was to identify and evaluate methods of improving vision for people with CFL; with focus on the effects of off-axis optical correction and stimulus motion on resolution acuity and contrast sensitivity. Off-axis optical errors were measured using a commercially-available COAS-HD VR open-view aberrometer. We used adaptive psychophysical methods to evaluate grating resolution acuity and contrast sensitivity in the peripheral visual field; drifting gratings were employed to   measure the effect of motion on these two measures of visual performance. The effect of sphero-cylindrical correction and stimulus motion on visual performance in healthy eyes and in subjects with CFL was also studied; in addition, the effect of adaptive optics aberration correction was examined in one subject with CFL. The COAS-HD aberrometer provided rapid and reliable measurements of off-axis refractive errors. Correction of these errors gave improvements in low-contrast resolution acuity in subjects with higher amounts of oblique astigmatism. Optical correction also improved high-contrast resolution acuity in most subjects with CFL, but not for healthy subjects. Adaptive optics correction improved both high and low contrast resolution acuity in the preferred retinal locus of a subject with CFL. The effect of stimulus motion depended on spatial frequency; motion of 7.5 Hz improved contrast sensitivity for stimuli of low spatial frequency in healthy and CFL subjects. Motion of 15 Hz had little effect on contrast sensitivity for low spatial frequency but resulted in reduced contrast sensitivity for higher spatial frequencies in healthy subjects. Finally, high-contrast resolution acuity was relatively insensitive to stimulus motion in the periphery. This thesis has served to broaden the knowledge regarding peripheral optical errors, stimulus motion and their effects on visual function, both in healthy subjects and in people with CFL. Overall it has shown that correction of off-axis refractive errors is important for optimizing peripheral vision in subjects with CFL; the use of an open-view aberrometer simplifies the determination of these errors. In addition, moderate stimulus motion can have a beneficial effect on contrast sensitivity for objects of predominantly low spatial frequency.