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.

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A portable device was constructed which presents moving, computer generated, sine-wave grating slide projections that range in spatial frequency from 0.4 to 20.5 cycles per degree. At each of two different testing sessions, the contrast sensitivities of 60 undergraduate psychology majors were measured at a static, 25 deg/sec, and 50 deg/sec target movement condition. The results indicate that as target velocity was increased, contrast sensitivity decreased at middle and high spatial frequencies but that contrast sensitivity was enhanced at very low spatial frequencies by target movement. Also, the area of peak sensitivity shifted toward lower spatial frequencies as target velocity increased. In addition, test, re-test reliability was demonstrated. The results are consistent with previous Dynamic Visual Acuity (DVA) research which has shown that the ability to resolve fine detail decreases as target velocities increase, presumedly due to limitations in eye movement control. The testing device, which was designed and constructed for the present study, has proven to be a reliable means for measuring dynamic contrast sensitivity (DCS) and has some distinct advantages over existing methods for measuring both DVA and DCS and, as such, will be valuable in future DVA and DCS research. / Master of Science

Fratricide is one of the most devastating consequences of any military conflict. Target identification failures have been identified as the last link in a chain of mistakes that can lead to fratricide. Other links include weapon and equipment malfunctions, command, control, and communication failures, navigation failures, fire discipline failures, and situation awareness failures. This research examined the effects of degraded vision and combat identification reliability on the time-stressed decision of a dismounted infantryman to engage friendly or threat targets. Twelve soldiers with the Military Occupational Specialty 95B (Military Police) participated in several live-fire scenarios while wearing goggles with various levels of transmissivity and shooting an M16A2 containing a combat identification system operating at 100% and 60% reliability. As expected, there was a significant main effect of Transmissivity Level [F(2, 22) = 8.168, p = 0.002] and Combat Identification Reliability [F(2, 22) = 38.467, p < 0.001] and a significant interaction effect of Transmissivity Level x Combat Identification Reliability [F(4, 44) = 3.111, p = 0.024] on the Number of Friendly Targets engaged. The main effects of Transmissivity Level and Combat Identification Reliability and their interaction effect on the Number of Missed Threat Targets were nonsignificant. An unexpected result was no practical increase in Mean Reaction Time using a combat identification system on the M16A2. As technology continues to improve the lethality of military weapon systems, a corresponding increase in target identification is required to avoid friendly fire causalities. Designers of future combat identification systems for the dismounted force will need to focus on operational reliability and ease of use to maximize the system benefits. / Master of Science

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.

Diss. (sammanfattning) Umeå : Umeå universitet, 2010. / Härtill 4 uppsatser. Även tryckt utgåva.

Most humans do not only have a preferred hand to use in different situations, they also exhibit a clear preference when it comes to eye usage. Few studies have assessed whether different tests of eye preference give congruent or incongruent results, and furthermore, there are conflicting findings on whether eye preference correlates with eye dominance, visual acuity, and handedness. The present study assessed whether these variables correlate, alongside factors such as age and sex. A total of 79 subjects, 45 males and 34 females, were tested. A microscope, telescope, photo camera, and caleidoscope were used to assess eye preference, the Dolman test was used to assess eye dominance, the Edinburgh Handedness Inventory was filled in to assess handedness, and visual acuity was measured using a Snellen chart. Care was taken to include subjects of various ages and both sexes. Descriptive statistics show that most subjects were right-handed, had a right-eye preference and were consistent across the four eye preference tasks, and had a dominant right eye. Significant correlations were found between visual acuity and handedness, as well as eye preference and eye dominance.

Introdução: As maiores causas mundiais de cegueira são preveníveis ou tratáveis. Mais de metade dos casos são devido a catarata ou erros de refração não corrigidos. Passo fundamental para a identificação precoce destas alterações, a triagem de acuidade visual pode ser feita por trabalhadores da saúde e educação habilitados para tal. A capacitação destas pessoas peca pela ausência de profissionais habilitados e disponíveis em número suficiente para esta tarefa. A possibilidade de aplicação de método eficaz de capacitação à distância por telemedicina pode ajudar o Brasil a alcançar as metas da OMS para o ano 2020. Métodos: Elaborou-se uma estratégia de educação à distância para trabalhadores de Equipes de Saúde da Família (ESF), por telemedicina, para o desenvolvimento de habilidade prática em área específica da saúde, aqui aplicada em oftalmologia. Aplicou-se a metodologia desenvolvida para a criação de um Instrumento Interativo de Capacitação em Triagem de Acuidade Visual (IICTAV). Baseado em objetos de aprendizagem sistematizados (em iconografia 3D e vídeos contextualizados) criados especificamente para este fim, associados a um simulador de casos, o IICTAV foi aplicado a trabalhadores da saúde de ESFs de todo o Brasil. Elaborou-se questionários para a avaliação da retenção de ganho de informação e da transformação desta informação em conhecimento, com aplicabilidade prática na correta triagem visual de pacientes. Resultados: Foram criados sete objetos de aprendizagem (OA), que podem ser utilizados isolados ou em conjunto. Associados a três simuladores de casos, os OAs foram aplicados em três cursos distintos, a 511 trabalhadores da ESFs, a maioria agentes comunitários de saúde, com 94,8% de acertos na avaliação conduzida. Conclusão: O IICTAV mostrou-se eficaz em habilitar os trabalhadores da saúde a ele expostos na técnica de avaliação da acuidade visual. A metodologia aplicada pode ser difundida por telemedicina para todo o Brasil, ampliando seu escopo para o desenvolvimento de outras habilidades práticas / Introduction: Most prevalent global causes of blindness are either preventable or treatable. More than fifty percent of blindness is due to cataract or unmet correction of refractive errors. Visual acuity screening is a major first step on the early detection of these conditions and may be performed by skilled health workers and teachers. Proper training of these workers lacks human resources both in quantity and availability. Being able to effectively teach health workers the skills to perform visual screening tests using telemedicine and distance education might help Brazil comply with WHO goals for 2020. Methods: A distance education strategy was planned for primary care health workers from Brazilian Family Health Teams to develop specific technical skills in health care. It was first applied to ophthalmology. The strategy was used to create an Interactive Visual Acuity Screening Skill Development Course (IVASSDC). The course was based on standardized learning objects (3D iconography and contextualization videos) who were specially designed and created as well as on a case simulator. The IVASSDC was applied to primary care health workers from all over Brazil. Questionnaires were created to address information retention and its development into knowledge that could allow an adequate visual acuity screening. Results: Seven learning objects and three case simulators were created to be used as a set or isolated. The set of educational tools was applied to 511 health workers from Brazilian Family Health Teams, most of them undergraduate community health agents. It proved effective in 94,8% of the evaluated participants. Conclusion: The Interactive Visual Acuity Screening Skill Development Course proved to be effective on the development of a specific skill in health workers from Brazil. The method can be spread through telemedicine to the whole country and can be applied to the development of other health techniques skills