Wayfinding and Glaucoma: A Virtual Reality Experiment.

PurposeWayfinding, the process of determining and following a route between an origin and a destination, is an integral part of everyday tasks. The purpose of this study was to investigate the impact of glaucomatous visual field loss on wayfinding behavior using an immersive virtual reality (VR) environment.MethodsThis cross-sectional study included 31 glaucomatous patients and 20 healthy subjects without evidence of overall cognitive impairment. Wayfinding experiments were modeled after the Morris water maze navigation task and conducted in an immersive VR environment. Two rooms were built varying only in the complexity of the visual scene in order to promote allocentric-based (room A, with multiple visual cues) versus egocentric-based (room B, with single visual cue) spatial representations of the environment. Wayfinding tasks in each room consisted of revisiting previously visible targets that subsequently became invisible.ResultsFor room A, glaucoma patients spent on average 35.0 seconds to perform the wayfinding task, whereas healthy subjects spent an average of 24.4 seconds (P = 0.001). For room B, no statistically significant difference was seen on average time to complete the task (26.2 seconds versus 23.4 seconds, respectively; P = 0.514). For room A, each 1-dB worse binocular mean sensitivity was associated with 3.4% (P = 0.001) increase in time to complete the task.ConclusionsGlaucoma patients performed significantly worse on allocentric-based wayfinding tasks conducted in a VR environment, suggesting visual field loss may affect the construction of spatial cognitive maps relevant to successful wayfinding. VR environments may represent a useful approach for assessing functional vision endpoints for clinical trials of emerging therapies in ophthalmology

Macular Pigment and Visual Function in Patients With Glaucoma: The San Diego Macular Pigment Study.

PurposeAlthough recent studies have shown that macular pigment (MP) is significantly lower in glaucoma patients, this relationship merits further investigation.MethodsThis cross-sectional study included 85 glaucoma patients and 22 controls. All subjects had standard automated perimetry (SAP) and retinal nerve fiber layer (RNFL) thickness measurements. Intake of lutein (L) and zeaxanthin (Z) was estimated using a novel dietary screener. The Heidelberg Spectralis dual-wavelength autofluorescence (AF) technology was employed to study the relationship between MP and glaucoma. The association between MP volume and glaucoma was investigated using linear regression models accounting for potential confounding factors.ResultsGlaucoma patients had significantly worse SAP mean deviation (MD) and lower RNFL thickness in the study eye compared to control subjects (P < 0.001 for both). MP (volume) was comparable between groups (P = 0.436). In the univariable model, diagnosis of glaucoma was not associated with MP volume (R2 = 1.22%; P = 0.257). Dietary intake of L and Z was positively and significantly related to MP in the univariable (P = 0.022) and multivariable (P = 0.020) models.ConclusionsThese results challenge previous studies that reported that glaucoma is associated with low MP. Dietary habits were found to be the main predictor of MP in this sample. Further research is merited to better understand the relationship between glaucoma, MP, and visual performance in these patients

One step synthesis of Cu2ZnSnS4 nanoflakes by microwave irradiation technique and effect of Cu concentration

The influence of cyclic microwave irradiation and effect of Cu concentration has been investigated for synthesis of pure phase Cu2ZnSnS4 powder. It has been observed that Cu concentration plays a vital role to get pure phase Cu2ZnSnS4. The optical properties, phase purity, crystallographic structure and morphology have been investigated by spectroscopic and microscopic techniques. The results reveal that single phase kesterite Cu2ZnSnS4 with no other secondary phase can be obtained by precisely controlling the cyclic microwave irradiation time and the precursor concentrations. The optical band gap of prepared Cu2ZnSnS4 powder, estimated from UV-Visible spectroscopy has been found to be ~ 1.45 eV which is superlative for photovoltaic application. Systematic Raman study confirms the formation of Cu2ZnSnS4 phase and suppression of CuS peak with proper control in copper concentration. TEM image shows nanoflakes kind of morphology having thickness of flakes between 25 nm to 45 nm. Further the crystal inter-planer spacing is found to be 0.32 nm, which is consistent with the XRD data and ascribed to (112) plane

Design of electron beam bending magnet system for electron and photon therapy: A simulation approach

The doubly achromatic electron beam bending magnet system using two sector magnets has been designed for the medical applications to treat the cancer. The aim of electron beam bending magnet system is to focus an electron beam having a spot size less than 3 mm × 3 mm, energy spread within 3% and divergence angle ≤ 3mrad at the target position. To achieve these parameters, the simulation has been carried out using Lorentz-3EM software. The beam spot, divergence angle and energy spread have been observed with respect to the variation in angles of sector magnets and drift distance. Based on the simulated results, it has been optimized that the first and second magnet has an angle 206° and 35° and the drift distance 80 mm. It is also observed that at the 1125, 1762, 2570, 3265 and 4155 Amp-turn, the optimized design produces 3369, 4972, 6384, 7584 and 9568 Gauss of magnetic field at median plane which require to bend 6, 9, 12, 15 and 18 MeV energy of electron, respectively, for the electron therapy application. The output beam parameters of the optimized design are energy spread ±3%, divergence angle ~3 mrad and spot size 2.6 mm. Moreover, for 6 MV and 15 MV photon therapy applications, an electron beam of energy 6.5 MeV and 15.5 MeV extracted from magnet system and focused on the bremsstrahlung target. Various materials have been studied for photon generation using Monte Carlo based Fluka code and Tungsten material has been optimized as bremsstrahlung target which produces continuous energy bremsstrahlung spectrum. For the photon therapy, the 1233 and 3327 amp-turn, in an optimized design produces 3616 and 7785 Gauss of magnetic field at median plane require to bend 6.5 and 15.5 MeV energy of electron, respectively, which further produces bremsstrahlung radiation from Tungsten target

Fear of falling and postural reactivity in patients with glaucoma

Purpose To investigate the relationship between postural metrics obtained by dynamic visual stimulation in a virtual reality environment and the presence of fear of falling in glaucoma patients. Methods This cross-sectional study included 35 glaucoma patients and 26 controls that underwent evaluation of postural balance by a force platform during presentation of static and dynamic visual stimuli with head-mounted goggles (Oculus Rift). In dynamic condition, a peripheral translational stimulus was used to induce vection and assess postural reactivity. Standard deviations of torque moments (SDTM) were calculated as indicative of postural stability. Fear of falling was assessed by a standardized questionnaire. The relationship between a summary score of fear of falling and postural metrics was investigated using linear regression models, adjusting for potentially confounding factors. Results Subjects with glaucoma reported greater fear of falling compared to controls (-0.21 vs. 0.27P = 0.039). In glaucoma patients, postural metrics during dynamic visual stimulus were more associated with fear of falling (R-2 = 18.8%P = 0.001) than static (R-2 = 3.0%P = 0.005) and dark field (R-2 = 5.7%P = 0.007) conditions. In the univariable model, fear of falling was not significantly associated with binocular standard perimetry mean sensitivity (P = 0.855). In the multivariable model, each 1 Nm larger SDTM in anteroposterior direction during dynamic stimulus was associated with a worsening of 0.42 units in the fear of falling questionnaire score (P = 0.001). Conclusion In glaucoma patients, postural reactivity to a dynamic visual stimulus using a virtual reality environment was more strongly associated with fear of falling than visual field testing and traditional balance assessment.National Institutes of Health/National Eye Institute [EY021818]Brazilian National Council for Scientific and Technological Development (CNPq) [233829/2014-8]Alcon Laboratories (Fort Worth, TX)Bausch & Lomb (Garden City, NY)Carl Zeiss Meditec (Jena, Germany)Heidelberg Engineering (Heidelberg, Germany)Merck (White House Station, NJ)Allergan (Irvine, CA)Sensimed (Lausanne, Switzerland)Topcon (Livermore, CA)Reichert (Dewey, NY)National Eye Institute (Bethesda, MD)Novartis (Basel, Switzerland)nGoggle (San Diego, CA)Duke Univ, Duke Eye Ctr, Durham, NC 27708 USADuke Univ, Dept Ophthalmol, Durham, NC 27708 USAUniv Fed Sao Paulo, Dept Ophthalmol & Vis Sci, Sao Paulo, BrazilUniv Calif San Diego, Dept Ophthalmol, La Jolla, CA 92093 USAUniv Fed Sao Paulo, Dept Ophthalmol & Vis Sci, Sao Paulo, BrazilCNPq [233829/2014-8]Web of Scienc