scholarly journals Visual acuity through Night Vision Goggles (NVGs): A comparative assessment between Gen 2++ and Gen 3 NVGs under different illumination conditions

2021 ◽  
Vol 65 ◽  
pp. 17-22
Author(s):  
D Sharma ◽  
NK Tripathy ◽  
V Raghunandan ◽  
BM Sekhar
Keyword(s):  
Visual Acuity ◽  
Full Moon ◽  
Night Vision ◽  
Dynamic Changes ◽  
Operational Conditions ◽  
Measure Design ◽  
Image Intensification ◽  
Night Sky ◽  
The Difference ◽  
Better Than

Introduction: During night flying operations, Night Vision Goggles (NVGs) help the aircrew to visualize by intensifying lights reflected from an object. Night sky illumination and image intensification mechanism are the two important factors that affect visual acuity (VA) through NVG. Hence, assessment of visual acuity through Gen 2++ and Gen 3 NVG under different illumination conditions and comparative analysis between the two NVGs was the desired objective of the study. Material and Methods: In a prospective repetitive measure design, a total of 60 volunteered subjects were examined for their VA through Gen 2++ and Gen 3 NVGs using USAF Tri-Bar Chart in the eye lane room of the NVG Lab. The VA was measured under four different illumination conditions; full moon (FM), half moon (HF)quarter moon (QM), and starlight (SL) conditions. The measured VA was converted to logMAR values and analyzed. Results: VA deteriorated significantly with decreasing illuminations through both Gen 2++ (χ2 = 149.9, P < 0.001) and Gen 3 NVGs (χ2 = 156.5, P < 0.001). For Gen 2++ NVG, the difference in VA was statistically significant in all conditions other than between FM and HM. Whereas, it was almost significant for all illumination conditions for Gen 3 NVG. The VA through Gen 2++ was better than Gen 3 in all conditions and the difference in VA widened with decreasing illuminations. Conclusion: VA declined with decreasing illuminations for Gen 2++ as well as Gen 3 NVG, even though, the difference was not significant between FM and HM for Gen 2++ NVG. VA was observed to be consistently better through Gen 2++ NVG compared to Gen 3 across all four illumination conditions. However, keeping in view the dynamic changes in night sky illuminations during flying operations, the findings of the study need to be validated in operational conditions.

scholarly journals A reassessment and comparison of the Landolt C and tumbling E charts in managing amblyopia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yu-Hung Lai ◽  
Horng-Jiun Wu ◽  
Shun-Jen Chang
Keyword(s):  
Visual Acuity ◽  
Prospective Observational Study ◽  
Characteristic Curve ◽  
Random Order ◽  
Repeated Testing ◽  
Tertiary Referral Center ◽  
Cutoff Values ◽  
The Difference ◽  
Better Than ◽  
Landolt C

AbstractCurrent criteria for amblyopia do not account for difference in visual acuity charts. This prospective observational study analyzed 100 children younger than 10 years treated at a tertiary referral center. Visual acuity was separately tested in each eye using Landolt C and tumbling E charts in a random order. For each chart, receiver operating characteristic curve analysis was performed to determine the best cutoff for visual acuity score. Main outcome measures included the difference in visual acuity scores between the two charts, the feasibility of repeated testing of visual acuity in each eye, and amblyopia cutoff values for each chart. Mean logMAR visual acuity scores obtained by tumbling E chart were significantly better than those obtained by Landolt C chart. For amblyopia, the best cutoff values were <  + 0.14 (20/27 Snellen equivalent) for tumbling E chart and <  + 0.24 (20/35 Snellen equivalent) for Landolt C chart. For children under 10 years old, visual acuity scores for tumbling E chart were significantly better than those for Landolt C chart. We suggest that amblyopia management in children should account for age and the type of visual acuity chart used.

scholarly journals Distance Visual Acuity Versus Near Visual Acuity in Amblyopia.

2021 ◽  
Author(s):  
masoumeh ahadi ◽  
Afsaneh Ebrahimi ◽  
Shahrokh Ramin
Keyword(s):  
Visual Acuity ◽  
Spherical Equivalent ◽  
Significant Relation ◽  
Distance Visual Acuity ◽  
Snellen Chart ◽  
History Of ◽  
Near Visual Acuity ◽  
The Mean ◽  
The Difference ◽  
Better Than

Abstract Purpose: To measure and compare distance and near visual acuity in amblyopic patients.Methods: This study was evaluated 167 patients with amblyopia between ages of 6 and 55 years. In all subjects, a comprehensive ophthalmic examination including visual acuity, refraction, slit lamp biomicroscopy, and funduscopy was performed. Distance visual acuity (DVA) was measured by Snellen chart at 4 m and near visual acuity (NVA) was measured by Snellen chart at 40 cm, and then DVA and NVA were compered and analyzed.Results:In our subjects, the mean distance and near visual acuity was 0.39± 0.30 log MAR and 0.30± 0.32 log MAR respectively. The mean NVA was 0.12±0.12 log MAR better than DVA and difference between them was statistically significant (P<0.001). In 40% of patients, there were no difference between DVA and NVA, and in 60% of them, NVA was 0.1 or more log MAR better than DVA. The difference between DVA and NVA was not significantly related with age (p=0.225), spherical equivalent (P=.820) and strabismus (P=.336) and type of amblyopia (P=.405). Although all of these subjects had subnormal DVA, but 43 subjects (26%) had normal NVA. In mild and moderate amblyopic groups, difference between DVA and NVA was 0.14±0.10 log MAR and 0.15±0.14 log MAR respectively, but in severe amblyopic group it was 0.03±0.08 log MAR. The difference between DVA and NVA showed a significant relation with severity of amblyopia (P<0.001). The difference between DVA and NVA was 0.16±0.11 log MAR in patients with history of amblyopia therapy and 0.07.± 0.11 log MAR in patients without treatment. This difference was statistically significant (P<0.001).Conclusion: Our results showed that near visual acuity in amblyopia especially in mild to moderate types was significantly better than distance visual acuity. More than 50% of subjects with mild amblyopia had normal near visual acuity. The difference between DVA and NVA showed no relation with age, spherical equivalent, strabismus, and type of amblyopia. Also, difference between the DVA and NVA in patients with history of amblyopia therapy was better than of it in non-treated subjects.

Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

1987 ◽  
Vol 45 ◽  
pp. 652-653
Author(s):  
John P. Langmore ◽  
Brian D. Athey
Keyword(s):  
Electron Diffraction ◽  
Phase Contrast ◽  
Low Dose ◽  
Dark Field ◽  
Biological Structure ◽  
Bright Field ◽  
Low Contrast ◽  
Negative Stain ◽  
The Difference ◽  
Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

PENERAPAN MODEL PEMBELAJARAN KOOPERATIF TIPE STAD DENGAN PENDEKATAN RME UNTUK MENINGKATKAN HASIL BELAJAR MATEMATIKA SISWA KELAS IX SMP MUHAMMADIYAH PADANG LUAS KECAMATAN TAMBANG KABUPATEN KAMPAR

2018 ◽  
Vol 2 (5) ◽  
pp. 744
Author(s):  
Zainur Zainur
Keyword(s):  
Action Research ◽  
Cooperative Learning ◽  
Student Learning ◽  
Learning Outcomes ◽  
Mathematics Learning ◽  
Student Learning Outcomes ◽  
Learning Model ◽  
Research Instrument ◽  
The Difference ◽  
Better Than

This research was motivated by the low learning outcomes of grade IX SMP Muhammadiyah Padang LuasKecamatan Tambang Kabupaten Kampar. This study aims to improve learning outcomes in mathematicslearning through STAD type cooperative learning with the RME approach in class IX SMP MuhammadiyahPadang Luas Kecamatan Tambang Kabupaten Kampar. The subjects of this study were all classes IX in SMPMuhammadiyah Padang Luas Kecamatan Tambang Kabupaten Kampar totaling 26 people. The form ofresearch is classroom action research. This research instrument consists of performance instruments and datacollection instruments in the form of teacher activity observation sheets and activities. The results of the studystated that there were significant differences between students' mathematics learning outcomes before applyingthe STAD type cooperative learning model with the RME approach with after applying the STAD typecooperative learning model with the RME approach. The difference shows student learning outcomes after theaction is better than before the action with completeness reaching 80.77% or 21 completed. Based on the resultsof the study and discussion it can be concluded that the application of STAD type learning model with RealisticMathematic Education (RME) approach can improve the learning outcomes of grade IX students of SMPMuhammadiyah Padang Luas Kecamatan Tambang Kabupaten Kampar on statistical material.

Reproducibility of Night Vision Goggle Visual Acuity Measurements Using Landolt C's

1999 ◽  
Author(s):  
Alan Pinkus ◽  
H. L. Task ◽  
Sharon Dixon ◽  
Charles Goodyear
Keyword(s):  
Visual Acuity ◽  
Night Vision

Comparison of the Effectiveness of Intravitreal Ranibizumab for Diabetic Macular Edema in Vitrectomized and Nonvitrectomized Eyes

2016 ◽  
Vol 236 (2) ◽  
pp. 67-73 ◽  
Author(s):  
Yoshito Koyanagi ◽  
Shigeo Yoshida ◽  
Yoshiyuki Kobayashi ◽  
Yuki Kubo ◽  
Muneo Yamaguchi ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Macular Edema ◽  
Diabetic Macular Edema ◽  
Treatment Option ◽  
Central Macular Thickness ◽  
Intravitreal Ranibizumab ◽  
Corrected Visual Acuity ◽  
The Mean ◽  
The Difference ◽  
Best Corrected Visual Acuity

Purpose: To compare the effectiveness of intravitreal ranibizumab (IVR) for diabetic macular edema (DME) between eyes with and without previous vitrectomy. Procedures: We prospectively assessed the best-corrected visual acuity (BCVA) and central macular thickness (CMT) after IVR for 6 months. Results: There were no significant differences in the baseline BCVA and CMT between both groups. In the nonvitrectomized group (n = 15), the mean changes of BCVA and CMT from baseline to month 6 were significant (p < 0.01). In the vitrectomized group (n = 10), the improvement appeared to be slower, and the mean BCVA improvement was not significant (p = 0.5), although the mean CMT decrease was significant (p < 0.05). There were no significant differences in the mean changes of BCVA and CMT between both groups at 6 months. Conclusions: The difference in the effectiveness of IVR between both groups was not significant. IVR can be a treatment option even for vitrectomized DME eyes.

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