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6 results on '"halo phenomena"'

3. Retinal straylight and light distortion phenomena in normal and post-LASIK eyes.

Author

Cerviño, Alejandro, Villa-Collar, Cesar, Gonzalez-Meijome, Jose, Ferrer-Blasco, Teresa, and García-Lázaro, Santiago

Subjects
*OPHTHALMIC surgery, *LASIK, *OPERATIVE surgery, *OPTOMETRY, *STATISTICAL correlation
Abstract

Purpose: To assess the relationship between measures of light distortion and retinal straylight in normal and post-LASIK subjects. Design: Cross-sectional, non-randomized, masked observational case series Setting: Clinica Oftalmologica Novovision, Madrid, Spain. Methods: Thirty eyes from 30 healthy subjects (mean age 33.9 ± 8.3 years old; mean spherical equivalent (MSE) −2.06 ± 1.40 D) and thirty six eyes from thirty six refractive surgery patients (mean age 36.1 ± 7.7 years old; mean preop MSE −3.43 ± 2.23 D) were examined with the Starlights and the C-Quant straylightmeter in a case-control study. Results: The age of both treated and control groups was not statistically different ( p > 0.05). Statistically significant differences between controls and post-LASIK eyes were found for luminous distortion index (LDI), but not for retinal straylight. Correlation analysis yielded significant correlation between retinal straylight Log(s) values and BCVA measures ( r = 0.379, p = 0.002). Control subjects showed significant correlation between MSE and retinal straylight Log(s) values ( r = -0.650, p < 0.001), while post-LASIK eyes showed a significant correlation between LDI and Log(s) values ( r = 0.338, p = 0.044) and between Log(s) values and BCVA ( r = 0.460, p = 0.005). Correlation between measures obtained by both methods was higher after LASIK than in control eyes, although values were quite scattered in any case. Conclusion: Light distortion phenomena and retinal straylight measures are correlated in both normal and postsurgical eyes. Both parameters are increased in LASIK subjects compared to control non-operated subjects. [ABSTRACT FROM AUTHOR]

Published
2011
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4. Halo-fenomen observerade i Uppsalatrakten från 1974 till 1976

Author

Rindert, Birger and Rindert, Birger

Abstract

De beskrivna halofenomenen eller halokomponenterna observerades under en obruten 3-årsperiod, från 1974 till 1976. Endast ett litet antal observationer utfördes i andra delar av landet. Dessa observationer är inte bara av intresse för meteorologer utan även för personer intresserade av optiska fenomen i atmosfären. Värt att nämna är här fotografer och personer med naturintresse. Upplevelsen av ett briljant och omfattande halofenomen är någonting man aldrig kommer att glömma! Mest framträdande är speciella optiska företeelser som multipla halon eller hägringar. Jag hänvisar här till 21 augusti 1974, ett halo-skådespel med sju halo-komponenter., The described halo phenomena or halo components were observed during an unbroken period of 8 years. Only a small number of the observations were made in other parts of the country. These observations are not only of interest for meteorologists but even for persons interested in optical events in the atmosphere. Worth to mention here are photographers and people interested in nature. The experience of a brilliant and comprehensive halo phenomena is something one will never forget! Most prominent are special optical events such as multiple halo or mirage. I here refer to August 21, 1974, a halo display with seven components. I strongly recommend the following scientific article describing the types of well formed ice crystals necessary to create the observed halo components. The author of the article was one of my teachers at Uppsala University: Liljequist, G. H. 1956. Halo-phenomena and ice-crystals. Norwegian-British-Swedish Antarctic Expedition, 1949-52: Scientific Results, Vol. II, Part 2A, Norsk Polarinstitutt, Oslo.

Published
2019

5. Retinal straylight and light distortion phenomena in normal and post-LASIK eyes

Author

Teresa Ferrer-Blasco, José Manuel González-Méijome, César Villa-Collar, Alejandro Cerviño, Santiago García-Lázaro, and Universidade do Minho

Subjects
Adult, Male, medicine.medical_specialty, Light, genetic structures, medicine.medical_treatment, Keratomileusis, Laser In Situ, Visual Acuity, Spherical equivalent, Retina, 03 medical and health sciences, Cellular and Molecular Neuroscience, chemistry.chemical_compound, 0302 clinical medicine, Optics, Refractive surgery, Distortion, Ophthalmology, Myopia, Medicine, Humans, Scattering, Radiation, Halo phenomena, Postoperative Period, Science & Technology, business.industry, Healthy subjects, LASIK, Retinal, Mean age, Sensory Systems, eye diseases, Retinal straylight, Cross-Sectional Studies, chemistry, Correlation analysis, 030221 ophthalmology & optometry, Oftalmología, Female, sense organs, business, 030217 neurology & neurosurgery, Disability glare
Abstract

Purpose To assess the relationship between measures of light distortion and retinal straylight in normal and post- LASIK subjects. Design Cross-sectional, non-randomized, masked observational case series Setting Clinica Oftalmologica Novovision, Madrid, Spain. Methods Thirty eyes from 30 healthy subjects (mean age 33.9±8.3 years old; mean spherical equivalent (MSE) −2.06± 1.40 D) and thirty six eyes from thirty six refractive surgery patients (mean age 36.1±7.7 years old; mean preop MSE −3.43±2.23 D) were examined with the Starlights and the C-Quant straylightmeter in a case-control study. Results The age of both treated and control groups was not statistically different (p>0.05). Statistically significant differences between controls and post-LASIK eyes were found for luminous distortion index (LDI), but not for retinal straylight. Correlation analysis yielded significant correlation between retinal straylight Log(s) values and BCVA measures (r=0.379, p=0.002). Control subjects showed significant correlation between MSE and retinal straylight Log(s) values (r=-0.650, p, This research was supported in part by a Universitat de Valencia Research Grant (#UV-AE-08-2291#) and a Ministry of Science and Innovation of Spain (#JC2008-00078) to Alejandro Cervino, from the Fundacao para a Ciencia e Tecnologia of Portugal through a Grant to Jose Manuel Gonzalez-Meijome (#PTDC/SAU-BEB/098392/2008#), and from the Ministry of Science and Innovation of Spain (Red Tematica de Investigacion en Optometria, SAF2008-01114-E).

Published
2011

6. Optical properties of contrail-induced cirrus: discussion of unusual halo phenomena

Author

Ralf Sussmann and Publica

Subjects
optical properties, halo phenomena, Materials Science (miscellaneous), Population, Astrophysics, relative humidity, Atmospheric sciences, Industrial and Manufacturing Engineering, remote sensing, Optics, Radiative transfer, ddc:550, climatic impact, Business and International Management, education, Optical depth, Physics, scattering phase function, education.field_of_study, Ice crystals, Scattering, business.industry, crystal growth, contrail, Refraction, Earth sciences, Cirrus, Halo, ice crystals, business, aircraft
Abstract

Photographs of a 120 degrees parhelion and a 22 degrees parhelion within persistent contrails are presented. These phenomena result from hexagonal plate-shaped ice crystals oriented horizontally with diameters between 300 mum and 2 mm. From our observations and reinvestigation of previous reports, we conclude that a subset of the population in persistent contrails can consist of highly regular, oriented, hexagonal plates or columns comparable to the most regular crystals in natural cirrus clouds. This is explained by measured ambient humidities below the formation conditions of natural cirrus. The resulting strong azimuthal variability of the scattering phase function impacts the radiative transfer through persistent contrails.

Published
1997

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