PubMed Health⌕ Search

Biomedical subjects

G T Chisum

Publications and source records attributed to G T Chisum.

18 recordsLinked to original sources
PubMed1987

The effect of spectrally selective filters on visual search performance.

The effect of five spectrally selective filters on the performance of an acuity-dependent visual search task was evaluated. The filters were: A) a neutral density filter (control condition); B) a 5200A green interference filter; C) a 3215-250 red filter; D) a neodymium visor; and E) a holographic visor. The observers were presented with 5 blocks of 10 slides per filter. Each slide projected a 6 degrees X 6 degrees field of 900 letter O's--each 10' of arc--which contained a single Landolt C. The observers were required to find the C and indicate the position of the opening in the C. The opening in the C subtended 2.64' corresponding to an acuity of 0.38. Response time, error rate, accommodative accuracy, and the number and duration of fixations were recorded for each slide presentation. The results demonstrated that filter type had no effect on any of the response measures. During the first three trial blocks, the observers appeared to optimize their search strategies, after which they began to revert to their initial performance levels. However, this effect was not supported statistically.

Accommodation, Ocular↗
PubMed1979

Laser eye protection for flight personnel.

Developments in laser technology have resulted in an expanding use of lasers in many field and laboratory situations. The implications of the use of lasers in military applications have been examined for flight personnel, and the requirement for eye protection determined. Recommendations for methods of providing that protection are made.

Aerospace Medicine↗
PubMed1977

Effect of virtual image projection distance on the accomodative response of the eye.

Virtual image displays utilize either aircraft-mounted or helmet-mounted beam splitters, or combining screens. The effect on the accomodative response of the projection distance of the virtual image was measured by photographing the first and fourth Purkinje images of a source. The results indicate possible effect on the accomodation response. Further exploration of the problem is indicated.

Accommodation, Ocular↗
PubMed1977

Prediction of airbone target detection.

The visibility of a uniformly luminous object depends on the apparent contrast between the object and its background, the angular subtense of the object, the contrast threshold of the observer at the level of luminance to which the eyes are adapted, the conditions and technique of observing, and the shape of the object. Techniques for combining the influence of the various factors have been applied to the problem of predicting airborne target detectability. Recommendations for achieving the desired detectability are made.

Aircraft↗
PubMed1976

Effect of pre-adapting spectral stimuli on visual responses.

Electroretinograms (ERGs) were recorded following pre-adapting exposures to radiometrically and photometrically matched spectral stimuli. The magnitudes of three aspects of the ERG varied as a function of the pre-adapting wavelength. Longer wavelenght pre-adapting stimuli produced less suppression of the response magnitudes than stimuli from the short wavelenght end of the spectrum. The implications of the findings for display design and cockpit-light-source design and management are discussed.

Adaptation, Ocular↗
PubMed1975

Electrical response of the eye at varying intervals following an adapting flash exposure.

Electroretinograms (ERG) were recorded at varying intervals following an adapting flash exposure. Both amplitude and latency variations are exhibited for short interflash intervals. The ERG following the longer interflash intervals are not significantly different from the dark-adapted ERG. The relationship between the electrophysiological and psychophysical data is discussed.

Adaptation, Ocular↗
PubMed1975

Laboratory assessment of the AN/PVS-5 night vision goggle.

Laboratory assessment of the AN/PVS-5 Night Vision Goggle was conducted. Visual fields, goggle infrared source, useable range, and detectability of targets with the goggle were measured. Illumination levels of -8.37 and -9.17 log lm/cm2 were adequate for 90% detection of 0.14 and 0.07 acuity targets, respectively. Calculations of distances at which various surface and airborne targets subtended comparable visual angles and tables of natural brightness conditions are presented to permit translation of laboratory values into field conditions. While further field evaluation is anticipated, the laboratory assessment indicates that the goggle can significantly facilitate aircrew night visual performance.

Aerospace Medicine↗