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Biomedical subjects

R W Flower

Publications and source records attributed to R W Flower.

At least 55 records · Page 3Linked to original sources
PubMed1978

The effect of blood on ocular fundus reflectance and determination of some optical properties of retinal blood vessels.

Light reflected from 50 micrometer diameter spots on the fundi of two adult rhesus monkeys was measured as a function of wavelength in 10 nm jumps from 400 to 900 nm. The areas measured were a retinal artery and vein, areas of the disk, macula, and retina devoid of visible blood vessels, and the foveola. The eyes of the two monkeys were then exsanguinated, the blood vessels were filled with normal saline, and reflectances of the same spots on the fundi were again measured. The pairs of reflectance curves were compared and demonstrated that blood is not the major determinant of the characteristic shapes of the retinal tissue spectral reflectance curves. From the pre-exsanguination and postexsanguination data, the isolated retinal artery and vein wall reflectances were determined to be 0.020 and 0.009, respectively, their transmittances 0.837 and 0,977, and the fractions of light absorbed by them 0.143 and 0.014, respectively, in the visible spectral region below 500 nm.

Animals↗
PubMed1977

Electroretinographic changes and choroidal defects in a case of central retinal artery occlusion.

A 62-year-old white woman with hypertensive diabetes had central retinal artery occlusion of her right eye. Serial electroretinographic (ERG) studies demonstrated reversible changes in the scotopic components but permanent reduction of the photopic b-wave. Serial simultaneous fluorescein and indocyanine green angiographic studies demonstrated a perfusion defect in the choroid involving part of the macula which subsided after reopening the retinal circulation. Differential hypoxic susceptibility of the ERG photopic and scotopic b-waves was demonstrated, and changes in the patient's retinal tissue oxygenation were postulated on the basis of retinal and choroidal angiographic studies performed during and after central retinal artery occlusion to account for the observed changes in serial ERGS.

Adaptation, Ocular↗
PubMed1977

Reflection of light by small areas of the ocular fundus.

Light reflected from 50 micrometer spots on the fundi of two rhesus monkeys and three human volunteers was measured as a function of wavelength in 10 nm. jumps from 400 to 900 nm. The areas measured were a retinal artery and vein, areas of the disk, macula, and retina devoid of visible blood vessels, and the fovea.

Adult↗
PubMed1976

Indocyanine green dye fluorescence and infrared absorption choroidal angiography performed simultaneously with fluorescein angiography.

The sensory retina of the eye is nourished by two essentially separate blood circulations. The more superficial of these, the retinal circulation, is easily evaluated by direct visualization or routine fluorescein angiography. However, the underlying choroidal circulation, which is attributed with maintenance of the outer layers of the retina is not easily visualized due to the pigment epithelial layer and choroidal pigment. Fluorescence and infrared absorption angiographic techniques using indocyanine green (ICG) dye, which can be used to evaluate the choroidal circulation routinely, are described in this paper. A method is also described which can provide these angiograms simultaneously with standard fluorescein fluorescence angiograms of the retina. Finally, a comparison of all three types of angiograms is made. Limitations to the resolution of fundus details in angiograms imposed by optics of the fundus camera, photographic films, and optics and anatomy of the eye are examined.

Absorption↗
PubMed1975

Visual cortex responses to abrupt changes in the periodicity of rapidly intermittent light.

Visually evoked potentials that are stimulated by period-jumps in a high-frequency modulated luminance have been detected and studied experimentally in monkeys. The visual responses are shown quantitatively by a Principal Components analysis to depend remarkably simply, in shape and in amplitude, on the period-jump stimulus. The response shape is nearly invariant, except that the early part of the response shows a distinctive (though slight) dependence on the sign of the period-jump. The response amplitude is approximately proportional to the magnitude of the period-jump of a given polarity. These features of the evoked potentials demonstrate an intimate association with a suprafusion transient phenomenon that has been observed psychophysically in man. The experimental behavior of the visual potentials also agrees well with theoretical predictions.

Animals↗
PubMed1975

Retinal and cortical electrophysiological responses to instantaneous frequency shifts in light modulated above fusion.

Simultaneously recorded visual-evoked responses and electroretinograms are reported for a transient response produced by an abrupt change in the frequency of a light modulated above fusion. A principal components analysis was made of the recorded waveforms, and results of this analysis and their possible significance to clinical electrophysiology are discussed.

Animals↗