PubMed Health⌕ Search

Biomedical subjects

F Delori

Publications and source records attributed to F Delori.

6 recordsLinked to original sources
PubMed1995

A reflectometric technique for assessing photoreceptor alignment.

Clinical studies of photoreceptor orientation are limited by the fact that psychophysical methods for measuring the Stiles-Crawford effect are time consuming and require excellent co-operation from the subject. We have developed a novel instrument, the photoreceptor alignment reflectometer (PAR), that determines photoreceptor alignment by measuring the distribution in the pupil of light reflected by one retinal location. This determination is accomplished in a measurement time of 4 sec and requires minimal co-operation from the subject. The technique is not significantly affected by reflections at the limiting membrane, or by changes in entrance and exit pupil configuration, or by location of bleaching light entry. The PAR was used to measure the orientation of foveal photoreceptors, their directionality, and the ratio of directional to diffuse flux in 20 normal subjects ranging in age from 20 to 60 yr.

Adaptation, Ocular↗
PubMed1995

Direct measurement of human-cone-photoreceptor alignment.

We have developed an imaging reflectometer to measure cone-photoreceptor alignment. One makes measurements by bleaching the cone photopigment and imaging the distribution of light returning from the retina, which is illuminated from a small source imaged in the plane of the eye's pupil. If the source is near the optimal entry pupil position as determined psychophysically, the distribution of light returning from the retina is peaked, and the magnitude of the peak depends on the location of the source in the pupil of the eye. If the source is far from the optimal entry pupil position, then there is no measurable peak. The location of the peak varies across individuals and coincides with the reported location of best visibility of the measuring light and with previous psychophysical and reflectometric measurements of the Stiles-Crawford peak. The source of this directionality must arise either from the photoreceptors or from behind the photoreceptors because the peak is not present if measurements are made when the cone photopigments have high optical density.

Adult↗
PubMed1988

Central sparing in annular macular degeneration.

Using fluorescein angiography and monochromatic photography, we measured the size of the central sparing in 45 patients with annular maculopathy (mean +/- S.D., 0.34 +/- 0.15 disk diameter; range, 0.10 to 0.65 disk diameter) and compared it with the size of macular yellow pigment in 40 subjects (mean +/- S.D., 0.31 +/- 0.12 disk diameter; range, 0.1 to 0.5 disk diameter). The close approximation of these values suggested that macular yellow pigment contributed to the annular pattern through a photoprotective mechanism.

Fluorescein Angiography↗
PubMed1976

Fluorescein angiography with an optimized filter combination.

The transmission characteristics of a new filter combination for fluorescein angiography were selected on the basis of in vivo measurements of the excitation and emission spectra of fluorescein dye during its transit in the fundus. This combination of filters was characterized by separation of 530 nm between the spectral ranges of transmission of the excitation and barrier filters. In the standard filter combinations this separation is at about 495 nm. Compared to the standard filters, the new filters enhanced the film exposure for all sites of the fundus, especially for the macular area and choroidal fluorescence. There was an improvement in demonstration of the choroidal vasculature, especially in the macular area, and better visibility of retinal detail in the macular area, but a slight decrease in contrast of the retinal vessels outside the macular region. Improved visibility of the fundus for the observer and reduction of scattering in the ocular media of older subjects improved the overall quality of angiograms made with the new filters.

Adolescent↗
PubMed1975

Optimized underwater diathermy for vitreous surgery.

The properties of radio frequency (RF) diathermy currents are briefly reviewed. The inadequacy of damped currents is stressed. The recommended machine generates a frequency of 13.56 MHz. It has a power amplifier, crystal control, coaxial lead from machine to handle, and an impedance of 200 ohms. The two types of electrodes and handles described are shielded from the electrode tip to the diathermy machine. One has a short handle, and an electrode angulated at 35degrees, used in open-sky vitrectomies. The other has a longer handle and straight probe, and is provided with a system for saline infusion. It is used in closed transscleral operations. Electrodes require 35 to 50% more current when used underwater than when used on dry sclera. If charring of tissue is to be avoided, it is advisable to keep the intensity near the level at which gas bubbles form at the electrode tip. Blood vessels can be closed reliably and safely with these electrodes.

Animals↗