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Biomedical subjects

F C Delori

Publications and source records attributed to F C Delori.

At least 37 records · Page 2Linked to original sources
PubMed1986

Anterior optic nerve blood flow decreases in clinical neurogenic optic atrophy.

Anterior optic nerve blood flow was studied in nine patients with unilateral neurogenic optic atrophy using noninvasive techniques. Disk reflectometry measurements from temporal sites demonstrated a significant reduction in the index of blood volume in atrophic optic nerves as compared with the contralateral optic nerves (P less than 0.00001). Laser Doppler measurements from the same temporal sites detected a significant reduction in the speed of blood (P less than 0.002). On average, blood volume was decreased by 49% +/- 11% and blood speed by 30% +/- 17%. Combining the results of these two techniques yielded a relative index of blood flow that showed a significant reduction in the atrophic nerves (P less than 0.0001), averaging 64% +/- 14% temporally. Nasally there was less reduction in blood flow. The results correlated well with clinical assessment of the degree of optic nerve damage (rho = 0.92, P less than 0.002). This study demonstrates that clinical neurogenic optic atrophy induces significant reductions in overall anterior optic nerve blood flow that are detected by these noninvasive techniques.

Adolescent↗
PubMed1986

[Effect of neurogenic optic atrophy on papillary blood flow].

Anterior optic nerve blood flow was measured in 9 patients with unilateral neurogenic optic atrophy. The noninvasive techniques of reflectometry and laser Doppler detected a decrease in capillary blood flow of the affected eyes as compared with the control fellow eyes as compared with the control fellow eyes (p less than 0.002) that averaged about 64% +/- 14%. There was a good correlation between the decrease in blood flow and the clinical severity of disease (p = 0.92, p less than 0.002). These noninvasive techniques provide a sensitive, safe, and accurate evaluation of the anterior optic nerve that is useful in both clinical research and patient care.

Humans↗
PubMed1986

Retinal pigment epithelial lipofuscin and melanin and choroidal melanin in human eyes.

Optical measurements of the pigments of the retinal pigment epithelium (RPE) and choroid were made on 38 human autopsy eyes of both blacks and whites, varying in age between 2 wk and 90 yr old. Lipofuscin in melanin-bleached RPE was measured as fluorescence at 470 mm following excitation at 365 nm and was found to be proportional to fluorescence measured at 560 nm in unbleached tissue. Transmission measurements of RPE and choroidal melanin were converted and expressed as optical density units. The choroidal melanin content increased from the periphery to the posterior pole. RPE melanin concentration decreased from the periphery to the posterior pole with an increase in the macula. Conversely, the amount of RPE lipofuscin increased from the periphery to the posterior pole with a consistent dip at the fovea. There was an inverse relationship between RPE lipofuscin concentration and RPE melanin concentration. The RPE melanin content was similar between whites and blacks. Lipofuscin concentration was significantly greater (P = 0.002) in the RPE of whites compared to blacks; whereas blacks had a significantly greater (P = 0.005) choroidal melanin content than whites. The amounts of both choroidal and RPE melanin showed a trend of decreasing content with aging, whereas the amount RPE lipofuscin tended to increase (whites greater than blacks). Per fundus area, the amount of choroidal melanin was always greater than that in the RPE. There was a statistically significant (P = 0.001) increase in RPE height with age, most marked in eyes of whites after age 50 and correlated with the increase in lipofuscin concentration.

Adolescent↗
PubMed1985

Relationship of senile macular degeneration to ocular pigmentation.

We prospectively evaluated 650 consecutive white patients with senile macular degeneration and compared them to a control group of 363 patients. Ocular pigmentation (iris color and fundus pigmentation) was recorded for each patient, as was hair color (as a child and young adult) and age at evaluation. Patients were from the New England states and Florida. Our most significant finding was that 494 patients with senile macular degeneration (76%) had light-colored irides compared with 145 of the controls (40%). Fundus pigmentation closely corresponded to iris pigmentation (P less than 0.01). Hair color was blond or light brown in 370 of the patients with senile macular degeneration (57%) and in 105 of the controls (29%). Further, there was a tendency for individuals with lightly pigmented irides to have senile macular degeneration at an earlier age than those with dark irides (P less than .01). Thus, increased ocular pigmentation tends to decrease the risk of developing senile macular degeneration.

Aged↗
PubMed1985

Vitreous fluorophotometry in diabetics: study of artifactual contributions.

A vitreous fluorophotometry study was performed on normal and diabetic subjects, with particular emphasis on instrumentation characterization (calibration and detection characteristics, axial resolution and intraocular optics). The role of lens fluorescence and post-lenticular spread function was explored, as well as the role of retinal fluorescence and pre-retinal spread function. Their influence on vitreous readings is discussed and the study of artifactual contributions presented.

Diabetes Mellitus↗
PubMed1985

Anterior optic nerve blood flow in experimental optic atrophy.

This study attempts to establish whether neurogenic optic atrophy induces changes in anterior optic nerve circulation and to determine how noninvasive techniques of measuring blood flow in vivo compare to microsphere distribution. Five cats underwent unilateral optic nerve transection in the orbital apex and a sham procedure in the contralateral eye. Two to three months later, no abnormalities were detected by fluorescein angiography. Laser Doppler measurements demonstrated a 53% decrease in red blood cell speed through the capillaries of the atrophic optic nerve heads in vivo. Optic disk reflectance measurements of anterior optic nerve blood volume in vivo demonstrated a 51% decrease in the estimated blood volume of the capillaries in atrophic optic nerve heads. Flow was calculated on the basis of these noninvasive measurements and demonstrated an average decrease of 74% in optic atrophy. Histologic studies of microsphere distribution demonstrated an average decrease of 80% in flow to the anterior optic nerve in optic atrophy. These results suggest that anterior optic nerve blood flow is significantly reduced in primary neurogenic optic atrophy. This study also demonstrates that the noninvasive measurements of blood flow are substantiated by histologic evaluation of microsphere distribution.

Animals↗
PubMed1984

Effect of vitreous detachment on vitreous fluorophotometry.

Twenty eyes of 17 normal subjects with or without posterior vitreous detachment (PVD) were examined to investigate the influence of various types of PVD on vitreous fluorophotometric readings. Biomicroscopic examinations of the vitreous body were performed with an El Bayadi - Kajiura preset lens, and the findings were classified according to the extent of vitreous detachment and the position of the posterior hyaloid membrane when the eye was stationary. Equivalent fluorescein concentration profiles along various directions in the vitreous cavity were obtained with vitreous fluorophotometry. The degree of PVD significantly affected the measurements. Close to the retina, fluorescein concentrations were significantly higher when the subhyaloid space was sampled than when the vitreous gel was sampled. Our findings have implications for vitreous fluorophotometric assessment of the permeability of the blood-retinal barrier.

Aged↗
PubMed1984

Corneal endothelial function and structure following cryo-injury in the rabbit.

Wide-field specular microscopy, fluorophotometry, pachymetry, and scanning electron microscopy are used to characterize a reproducible, in vivo model of corneal endothelial injury and recovery in the rabbit. Following an 8-mm central cryo-injury, the cornea remains thickened for as long as 3 weeks. Mean endothelial permeability to fluorescein is above normal for 10 days following injury, but by 14 days postinjury the endothelial permeability to fluorescein is not statistically significantly different from preinjury control values, thus indicating that endothelial permeability probably returns to normal by approximately 2 weeks postinjury. Cell morphology, as determined by scanning electron microscopy, is also essentially normal by 2 weeks postinjury. Endothelial permeability appears to recover before stromal thickness normalizes, suggesting a lag in recovery of endothelial pump function.

Animals↗
PubMed1984

The macular pigment. I. Absorbance spectra, localization, and discrimination from other yellow pigments in primate retinas.

The nonbleaching yellow pigments of the primate fovea were studied by microspectrophotometry (MSP). Retinas fixed with glutaraldehyde/paraformaldehyde mixtures retained yellow pigments with absorbance spectra very similar to those recorded by MSP in fresh retinas. This allowed the authors to prepare retinal sections for localization of the pigments. The spectrum of the macular pigment in fixed tissue is shifted slightly (about 6 nm) toward longer wavelengths, with maximum absorbance at 460 nm. Two short-wavelength yellow pigments also have been identified, with absorbance maxima at 410 nm ( P410 ) and 435 nm ( P435 ), respectively. All three yellow pigments are present in the fovea. The short-wavelength pigments are detected more easily outside the central foveal region because the macular pigment does not obscure them there. They are especially apparent when the MSP beam is confined to the outer nuclear layer or the inner segment layer of retinal sections. The macular pigment is most dense in the fiber layers (receptor axon layer and inner plexiform layer); its density declines markedly with retinal eccentricity. The maximal absorbance of P410 and P435 is usually lower than that of the macular pigment in the central fovea, but their densities and relative proportions change more gradually with eccentricity. Consequently, their maximal absorbance is higher than that of the macular pigment outside the foveal center. The P410 and P435 pigments may be two different oxidation states of one or more respiratory hemoproteins. Commonly used procedures for estimating the absorbance spectrum of the macular pigment by comparing the foveal center with a parafoveal region may be influenced by the amounts and the oxidation states of the short-wavelength pigments in the living eye.

Animals↗
PubMed1984

The macular pigment. II. Spatial distribution in primate retinas.

The spatial density distribution of macular pigment in primate retinas was described by two-wavelength microdensitometry of retinal sections. The macular pigment is most dense along the path of the receptor axons in the center of the fovea. Another band of high density is present in the inner plexiform layer in many retinas. The density in both fiber layers declines to low, relatively constant levels within 1 mm eccentricity. Both the total retinal density of macular pigment and the contributions of subsets of the retinal layers were estimated by integrating along the path of light traversing the retina from the vitreal surface to the outer segments. The integrated densities were measured at several eccentricities to establish the profile of macular pigment density along a diameter through the fovea. The macular pigment profile was unimodal in some cases and trimodal in others. The main central peak always occurred in the center of the fovea. The total retinal density of the central peak ranged from 0.42-1.0 absorbance. Most of the pigment is interposed between the outer segments and the stimulating light and is effective as a visual filter. The macular pigment is dichroic, with the major axis of absorption oriented tangential to a circle centered on the fovea. This is consistent with commonly accepted explanations of Haidinger 's brushes.

Animals↗
PubMed1984

Vitreous fluorophotometric evaluation of diabetics.

Vitreous fluorophotometry measurements taken from diabetic patients with different degrees of retinopathy and from normal volunteers were used to evaluate the integrity of the blood-ocular barrier. The contributions of lens and retinal fluorescence to the measured vitreous fluorescence were investigated. Lens autofluorescence was significantly higher for diabetics than for age-matched normals, and in age-matched diabetics the lens autofluorescence increased significantly with the progression of diabetic retinopathy. Natural ocular fluorescence was corrected for by subtracting baseline values from all vitreous measurements. Analysis of the baseline-corrected vitreous fluorescence values showed that both degree of retinopathy and age significantly affected the measured fluorescence. In age-matched groups, vitreous fluorescence values were greater in diabetics than in normals, and these values increased with the progression of retinopathy. Our results suggest that clinical vitreous fluorophotometry may be useful in evaluating the activity and predicting the progression of diabetic retinopathy.

Adult↗
PubMed1983

Potential retinal hazards. Instrument and environmental light sources.

Light can cause retinal damage by mechanical, thermal, or photochemical mechanisms. Mechanical and thermal injury require a very intense light exposure, but photochemical injury is caused by a prolonged exposure to light levels that probably would be well tolerated if experienced only transiently. The existence of photochemical retinal damage has prompted concern about its possible role in macular degeneration, and reexamination of the safety of clinical light sources. An analysis of the potential hazardousness of these light sources is presented, in addition to a review of retinal damage mechanisms, and suggestions for pertinent patient counseling.

Animals↗
PubMed1981

Historic perspectives. Macular yellow pigment. The first 200 years.

Since 1782 there has been continuing controversy concerning the curious central coloration referred to as "macular yellow," but no cumulative source of information on the subject exists. This paper reviews the research efforts of two centuries to determine the existence, nature, location, and function of a specialized pigment in the foveal region. Using white-light illumination, it is difficult to see a macular yellow spot in the living eye; it is best observed and documented by red-free ophthalmoscopy and blue-light monochromatic photography. Histologic, biochemical, and spectral absorption data suggest that the yellow color is due to a xanthophyllic pigment, lutein, that is distributed in all retinal layers internal to the outer nuclear layer, with greatest concentration in the outer and inner plexiform layers. Clinically absent in newborns, the pigment gradually accumulates from dietary sources and appears to serve both as an optical filter, by absorbing blue light and reducing chromatic aberration, and in a protective capacity, preventing actinic damage. The absorption characteristics of the yellow pigment contribute to the central dark spot seen during fluorescein angiography and to the risk of photocoagulation near the fovea. Its apparent absence in albinos and the reported functional improvement in certain degenerative retinopathies following supplemental xanthophyll administration suggest a possible role in hereditary or acquired maculopathies.

Carotenoids↗