Search results for "Scotopic vision"

Rev-Erb modulates retinal visual processing and behavioral responses to light

2016

International audience; The circadian clock is thought to adjust retinal sensitivity to ambient light levels, yet the involvement of specific clock genes is poorly understood. We explored the potential role of the nuclear receptor subfamily 1, group D, member 1 (REV-ERB; or NR1D1) in this respect. In light-evoked behavioral tests, compared with wild-type littermates, Rev-Erb(-/-) mice showed enhanced negative masking at low light levels (0.1 lx). Rev-Erb(-/-) mouse retinas displayed significantly higher numbers of intrinsically photosensitive retinal ganglion cells (ipRGCs; 62% more compared with wild-type) and more intense melanopsin immunostaining of individual ipRGCs. In agreement with a…

Color and lightness constancy in different perceptual tasks

1998

Color and lightness constancy with respect to changing illumination was studied with three different perceptual tasks: ranking of colored papers according (1) to their lightness and (2) to their chromatic similarity in photopic, mesopic, and scotopic states of adaptation, and (3) recognition of remembered colored papers after changes of illumination in photopic vision. Constancy was found in the second task, only. Excitations of light receptors and luminance channels were computed to simulate the empirical rank orders. Results of the first task can be predicted with the hypothesis that luminance channels are activated, if lightness is asked for. Sequences arranged with respect to chromatic …

Methodological Aspects of the Application of the Naka-Rushton Equation to Clinical Electroretinogram

1993

The nonlinear relation between stimulus intensity and response amplitude of the electroretinogram (ERG) scotopic b wave can be described by a curve based on the Naka-Rushton (NR) equation. Up to now, the NR equation has been used to assess the features of the normal and pathological ERG, but the best approach for a correct evaluation of the parameters is still debatable. The parameters are thought to be related to the different conditions of retinal activities. The method is well known in experimental laboratories but is quite unusual at the clinical level. In the present paper the derivative analysis of the NR function is proposed as an easier approach to understand the variations of the N…

Electrophysiological findings of neuronal ceroid lipofuscinosis in heterozygotes.

1988

Nineteen obligate heterozygotes, 8 individuals at risk of being heterozygote, and 10 patients afflicted with four different forms of neuronal ceroid lipofuscinosis were examined electrophysiologically. The group of obligate heterozygotes was compared to age-matched control groups. Statistically significant differences were found between scotopic b-wave amplitudes, P-ERG amplitudes, and EOG light peaks of the obligate carriers of the juvenile type and the control subjects. The photopic L-ERGs and the latencies of the VEPs were mostly within the normal range. The findings represent the first evidence of functional ophthalmological changes in obligate carriers of neuronal ceroid lipofuscinosis…

Monocular versus binocular pupillometry.

2004

Purpose To quantify differences between monocular and binocular pupil size measurement under scotopic and mesopic conditions. Setting Department of Ophthalmology, Johannes Gutenberg-University, and Department of Medical Biometry, Epidemiology and Informatics, University of Mainz, Mainz, Germany. Methods Computerized dynamic pupillometry (P2000 SA, Procyon Instruments Ltd.) was used at 3 illumination levels: scotopic at 0.03 lux, mesopic low at 0.82 lux, and mesopic high at 6.4 lux. One hundred forty eyes of 70 healthy volunteers without ocular pathology were examined. The subjects were divided into 2 groups. In the first group, the pupil diameter was measured binocularly first. In the secon…

Photoreceptors, lightness constancy and color vision.

1986

Absence of lightness constancy as a deficit of monochromatic vision

1995

Dark-adapted human subjects arranged a collection of colored papers in a sequence according to their lightness. The sequence of the papers (which appeared gray to the subjects) varied under different illuminant spectra. These variations could be predicted quantitatively from the radiometric data and human scotopic spectral sensitivity. By substitution of natural daylight spectra in the computation it was shown that monochromats cannot perceive lightness reliably under the changing illuminant spectra of our planet. Animals need some degree of lightness constancy to detect figures against a background reliably. This can be achieved only with the help of additional light receptors of different…

Transient reduction of the ocular perfusion pressure and the oscillatory potentials of the ERG

2005

Abstract Purpose. To evaluate the changes of the Oscillatory Potentials (OPs) of Electroretinogram (ERG) caused by short-term hypertension in human subjects, and their relationship with ocular perfusion pressure (OPP). Methods. Suction cup technique in 12 normal volunteers with OPs simultaneously recording. Results. Scotopic and photopic OPs were altered during OPP drop. Scotopic OPs showed more sensitiveness, with higher reduction (from 21% to 47%), when compared to the basal value, than in photopic recordings (from 14% to 34%). In both conditions, the relationship between OPP and OPs presented a steady amplitude before the trough after the +30 step, and rapid recovery after OPP normalisat…

A novel murine model of aging of the human retina

2008

Purpose Accumulation of lipids, and especially of cholesteryl esters, under the retinal pigment epithelium and within Bruch’s membrane is a normal feature of aging and has also been observed in human eyes with age-related maculopathy. Our objective was to evaluate the retinal phenotype of apoB100,LDLR-/- mice, a model for lipid metabolism dysfunction and potentially of aging of the retina. Methods ApoB100,LDLR-/- mice were studied at 7 and 14 months of age by standard scotopic and photopic electroretinography by comparison to control animals. Fundus images were obtained with a confocal SLO (Heidelberg Retina Angiograph). The integrity of the vascular system was investigated by means of fluo…

PRCD is concentrated at the base of photoreceptor outer segments and is involved in outer segment disc formation.

2019

Abstract Mutations of the PRCD gene are associated with rod-cone degeneration in both dogs and humans. Prcd is expressed in the mouse eye as early as embryonic day 14. In the adult mouse retina PRCD is expressed in the outer segments of both rod and cone photoreceptors. Immunoelectron microscopy revealed that PRCD is located at the outer segment rim, and that it is highly concentrated at the base of the outer segment. Prcd-knockout mice present with progressive retinal degeneration, starting at 20 weeks of age and onwards. This process is reflected by a significant and progressive reduction of both scotopic and photopic electroretinographic responses, and by thinning of the retina, and spec…