Search results for "Dark Adaptation"
showing 10 items of 13 documents
Some physiological and psychological characteristics of myopic and non-myopic young men.
2009
As a part of a research project on the health and functional capacity of men at different ages a comparison of selected physiological and psychological characteristics of myopic and non-myopic 31–35 year-old men was made. The random sample studied consisted of 31 myopic and 100 non-myopic men. It was found that the body mass index and fat content were lower among the myopic than among the non-myopic. No significant differences were found in the elastic properties of skin, in blood pressure or in haematological assays studied between the groups. With respect to physical performance it was observed that the myopic had a higher aerobic capacity whereas there were no significant differences in …
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…
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…
The translocation of signaling molecules in dark adapting mammalian rod photoreceptor cells is dependent on the cytoskeleton.
2008
In vertebrate rod photoreceptor cells, arrestin and the visual G-protein transducin move between the inner segment and outer segment in response to changes in light. This stimulus dependent translocation of signalling molecules is assumed to participate in long term light adaptation of photoreceptors. So far the cellular basis for the transport mechanisms underlying these intracellular movements remains largely elusive. Here we investigated the dependency of these movements on actin filaments and the microtubule cytoskeleton of photoreceptor cells. Co-cultures of mouse retina and retinal pigment epithelium were incubated with drugs stabilizing and destabilizing the cytoskeleton. The actin a…
ApoB100,LDLR-/- mice exhibit reduced electroretinographic response and cholesteryl esters deposits in the retina
2008
International audience; PURPOSE. To evaluate the retinal phenotype of 7- and 14-month-old apoB100,LDLR–/– mice, a relevant animal model of lipid metabolism dysfunction. METHODS. Single-flash electroretinograms were obtained from 7- and 14-month-old apoB100,LDLR–/– and control mice fed a standard diet under both scotopic and photopic conditions. Visual cycle retinoids were analyzed in eyes from dark-adapted mice. Retinal and choroidal vascularization was evaluated with scanning laser ophthalmoscopy. Fatty acids were analyzed in the retina. Esterified and free cholesterol was detected in eye cryosections. RESULTS. Scotopic and photopic b-wave amplitudes were significantly reduced in apoB100,L…
Synaptic vesicle alterations in rod photoreceptors of synaptophysin-deficient mice.
2001
Abstract The abundance of the integral membrane protein synaptophysin in synaptic vesicles and its multiple possible functional contributions to transmitter exocytosis and synaptic vesicle formation stand in sharp contrast to the observed lack of defects in synaptophysin knockout mice. Assuming that deficiencies are compensated by the often coexpressed synaptophysin isoform synaptoporin, we now show that retinal rod photoreceptors, which do not synthesize synaptoporin either in wild-type or in knockout mice, are affected by the loss of synaptophysin. Multiple pale-appearing photoreceptors, as seen by electron microscopy, possess reduced cytoplasmic electron density, swollen mitochondria, an…
Mouse photoreceptor synaptic ribbons lose and regain material in response to illumination changes
2004
Abstract Chemical synapses equipped with ribbons are tonically active, high-output synapses. The ribbons may play a role in the trafficking of synaptic vesicles. Recent findings in retinal rod cells of BALB/c mice indicate that ribbons are large and smooth in the dark phase, and, due to the formation and release of protrusions, small during the light phase. As a consequence of these changes, ribbons may traffick fewer vesicles in the light than in the dark phases. The aim of the present study was to find out whether the above ribbon changes in this mouse strain are strictly illumination-dependent and which signalling processes may be involved. Here, we show that ribbons form protrusions and…
Electroretinographic response in WAG/Rij rats after low-intensity cyclic light exposure.
1993
In order to investigate the combined influence of age and light, the b-wave and oscillatory potentials (OPs) of the electroretinogram (ERG) were recorded in 1.5-, 7- and 12-month-old WAG/Rij rats, reared under homogenous low-intensity cyclic light exposure. Wistar albino rats of the same ages, reared under the same conditions, served as controls. The b-wave amplitude decreased, and its implicit time increased in the older age groups significantly more in WAG/Rij than in Wistar rats. Statistical analysis indicated that the b-wave amplitude is a more suitable parameter than implicit time in differentiating the ERG variations of one rat strain from the other. The added amplitude of the OPs als…
Visual Acuity and Contrast Sensitivity in Eyes Implanted with Aspheric and Spherical Intraocular Lenses
2009
Purpose To compare visual acuity and contrast sensitivity (CS) in eyes implanted with aspheric and spherical intraocular lenses (IOLs) after cataract surgery. Design Randomized, prospective study. Participants Five hundred twenty-four eyes from 262 cataract surgery patients implanted with 2 IOL models: the AcrySof IQ (262 eyes) and AcrySof SN60AT (262 eyes; Alcon Laboratories, Fort Worth, TX). Methods High-contrast photopic best-corrected distance visual acuity (BCVA) and CS under photopic (85 cd/m 2 ) and mesopic (6 cd/m 2 ) conditions were measured. Pupil diameter was analyzed for distance vision under both lighting conditions. Follow-up was carried out for 6 months in all patients. Main …
Separate processing of “color” and “brightness” in goldfish
1991
Spectral sensitivity was measured under different adaptation levels using a behavioral training technique in which the fish had to discriminate between a dark test field and a test field illuminated with monochromatic light. Depending on which of the two test fields was used as training test field, two functions were obtained which differ (1) in absolute sensitivity and (2) in shape. When trained on the dark test field, the fish seems to discriminate on the basis of a "color" cue, but it uses a "brightness" cue when trained on the illuminated test field. This was concluded from measurements of wavelength discrimination. Under low levels of the adaptation light (1.5 and 0.2 lx instead of 20 …