PubMed Health⌕ Search

Biomedical subjects

C J Bassi

Publications and source records attributed to C J Bassi.

At least 19 recordsLinked to original sources
PubMed1995

Review of the visual system in Parkinson's disease.

In an era when the prevalence of Parkinson's disease (PD) is increasing because our population is aging, eye care professionals need to become aware of the visual changes experienced by PD patients. This paper reviews the visual pathophysiology of PD and the results of the lack of dopamine on the retina and visual cortex. It also discusses the impact of PD on the oculomotor system and the visual sensory pathways with the consequent effects on reading, balance, and driving abilities of PD patients. Further research on the visual system and PD may provide improved means for early diagnostic testing as well as the possibility of vision rehabilitation for treatment of visual performance impairments.

Dopamine↗
PubMed1995

Clinical evaluation of five portable tonometers.

BACKGROUND: Intraocular pressure (IOP) measurements obtained with five commercially available portable tonometers (Keeler Pulsair 2000, Tomey Pro-Ton, Tono-Pen XL, Perkins, and Shiotz) were compared to IOPs measured with a Goldmann tonometer in order to predict whether instrument accuracy justified substitution of a portable instrument for the Goldmann in all or specific circumstances. METHODS: A total of 31 patients (59 eyes) were assessed. The order of techniques was random except that in each case Goldmann tonometry was performed first and Shiotz tonometry was performed last. Examiners were masked to all other IOP measurements. Correlation and regression analyses were used to predict Goldmann IOP from the other portable tonometer readings. In addition, the difference in pressure readings was compared to mean pressure readings. RESULTS: Comparisons of means, correlations, regression equations, and box plots of difference scores were performed to determine which techniques were more accurate. The results varied slightly depending on the method used. All IOPs obtained with portable tonometers showed significant correlation and regression equations compared to the Goldmann IOPs. The correlation ranged from (r = 0.75) for the Keeler Pulsair to (r = 0.66) for the Schiotz. Three tonometers (Tono-Pen, Schiotz, and the Pro-Ton) showed a small significant underestimation of the Goldmann IOPs. CONCLUSIONS: All portable tonometers were able to accurately predict Goldmann IOPs. While three of the tonometers were found to underestimate Goldmann IOP on average, these results can be corrected by either adding the underestimation or by using the best fitting regression equation.

Evaluation Studies as Topic↗
PubMed1993

Comparison of the Farnsworth-Munsell 100-Hue, the Farnsworth D-15, and the L'Anthony D-15 desaturated color tests.

OBJECTIVE: The Farnsworth-Munsell 100-Hue, the Farnsworth D-15, and the L'Anthony D-15 desaturated color tests were administered to patients with glaucoma to determine whether the D-15 or D-15 desaturated color tests could be used to predict performance on the 100-Hue test in clinical populations. METHODS: The three color tests were administered to 35 patients with glaucoma. The results were analyzed using the method of Vingrys and King-Smith that calculates an angle (type of color loss) score, S-index (measure of the randomness of cap arrangement), and a C-index (a measure of the severity of color loss) based on the cap arrangement. RESULTS: The 100-Hue error score was significantly related to the D-15 and D-15 desaturated C-indexes. Furthermore, the 100-Hue S-index could be predicted from the D-15 or D-15 desaturated S-indexes. The 100-Hue angle could not be predicted from the D-15 or D-15 desaturated color tests. CONCLUSIONS: The D-15 desaturated color test (which requires significantly less time to administer) may be used to assess the severity of color vision deficit in some patient populations.

Color Perception Tests↗
PubMed1993

Vision in aging and dementia.

PURPOSE: This study was designed to determine the extent of visual deficits in Alzheimer's disease (AD) patients relative to normal aging changes and to patients with other types of dementia. METHODS: Four groups of subjects were tested: patients with probable AD (N = 10), patients with other dementias (N = 10), age-matched controls (N = 11), and young controls (N = 10). Color vision was assessed with the L'Anthony D-15 desaturated color test, contrast sensitivity with the Pelli-Robson chart, and stereoacuity with the RAN-DOT test. RESULTS: Visual changes were found in AD patients that can be accounted for by age-related deficits (color vision), deficits found in other types of dementia (stereoacuity), and deficits specific to AD (low spatial frequency contrast sensitivity). CONCLUSION: We conclude that AD patients show a variety of visual deficits. With our tests, only deficits in contrast sensitivity were specific to AD.

Adult↗
PubMed1991

Binocular visual impairment in glaucoma.

Monocular and binocular vision was assessed in patients with glaucoma (n = 21), in patients with ocular hypertension (n = 20), and in age-matched visual control subjects (n = 20) using three tests: color vision with the Lanthony Desaturated D-15 test, low spatial frequency contrast sensitivity with the Pelli-Robson chart, and stereoacuity with the RANDOT test. No significant differences were found among the groups in the severity or type of color vision loss. Monocular contrast sensitivity testing showed considerable overlap among groups but a significant loss of contrast sensitivity in the glaucoma patients relative to ocular hypertensives and control subjects. Binocular testing also showed a significant loss of contrast sensitivity in the glaucoma patients compared with both the ocular hypertensives and the control subjects. Stereoacuity also was significantly impaired in the glaucoma patients. These results indicate that two tests of binocular function, stereoacuity and binocular contrast sensitivity testing, may have utility in identifying early glaucomatous damage.

Aged↗
PubMed1991

Green-sensitive cone photoreceptors are selectively labeled by Procion yellow dye in goldfish retina.

Selective labeling of intravitreal Procion yellow dye by presumed blue-sensitive cone photoreceptors has been demonstrated in primate retina. To determine whether Procion yellow is selective for this cone type in an unrelated vertebrate species, labeling by this dye was studied in goldfish retina, where cone pigment type can be directly inferred from photoreceptor morphology. At low vitreal concentrations of the dye (less than 0.4%), only cone outer segments were labeled. At vitreal concentrations of 0.4-0.5%, the inner segments of short-double cones and a subset of long single cones (presumed green-sensitive cones) were selectively stained. At still higher vitreal concentrations (0.6-0.7%), the inner segments of short-single cones and miniature short-single cones (presumed blue-sensitive cones) showed evidence of Procion label, but were not as heavily labeled. The inner segments of long-double cones and a subset of long-single cones (presumed red-sensitive cones) did not label at any of these concentrations. These results show that Procion yellow is not a selective marker for blue-sensitive cones in the goldfish retina. In addition, stained rod and cone nuclei were observed at each dye concentration, including those concentrations at which no inner segments were labeled.

Animals↗
PubMed1990

Optic nerve damage in Alzheimer's disease.

Optic nerves from ten patients with Alzheimer's disease were histologically examined and compared with those from age-matched controls. Specific and nonspecific measures of degeneration were noted in eight of ten Alzheimer's disease optic nerves; no degeneration was noted in any of the controls. Results of histologic examination of the retinas of one eye of three Alzheimer's disease patients also showed degeneration of retinal ganglion cells and their axons in the nerve fiber layer. Morphometric analysis suggested that in many cases of Alzheimer's disease, the optic nerve showed predominant loss of the largest class of retinal ganglion cells (M-cells) that contribute large caliber fibers to the optic nerve. The M-cell system is known to mediate specific visual functions, and selective involvement of the M-cell population leads to clinically measurable neuro-ophthalmic and psychophysical impairments in many Alzheimer's disease patients.

Aged↗
PubMed1990

Clinical implications of parallel visual pathways.

Visual information travels from the retina to visual cortical areas along at least two parallel pathways. In this paper, anatomical and physiological evidence is presented to demonstrate the existence of, and trace these two pathways throughout the visual systems of the cat, primate, and human. Physiological and behavioral experiments are discussed which establish that these two pathways are differentially sensitive to stimuli that vary in spatial and temporal frequency. One pathway (M-pathway) is more sensitive to coarse visual form that is modulated or moving at fast rates, whereas the other pathway (P-pathway) is more sensitive to spatial detail that is stationary or moving at slow rates. This difference between the M- and P-pathways is related to some spatial and temporal effects observed in humans. Furthermore, evidence is presented that certain diseases selectively comprise the functioning of M- or P-pathways (i.e., glaucoma, Alzheimer's disease, and anisometropic amblyopia), and some of the spatial and temporal deficits observed in these patients are presented within the context of the dysfunction of the M- or P-pathway.

Animals↗
PubMed1990

Shedding of rod outer segments is light-driven in goldfish.

Rod outer segment (ROS) shedding in goldfish was quantified by measuring the number of phagosomes in the retinas of goldfish that were maintained under natural or artificial cyclic light, constant light, or constant dark conditions. Fish maintained in cyclic light, whether natural or artificial, had robust daily rhythms of ROS shedding. The ROS tips were shed primarily during the light phase of the cycle, and maximum shedding occurred 2-4 hours into the light period. Fish maintained for 1, 3, or 7 days in constant light or constant dark had no daily rhythms in ROS shedding. In these fish, ROSs lengthened, on average, 2.3 microns/day in constant light and 1.5 microns/day in constant dark. After 3 days in constant light, shedding was induced by placing fish in darkness for 2 hours, then returning them to light. Placing fish in darkness for 0.5 hours did not induce shedding, nor did placing them in darkness for 3 hours without returning them to light. ROS shedding thus appears to be goldfish is completely dependent on changes in ambient illumination; no circadian or endogenous components were found. Previous observations of circadian changes in behavioral visual sensitivity therefore cannot be due to endogenous changes in ROS length.

Animals↗
PubMed1990

Rod outer segment length and visual sensitivity.

Detection threshold for the rod system was measured psychophysically in adult goldfish before and after exposure to constant illumination of 340 lux (91 microW/cm2) for 7 days. As shown in the previous paper, rod outer segment (ROS) length increases an average of 60% under these conditions. The present work shows that visual sensitivity also increases, in approximate proportion to the additional optical density predicted by the longer ROSs. These results are the first to show that exposure to constant light can enhance visual sensitivity. They imply further that detection threshold is related to ROS length. Apparently, the photopigment in the ROS tips that is normally shed on a daily basis retains its photon-catching ability.

Animals↗
PubMed1988

Visual detection by the rod system in goldfish of different sizes.

New rods are continually generated and inserted across the entire differentiated retina in juvenile and adult goldfish; no other retinal cells share this characteristic. How does the preferential addition of rods affect visual function? To examine the relation between continued rod addition and visual sensitivity, we measured absolute threshold in fish of different sizes. Twenty-nine fish were trained in a classical conditioning paradigm, and psychometric functions were obtained for each of them for detection of a 532 nm light 5 sec in duration, 140 deg in angular subtense, presented while the fish was fully dark adapted. We found that absolute threshold (expressed in terms of retinal photon density) was lower in larger fish, but by a very small amount; on average, large fish (15.4 +/- 0.5 cm standard body length) were 1.45 times more sensitive than small fish (4.3 +/- 0.3 cm). Morphometric analysis showed that the planimetric density of rods in goldfish retina increases at a similar rate between small and large fish, while the density of retinal ganglion cells declines between small and large fish (by a factor of 3.8). The ratio of rods to ganglion cells (a possible indicator of neural convergence) increased, but by a factor that is too large to reconcile with the psychophysical results (5.3 x). The results suggest that absolute visual threshold in the goldfish is closely related to the density of rods in the retina.

Animals↗
PubMed1988

Lighting conditions and retinal development in goldfish: photoreceptor number and structure.

The retinas of 63 goldfish were examined after varying durations of exposure to one of three environmental lighting conditions beginning before hatching: constant light (340 lux), cyclic light (12 hr 320 lux, 12 hr dark) and constant dark. Up to 8 months, no effects of constant light or dark on photoreceptor numbers or structure were apparent. Densities of rod and cone nuclei were normal and all retinal layers appeared normal by light microscopy. Exposure to constant light for 12 months or longer resulted in a reduction in rod density by 37%. Cone numbers were unaffected by constant light, even with exposures of 3 yr, and rod and cone outer segments were normal in length at 11-20 months under all environmental conditions. Due to poor survival, only one animal was available for quantitative examination from the group reared in constant dark 12 months or longer. Photoreceptor size and number in this retina were similar to those in the constant light condition. The results suggest that the formation and maturation of rods and cones in goldfish retina is unaffected by rearing in constant light. However, long-term exposure (greater than or equal to 12 months) may disrupt maintenance of differentiated rods.

Aging↗
PubMed1988

Lighting conditions and retinal development in goldfish: absolute visual sensitivity.

Goldfish (Carassius auratus) were reared from hatching in constant light (340 lux), cyclic light (12 hr 320 lux, 12 hr dark) or constant dark. Absolute visual threshold was determined psychophysically in animals that still responded to visual stimuli after 1-3 years of exposure, by means of a classically conditioned respiration suppression technique wherein animals were presented with different intensities of large diffuse flashes of monochromatic light. Fish reared in constant light and fish reared in cyclic light responded reliably to stimuli above threshold, but fish reared in constant light were on average 0.58 log unit less sensitive at 532 nm, near the peak of the rod action spectrum. Two of the four fish reared in darkness did not respond to the stimuli, and thus could not be conditioned, and another fish reared in darkness responded only occasionally; threshold could not be measured in these three fish. The one fish reared in darkness that responded consistently enough to be conditioned was more than 5 log units less sensitive than normally reared fish on the first day of testing, and became progressively less sensitive over the next 2 days. Rearing under constant dark or constant light had no obvious effect on spectral sensitivity at absolute threshold. The effect of rearing in constant light on absolute threshold correlates with morphological changes in rod density, but the effect of rearing in constant darkness does not.

Animal Husbandry↗
PubMed1987

Assessment of visual impairment in patients with Alzheimer's disease.

We examined five patients with Alzheimer's disease who complained of poor vision. Two patients had mild Alzheimer's disease; they complained of problems with reading and of "bumping into things," yet both had normal visual acuities. One patient with moderate Alzheimer's disease had abnormal eye movements, visual-evoked potentials, and contrast sensitivity. The other two patients had severe Alzheimer's disease. Despite difficulties in performing the examination, we were able to see moderate impairments in visual acuity and visual fields, as well as marked dyschromatopsia, severe deficits in contrast sensitivity, and markedly abnormal eye movements and visual-evoked potentials.

Aged↗
PubMed1987

Circadian rhythm in goldfish visual sensitivity.

To determine whether rod-mediated vision in goldfish is regulated by a circadian clock, absolute threshold was measured psychophysically in animals maintained in constant darkness. Responses were recorded approximately every 4 hr to a diffuse 532 nm stimulus, 5 sec in duration, with no background light present. Visual threshold tended to be lowest at the time of transition from light to dark, as experienced by the fish before it was placed in constant darkness. Threshold tended to be highest at the time of transition from dark to light. The average peak-to-trough fluctuation for five fish was 0.5 log unit in amplitude, and its period was about 24 hr. The results show that the rhythm in visual threshold can still be detected after 7 days of darkness, and that it can be entrained to a new light-dark cycle. These properties are characteristic of regulation by a circadian oscillator.

Animals↗