Biomedical subjects

C J Bassi

Publications and source records attributed to C J Bassi.

22 records · Page 2Linked to original sources

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↗

PubMed1986

Daily fluctuations in the detectability of dim lights by humans.

Several aspects of retinal physiology are known to vary on daily or circadian cycles, suggesting that certain aspects of visual function might also vary. We measured absolute threshold--the dimmest visual stimulus that can be reliably detected--in seven human observers at mid-day (1200-1400) and mid-night (0000-0200), by means of standard psychophysical techniques. Five of the subjects were slightly more sensitive at night: they could detect stimuli that were on the average 20% dimmer at night than during the day, and this difference was not due to changes in the criterion for detection. Three of four subjects whose thresholds were measured hourly while they remained otherwise in total darkness for greater than 24 hours showed changes in absolute visual threshold that correlated with hourly changes in body temperature. These results suggest that the ability to detect dim lights varies systematically with time of day in many human observers.

Body Temperature↗

PubMed1984

Light transmittance by goldfish eyes of different sizes.

The transmittance of the optic media was measured in eyes from small (4.3-5.5 cm standard body length), medium (8.3-10.0 cm) and large (14.2-17.5 cm) goldfish. Few differences were observed over this size range, despite a doubling in diameter of the globe. Relative transmittance was constant (+/- 0.04 log unit) between 450-700 nm, and absolute transmittance through the lens was approximately constant as well. Changes did occur, however, in the shorter wavelengths: at 350 nm, transmission of large eyes was diminished by about 0.40 log unit relative to small eyes.

Animals↗