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L Reymond

Publications and source records attributed to L Reymond.

7 recordsLinked to original sources
PubMed1987

Spatial visual acuity of the falcon, Falco berigora: a behavioural, optical and anatomical investigation.

In the brown falcon the relationship between acuity, as measured using a task designed to test minimum-separable acuity, and luminance was investigated as well as the possible determinants of that relationship. The maximum acuity was 73 c/deg and was found to be resistant to decreases in luminance. Maximum behavioural acuity corresponds closely with the maximum anatomical resolving power of the eye, though it is postulated that, in the first instance, acuity is optically constrained. The flat acuity-luminance function of the falcon results from adaptations which increase the optical sensitivity of the eye compared with the globose eye of strongly diurnal falconiformes.

Animals↗
PubMed1985

A further look at the binocular visual field of the pigeon (Columba livia).

The binocular visual field of the pigeon, measured ophthalmoscopically, is ovoid in shape. It is 114 degrees in vertical extent and centered and widest (37 degrees) about the eye-beak axis (i.e. the line passing through the straight edge of the beak and the midpoint of a line connecting the centres of the pupils). The area dorsalis projects 10 degrees-15 degrees below the eye-beak axis where the field is 35 degrees wide. The stereotyped peck response of the pigeon entails birds pausing twice. At the first fixation, the image of a grain is on the area dorsalis and at the final fixation the grain is centered within the widest part of the binocular field.

Animals↗
PubMed1985

Spatial visual acuity of the eagle Aquila audax: a behavioural, optical and anatomical investigation.

Behavioural acuity of the wedge-tailed eagle was determined across a range of luminance. Maximum acuity is between 132 and 143 c/deg and with decreasing luminance acuity declines sharply. The maximum anatomical resolving power of the eagle's deep fovea was calculated as 140 c/deg. This calculation was based upon ophthalmoscopic measurement of posterior nodal distance and estimates of photoreceptor spacings made from fixed foveal tissue and corrected for shrinkage. Maximum behavioural acuity and anatomical resolving power correspond closely and approach the highest frequency (157 c/deg) transmitted by the minimum pupil diameter of the eye. These findings are discussed with reference to current theories of visual functioning.

Animals↗
PubMed1984

Relation between simultaneous spatial-discrimination thresholds and luminance in man.

Simultaneous spatial-discrimination thresholds of 6 human subjects were measured at luminances between 0.2 and 2000 cd/m2. Subjects were tested on a forced-choice discrimination task which required them to distinguish between test and control stimuli of high contrast square-wave gratings with similar space-average luminances. The form of the function depicting the relationship between acuity and luminance is similar to that obtained by other researchers. The estimated maximum acuity of 72 cycles/degree (c/deg) is higher than the commonly cited value of 60 c/deg and this is probably due to the combination of the high stimulus luminance and the psychophysical technique employed in this study.

Adult↗