Telephoto lens system of falconiform eyes

  title={Telephoto lens system of falconiform eyes},
  author={Allan W. Snyder and William H. Miller},
VISUAL ACUITY in falconiform birds has been shown to be higher than man. For instance, vultures with eyes similar in size to those of man have a grating detectability of about twice the spatial frequency of man1. This is consistent with measured image quality in an eagle eye similar in size to the human eye2. Recently a falcon (Falco sparverius) has been shown to have a grating detectability 2.6 greater than that of man3. Although the image quality of these falconiform eyes is at least twice as… 
Falcon visual sensitivity to grating contrast
It is reported that the cut-off frequency (a measure of visual acuity) is twice the expected value and is the same for kestrel and human eyes.
Müller cell alignment in bird fovea: possible role in vision.
This work describes how the endfeet of Müller cells line the walls of the foveal pit in the Pied Flycatcher, and how the Müller cell body extends its processes towards individual cones, forming machinery that could allow for light transfer from the pit wall to the photoreceptor layer alongside the pit.
Analysis and implementation of the foveated vision of the raptor eye
A foveated optical system has non-uniform resolution across its field of view. Typically, the resolution of such a lens is peaked in the center region of field of view, such as in the human eye. In
Optical Function of the Convexiclivate Fovea with Particular Regard to Notosudid Deep-sea Teleosts
The optical function of the deep symmetrical convexiclivate purecone fovea of deep-sea notosudids has been examined within the limits of geometrical optics, assuming, inter alia, that the full lens
Ocular Optical Filtering
The purpose of this chapter is to review the effects of optical filtering on eye function emphasizing such unresolved issues, for example, as the function of optical filters in the eyes of animals with high (suprahuman) visual acuity.
Some observations on the visual optics of kingfishers (Aves, Coraciformes, Alcedinidae)
The relationship between angle α and angle ϑ suggests one strategy which could be used by kingfishers to maximize their visual capabilities when hunting from a perch above the substrate.
Form and Function in the Optical Structure of Bird Eyes
The anatomy of bird eyes has often been described in near eulogistic terms. Polyak (1957, p. 852), for example, reported that the eyes of swallows (Hirundo rustica) exhibit “extraordinary
Problems of deep foveas.
  • N. A. Locket
  • Environmental Science
    Australian and New Zealand journal of ophthalmology
  • 1992
Deep or convexiclivate foveas occur in some birds, including raptors, some lizards and certain deep-sea fishes. Theories on their function are reviewed. Common to raptor and deep-sea fish foveas is a
The principal eyes of a jumping spider have a telephoto component
This work has found that in Portia fimbriata (Doleschall) and some other species, this pit has a refracting interface that increases the focal length of the eye beyond its axial length, thereby magnifying the retinal image and increasing visual resolving power above that possible with only a corneal lens.
Spatial Vision in Birds: Anatomical investigation of spatial resolving power
This thesis presents four studies on different aspects of spatial vision in parrots, procellariiform seabirds and birds of prey, and indicates, that single cones, not double cones, mediate the high spatial resolution in the raptor fovea.


The deep fovea as a focus indicator
It is shown how the deep convexiclivate fovea can act as a sensitive, directional focus indicator over a small area of image.
A comparative study of deep avian foveas.
Comparisons of foveal cell densities across species showed an increase in the average number of cells/visual degree2 with increasing eye size; similarly, an increase occurred in receptor nuclei relative to ganglion cell density; thus, smaller eyes showed a coarser retinal grain and a lower 'concidence ratio' of receptors toganglion cells than was found in the largest eyes.
The Theory of the Fovea
The results strongly suggest that the convexiclivate fovea is a device for achieving improved fixation and improved sensitivity to movement of objects in the visual field at some sacrifice of acuity.
Falcon visual acuity.
This behavioral test of falcon acuity supports the common belief that Falconiformès have superb vision, although Falcon acuity was much more dependent on lumanance, declining sharply with decreases in luminance.
  • R. Sidman
  • Biology
    The Journal of biophysical and biochemical cytology
  • 1957
Fragments of freshly obtained retinas of several vertebrate species were studied by refractometry, with reference to the structure of the rods and cones. The findings allowed a reassessment of
  • T. Henderson
  • Medicine
    The British journal of ophthalmology
  • 1943
The list of conditio'ns which Major Wright indicates may be included in Parinaud's oculoglandular syndrome lends support to his view that this syndrome is liberal in its clinical confines; it would seem that such a label can' add little information to a particular case.
An Eagle's Eye: Quality of the Retinal Image
The optical quality of a living eagle's eye was determined by an ophthalmoscopic method. The performance of the eye was substantially better than that reported for humans, but did not confirm some of
Coupled-Mode Theory for Optical Fibers
A set of coupled-mode equations is derived to describe mode propagation in uniform and slightly nonuniform cylindrical optical-fiber systems. The coupling between fibers of an array made up of n
Replamineform: A New Process for Preparing Porous Ceramic, Metal, and Polymer Prosthetic Materials
By means of this technique, prosthetic materials having a controlled pore microstructure for optimum strength and tissue ingrowth may be obtained.