Some reflective properties of the tapetum lucidum of the cat's eye

Coles, Jonathan A.

doi:10.1113/jphysiol.1971.sp009331

Cited by 46 publications

(41 citation statements)

References 11 publications

(20 reference statements)

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“…The evidence cited above thus points to the fundus of the cat eye acting as a diffuse reflector although it retains polarization, much like an aluminized projection screen, as concluded for the human fundus by Campbell & Gubisch (1966). This is entirely compatible with the recent findings of Coles (1971). He showed that the cat fundus is 'composed of multilayer reflectors (domains) each being less than 6 ,um in diameter' (less than 0.03°r etinal subtense).…”

Section: Discussionsupporting

confidence: 77%

Image quality of the cat eye measured during retinal ganglion cell experiments

Bonds¹,

Enroth‐Cugell²,

Pinto³

1972

The Journal of Physiology

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SUMMARY1. The modulation transfer function (MTF) of the dioptrics of fifteen cat eyes was determined. The aerial image, formed by the eye of a standard object (a 0-5-1-0°annulus), was photographed. The transmission of the film negative was measured with a scanning microdensitometer to yield the light distribution within the aerial image. Correcting for the double passage, this experimentally determined light distribution and the known object light distribution were used to obtain the MTF, applying Fourier methods. Each MTF was used to calculate the light distribution within the retinal image of stimuli of various geometry used in experiments on retinal ganglion cells in the same eye.2. When the eye was equipped with an artificial pupil of the same size as that used in the neurophysiological experiments (4.0-4.8 mm diam.) the MTF had fallen to 0 5 at 2-43 c/deg. When the pupil was removed the MTF had fallen to 0 5 at a much lower spatial frequency (1.0 c/deg). This shows that even when one uses an artificial pupil too large to provide optimal image quality there is a vast improvement over using no pupil.3. These image quality measurements were prompted by the need to know the actual stimulus image in experiments on the functional organization of the receptive field, a need exemplified in this paper by a few specific physiological results. The full neurophysiological results appear in the next two papers.

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Section: Discussionsupporting

confidence: 77%

Image quality of the cat eye measured during retinal ganglion cell experiments

Bonds¹,

Enroth‐Cugell²,

Pinto³

1972

The Journal of Physiology

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“…This will produce numerous small reflections from the highly refractive material (Huxley 1968;Coles 1971). If the reflective material is randomly arranged, a diffuse reflectance will occur.…”

mentioning

confidence: 99%

“…If however the highly refractive structures are of a constant size and separated by a constant spacing, the small reflections will sum in a constructive fashion and a higher reflection will be achieved (Denton 1970(Denton , 1971Denton and Land 1971;Land 1972). For optimal constructive interference to occur, the optical thickness (actual thickness x refractive index) of the reflective material should be a quarter of the wavelength of the incident light, and the reflective units should be separated by the same distance (Coles 1971;Land 1972).…”

mentioning

confidence: 99%

Fine structure of the choroidal tapetum lucidum in the Port Jackson shark (Heterodontus phillipi)

Braekevelt

1994

Anat Embryol

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The choroidally located tapetum lucidum of the Port Jackson shark (Heterodontus phillipi) was examined by light and electron microscopy in light-adapted specimens. In this species the tapetum consists of a single layer of overlapping cells oriented at an angle of about 30 degrees to the incoming light and situated immediately external to the choriocapillaris. These tapetal cells alternate with and are separated from one another by melanocytes which extend beyond the tapetal cells to intervene between the tapetal cells and the incoming light. The tapetal cells and the melanocytes are flattened plate-like cells with their widest dimension facing the retina. Internally the tapetal cells display a peripherally located vesicular nucleus with most organelles in a paranuclear location. The bulk of a tapetal cell is packed with regularly spaced crystals reported to be guanine. The size and spacing of these reflective crystals is commensurate with the principles of constructive interference. In light adaptation, the melanosomes of the intervening melanocytes are widely dispersed and for the most part block the passage of light to the tapetal cells. Although dark-adapted specimens were not available, it seems reasonable to assume that in dark adaptation these melanosomes will retreat to unmask the tapetum and allow it to function as a known reflective layer.

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“…The reflective material varies in chemical composition between different species (Vukusic 2004; Vukusic and Sambles 2003; Ollivier et al 2004). For example, in animals such as cats and lemurs, riboflavin, the vitamin B 2 metabolite, was found to be the reflecting material, forming rodlet-shaped crystals which are grouped in bundles arranged in a very regular hexagonal lattice pattern (Braekevelt 1990a, b; Coles 1971; Pirie 1959). Riboflavin absorbs light at a low wavelength and fluoresces at 520 nm, which is approximately the maximum absorption of rhodospin (500 nm).…”

Section: Naturally Accruing Functional Metabolite Assembliesmentioning

confidence: 99%

Functional metabolite assemblies—a review

et al. 2018

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Metabolites are essential for the normal operation of cells and fulfill various physiological functions. It was recently found that in several metabolic disorders, the associated metabolites could self-assemble to generate amyloid-like structures, similar to canonical protein amyloids that have a role in neurodegenerative disorders. Yet, assemblies with typical amyloid characteristics are also known to have physiological function. In addition, many non-natural proteins and peptides presenting amyloidal properties have been used for the fabrication of functional nanomaterials. Similarly, functional metabolite assemblies are also found in nature, demonstrating various physiological roles. A notable example is the structural color formed by guanine crystals or fluorescent crystals in feline eyes responsible for enhanced night vision. Moreover, some metabolites have been used for the in vitro fabrication of functional materials, such as glycine crystals presenting remarkable piezoelectric properties or indigo films used to assemble organic semiconductive electronic devices. Therefore, we believe that the study of metabolite assemblies is not only important in order to understand their role in normal physiology and in pathology, but also paves a new route in exploring the fabrication of organic, bio-compatible materials.

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Some reflective properties of the tapetum lucidum of the cat's eye

Cited by 46 publications

References 11 publications

Image quality of the cat eye measured during retinal ganglion cell experiments

Image quality of the cat eye measured during retinal ganglion cell experiments

Fine structure of the choroidal tapetum lucidum in the Port Jackson shark (Heterodontus phillipi)

Functional metabolite assemblies—a review

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