The directional sensitivity of retinal rods.

Alpern, Mathew; Ching, Cheng-Chao; Kono, Kenji

doi:10.1113/jphysiol.1983.sp014911

Cited by 33 publications

(31 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The p coefficients (eqn 1 ) of the best-fitting parabolas drawn through the points are 0017 for P. S., 0g007 for S. B. and 0 I for the trichromat. These are also in good agreement with, if not a little flatter than, those of the parafoveal rods of normal observers (Crawford, 1937;Stiles, 1939;Flamant & Stiles, 1948;Van Loo & Enoch, 1975;Alpern et al 1983) and the rods of the typical complete achromat .…”

Section: Increment Threshold and Directional Sensitivity Measurementssupporting

confidence: 73%

The photoreceptors in atypical achromatopsia.

Hess

Mullen

Sharpe

et al. 1989

The Journal of Physiology

View full text Add to dashboard Cite

SUMMARY1. The receptoral mechanisms underlying the vision of two atypical achromats of the complete variety were studied with standard psychophysical procedures.2. Under scotopic conditions the spectral sensitivity of each achromat was well described by the CIE (Commission Internationale de l'Eclairage) scotopic sensitivity function and the recovery of sensitivity after a retinal bleach showed characteristic duplex behaviour with the time constant of recovery of the slower phase matching that of normal rod vision for both foveal and peripheral stimulation.3. Their spectral sensitivity was measured under conditions of chromatic adaptation in order to reveal any residual middle or long wavelength cone activity. Only one photopic spectral response was found and this was adequately described by the spectral sensitivity function of Stiles' H3 mechanism of normal vision.4. Increment threshold measurements as a function of background intensity revealed a double-branched function in the fovea. The lower branch was found to have the spectral sensitivity of the rods; the upper branch that of Stiles' n3 mechanism. Stiles-Crawford measurements of directional sensitivity confirmed that the branch with the rhodopsin action spectrum had the directional sensitivity of rods and that the branch with the action spectrum of rI3 had the directional sensitivity of cones.5. These was no evidence for hue discrimination under photopic conditions. Regions of apparently normal performance on hue discrimination tests on more careful examination could be explained by luminosity judgements mediated by short wavelength-absorbing receptors.6. We reject the notion of there being rhodopsin-filled cones in the fovea of these subjects. The foveal and peripheral vision of each of these achromats can be adequately described in terms of the participation of only two types of receptor, namely normally functional rods under scotopic conditions and normally functioning short wavelength-absorbing cones under photopic conditions. They are therefore functional blue mono-cone monochromats, an explanation which was originally proposed by Blackwell & Blackwell (1957) over thirty years ago.

show abstract

Section: Increment Threshold and Directional Sensitivity Measurementssupporting

confidence: 73%

The photoreceptors in atypical achromatopsia.

Hess

Mullen

Sharpe

et al. 1989

The Journal of Physiology

View full text Add to dashboard Cite

show abstract

“…This agrees with psychophysical observations [32][33][34]. A narrow outer segment has reduced directionality which accounts for the fact that rods are less directional sensitive than cones [35]. For N = 1000: ρ = 0.044/mm 2 for d = 1.0 µm (for simplicity not shown here) and ρ = 0.0763/mm 2 for d = 2.0 µm.…”

Section: Arrayed Aperture Model Of Outer-segment Pigment Discssupporting

confidence: 78%

Directional sensitivity of the retina: A layered scattering model of outer-segment photoreceptor pigments

Vohnsen

2014

Biomed. Opt. Express

View full text Add to dashboard Cite

Photoreceptor outer segments have been modeled as stacked arrays of discs or membrane infoldings containing visual pigments with light-induced dipole moments. Waveguiding has been excluded so fields diffract beyond the physical boundaries of each photoreceptor cell. Optical reciprocity is used to argue for identical radiative and light gathering properties of pigments to model vision. Two models have been introduced: one a macroscopic model that assumes a uniform pigment density across each layer and another microscopic model that includes the spatial location of each pigment molecule within each layer. Both models result in highly similar directionality at the pupil plane which proves to be insensitive to the exact details of the outer-segment packing being predominantly determined by the first and last contributing layers as set by the fraction of bleaching. The versatility of the microscopic model is demonstrated with an array of examples that includes the Stiles-Crawford effect, visibility of a focused beam of light and the role of defocus.

show abstract

“…This is in part because its magnitude is associated with the shape of the photoreceptors: directional sensitivity is most pronounced for the squat parafoveal cones (Westheimer, 1967), slightly smaller for the elongated (rod-like) central foveal cones (Westheimer, 1967) and considerably smaller for the rods (Crawford, 1937;Stiles, 1939;Flamant & Stiles, 1948;Van Loo & Enoch, 1975;Alpern, Ching & Kitahara, 1983). In fact, differences between the directional sensitivities of the rods and cones are so profound that the SCE1 can be used effectilely to differentiate between the photopic and scotopic systems (Donner & Rushton, 1959;Fuortes, Gunkel & Rushton, 1961;Alpern et al 1983). …”

Section: Methodsmentioning

confidence: 99%

“…No comparable corrections for losses resulting from reflection at the cornea were made because the angles of incidence of the rays traversing the different parts of the pupil were nearly the same. Following Weale (1961), Enoch & Stiles (1961), Vos & van Os (1975) and Alpern et al (1983), it was assumed that the losses in the lens arise from a single pigment of the same concentration uniformly distributed throughout the lens. The absolute absorption values of the most central part of the lens were estimated by the procedure outlined in van Norren & Vos (1974).…”

Section: Data Treatmentmentioning

confidence: 99%

The directional sensitivity of the photoreceptors in the human achromat.

Nordby

Sharpe

1988

The Journal of Physiology

View full text Add to dashboard Cite

SUMMARY1. The anatomical nature of the retinal photoreceptors in a typical, complete achromat was investigated by measuring their directional sensitivity.2. A small (05 deg), brief (94 ms) test flash was placed at threshold by varying either its intensity (indirect method) or the intensity of a large (5 deg) adapting field (direct method). The dependent variable was the intensity of light required for the detection threshold as a function of the position of entry in the pupil. An infra-red viewing system was used to monitor the achromat's pupil and eye position.3. At both scotopic and mesopic adapting field luminances, the complete achromat's receptors displayed only a small directional sensitivity effect. The effect was not wavelength dependent and could be attributed solely to the rods.4. The results are consistent with other psychophysical evidence indicating that the complete achromat's retinae lack the post-receptoral function of the cone photoreceptors. Therefore they do not confirm previous reports that complete achromats have a second, high-intensity type of photoreceptor.

show abstract

The directional sensitivity of retinal rods.

Cited by 33 publications

References 16 publications

The photoreceptors in atypical achromatopsia.

The photoreceptors in atypical achromatopsia.

Directional sensitivity of the retina: A layered scattering model of outer-segment photoreceptor pigments

The directional sensitivity of the photoreceptors in the human achromat.

Contact Info

Product

Resources

About