Visual acuity and the resolving power of the eye

Hartridge, H.

doi:10.1113/jphysiol.1922.sp002042

Cited by 66 publications

(32 citation statements)

References 2 publications

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“…Calling the intensity on the brighter row 100 per cent, that of the dimmer one is about 75 per cent, a difference of about 25 per cent. Calculations made by Hartridge (1922) show that in the image of a just resolvable single line the maximum intensity difference on two adjacent rows of cones is only about 10 per cent. The difference for the grating comes out to be over twice that value, indicating that perhaps the intensity difference in the image is not the limiting factor.…”

Section: Factors Limiting the Resolving Power Of The Eye For A Gratingmentioning

confidence: 99%

“…The distribution of light in an image of a grating corresponding to a visual acuity of 1.7 on the retina when chromatic aberration and diffraction are taken into account. curve computed by Hartridge (1922) and reproduced in Fig. 6A that gives the distribution of intensity across the retinal image of an edge when chromatic aberration and diffraction are taken into account, the distribution of intensity in the image of the grating corresponding to a visual acuity of 1.7 was computed.…”

Section: Factors Limiting the Resolving Power Of The Eye For A Gratingmentioning

confidence: 99%

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The Relation Between Visual Acuity and Illumination

Shlaer

1937

Journal of General Physiology

282

129

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1. An apparatus for measuring the visual acuity of the eye at different illuminations is described. The test object is continuously variable in size and is presented at a fixed distance from the eye in the center of a 30° field. Observation of the field is through an artificial pupil. The maximum intensity obtainable is more than enough to cover the complete physiological range for the eye with white light though only 110 watts are consumed by the source. Means for varying the intensity over a range of 1:1010 in small steps are provided. 2. The relation of visual acuity and illumination for two trained observers was measured, using two different types of test object, a broken circle and a grating. The measurements with both test objects show a break at a visual acuity of 0.16, all values below that being mediated by the rods and those above by the cones. The grating gives higher visual acuities at intensities less than about 30 photons and lower visual acuities above that. The maximum visual acuity attainable with the grating under the same conditions is about 30 per cent lower than that with the C. It is shown that the limiting factor in the resolution of the eye for the grating is the diameter of the pupil when it is less than 2.3 mm. and the size of the central cones when the pupil is larger than that. The value of the diameter of the cone derived on that basis from the visual acuity data agrees with that derived from direct cone count in a unit of area. 3. The data for the cones made with both test objects are adequately described by one and the same form of the stationary state equation derived by Hecht for the photoreceptor system. This fact, together with certain considerations about the difference in the nature of the two test objects with regard to the resolvable area, leads to the conclusion that detail perception is a function of a distance rather than an area. All the data for the rods can likewise be described by another variety of the same equation, although the data are too fragmentary to make the choice of the form as certain as might be desired.

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Section: Factors Limiting the Resolving Power Of The Eye For A Gratingmentioning

confidence: 99%

Section: Factors Limiting the Resolving Power Of The Eye For A Gratingmentioning

confidence: 99%

The Relation Between Visual Acuity and Illumination

Shlaer

1937

Journal of General Physiology

282

129

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“…What then does set the limit to the resolving power of the eye? Hartridge (1922) advocated intensity discrimination of the retina as the limiting factor in the resolving power of the eye. He argued that because of the chromatic aberration of the eye and of the diffraction of the light by the pupil, the image of small objects on the retina is very diffuse, and that unless the object is large enough to produce at least a 10 per cent reduction in intensity on a retinal element, it could not be resolved.…”

Section: Factors Limiting Maximum Visual Acuitymentioning

confidence: 99%

Visual Acuity and Illumination in Different Spectral Regions

Shlaer

Smith

Chase

1942

Journal of General Physiology

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The relation between visual acuity and illumination was measured in red and blue light, using a broken circle or C and a grating as test objects. The red light data fall on single continuous curves representing pure cone vision. The blue light data fall on two distinct curves with a transition at about 0.03 photons. Values below this intensity represent pure rod vision. Those immediately above represent the cooperative activity of rods and cones, and yield higher visual acuities than either. Pure cone vision in this intensity region is given by central fixation (C test object). All the rest of the values above this transition region represent pure cone vision. In blue light the rod data with the C lie about 1.5 log units lower on the intensity axis (cone scale) than they do in white light, while with the grating they lie about 1.0 log unit lower than in white light. Both the pure rod and cone data with the C test object are precisely described by one form of the stationary state equation. With the grating test object and a non-limiting pupil, the pure rod and cone data are described by another form of the same equation in which the curve is half as steep. The introduction of a small pupil, which limits maximum visual acuity, makes the relation between visual acuity and illumination appear steeper. Determinations of maximum visual acuities under a variety of conditions show that for the grating the pupil has to be larger, the longer the wavelength of the light, in order for the pupil not to be the limiting factor. Similar measurements with the C show that when intensity discrimination at the retina is experimentally made the limiting factor in resolution, visual acuity is improved by conditions designed to increase image contrast. However, intensity discrimination cannot be the limiting factor for the ordinary test object resolution because the conditions designed to improve image contrast do not improve maximum visual acuity, while those which reduce image contrast do not produce proportional reductions of visual acuity.

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“…10. Hartridge (1918Hartridge ( , 1922 was the first to estimate the light distribution in the retinal image of a sharp black/white edge, which was known to have a sigmoidal shape, with a scale along the axis of abscissae that enabled the comparison with retinal structures. In this figure, based on Hartridge's data, the width of a foveal cone would be 0.39 arcmin.…”

Section: Fig 7 Relationship Between Retinal Location Of a Peripheramentioning

confidence: 99%

“…Analogous to the interferencefringe method, it enabled the measurement of two-point resolution at the retina by a procedure largely detached from focus and aberration defects in the eye (which in any case could be neutralized if the method were coupled to an adaptive optics device). But as compared with the ordinary two-line resolution experiments of, e.g., Hartridge (1922), it permitted for the first time to explicitly decouple and separately control separation of the peaks and the contrast, in this case the depth of the intervening trough. This is the kind of procedure that is needed for the disambiguation of the retinal and central visual components in localized visual resolution thresholds.…”

Section: Changing the Amplitude Of The Wavefrontmentioning

confidence: 99%

Specifying and controlling the optical image on the human retina

Westheimer

2006

Progress in Retinal and Eye Research

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A review covering the trends that led to the current state of knowledge in the areas of:(a) schematic models of the eye, and the definition of the retinal image in terms of first-order optics; (b) the description of the actual image on the retina and methods for accessing and characterizing it; (c) available procedures for controlling the quality of the retinal image in defined situations; and (d) intra-receptoral optical effects that cause differences between the light distribution on the retinal surface and at the level of interaction with photopigment molecules.

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Visual acuity and the resolving power of the eye

Cited by 66 publications

References 2 publications

The Relation Between Visual Acuity and Illumination

The Relation Between Visual Acuity and Illumination

Visual Acuity and Illumination in Different Spectral Regions

Specifying and controlling the optical image on the human retina

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