Abstract

Detecting the position of the gap in a Landolt C is adversely affected by black bars placed tangential to the C and at a certain distance from it. The maximum bar separation affording interaction is proportional to the minimum angle of resolution, even in cases of amblyopia where resolution is presumably not limited by optical spread of the image. It is suggested that this contour interaction is related to the size of the receptive field (and hence to the resolving capacity) associated with the retinal region used to fixate the target.

© 1963 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. W. Korte, Z. Psychol. 93, 17 (1923).
  2. R. H. Davage and F. C. Summer, J. Psychol. 30, 191 (1950).
    [Crossref]
  3. P. Müller, Ophthalmologica (Basel) 121, 143 (1951).
    [Crossref]
  4. H. Goldmann, discussion in Ref. 3, p. 148.
  5. A. Franceschetti, discussion in Ref. 3, p. 149.
  6. J. H. Prince, Am. J. Optom. and Arch. Am. Acad. Optom. 34, 581 (1957).
    [Crossref]
  7. E. Averbach and A. S. Coriell, Bell System Tech. J. 40, 309 (1961).
    [Crossref]
  8. Amblyopia (Greek, “blunt sight”) is a loose term applied to cases of low visual acuity not explainable by obvious structural or optical abnormality. It is usually unilateral often being associated with a large difference in refractive error between the two eyes or with a deviation (heterotropia) of the amblyopic eye. Monocular fixation with an amblyopic eye is generally unsteady and often nonfoveal.
  9. An equation which permits calculation of visual efficiency (E) from the minimum angle of resolution (A) is log E=2.0777−0.0777A.
  10. There is no evidence that the basis of amblyopia is unsharp retinal imagery. A small artificial pupil does not improve the acuity of an amblyopic eye. Amblyopes are often quite insistent that imagery with the affected eye is not “blurred” in comparison with the normal eye. Placing an added lens of+0.25 or+0.50 D. before an amblyopic eye will usually evoke a response of “blur.”
  11. F. W. Weymouth, Am. J. Ophthalmol. 46, 102 (1958), No. 1, Pt. II
    [PubMed]
  12. D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 154, 572 (1960).
  13. T. N. Wiesel, J. Physiol. (London) 153, 583 (1960).
  14. D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 160, 106 (1962).
  15. M. C. Flom and F. W. Weymouth, Arch. Ophthalmol. 66, 260 (1961).
    [Crossref] [PubMed]
  16. J. Lorenz, Arch. Ges. Psychol. 24, 313 (1912).
  17. R. Pauli, Z. Biol. 81, 93 (1924).
  18. J. Nachmias, J. Opt. Soc. Am. 51, 761 (1961).
    [Crossref] [PubMed]
  19. K. Gaarder, Science 132, 471 (1960).
    [Crossref] [PubMed]
  20. J. Stuart and H. M. Burian, Am. J. Ophthalmol. 53, 471 (1962).
    [PubMed]

1962 (2)

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 160, 106 (1962).

J. Stuart and H. M. Burian, Am. J. Ophthalmol. 53, 471 (1962).
[PubMed]

1961 (3)

M. C. Flom and F. W. Weymouth, Arch. Ophthalmol. 66, 260 (1961).
[Crossref] [PubMed]

J. Nachmias, J. Opt. Soc. Am. 51, 761 (1961).
[Crossref] [PubMed]

E. Averbach and A. S. Coriell, Bell System Tech. J. 40, 309 (1961).
[Crossref]

1960 (3)

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 154, 572 (1960).

T. N. Wiesel, J. Physiol. (London) 153, 583 (1960).

K. Gaarder, Science 132, 471 (1960).
[Crossref] [PubMed]

1958 (1)

F. W. Weymouth, Am. J. Ophthalmol. 46, 102 (1958), No. 1, Pt. II
[PubMed]

1957 (1)

J. H. Prince, Am. J. Optom. and Arch. Am. Acad. Optom. 34, 581 (1957).
[Crossref]

1951 (1)

P. Müller, Ophthalmologica (Basel) 121, 143 (1951).
[Crossref]

1950 (1)

R. H. Davage and F. C. Summer, J. Psychol. 30, 191 (1950).
[Crossref]

1924 (1)

R. Pauli, Z. Biol. 81, 93 (1924).

1923 (1)

W. Korte, Z. Psychol. 93, 17 (1923).

1912 (1)

J. Lorenz, Arch. Ges. Psychol. 24, 313 (1912).

Averbach, E.

E. Averbach and A. S. Coriell, Bell System Tech. J. 40, 309 (1961).
[Crossref]

Burian, H. M.

J. Stuart and H. M. Burian, Am. J. Ophthalmol. 53, 471 (1962).
[PubMed]

Coriell, A. S.

E. Averbach and A. S. Coriell, Bell System Tech. J. 40, 309 (1961).
[Crossref]

Davage, R. H.

R. H. Davage and F. C. Summer, J. Psychol. 30, 191 (1950).
[Crossref]

Flom, M. C.

M. C. Flom and F. W. Weymouth, Arch. Ophthalmol. 66, 260 (1961).
[Crossref] [PubMed]

Franceschetti, A.

A. Franceschetti, discussion in Ref. 3, p. 149.

Gaarder, K.

K. Gaarder, Science 132, 471 (1960).
[Crossref] [PubMed]

Goldmann, H.

H. Goldmann, discussion in Ref. 3, p. 148.

Hubel, D. H.

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 160, 106 (1962).

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 154, 572 (1960).

Korte, W.

W. Korte, Z. Psychol. 93, 17 (1923).

Lorenz, J.

J. Lorenz, Arch. Ges. Psychol. 24, 313 (1912).

Müller, P.

P. Müller, Ophthalmologica (Basel) 121, 143 (1951).
[Crossref]

Nachmias, J.

Pauli, R.

R. Pauli, Z. Biol. 81, 93 (1924).

Prince, J. H.

J. H. Prince, Am. J. Optom. and Arch. Am. Acad. Optom. 34, 581 (1957).
[Crossref]

Stuart, J.

J. Stuart and H. M. Burian, Am. J. Ophthalmol. 53, 471 (1962).
[PubMed]

Summer, F. C.

R. H. Davage and F. C. Summer, J. Psychol. 30, 191 (1950).
[Crossref]

Weymouth, F. W.

M. C. Flom and F. W. Weymouth, Arch. Ophthalmol. 66, 260 (1961).
[Crossref] [PubMed]

F. W. Weymouth, Am. J. Ophthalmol. 46, 102 (1958), No. 1, Pt. II
[PubMed]

Wiesel, T. N.

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 160, 106 (1962).

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 154, 572 (1960).

T. N. Wiesel, J. Physiol. (London) 153, 583 (1960).

Am. J. Ophthalmol. (2)

F. W. Weymouth, Am. J. Ophthalmol. 46, 102 (1958), No. 1, Pt. II
[PubMed]

J. Stuart and H. M. Burian, Am. J. Ophthalmol. 53, 471 (1962).
[PubMed]

Am. J. Optom. and Arch. Am. Acad. Optom. (1)

J. H. Prince, Am. J. Optom. and Arch. Am. Acad. Optom. 34, 581 (1957).
[Crossref]

Arch. Ges. Psychol. (1)

J. Lorenz, Arch. Ges. Psychol. 24, 313 (1912).

Arch. Ophthalmol. (1)

M. C. Flom and F. W. Weymouth, Arch. Ophthalmol. 66, 260 (1961).
[Crossref] [PubMed]

Bell System Tech. J. (1)

E. Averbach and A. S. Coriell, Bell System Tech. J. 40, 309 (1961).
[Crossref]

J. Opt. Soc. Am. (1)

J. Physiol. (London) (3)

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 154, 572 (1960).

T. N. Wiesel, J. Physiol. (London) 153, 583 (1960).

D. H. Hubel and T. N. Wiesel, J. Physiol. (London) 160, 106 (1962).

J. Psychol. (1)

R. H. Davage and F. C. Summer, J. Psychol. 30, 191 (1950).
[Crossref]

Ophthalmologica (Basel) (1)

P. Müller, Ophthalmologica (Basel) 121, 143 (1951).
[Crossref]

Science (1)

K. Gaarder, Science 132, 471 (1960).
[Crossref] [PubMed]

Z. Biol. (1)

R. Pauli, Z. Biol. 81, 93 (1924).

Z. Psychol. (1)

W. Korte, Z. Psychol. 93, 17 (1923).

Other (5)

H. Goldmann, discussion in Ref. 3, p. 148.

A. Franceschetti, discussion in Ref. 3, p. 149.

Amblyopia (Greek, “blunt sight”) is a loose term applied to cases of low visual acuity not explainable by obvious structural or optical abnormality. It is usually unilateral often being associated with a large difference in refractive error between the two eyes or with a deviation (heterotropia) of the amblyopic eye. Monocular fixation with an amblyopic eye is generally unsteady and often nonfoveal.

An equation which permits calculation of visual efficiency (E) from the minimum angle of resolution (A) is log E=2.0777−0.0777A.

There is no evidence that the basis of amblyopia is unsharp retinal imagery. A small artificial pupil does not improve the acuity of an amblyopic eye. Amblyopes are often quite insistent that imagery with the affected eye is not “blurred” in comparison with the normal eye. Placing an added lens of+0.25 or+0.50 D. before an amblyopic eye will usually evoke a response of “blur.”

Cited By

OSA participates in Crossref's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (7)

Fig. 1
Fig. 1

For a 22-mm diam Landolt C placed at the viewing distances indicated, the percent of correct answers are plotted as a function of the angular separation, α, of 4 surrounding bars for one amblyopic (broken line) and two normal eyes (solid line). Each circle represents 144 presentations for subject D.B. and about 50 for R.A. Percentages have been adjusted for 1 chance in 4 of guessing correctly. The 20-ft Snellen notation corresponding to the “interaction-free” situation (no bars) is indicated for each eye. The maximum bar separation affording interaction is specified by Point x, the bar separation producing greatest interaction is designated as Point y.

Fig. 2
Fig. 2

Relation between the maximum bar separation affording interaction and the minimum angle of resolution (“interaction-free”) for seven normal eyes (circles) and four amblyopic eyes (triangles). The regression line passes near the origin and has a slope of 6.7 indicating that the ratio between these two variables is approximately constant over the range studied.

Fig. 3
Fig. 3

The probability of seeing data of Fig. 1 plotted as a function of the linear separation d between C and bars. Unlike Fig. 1, the viewing distance is disregarded in this plot and the bar separations are thus represented as multiples of the gap width. The arrow specifies the maximum bar separation affording interaction. The similarity between the curves for the amblyopic and normal eyes is notable in this plot.

Fig. 4
Fig. 4

Same plot as Fig. 3 for an additional five normal (solid line) and three amblyopic (broken line) eyes. Each circle represents the percent of correct answers for 32 or more presentations of the four-position Landolt C; percentages have been adjusted for one chance in four of guessing correctly.

Fig. 5
Fig. 5

Psychometric function for two subjects showing the comparative impairment of resolution performance (corrected for guessing) for three targets that provide different degrees of interaction. The reciprocal of the acuity notations (abscissa) represents the width of the gap in the C in min arc. Probit method was used to fit curves to datum points, each representing about 40 presentations of the C. The 80% threshold is shown on the curves for the normal (solid lines) and amblyopic (broken lines) eyes.

Fig. 6
Fig. 6

Relationship between 50% threshold acuity and the separation d between C and bars. Acuity given both in Snell–Sterling visual efficiency units and in Snellen units.

Fig. 7
Fig. 7

The “S” target. The eight Landolt C’s are the test letters and the 17 E’s provide additional interaction. Interletter spacing equals one letter diameter.

Tables (3)

Tables Icon

Table I For 16 interaction targets, the separation between the Landolt C (diam=2.2 cm, gap=0.44 cm) and 4 surrounding bars (length=2.2 cm, width=0.44 cm).

Tables Icon

Table II Subjects’ clinical information.

Tables Icon

Table III Relation between “interaction-free” minimum angle of resolution (MAR) for a 4-position Landolt C and the critical separation of 4 surrounding bars. The greatest bar separation affording interaction is expressed in min arc (Point x) and in multiples of MAR. The bar separation for greatest interaction is given in min arc (Point y), in multiples of MAR, and in relation to Point x. Both eyes of amblyopic subjects were tested; the amblyopic eye is italicized.