Abstract

The electroretinogram (ERG) can be used to evaluate retinal processes. Electrophysiologic studies of lower-order species indicate that important color-vision coding occurs in the outer plexiform layer. In the monkey, a color-opponent R–G-cone difference signal has been reported in the intraretinally recorded foveal local ERG. We have searched for a similar signal in the corneal ERG. Steady-state ERG waveforms were elicited with long-wavelength, sinusoidally flickering stimuli that subtended either 45 or 17°. Waveform analyses reveal two primary components that are differentially affected by changes in illuminance, temporal frequency, and chromatic adaptation. Similarities between the foveal local ERG and corneal ERG data with regard to amplitude and phase indicate that one of these corneal ERG components is the R–G-cone difference signal. Our findings raise the possibility that the integrity of the outer plexiform layer can be monitored by means of the corneally recorded ERG and that distal-retinal color-coding phenomena can be studied in man.

© 1982 Optical Society of America

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References

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  1. C. R. Ingling, “The spectral sensitivity of the opponent-color channels,” Vision Res. 17, 1083–1089 (1977).
    [Crossref] [PubMed]
  2. R. M. Boynton, Human Color Vision (Holt, Rinehart and Winston, New York, 1979), pp. 207–229.
  3. D. van Norren and W. S. Baron, “Increment spectral sensitivities of the primate late receptor potential and b-wave,” Vision Res. 17, 807–810 (1977).
    [Crossref] [PubMed]
  4. W. S. Baron, “Cone difference signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. 19, 1442–1448 (1980).
    [PubMed]
  5. W. S. Baron, “R–G opponent color signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. Suppl. 20, 53 (1981).
  6. W. S. Baron and R. M. Boynton, “The primate foveal local electroretinogram: an indicator of photoreceptor activity,” Vision Res. 14, 495–501 (1974).
    [Crossref] [PubMed]
  7. W. S. Baron and R. M. Boynton, “Response of primate cones to sinusoidally flickering homochromatic stimuli,” J. Physiol. 246, 311–331 (1975).
  8. D. van Norren and P. Padmos, “Human and macaque blue cones studied with electroretinography,” Vision Res. 13, 1241–1254 (1973).
    [Crossref]
  9. J. C. Armington, The Electroretinogram (Academic, New York, 1974), pp. 339–379.
  10. M. Korth and S. Sokol, “Electroretinographic and psychophysical measures of cone spectral mechanisms using the two-color threshold technique,” Vision Res. 20, 205–212 (1980).
    [Crossref]
  11. L. A. Riggs and B. R. Wooten, “Electrical measures and psychophysical data on human vision,” in Handbook of Sensory Physiology, D. Jameson and L. M. Hurvich, eds. (Springer-Verlag, New York, 1972), Sec. VII/4.
    [Crossref]
  12. L. A. Riggs, E. P. Johnson, and A. M. L. Schick, “Electrical responses of the human eye to changes in wavelength of the stimulating light,” J. Opt. Soc. Am. 56, 1621–1627 (1966).
    [Crossref]
  13. A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
    [PubMed]
  14. L. A. Riggs, R. N. Berry, and M. A. Wayner, “A comparison of electrical and psychophysical determinations of the spectral sensitivity of the human eye,” J. Opt. Soc. Am. 39, 427–436 (1949).
    [Crossref] [PubMed]
  15. E. D. Adrian, “The electrical response of the human eye,” J. Physiol. 104, 84–104 (1945).
  16. R. L. DeValois, “Behavioral and electrophysiological studies of primate vision,” in Contributions to Sensory Physiology, W. D. Neff, ed. (Academic, New York, 1965), Vol. 1, pp. 137–178.
  17. R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
    [Crossref]
  18. R. L. DeValois, H. C. Morgan, and D. M. Snodderly, “Psychophysical studies of monkey vision—III. Spatial luminance contrast sensitivity tests of macaque and human observers,” Vision Res. 14, 75–82 (1974).
    [Crossref]
  19. A. Monjan, “Chromatic adaptation in the macaque,” J. Comp. Physiol. 62, 76–83 (1966).
  20. H. G. Sperling and R. S. Harwerth, “Red–green cone interactions in the increment threshold spectral sensitivity of primates,” Science 172, 180–184 (1971).
    [Crossref] [PubMed]
  21. W. S. Baron, “Maxwellian view stimulator for electrophysiological or psychophysical work,” Appl. Opt. 12, 2560–2562 (1973).
    [Crossref] [PubMed]
  22. G. Westheimer, “The Maxwellian view,” Vision Res. 6, 669–682 (1966).
    [Crossref] [PubMed]
  23. W. S. Baron, “Chromatic adaptation and flicker-frequency effects on primate R–G-cone difference signal,” J. Opt. Soc. Am. 72, 1008–1013 (1982).
    [Crossref] [PubMed]
  24. D. Barber, D. J. Cotterill, and J. R. Larke, “A new contact lens electrode,” in Documenta Ophthalmologica Proceedings Series, T. Lawwill, ed. (Dr. W. Junk bv, The Hague, 1977), Vol. 13, pp. 385–392.
  25. W. S. Baron, R. M. Boynton, and D. van Norren, “Primate cone sensitivity to flicker during light and dark adaptation as indicated by the foveal local electroretinogram,” Vision Res. 19, 109–116 (1979).
    [Crossref] [PubMed]
  26. W. S. Baron, “Electroretinogram a-wave slope as a measure of response amplitude,” J. Opt. Soc. Am. 72, 296–298 (1982).
    [Crossref]
  27. J. J. Vos and P. L. Walraven, “On the derivation of the foveal receptor primaries,” Vision Res. 11, 799–818 (1971).
    [Crossref] [PubMed]

1982 (2)

1981 (2)

W. S. Baron, “R–G opponent color signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. Suppl. 20, 53 (1981).

A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
[PubMed]

1980 (2)

W. S. Baron, “Cone difference signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. 19, 1442–1448 (1980).
[PubMed]

M. Korth and S. Sokol, “Electroretinographic and psychophysical measures of cone spectral mechanisms using the two-color threshold technique,” Vision Res. 20, 205–212 (1980).
[Crossref]

1979 (1)

W. S. Baron, R. M. Boynton, and D. van Norren, “Primate cone sensitivity to flicker during light and dark adaptation as indicated by the foveal local electroretinogram,” Vision Res. 19, 109–116 (1979).
[Crossref] [PubMed]

1977 (2)

C. R. Ingling, “The spectral sensitivity of the opponent-color channels,” Vision Res. 17, 1083–1089 (1977).
[Crossref] [PubMed]

D. van Norren and W. S. Baron, “Increment spectral sensitivities of the primate late receptor potential and b-wave,” Vision Res. 17, 807–810 (1977).
[Crossref] [PubMed]

1975 (1)

W. S. Baron and R. M. Boynton, “Response of primate cones to sinusoidally flickering homochromatic stimuli,” J. Physiol. 246, 311–331 (1975).

1974 (3)

W. S. Baron and R. M. Boynton, “The primate foveal local electroretinogram: an indicator of photoreceptor activity,” Vision Res. 14, 495–501 (1974).
[Crossref] [PubMed]

R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
[Crossref]

R. L. DeValois, H. C. Morgan, and D. M. Snodderly, “Psychophysical studies of monkey vision—III. Spatial luminance contrast sensitivity tests of macaque and human observers,” Vision Res. 14, 75–82 (1974).
[Crossref]

1973 (2)

D. van Norren and P. Padmos, “Human and macaque blue cones studied with electroretinography,” Vision Res. 13, 1241–1254 (1973).
[Crossref]

W. S. Baron, “Maxwellian view stimulator for electrophysiological or psychophysical work,” Appl. Opt. 12, 2560–2562 (1973).
[Crossref] [PubMed]

1971 (2)

H. G. Sperling and R. S. Harwerth, “Red–green cone interactions in the increment threshold spectral sensitivity of primates,” Science 172, 180–184 (1971).
[Crossref] [PubMed]

J. J. Vos and P. L. Walraven, “On the derivation of the foveal receptor primaries,” Vision Res. 11, 799–818 (1971).
[Crossref] [PubMed]

1966 (3)

G. Westheimer, “The Maxwellian view,” Vision Res. 6, 669–682 (1966).
[Crossref] [PubMed]

A. Monjan, “Chromatic adaptation in the macaque,” J. Comp. Physiol. 62, 76–83 (1966).

L. A. Riggs, E. P. Johnson, and A. M. L. Schick, “Electrical responses of the human eye to changes in wavelength of the stimulating light,” J. Opt. Soc. Am. 56, 1621–1627 (1966).
[Crossref]

1949 (1)

1945 (1)

E. D. Adrian, “The electrical response of the human eye,” J. Physiol. 104, 84–104 (1945).

Adrian, E. D.

E. D. Adrian, “The electrical response of the human eye,” J. Physiol. 104, 84–104 (1945).

Armington, J. C.

J. C. Armington, The Electroretinogram (Academic, New York, 1974), pp. 339–379.

Barber, D.

D. Barber, D. J. Cotterill, and J. R. Larke, “A new contact lens electrode,” in Documenta Ophthalmologica Proceedings Series, T. Lawwill, ed. (Dr. W. Junk bv, The Hague, 1977), Vol. 13, pp. 385–392.

Baron, W. S.

W. S. Baron, “Electroretinogram a-wave slope as a measure of response amplitude,” J. Opt. Soc. Am. 72, 296–298 (1982).
[Crossref]

W. S. Baron, “Chromatic adaptation and flicker-frequency effects on primate R–G-cone difference signal,” J. Opt. Soc. Am. 72, 1008–1013 (1982).
[Crossref] [PubMed]

W. S. Baron, “R–G opponent color signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. Suppl. 20, 53 (1981).

W. S. Baron, “Cone difference signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. 19, 1442–1448 (1980).
[PubMed]

W. S. Baron, R. M. Boynton, and D. van Norren, “Primate cone sensitivity to flicker during light and dark adaptation as indicated by the foveal local electroretinogram,” Vision Res. 19, 109–116 (1979).
[Crossref] [PubMed]

D. van Norren and W. S. Baron, “Increment spectral sensitivities of the primate late receptor potential and b-wave,” Vision Res. 17, 807–810 (1977).
[Crossref] [PubMed]

W. S. Baron and R. M. Boynton, “Response of primate cones to sinusoidally flickering homochromatic stimuli,” J. Physiol. 246, 311–331 (1975).

W. S. Baron and R. M. Boynton, “The primate foveal local electroretinogram: an indicator of photoreceptor activity,” Vision Res. 14, 495–501 (1974).
[Crossref] [PubMed]

W. S. Baron, “Maxwellian view stimulator for electrophysiological or psychophysical work,” Appl. Opt. 12, 2560–2562 (1973).
[Crossref] [PubMed]

Berry, R. N.

Boynton, R. M.

W. S. Baron, R. M. Boynton, and D. van Norren, “Primate cone sensitivity to flicker during light and dark adaptation as indicated by the foveal local electroretinogram,” Vision Res. 19, 109–116 (1979).
[Crossref] [PubMed]

W. S. Baron and R. M. Boynton, “Response of primate cones to sinusoidally flickering homochromatic stimuli,” J. Physiol. 246, 311–331 (1975).

W. S. Baron and R. M. Boynton, “The primate foveal local electroretinogram: an indicator of photoreceptor activity,” Vision Res. 14, 495–501 (1974).
[Crossref] [PubMed]

R. M. Boynton, Human Color Vision (Holt, Rinehart and Winston, New York, 1979), pp. 207–229.

Cotterill, D. J.

D. Barber, D. J. Cotterill, and J. R. Larke, “A new contact lens electrode,” in Documenta Ophthalmologica Proceedings Series, T. Lawwill, ed. (Dr. W. Junk bv, The Hague, 1977), Vol. 13, pp. 385–392.

DeValois, R. L.

R. L. DeValois, H. C. Morgan, and D. M. Snodderly, “Psychophysical studies of monkey vision—III. Spatial luminance contrast sensitivity tests of macaque and human observers,” Vision Res. 14, 75–82 (1974).
[Crossref]

R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
[Crossref]

R. L. DeValois, “Behavioral and electrophysiological studies of primate vision,” in Contributions to Sensory Physiology, W. D. Neff, ed. (Academic, New York, 1965), Vol. 1, pp. 137–178.

Fiorentini, A.

A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
[PubMed]

Harwerth, R. S.

H. G. Sperling and R. S. Harwerth, “Red–green cone interactions in the increment threshold spectral sensitivity of primates,” Science 172, 180–184 (1971).
[Crossref] [PubMed]

Hull, E. M.

R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
[Crossref]

Ingling, C. R.

C. R. Ingling, “The spectral sensitivity of the opponent-color channels,” Vision Res. 17, 1083–1089 (1977).
[Crossref] [PubMed]

Johnson, E. P.

Korth, M.

M. Korth and S. Sokol, “Electroretinographic and psychophysical measures of cone spectral mechanisms using the two-color threshold technique,” Vision Res. 20, 205–212 (1980).
[Crossref]

Larke, J. R.

D. Barber, D. J. Cotterill, and J. R. Larke, “A new contact lens electrode,” in Documenta Ophthalmologica Proceedings Series, T. Lawwill, ed. (Dr. W. Junk bv, The Hague, 1977), Vol. 13, pp. 385–392.

Maffei, L.

A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
[PubMed]

Mead, W. R.

R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
[Crossref]

Monjan, A.

A. Monjan, “Chromatic adaptation in the macaque,” J. Comp. Physiol. 62, 76–83 (1966).

Morgan, H. C.

R. L. DeValois, H. C. Morgan, and D. M. Snodderly, “Psychophysical studies of monkey vision—III. Spatial luminance contrast sensitivity tests of macaque and human observers,” Vision Res. 14, 75–82 (1974).
[Crossref]

R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
[Crossref]

Padmos, P.

D. van Norren and P. Padmos, “Human and macaque blue cones studied with electroretinography,” Vision Res. 13, 1241–1254 (1973).
[Crossref]

Pirchio, M.

A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
[PubMed]

Polson, M. C.

R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
[Crossref]

Porciatti, V.

A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
[PubMed]

Riggs, L. A.

Schick, A. M. L.

Snodderly, D. M.

R. L. DeValois, H. C. Morgan, and D. M. Snodderly, “Psychophysical studies of monkey vision—III. Spatial luminance contrast sensitivity tests of macaque and human observers,” Vision Res. 14, 75–82 (1974).
[Crossref]

Sokol, S.

M. Korth and S. Sokol, “Electroretinographic and psychophysical measures of cone spectral mechanisms using the two-color threshold technique,” Vision Res. 20, 205–212 (1980).
[Crossref]

Sperling, H. G.

H. G. Sperling and R. S. Harwerth, “Red–green cone interactions in the increment threshold spectral sensitivity of primates,” Science 172, 180–184 (1971).
[Crossref] [PubMed]

Spinelli, D.

A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
[PubMed]

van Norren, D.

W. S. Baron, R. M. Boynton, and D. van Norren, “Primate cone sensitivity to flicker during light and dark adaptation as indicated by the foveal local electroretinogram,” Vision Res. 19, 109–116 (1979).
[Crossref] [PubMed]

D. van Norren and W. S. Baron, “Increment spectral sensitivities of the primate late receptor potential and b-wave,” Vision Res. 17, 807–810 (1977).
[Crossref] [PubMed]

D. van Norren and P. Padmos, “Human and macaque blue cones studied with electroretinography,” Vision Res. 13, 1241–1254 (1973).
[Crossref]

Vos, J. J.

J. J. Vos and P. L. Walraven, “On the derivation of the foveal receptor primaries,” Vision Res. 11, 799–818 (1971).
[Crossref] [PubMed]

Walraven, P. L.

J. J. Vos and P. L. Walraven, “On the derivation of the foveal receptor primaries,” Vision Res. 11, 799–818 (1971).
[Crossref] [PubMed]

Wayner, M. A.

Westheimer, G.

G. Westheimer, “The Maxwellian view,” Vision Res. 6, 669–682 (1966).
[Crossref] [PubMed]

Wooten, B. R.

L. A. Riggs and B. R. Wooten, “Electrical measures and psychophysical data on human vision,” in Handbook of Sensory Physiology, D. Jameson and L. M. Hurvich, eds. (Springer-Verlag, New York, 1972), Sec. VII/4.
[Crossref]

Appl. Opt. (1)

Invest. Ophthalmol. Vis. Sci. (2)

W. S. Baron, “Cone difference signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. 19, 1442–1448 (1980).
[PubMed]

A. Fiorentini, L. Maffei, M. Pirchio, D. Spinelli, and V. Porciatti, “The ERG in response to alternating gratings in patients with diseases of the peripheral visual pathway,” Invest. Ophthalmol. Vis. Sci. 21, 490–493 (1981).
[PubMed]

Invest. Ophthalmol. Vis. Sci. Suppl. (1)

W. S. Baron, “R–G opponent color signal in foveal local electroretinogram of primate,” Invest. Ophthalmol. Vis. Sci. Suppl. 20, 53 (1981).

J. Comp. Physiol. (1)

A. Monjan, “Chromatic adaptation in the macaque,” J. Comp. Physiol. 62, 76–83 (1966).

J. Opt. Soc. Am. (4)

J. Physiol. (2)

E. D. Adrian, “The electrical response of the human eye,” J. Physiol. 104, 84–104 (1945).

W. S. Baron and R. M. Boynton, “Response of primate cones to sinusoidally flickering homochromatic stimuli,” J. Physiol. 246, 311–331 (1975).

Science (1)

H. G. Sperling and R. S. Harwerth, “Red–green cone interactions in the increment threshold spectral sensitivity of primates,” Science 172, 180–184 (1971).
[Crossref] [PubMed]

Vision Res. (10)

G. Westheimer, “The Maxwellian view,” Vision Res. 6, 669–682 (1966).
[Crossref] [PubMed]

J. J. Vos and P. L. Walraven, “On the derivation of the foveal receptor primaries,” Vision Res. 11, 799–818 (1971).
[Crossref] [PubMed]

W. S. Baron, R. M. Boynton, and D. van Norren, “Primate cone sensitivity to flicker during light and dark adaptation as indicated by the foveal local electroretinogram,” Vision Res. 19, 109–116 (1979).
[Crossref] [PubMed]

D. van Norren and P. Padmos, “Human and macaque blue cones studied with electroretinography,” Vision Res. 13, 1241–1254 (1973).
[Crossref]

M. Korth and S. Sokol, “Electroretinographic and psychophysical measures of cone spectral mechanisms using the two-color threshold technique,” Vision Res. 20, 205–212 (1980).
[Crossref]

W. S. Baron and R. M. Boynton, “The primate foveal local electroretinogram: an indicator of photoreceptor activity,” Vision Res. 14, 495–501 (1974).
[Crossref] [PubMed]

C. R. Ingling, “The spectral sensitivity of the opponent-color channels,” Vision Res. 17, 1083–1089 (1977).
[Crossref] [PubMed]

D. van Norren and W. S. Baron, “Increment spectral sensitivities of the primate late receptor potential and b-wave,” Vision Res. 17, 807–810 (1977).
[Crossref] [PubMed]

R. L. DeValois, H. C. Morgan, M. C. Polson, W. R. Mead, and E. M. Hull, “Psychophysical studies of monkey vision—I. Macaque luminosity and colour vision tests,” Vision Res. 14, 53–68 (1974).
[Crossref]

R. L. DeValois, H. C. Morgan, and D. M. Snodderly, “Psychophysical studies of monkey vision—III. Spatial luminance contrast sensitivity tests of macaque and human observers,” Vision Res. 14, 75–82 (1974).
[Crossref]

Other (5)

R. L. DeValois, “Behavioral and electrophysiological studies of primate vision,” in Contributions to Sensory Physiology, W. D. Neff, ed. (Academic, New York, 1965), Vol. 1, pp. 137–178.

R. M. Boynton, Human Color Vision (Holt, Rinehart and Winston, New York, 1979), pp. 207–229.

L. A. Riggs and B. R. Wooten, “Electrical measures and psychophysical data on human vision,” in Handbook of Sensory Physiology, D. Jameson and L. M. Hurvich, eds. (Springer-Verlag, New York, 1972), Sec. VII/4.
[Crossref]

J. C. Armington, The Electroretinogram (Academic, New York, 1974), pp. 339–379.

D. Barber, D. J. Cotterill, and J. R. Larke, “A new contact lens electrode,” in Documenta Ophthalmologica Proceedings Series, T. Lawwill, ed. (Dr. W. Junk bv, The Hague, 1977), Vol. 13, pp. 385–392.

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Figures (6)

Fig. 1
Fig. 1

Foveal LERG and corneal ERG waveforms obtained in response to 660-nm, 8-Hz, flickering stimuli of similar illuminance. Both responses have been positioned horizontally to reflect accurately the phase shift between each response and the stimulus. In this and all subsequent figures, the foveal LERG and corneal ERG components being compared have opposite polarities because of the location of the recording electrodes. Upward-pointing arrows denote the ERG rho component or the troughs of the LERG LRP. Downward-pointing arrows denote the peaks of the positive ERG or the negative LERG R–G-cone difference signals.

Fig. 2
Fig. 2

Corneal ERG waveforms in response to long-wavelength, 5-Hz, sinusoidal flicker over a range of illuminances. Test illuminance appears to the right of each waveform, voltage per calibration mark to the left. The test stimulus consisted of Kodak W29-filtered tungsten illumination (which matches a 632-nm light for a color-normal human observer). The amplitude and phase of the corneal-positive component (downward-pointing arrows) relative to the rho component (upward-pointing arrows) varies with illuminance in a manner similar to that observed for the foveal LERG.4

Fig. 3
Fig. 3

Corneal ERG responses to 670-nm, 15-td sinusoidal flicker at various frequencies. For each waveform, the flicker frequency is denoted at the right and the stimulus is depicted underneath. The vertical calibration marks represent 3.9 μV. Between 4 and 8 Hz, the amplitude of the corneal-positive R–G-cone difference component (downward-pointing arrows) relative to the rho component (upward-pointing arrows) changes little, if at all. At 10 Hz a small increase, and at 12 Hz a larger increase, in the relative amplitude of the R–G-cone difference signal is observed. The total phase shift for this corneal-positive component between 4 and 12 Hz is −206°.

Fig. 4
Fig. 4

Phase shift as a function of temporal frequency for the LERG and ERG components. The phase shifts of the foveal LERG LRP23 and of the ERG rho components are displayed in the upper figure; the phase shifts of the foveal LERG and of the ERG R–G-cone difference signals are displayed in the lower figure. Note that the LERG test illuminance is intermediate to the ERG test illuminances. Based on five replications, an error bar, denoting ±1 standard deviation, is shown for the 8-Hz, 151-td ERG R–G-cone difference signal. The phase-versus-frequency function for this corneal-positive component has a slope similar to that for the foveal LERG R–G-cone difference signal. The 30–35° frequency-independent phase shift is not significant, given intersession variability.25 Frequency is plotted on a parabolic scale.

Fig. 5
Fig. 5

Corneal ERG responses obtained on 660- and 480-nm backgrounds with a 660-nm, 120-td, 8-Hz, sinusoidally flickering test stimulus. For the top set of waveforms, background illuminances are denoted to the right; for the bottom set, times after extinction of the background are denoted to the right. Voltage calibrations, listed to the left, refer to the calibration mark at the bottom. (a) As the 660-nm background illuminance is increased, the relative amplitude of the corneal-positive component (downward-pointing arrows) diminishes, and its phase decreases substantially. On extinction of the 660-nm, 575-td background, this positive-going component is absent at first and then recovers slowly during the next 3–5 min. (b) As the 480-nm background illuminance is increased, the relative amplitude of the corneal-positive component diminishes but its phase remains constant. On extinction of the 480-nm, 550-td background, this positive-going component reappears within 5 sec.

Fig. 6
Fig. 6

Corneal ERG responses obtained on a 500-nm background with a 660-nm, 120-td, 8-Hz, sinusoidally flickering test stimulus. Background illuminances, recovery times, and calibrations are denoted as in the previous figure. As the 500-nm background illuminance is increased, the relative amplitude of the corneal-positive component (downward-pointing arrows) decreases but with little or no change in its phase. When the 1622-td, 500-nm background is shut off, this positive-going R–G-cone difference signal is prominent within seconds.