Arthur Bradley
Indiana University School of Optometry; 800 E. Atwater Ave.; Bloomington, IN 47405; USA
Phone: 812-855-2465
Fax: 812-855-7045
E-mail: bradley@indiana.edu
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Arthur Bradley, PhD
Professor of Optometry

PhD 1983
(University of California, Berkeley)

Dr. Arthur Bradley has been a member of the IU School of Optometry faculty since 1985. He has played an active role in teaching visual perception, binocular vision, and optics in the O.D. program. Dr. Bradley has taught extensively in the graduate program (visual optics, spatial vision, non-invasive visual assessment, visual neurophysiology), and he maintains an active psychophysics and optics research laboratory.

bulletResearch
  bulletTeaching
  • V664 Monocular Visual Function
  • V666 Binocular Vision

  bulletRepresentative Publications
  bulletUseful Links

Research

(1) Effect of the Eye's Optical Aberrations on Visual Perception:

We tend to think that optical aberrations, and defocus simply produce image blurring. We also tend to think that image degradation is a one-dimensional process (images are either better or worse). We have been investigating the often complex perceptual consequences of optical defocus and aberrations (see publications on optics). For example, the familiar oscillating MTF seen in defocused optical systems can be visualized by comparing the contrast changes and phase shifts in the star-burst patterns below. We have recently been able to show that it is the phase shifts and not the amplitude changes that limit defocused visual acuity for hyperopes but not for myopes. Examples of a Ð1 diopter defocused letter E is shown below, the top E was imaged in front of the retina (myopia), while the bottom E was imaged behind (hyperopia/presbyopia). Notice that the phase reversals produced by the blur completely change the appearance of the hyperopic E.

starburst/E images

In addition to examining the impact of phase shifts caused by blur, we have also studied the image doubling effects of blur. For example, hyperopic defocus with astigmatism and spherical aberration will create monocular diplopia as shown in the images below. Many subjects report this diplopia.

diplopia images

We have also examined the role of color and wavelength on visual perception of location and depth, and we have examined the feasibility of correcting for aberrations to improve retinal image quality and thus vision.

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(2) Neural Sampling:

The continuous optical image created at the retina is immediately packaged into discrete samples of neural activity by the photoreceptors, and the sampling process continues on throughout the visual system. We have been studying the perceptual consequences of this sampling process. In order to visualize the sampling process we must input stimuli that exceed the sampling array's maximum frequency that can be coded accurately (the Nyquist frequency). Beyond this frequency, signals are misrepresented and seen as aliases. For example, high spatial frequencies in peripheral vision, stimuli can appear to have the wrong orientation, to move in the wrong direction, and to have a spatial structure unlike that of the stimulus. The specific nature of these aliases provides insight into the underlying biology of the sampling array. An example showing the inaccurate output of an undersampled image is shown schematically below. We are particularly interested in extending the approaches we developed for the retina into the visual cortex. Our hypothesis is that the misperceptions of human amblyopes (see two examples below) reflect cortical undersampling.

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Representative Publications

Visual Optics

  1. Howarth, P.A. and Bradley, A. (1986) The longitudinal aberration of the human eye and its correction. Vision Res., 26, 361-366.

  2. Applegate, R.A., Adams, A.J., Bradley, A., and Elsner, A. (1986). Total occlusion does not disrupt photoreceptor alignment. Invest. Ophthalmol. and Visual Sc., 27, 441-443.

  3. Howarth, P.A. and Bradley, A. (1986) The longitudinal chromatic aberration of the eye. Proceedings of the Northeastern State Symposium on theoretical and clinical optometry. pp124-137.

  4. Thibos, L.N., Bradley, A., Still, D.L. and Henderson, P. (1987) Do white-light interferometers bypass the eye's optics? Clinical implications of decentering the optical beam in the pupil. Optical Society of America Technical digest: Topical meeting on noninvasive assessment of the visual system. 80-82.

  5. Thibos, T., Bradley, A. and Still, D. (1989) Visual acuity measured with clinical maxwellian view systems: effects of beam entry location. Opt. Soc. Am. Digest: Topical Meeting on Non-invasive Assessment of the visual system, 7, 94-97.

  6. Howarth, P.A., Zhang, X., Bradley, A.B., Still, D.L. and Thibos, L.N. (1988) Does the chromatic aberration of the eye vary with age? J. Opt. Soc. Amer. A 5, 2087-2092.

  7. Thibos, L.N., Bradley, A., Still, D.L., Zhang, X. and Howarth, P.A. (1990) Theory and measurement of ocular chromatic aberration. Vision Res. 30, 33-49.

  8. Geddes, L., Patel, B., and Bradley, A. (1990) Comparison of Snellen and Interferometric visual acuity in an aging non-cataractous population. Optom. Vis. Sci., 67, 361-365.

  9. Bradley, A., Thibos, L.N. and Still, D. L. (1990). Visual acuity measured with clinical Maxwellian-view systems: effects of beam entry location. Optom. Vis. Sci., 67, 811-817.

  10. Bradley, A., Zhang, X. and Thibos, L.N. (1991). Achromatizing the human eye. Optom. Vis. Sci. 68, 608-616.

  11. Thibos, L.N., Bradley, A. and Still, D. (1991). Interferometric measurement of visual acuity and the effect of ocular chromatic aberration. Appl. Opt. 30, 2079-2087.

  12. Thibos, L.N., Bradley, A. and Zhang, X. (1991). The effect of ocular chromatic aberration on monocular visual performance. Optom. Vis. Sci. 68, 599-607.

  13. Zhang, X., Bradley, A. and Thibos, L.N. (1991). Achromatizing the human eye: the problem of chromatic parallax. J. Opt. Soc. Am. A. 8,686-691.

  14. Zhang, X., Thibos, L.N. and Bradley, A. (1991). A simple model to describe the relationship between the chromatic difference of focus and chromatic difference of magnification in human eyes. Optom. Vis. Sci. 68, 456-458.

  15. Bradley, A., Hook, J., and Haeseker, J. (1991) A comparison of clinical acuity and contrast sensitivity charts: Effect of uncorrected Myopia. Ophth. Physiol. Optics 11, 218-226.

  16. Ye, M., Bradley, A., Thibos, L.T., and Zhang, X.X. (1991) Interocular differences in transverse chromatic aberration determine chromostereopsis. Vision Res 31, 1787-1796.

  17. Bradley, A., Huerres, M., Kalaher, M., and Thomas, (1991) Effects of spherical and astigmatic defocus on acuity and contrast sensitivity: A comparison of three clinical charts. Optom. Vis. Sci. 68, 418-426.

  18. Bradley, A. (1992) Perceptual manifestations of imperfect optics in the human eye: Attempts to correct for ocular chromatic aberration (Glenn Fry Award Lecture). Optometry and Vision Science, 69, 515-521.

  19. Bradley, A., Zhang, X., and Thibos, L.N. (1992) Failures of isoluminance caused by ocular chromatic aberrations Applied Optics, 31, 3657-67.

  20. Bradley, A., Thibos, L.N., Wang, Y., Haggerty, K., and Poorman A. (1992) Imaging FWC. Ophthalmic and Physiological Optics, 12, 128-9.

  21. Ye, M., Bradley, A., Zhang, X., Thibos, L.N. (1992) The effect of pupil size on chromostereopsis and chromatic diplopia: Interaction between the Stiles-Crawford Effect and chromatic aberration. Vision Research , 32, 2121-28.

  22. Thibos, L.N., Ye M, Zhang, X, and Bradley, A. (1992) The Chromatic Eye: A new reduced-eye model of Ocular Chromatic Aberration in humans, Applied Optics, 31, 3594-600.

  23. Atchison, A.A., Ye, M., Bradley, A., Collins, M.J., Zhang, X., Thibos, L., and Rahman, A. (1992) Chromatic Aberration and Optical Power of a Diffraction Bifocal Contact Lens. Optometry and Vision Science, 69, 515-521.

  24. Thibos, L.N. and Bradley, A. (1992) Use of interferometric visual stimulators in Optometry. Ophthalmic and Physiological Optics, 12, 206-8.

  25. Applegate, R.A., Bradley, A, and Thibos, L.N. (1992) Visual Acuity and Pupil Size in Maxwellian and Free View Systems with and without Refractive Error. Optical Society of America Digest for the 1992 Non-invasive Assessment of the Visual System Topical Meeting. Vol 1, 170-4.

  26. Zhang, X., Bradley, A., Ye M. and Thibos, L.N. (1992) An experimental model of bifocal vision. Opt. Soci. of Am. Digest 1992 Ophth. and Vis. Opti.Topical Meeting. vol 1, 62-5.

  27. Zhang, X., Bradley, A., and Thibos, L.N. (1993) Experimental determination of the chromatic difference of magnification of the human eye and the location of the anterior nodal point. J. Opt. Soc. Am. A 10, 213-220.

  28. Thibos, L.N. and Bradley A. (1993) New Methods for discriminating neural and optical losses of vision. Optom. Vis. Sci. 70, 279-287.

  29. Bradley, A., Rahman, H.A., Soni, S. and Zhang, X. (1993) Effects of target distance and pupil size on letter contrast sensitivity with simultaneous vision bifocal contact lenses. Optom. Vis. Sci. 70, 476-481.

  30. Thibos, LN, Ye, M, Zhang, X, and Bradley, A (1993) A new model of the human eye. Optics and Photonics News, Dec., 1993, p. 12.

  31. Zhang, H., Bradley, A., Thibos, L.N., Applegate R.A., and Elsner, A. (1994) Comparison of Entoptic, Fundus Photographic and Fluorescein Angiographic Methods for Viewing the Retinal Vasculature. Optical Soc. Am. Technical Digest, vol 2 (Vision and its Applications). pp 228-231.

  32. Bradley, A. (1994) AR Coatings can improve Visual Acuity. Optometry Today, Sept. 1994, p 37.

  33. Atchison D., Bradley A., Thibos L.N., and Smith G., (1995) Useful variations of the Badal Optometer. Optical Soc. Am. Technical Digest, vol 2 (Vision and its Applications). pp 155-8.

  34. Winn, B., Bradley, A., Strang, N.C., McGraw, P.V. and Thibos, L.N. (1995). Reversals of the colour-depth illusion explained by ocular chromatic aberration. Vision Research, 35, 2675-2684.

  35. Atchison, D.A., Smith, G., Bradley, A. and Thibos, L.N. Useful variations of the Badal optometer. (1995) In Vision Science and its Applications (OSA Technical Digest Series, Vol 1.) (pp. 155-158). Washington, DC: Optical Society of America.

  36. Atchison, D.A., Smith, G., Bradley, A. and Thibos, L.N. (1996) Useful variations of the Badal optometer. Optom. Vis. Scis, 72, 279-284.

  37. Woods, R.L., Bradley, A and Atchison, D.A. (1996) Monocular diplopia caused by ocular aberrations and hyperopic defocus. Vision Research, 22, 3597-3606.

  38. Woods, R.L., Bradley, A. and Atchison, D.A. (1996) Consequences of monocular diplopia for the contrast sensitivity function. Vision Research, 22, 3587-3596.

  39. Rynders, M.C., Thibos, L.N., Bradley, A. (1996) Apodization neutralization: a new technique for investigating the impact of the Stiles-Crawford effect on visual function. In Basic and Clinical Applications of Vision Science, Lakshminarayanan, V. (ed), Dordrecht, The Netherlands: Kluwer Academic Publishers

  40. Wang, Y.Z., Thibos, L.N. and Bradley, A. (1997) Effects of refractive error on detection acuity and resolution acuity in peripheral vision. Investigative Ophthalmology and Visual Science, (in press).

  41. Ross, J. and Bradley, A. (1997) Visual performance and patient preference: a comparison of anti-reflection coated and uncoated lenses. J. Am. Optometric Ass. 68, 361-366.

  42. Thibos, L.N., Ye, M., Zhang, X., and Bradley, A. (1997) Spherical aberration of the reduced schematic eye with elliptical refracting surface. Optometry and Vision Science , 74, 548-556.

  43. Zhang, X., Thibos, L.N., and Bradley, A. (1997) Wavelength-dependent magnification and polychromatic image quality in eyes corrected for longitudinal chromatic aberration. Optometry and Vision Science , 74, 563-569.

  44. Kato, M. and Bradley, A. (1997) A comparison of the effects of defocus letter acuity and contrast sensitivity. Japanese Optometric Association J. 15, 10-24.

  45. Thibos, L.N. and Bradley, A. (1997) Use of liquid crystal adaptive optics to alter the refractive state of the eye. Optometry and Vision Science , 74, 581-587.

  46. Strang, N.C., Winn, B., and Bradley A. (1998) The role of neural and optical factors in limiting visual resolution in myopia. Vision Res. 38, 1713-1721.

  47. Atchison, D.A., Woods, R.L. and Bradley, A. (1998) Ocular transverse aberrations predict the complex effects of optical defocus on human contrast sensitivity. J. Opt. Soc. Am. A 15, 2536-2544.

  48. Salmon, T.O., Thibos, L.N., and Bradley, A. (1998) Comparison of the eye's wavefront aberration measured psychophysically and with the Shack-Hartmann wavefront sensor. J. Opt. Soc. Am. A 15, 2457-2465.

  49. Zhang, X., Ye, M., Bradley, A., and Thibos, L. (1999) Apodization by the Stiles-Crawford Effect moderates the visual impact of retinal image defocus. J. Opt. Soc. Am. A. 16, 812-820.

  50. Applegate R, Thibos LN, Bradley, A, Marcos S, Roorda A, and Salmon, T (2000) Reference axis selection: A subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye. Opt. Soc. Am. VSIA Technical Digest, 2000, pp 146-149.

  51. Cheng, Hong, Thibos, Bradley, Himebaugh, Riley and Miller (2000) Increased Optical Aberrations in Myopia, Proceedings of the VIII International Conference on Myopia, pages122-126.

  52. Tutt, Bradley, Begley and Thibos (2000) Optical and visual Impact of tear Break-up. Invest. Ophthal. Vis. Sci 41:4117-23.

  53. Nikole L. Himebaugh, Larry N. Thibos, Carolyn G. Begley, Arthur Bradley, and Graeme Wilson (2000) Predicting optical effects of tear film break-up on retinal image quality using the Shack-Hartmann aberrometer and computational optical modeling. Proceedings of the Third International Conference on the Lacrimal Gland, Tear Film, and Dry Syndromes: Basic Science and Clinical, in Advances in Experimental Medicine and Biology.

  54. Bradley, A (2000) The changing face of refractive surgery. Indiana J. of Optometry vol 3, 5-12.

  55. Hong, X., Thibos, L.N., Bradley, A., Miller, D., Cheng, X. and Himebaugh, N. (2001) Statistics of aberrations among healthy young eyes. In: Vision Science and Its Applications, Technical Digest (Optical Society of America, Washington, D.C.) pp. 90-

  56. Thibos LN, Hong X, Bradley A, Cheng X Statistical variation of aberration structure and image quality in a normal population of healthy eyes. J Opt Soc Am A Opt Image Sci Vis. 2002 Dec;19(12):2329-48.

  57. Thibos LN, Bradley A, Hong X. A statistical model of the aberration structure of normal, well-corrected eyes. Ophthalmic Physiol Opt. 2002 Sep;22(5):427-33.

  58. Thibos, L.N., Cheng, X., and Bradley, A. (2002) Design principles and limitations of wavefront-guided contact lenses. Eye Contact Lens. 2003 Jan;29(1 Suppl):S167-7.

  59. Himebaugh, N.L., Wright, A.R., Bradley, A., Begley, C.G., and Thibos, L.N. (2003) Use of retroillumination to visualize optical aberrations caused by tear film break-up. Optometry and Vision

  60. Cheng, Xu, Arthur Bradley, Xin Hong, Larry N. Thibos, Relationship between Refractive Error and Monochromatic Aberrations of the Eye, Optom Vis Sci. 2003 Jan;80(1):43-9.

  61. Bradley, A, Special Review: Colored Filters and Vision Care, part I, Indiana Journal, 2003, vol 6, p 13-17.

  62. Cheng, X., Himebaugh, N. L., Kollbaum, P. S., Thibos, L. N., & Bradley, A. (2003). Validation of a clinical Shack-Hartmann aberrometer. Optom Vis Sci, 80, 587-95.

  63. Cheng, X., Thibos, L. N., & Bradley, A. (2003). Estimating visual quality from wavefront aberration measurements. J Refract Surg, 19, S579-84.

  64. Cheng, X., Himebaugh, N. L., Kollbaum, P. S., Thibos, L. N., & Bradley, A. (2004). Test-Retest Reliability of Clinical Shack-Hartmann Measurements. Investigative Ophthalmology and Visual Science, (in press).

  65. Zhou, F., Hong, X., Miller, D. T., Thibos, L. N., & Bradley, A. (2004). Validation of a combined corneal topographer and aberrometer based on Shack-Hartmann wavefront sensing. J Opt Soc Am A Opt Image Sci Vis, (in press)

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Aliasing, Amblyopia, and Cortical Processing

  1. Freeman, R.D. and Bradley, A. (1980) Monocularly deprived humans: Non-deprived eye has super-normal acuity. J. Neurophysiol., 43, 1645-1652.

  2. Hess, R.F. and Bradley, A. (1980) Contrast perception above threshold is only minimally impaired in human amblyopia. Nature (Lond.), 287, 463-464.

  3. Bradley, A. and Freeman, R.D. (1981) Contrast sensitivity in anisometropic amblyopia. Invest. Ophthalmol. and Visual Sc., 21, 467-472.

  4. Bradley, A., Rabin, J., and Freeman, R.D. (1983) Non-optical determinants of aniseikonia. Invest. Ophthalmol. and Visual Sc. , 24, 507-512.

  5. Rabin, J., Bradley, A., and Freeman, R.D. (1983). The relationship between aniseikonia and axial anisometropia. Am. J. Optom. and Physiol. Optics, 60, 553-558.

  6. Hess, R.F., Bradley, A., and Piotrowski , L. (1983) Contrast coding in amblyopia I: Differences in the neural basis of amblyopia. Proc. Roy. Soc. B., 217, 309-330.

  7. Bradley, A. (1983) Psychophysical studies of human amblyopia. Ph.D. Thesis, University of California, Berkeley.

  8. Bradley, A. and Skottun, B.C. (1984) The effects of large orientation and spatial frequency differences on spatial discriminations. Vision Res., 24, 1889-1896.

  9. Bradley, A. and Freeman, R.D. (1985) Temporal sensitivity in amblyopia: An explanation of conflicting reports. Vision Res., 25, 39-46.

  10. Bradley, A. and Freeman, R.D. (1985) Is reduced vernier acuity in amblyopia due to position, contrast, or fixation deficits? Vision Res., 25, 55-66.

  11. Bradley, A., Freeman, R.D., and Applegate, R.A. (1985) Is amblyopia spatial frequency or retinal locus specific? Vision Res., 25, 47-54.

  12. Bradley, A., Skottun, B.C., Ohzawa, I., Sclar, G., and Freeman, R.D. (1985) A neurophysiological evaluation of the differential response model for orientation and spatial frequency discrimination. J. Opt. Soc. Am. A., 2, 1607-1610.

  13. Skottun, B.C., Bradley, A., and Freeman, R.D. (1986) Orientation discrimination in amblyopia. Invest. Ophthalmol. and Visual Sc., 27, 532-537.

  14. Bradley, A. and Ohzawa, I. (1986) A comparison of contrast detection and discrimination. Vision Res. 26, 991-997.

  15. Bradley, A., Dahlman, C., Switkes, E., and DeValois, K.K. (1986) A comparison of color and luminance discrimination in amblyopia. Invest. Ophthalmol. and Visual Sc. 27, 1404-1409.

  16. Skottun, B.C., Bradley, A., and Ramoa, A.S. (1986) Effect of contrast on spatial frequency tuning of neurons in area 17 of cat's visual cortex. Exp. Br. Res. 63, 431-435.

  17. Bradley, A., Skottun, B.C., Ohzawa, I., Sclar, G., and Freeman, R.D. (1987) Orientation and spatial frequency discrimination: A comparison of single cells and behavior. J. Neurophysiol., 57, 755-722.

  18. Skottun, B.C., Bradley, A., Sclar, G., Ohzawa, I., and Freeman, R.D. (1987) Effects of contrast on orientation and spatial frequency discrimination: a comparison of single cells and behavior. J . Neurophysiol., 57, 773-786.

  19. Bradley, A. and Skottun, B.C. (1987) Effects of contrast and spatial frequency on vernier acuity. Vision Res., 27, 1817-1824.

  20. Bradley, A., Switkes, E., and DeValois, K.K. (1988) Orientation and spatial frequency selectivity of adaptation to color and luminance gratings. Vision Res., 28, 841-856.

  21. Switkes, E., Bradley, A., and DeValois, K.K. (1988) Contrast dependence and mechanisms of masking interactions among chromatic and luminance gratings. J. Opt. Soc. Amer. A , 5, 1149-1162.

  22. Bradley, A. and Schor, C. (1988) The role of eye-movements and masking in monocular rivalry. Vision Res. , 28, 1129-1137.

  23. Thibos, L.N., Still, D. L. and Bradley, A. (1996). Characterization of spatial aliasing and contrast sensitivity in peripheral vision. Vision Research, 36, 249-258.

  24. Wang, Y. Z., Thibos, L.N. and Bradley, A. (1996). Undersampling produces non-veridical motion perception, but not necessarily motion reversal, in peripheral vision. Vision Research, 36, 1737-1744.

  25. Wang, Y.Z., Thibos, L.N., Lopez, N., Salmon, T. and Bradley, A. (1996). Subjective refraction of the peripheral field using contrast detection acuity. Journal of the American Optometric Association, 67, 584-589.

  26. Wang, Y., Bradley, A. and Thibos, L.N. (1997) Aliased frequencies enable the discrimination of compound gratings in peripehral vision. Vision Research, 37, 283-90.

  27. Wang, Y.Z., Bradley, A. and Thibos, L.N. (1997). Interaction between sub- and supra-Nyquist spatial frequencies in peripheral vision. Vision Research, 37, 2545-2552.

  28. Barrett, BT, Whitaker, D and Bradley, A (1999) Vernier acuity with compound gratings: The whole is equal to the better of its parts Vision Res. 39, 3681-3691.

  29. Hilmantel G, Applegate RA, van Heuven WA, Stowers SP, Bradley A, Lee BL. (1999) Entoptic foveal avascular zone measurement and diabetic retinopathy. Optom Vis Sci. 76, 826-31.

  30. Bingham J, Bradley A, Bailey, M and Vinner R (2000) Accommodation, occlusion and disparity matching are used to guide reaching: A comparison of actual vs. virtual environments. J. Exp. Psychol: Hum Perc. & performance 27, 1-21.

  31. Wang, Y.Z., Thibos, L.N., and Bradley, A. (2001) Modeling the sampling properties of human cone photoreceptor mosaic. In: Vision Science and Its Applications, Technical Digest (Optical Society of America, Washington, D.C.) pp. 20-23.

  32. B.T. Barrett, I.E. Pacey, A. Bradley, L.N. Thibos, P. Morrill . Non-Veridical Visual Perception in Human Amblyopia., Invest Ophthalmol Vis Sci. 2003 Apr;44(4):1555-67

  33. Brendan T. Barrett, Paul V. McGraw & Arthur Bradley Understanding the Neural Basis of Amblyopia, Continuing Education Optometry, 2003, vol 5, 83-87.

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