May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Quantification of Visual Resolution in the Contrast Domain
Author Affiliations & Notes
  • J.C. Rabin
    College of Optometry, Pacific University, Forest Grove, OR
  • L. Kim
    College of Optometry, Pacific University, Forest Grove, OR
  • G. Leon
    College of Optometry, Pacific University, Forest Grove, OR
  • J. Matsumoto
    College of Optometry, Pacific University, Forest Grove, OR
  • K. Martinez
    College of Optometry, Pacific University, Forest Grove, OR
  • A. Mendez–Roberts
    College of Optometry, Pacific University, Forest Grove, OR
  • Footnotes
    Commercial Relationships  J.C. Rabin, None; L. Kim, None; G. Leon, None; J. Matsumoto, None; K. Martinez, None; A. Mendez–Roberts, None.
  • Footnotes
    Support  none
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 4351. doi:
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      J.C. Rabin, L. Kim, G. Leon, J. Matsumoto, K. Martinez, A. Mendez–Roberts; Quantification of Visual Resolution in the Contrast Domain . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4351.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose:Advances in keratorefractive surgery and optical wave–front analysis make it essential to quantify subtle decrements and enhancements in visual performance under diverse conditions, including reduced luminance and glare. We describe the theoretical basis, sensitivity and repeatability of new measures of contrast sensitivity (CS) in comparison to standard tests of visual acuity (VA). Methods: The stimulus was a series of four letter charts (Precision Vision, Inc.) retro–illuminated by a fluorescent light box in an otherwise dark room. The limited field size (3.3 x 5.1 deg at 4 m) and dark surround encouraged moderate pupil dilation. The chart series included high (96%) and low contrast (5%) VA and small letter CS (20/40 and 20/50 letter size Precision Vision prototype CS charts; contrast range: 96% to 1.25%). The VA and CS series was administered to 35 visually normal observers at various levels of optical defocus (0 to +1.5 D; 0.25D steps), and at normal (100 cd/m2) and low photopic luminance levels (25 and 10 cd/m2) achieved by placing neutral filters before the charts. Disability glare was assessed for low photopic CS (10 cd/m2 central target) with diffuse surrounding glare (100 cd/m2; 3.3 x 5.1 deg surround). Results: All measures showed a significant linear relation between log score and optical defocus (r2>0.96), but the slope of this relation was 3X greater for CS (0.3 log CS per 0.25D) as compared to VA (0.1 log MAR per 0.25D). The greater sensitivity of 20/50 CS was still evident after correction for variability, by expressing all scores as standard deviations (SDs) from the mean (2.7 SDs per 0.25D defocus for CS; 2.1 SDs per 0.25D defocus for VA). Modest decrements in photopic luminance (from 100 to 10 cd/m2) produced significant decrements (>2SDs) in low contrast VA and 20/50 CS. Surround glare resulted in additional significant decrements in low photopic CS (>4 SDs below the photopic mean). Control measures indicated that CS decrements at low photopic luminance reflect optical factors, as opposed to stimulus factors (i.e, quantal fluctuations) which limit small letter CS at mesopic levels. Conclusions:CS measurement with 20/50 letters is a sensitive approach to quantify visual resolution in the contrast domain. Subtle optical and media effects can be revealed despite minimal impact on VA. The 20/50 CS test has potential application in refractive surgery, cataract evaluation, night vision assessment, and for evaluation of disability glare. In addition, the extended contrast scale used in this approach will allow for quantification of super–normal vision, an outcome expected with correction of higher–order aberrations.

Keywords: contrast sensitivity • visual acuity • refractive surgery 
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