Journal of Cataract & Refractive Surgery
Volume 30, Issue 11 , Pages 2377-2382, November 2004

Normal values for a clinical test of letter-recognition contrast thresholds☆☆☆★

  • Arshad M. Khanani, MD

      Affiliations

    • Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, TX, USA
    • ,
  • Sandra M. Brown, MD

      Affiliations

    • Corresponding Author InformationReprint requests to Sandra Brown, MD, 3601 Fourth Street STOP 7217, Lubbock, Texas 79430-7217, USA.
    • Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, TX, USA
    • ,
  • Ke Tom Xu, PhD

      Affiliations

    • Department of Health Services Research and Management, Texas Tech University Health Sciences Center, Lubbock, TX, USA

Accepted 30 March 2004.

Abstract 

Purpose: To investigate the contrast thresholds (CTs) in normal subjects using a high-luminance, letter-recognition task under clinically relevant testing conditions.

Setting: Texas Tech University Health Sciences System, Lubbock, Texas, USA.

Methods: Sixty normal subjects aged 20 to 49 years with a best corrected visual acuity of 20/20 or better in both eyes participated. M & S Technologies software was used to display black-on-white Sloan letters at contrast levels of 25%, 20%, 15%, 12%, and 10% through 1% in 1% decrements. The effects of age, sex, optotype size, eye dominance, ambient illumination level (bright = 625 − 630 lux; dim = <3 lux), and direction of approach to threshold were analyzed using a multivariate, ordinary, least-squares analysis.

Results: Age and sex did not influence CTs. Ascending versus descending testing was not statistically significant (P>.5). The effects of room illumination and eye dominance were significant (P<.01). Significant differences were found between 20/30 and 20/50, 20/30 and 20/70, and 20/50 and 20/70 optotype sizes (P<.01 for all comparisons).

Conclusions: A commercially available, computer-based test of CTs was easy to administer and apparently easy for inexperienced subjects to perform. The results suggest criteria for detecting visual problems concerned with familiar but complex spatial-image shapes. This information might be used to assess the effects of treatments such as laser refractive surgery on recognition contrast. Further study is warranted.

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☆ Supported by a grant from M & S Technologies, Chicago, Illinois, USA. Software designed by Steven Nordstrom. Mr. Nordstrom is a partner in M & S Technologies, USA.

☆☆ Mr. Khanani received a research stipend at the conclusion of the study. No author has a commercial or proprietary interest in any product mentioned.

★ Rockefeller Young, PhD, assisted with the study design, interim statistical analysis, and manuscript review.

PII: S0886-3350(04)00562-0

doi:10.1016/j.jcrs.2004.05.027

Journal of Cataract & Refractive Surgery
Volume 30, Issue 11 , Pages 2377-2382, November 2004

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