Contrast Sensitivity Testing — Complete User Guide
Contrast sensitivity function, Pelli-Robson chart usage, and clinical interpretation for early cataract and retinal disease detection.
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What is Contrast Sensitivity?
Contrast sensitivity measures the ability to detect differences in luminance between an object and its background. While high-contrast visual acuity (black letters on white chart) tests only one aspect of vision, contrast sensitivity provides a more comprehensive assessment of visual function.
Clinical Importance
- Early disease detection: Contrast sensitivity often decreases before high-contrast acuity in early cataract, glaucoma, retinal disease
- Functional vision: Better correlates with real-world visual function (night driving, reading small print)
- Treatment monitoring: Sensitive to small changes in disease progression or treatment effect
Pelli-Robson Chart
Most commonly used clinical chart for contrast sensitivity measurement:
- Letters at constant size, decreasing contrast
- Testing distance: 1 meter
- Score range: 0.00 to 2.25 log units
- Normal: ≥1.65 log units
Interpretation
| Score (log CS) | Interpretation |
|---|---|
| ≥1.65 | Normal |
| 1.35-1.50 | Mild impairment |
| 1.00-1.30 | Moderate impairment |
| <1.00 | Severe impairment |
References
- Pelli DG, et al. The contrast sensitivity function. Scand J Psychol. 1988.
- Elliott DB, et al. Contrast sensitivity and early cataract. Invest Ophthalmol Vis Sci. 1990.