Visual Contrast Test
16 contrast levels: the scale goes from 0.00 LogCS (pure black) to 2.25 LogCS (nearly imperceptible).
Same-size letters: unlike Snellen, contrast decreases, not size.
Immediate result: automatic interpretation in 4 clinical categories.
Calibrated screen: set brightness to 75% for maximum reliability.
# Contrast Sensitivity Test: Beyond 20/20 Vision
Vision is not only acuity (how small the letters we can see are), but also contrast (how faint an object can be before blending into the background). The Pelli-Robson Test is the clinical standard for measuring this capacity, providing information that the traditional Snellen chart often misses.Many patients with perfect 20/20 vision experience real difficulties: problems driving at night, reading under dim lights, or seeing steps in low-light conditions. This is frequently due to a loss of contrast sensitivity, a parameter that the Pelli-Robson test detects with precision.# Results Interpretation Table
| Score (LogCS) | Vision Level | Description |
|---|---|---|
| 2.00 or higher | Superior | Exceptional range, typical in healthy young people or professional pilots. |
| 1.65 to 1.95 | Normal | Standard level for an adult without visual pathologies. |
| 1.20 to 1.50 | Low | Moderate difficulty. Possible presence of cataracts or severe dry eye. |
| Below 1.00 | Deficient | Significant functional loss. High risk in night driving. |
# Who Should Take This Test?
- Cataracts: Lens opacity scatters light, drastically reducing contrast even if acuity remains high.
- Glaucoma: Damage to the optic nerve often manifests first as a loss in grey detection.
- Macular Degeneration (AMD): The health of retinal photoreceptors is key for central contrast.
- Diabetic Retinopathy: Early vascular changes affect the perception of faint tones.
- Post-Refractive Surgery: Some LASIK patients experience transient contrast loss after the procedure.
Contrast Sensitivity Function
Scientifically, we perceive the world through different spatial frequencies. The Pelli-Robson test focuses on low and medium frequencies, responsible for detecting large shapes like faces, obstacles on the pavement, or cars in the rain.
Test Conditions
To obtain a reliable result in this digital version, set your screen brightness to 75-80%, avoid direct reflections on the monitor, and perform the test at a comfortable reading distance (40-60 cm).# Importance in Daily Life
- Road Safety: Seeing a pedestrian in dark clothing on a rainy night depends entirely on contrast.
- Fall Prevention: In elderly people, contrast is the #1 factor for detecting uneven ground.
- Efficient Reading: Visual fatigue when reading on screens is often linked to a lack of optimal contrast.
- Action Sports: Following a ball or dodging obstacles at high speed requires an instant visual response to contrast.