Objective: Find the faintest letter contrast you can still read. Regular eye charts test how small you can read at full black-on-white contrast; this test keeps the letters large and instead fades them toward the background gray.
How it works:
- A single letter (from the ten letters used on clinical charts: C, D, H, K, N, O, R, S, V, Z) appears on a gray panel
- Tap the letter you see; if you truly see nothing, use "I can't see any letter". On desktop you can also type the letter, or press Space for "I can't see any letter"
- The test adapts: each correct answer makes the next letter fainter, and each miss makes it noticeably bolder
- This adaptive staircase estimates the contrast range where your answers start becoming unreliable — that borderline zone is your threshold
Your results:
- Contrast Threshold — the faintest contrast you could reliably read, as a percentage (lower is better)
- Log Sensitivity — the standard clinical way of expressing the same thing (higher is better); healthy adults on chart-based tests typically score in the region of 1.5–2.0, though on-screen results are not directly comparable
For consistent results:
- Set screen brightness to maximum, disable night-mode/blue-light filters, and clean your screen
- Test in the same lighting and at the same viewing distance each time — compare only your own results over time on the same device
- Guessing is allowed and expected near your threshold — that's how the method works
Important: This is not a medical vision test. Results depend heavily on your screen, its brightness settings, and room lighting, so they cannot be compared to clinical measurements. Contrast sensitivity loss can be an early sign of eye conditions — if you have any concerns about your vision, see an optometrist or ophthalmologist for a professional examination.