see what your eye chart misses.
Check how well you see faint patterns. First test free, with a PDF report. A screening signal, not a diagnosis.
Stripe width and contrast vary across this illustration. It does not measure your own curve.
one test. your full contrast sensitivity curve.
About 7 minutes all in: a couple of minutes to set up, then about 5 minutes for the test itself, five spatial frequencies, from coarse to fine, measured on your phone, tablet, or computer. Your first test is free.
calibrate your screen
Choose your device or match a card to your screen. Enter your viewing distance, or use the guided blind-spot check. Setup takes a couple of minutes.
see faint patterns
Tap whether each striped pattern tilts left or right. If you cannot tell, choose Not sure. The patterns get fainter as the test finds your threshold.
get your report
See your sensitivity at the pattern sizes you tested, with a plain-English explanation. Download a PDF to keep or discuss with your clinician.
contrast sensitivity isn’t acuity.
A 20/20 chart asks one question: can you read tiny, very high-contrast letters? Contrast sensitivity asks the whole map — how faint a pattern you can see, across a range of pattern sizes measured in cycles per degree (cpd).
Our screening uses adaptive judgments of striped patterns, drawing on contrast-sensitivity research. Results from a consumer screen are not interchangeable with clinical chart scores. This screening does not replace a medical evaluation.
Illustrative curve and shading, not measured results or a validated normal range. A test estimates sensitivity at several pattern sizes.
conditions associated with contrast sensitivity loss.
Contrast sensitivity is a non-specific signal. A dip can have many causes — uncorrected refraction, fatigue, dry eye, lighting, or a real change in visual processing. The conditions below are commonly discussed in the research; none are diagnosed by this test.
vision after a concussion
Letter-chart acuity often reads 20/20 after concussion while contrast sensitivity is degraded.
MS visual symptoms
A sensitive probe of optic-pathway involvement — often abnormal when acuity is still 20/20.
early signs
Can pick up an early signal before standard tests register it — not a substitute for an ophthalmologist.
cataract & night driving
Why an eye exam can say 20/20 while glare and dim-light contrast make night driving hard.
brain fog with a vision layer
Early reports describe contrast changes; the literature is small and still open.
the Shoemaker pattern contested
A mid-band loss has been associated with biotoxin exposure in some literature — many other conditions produce the same pattern.
the science we build on.
These papers explain contrast measurement and related adaptive methods. They provide research context, not clinical validation of this browser screening.
Pelli D, Robson J, Wilkins A. The design of a new letter chart for measuring contrast sensitivity. Clinical Vision Sciences. 1988;2(3):187–199.
The Pelli-Robson chart. Introduced a clinical chart with fixed-size letters and decreasing contrast. Our screening uses striped patterns and a different testing procedure.
Mäntyjärvi M, Laitinen T. Normal values for the Pelli-Robson contrast sensitivity test. Journal of Cataract and Refractive Surgery. 2001;27(2):261–266.
Reference values for a letter chart. Reported Pelli-Robson scores across age groups. Those letter-chart values do not establish normal ranges at each spatial frequency for this screening.
Lesmes LA, Lu ZL, Baek J, Albright TD. Bayesian adaptive estimation of the contrast sensitivity function: the quick CSF method. Journal of Vision. 2010;10(3):17.
The quick CSF method. Estimated the CSF with Bayesian adaptive sampling. It is a related research method, distinct from the two-down, one-up staircase used here.
Watson AB, Pelli DG. QUEST: a Bayesian adaptive psychometric method. Perception & Psychophysics. 1983;33(2):113–120.
The QUEST method. Estimates a threshold with Bayesian updates. Contrast Screen uses a two-down, one-up staircase rather than QUEST.
The full protocol — stimulus, frequencies, staircase rule, calibration — lives on the methodology page.
$20. once. no subscription.
Try it free. If it’s useful, twenty dollars unlocks unlimited testing for life — no recurring charge, no upsell, no “pro” tier.
first test
free account, first test free
- One full calibrated test
- Your CSF curve & plain-English read
- Printable PDF report & email-yourself summary
- Result saved to your account and this device
- Retests and shareable links require unlimited
unlimited
everything, forever
- Unlimited tests — retest every 2 weeks, watch the trend
- History saved with a comparison view
- Shareable result link
- Bring an actual curve to your clinician
One-time payment. No subscription, no auto-renew. 30-day money-back guarantee — email us for a full refund.
get your CSF report, and track the trend.
Create a free account; after every test, one click emails your report to you, so the next test compares against this one. One test is a snapshot; a trend is a signal.
Your first test is free. We email your results, plus a few short notes over the first weeks to help you get the most from the test. Unsubscribe anytime.
Just want the notes? One email when the test changes or a research note goes up — no account needed.
a pre-visit screen your patients can run from their phone.
A calibrated CSF curve, a PDF, and a per-frequency read your patient brings to the visit. A screening signal that supports the conversation — never the basis for a decision. A provider tier is in the works.
questions people ask.
No. It's a screening signal, not a diagnostic test or an eye examination. Results can be affected by your vision, the screen, setup, and response variability. Discuss new symptoms or concerns with your healthcare provider regardless of your score.
Contrast is relative to a background. A mid-gray test surface and setup estimates of pixel pitch, viewing distance, and display gamma help control the patterns shown. Consumer screens still differ, so results should not be treated as interchangeable across devices or with clinical instruments.
Allow a couple of minutes to set up, then about 5 minutes for the test itself: five spatial frequencies, each measured with a short staircase of tilted patterns, giving your full CSF curve — about 7 minutes all in. Measured across real tests, not a guess; the exact time varies with your answers and device, and your report shows how long yours took.
Yes. $20 one-time, lifetime unlimited. There's no recurring charge, no auto-renew, and no "premium" tier above it. Your first test is free so you can decide before paying, and there's a 30-day money-back guarantee: email us and we'll refund in full.
Your results are saved to your account so you can compare tests over time, and a copy stays on the device you tested on. We keep the curve, the calibration values, and the timestamps — not your per-trial answers, and never a name or address. We don’t sell data. Product analytics (PostHog, here and on the test app) is on by default, honors Do Not Track, and can be switched off with the one switch on the privacy page — the choice covers both apps. That page has the full list.
You get a sensitivity estimate at each measured frequency and an AULCSF summary. The report's reference band and range labels are approximate screening guides, not validated clinical cutoffs for this test. Setup and response variability can affect a result; a score alone cannot establish a cause or rule out an eye condition.
Every 2 weeks — a quick, easy test, especially while you are tracking something: recovery, a treatment, a new symptom. One test is a snapshot; the trend is the signal, and a test every 2 weeks averages out the normal test-to-test noise. Your first test is free; retests need unlimited ($20 once).
ready to see your CSF?
Your first full CSF test is free with an account. Unlimited testing is $20, once.
take the test