Adaptive Vision Testing
Triad
Tri-dimensional Rapid Interleaved Acuity Dissociation
A letter chart measures one thing. TRIAD measures three — visual acuity, contrast sensitivity, and crowding resistance — in a single adaptive session of 45 trials, with three Bayesian staircases interleaved by uncertainty and an AI interpretation of the result.
The Trial Screen
One screen. Three staircases.
Channels aren't tested in blocks — every trial, the engine picks whichever channel has the most uncertainty left and presents a single Sloan letter. The patient answers from ten choices; the posterior updates; repeat.
Which letter did you see?
The Three Channels
Three dimensions of sight.
Visual Acuity
The familiar dimension — the smallest letter the patient can resolve. A white Sloan letter on black, sized adaptively along the logMAR axis.
Contrast Sensitivity
The dimension letter charts miss. Letter size stays fixed at 2.0× the running acuity estimate while the grey level fades toward the background.
Crowding Resistance
How close can flankers get before recognition breaks down? Bars above and below the letter move inward adaptively — the psychophysics of amblyopia and cortical processing.
How It Works
45 trials. Zero wasted questions.
Pick the noisiest channel
Before every trial, the engine compares the posterior uncertainty of all three staircases and tests whichever channel it knows least about — so no trial is spent confirming what's already certain.
Fixate, then flash
A 350 ms crosshair centers the patient's gaze, then a single Sloan letter appears — sized, faded, or flanked according to the active channel's next most informative stimulus level.
Ten-alternative forced choice
The patient picks from the ten Sloan letters (C D E F H K N O R S) on screen or keyboard. Guessing is built into the model — a 10% guess rate is part of the psychometric function, not a source of error.
Bayesian update
Each response updates that channel's QUEST+ posterior over threshold and slope. Fifteen trials per channel later, TRIAD reports thresholds with their standard deviations — you know the number and how much to trust it.
Instant Classification
Six clinical patterns.
The three normalized scores classify every result the moment the last trial ends — a triage signal, not a diagnosis.
Within normal limits
All scores ≥ 70%
Acuity, contrast, and crowding all fall in the expected range. Routine monitoring.
Optical / media loss
Acuity < 50% · Contrast < 50% · Crowding ≥ 60%
Acuity and contrast reduced together while crowding is preserved — consistent with refractive error, cataract, or media opacity. Refraction and slit-lamp first.
Early neural sensitivity loss
Contrast < 50% · Acuity ≥ 50% · Crowding ≥ 50%
Isolated contrast loss with intact acuity — the signature that letter charts miss. Warrants retinal and optic nerve evaluation.
Cortical processing deficit
Crowding < 50% · Acuity ≥ 40% · Contrast ≥ 50%
Disproportionate crowding weakness — associated with amblyopia and cortical visual processing differences.
Multi-dimensional loss
All scores < 40%
Every channel reduced. Suggests significant pathology or unreliable responses — comprehensive workup indicated.
Borderline result
Everything else
Mixed scores that don't match a classic pattern. Repeat testing or targeted follow-up on the weakest channel.
The CCR Biomarker
The Crowding–Contrast Ratio compares the two non-acuity channels against each other. A ratio near baseline is typical; drifting above zero means crowding is deteriorating faster than contrast (a cortical/amblyopic direction), while a ratio far below baseline points at contrast-dominant loss (an optical, media, or retinal direction).
After The Last Trial
Numbers,pattern,narrative.
TRIAD hands all ten numeric outputs — three thresholds, their standard deviations, the normalized scores, and the CCR — to Claude, which returns a two-to-three sentence clinical narrative plus three or four concrete considerations. It's prompted to respect uncertainty (an SD above 0.15 is called out, not glossed over) and to stay non-alarmist: language for a clinician's note, not a scare.
Run TRIAD In Your Lane ↗All three channels fall within normal limits, led by strong crowding resistance. The acuity threshold of 0.10 logMAR (≈20/25) and contrast sensitivity of 1.60 logCS are unremarkable for a routine exam; the CCR of −0.07 sits slightly above the −0.17 baseline but within measurement uncertainty.
- Routine recall interval appropriate based on this result
- Contrast SD of ±0.09 is acceptable; repeat only if symptoms suggest otherwise
- Consider a dedicated contrast workup if night-vision complaints arise
The Science
Built on
psychophysics.
QUEST+ Adaptive Estimation
Each channel runs a full Bayesian QUEST+ staircase (Watson, 2017) over a Weibull psychometric function — every stimulus is placed where it's expected to be most informative about the threshold.
Crowding, Quantified
Channel C operationalizes Bouma's law — recognition collapses when flanker spacing falls below a critical fraction of eccentricity. TRIAD measures that critical spacing directly at fixation.
References
- Watson, A. B. (2017). QUEST+: A general multidimensional Bayesian adaptive psychometric method. Journal of Vision, 17(3):10.
- Bouma, H. (1970). Interaction effects in parafoveal letter recognition. Nature, 226, 177–178.
- Pelli, D. G., Robson, J. G., & Wilkins, A. J. (1988). The design of a new letter chart for measuring contrast sensitivity. Clinical Vision Sciences, 2, 187–199.
- Levi, D. M. (2008). Crowding — an essential bottleneck for object recognition. Vision Research, 48(5), 635–654.
- Strasburger, H., Rentschler, I., & Jüttner, M. (2011). Peripheral vision and pattern recognition: a review. Journal of Vision, 11(5):13.
Where You Get It
Two distances. One test.
TRIAD Distance
Runs on every activated exam lane at your calibrated testing distance — no extra hardware, no add-on fee. Open it straight from the lane's chart menu, on the same screen your acuity charts run on.
Get started free →TRIAD Near
The same three-channel engine at near working distance (33 cm default), part of the Ocular Edge Clinical near-testing suite alongside PHOTOSTRESS recovery and WARP metamorphopsia mapping. Enabled per-account — talk to us.
Contact us to enable →See all three
dimensions.
20/20 tells you one number. TRIAD tells you three — with the uncertainty, the pattern, and the narrative to act on them. Free account setup, no credit card required.