Stereotest Clinical Comparison - Frisby vs Randot, TNO, Titmus & Lang

	Frisby Stereotest	Randot (Stereo Optical)	TNO	Titmus / Wirt Fly	Lang I / II
Depth mechanism	Real physical depth	Printed random dot stereogram (RDS), polarised	Printed RDS, anaglyph	Printed contour stereo	Lenticular RDS
Glasses required	None required	Polarised glasses	Red-green anaglyph glasses	Polarised glasses	None required
Monocular cues eliminated	Yes — true disparity only	Partial (if glasses worn correctly)	Yes	No — contour cues present	Yes
Age range	from 6 months +	2 years + (preschool version available)	3 years +	3 years +	from 6 months +
Threshold range (arc seconds)	5 – 600″	20 – 400″	15 – 480″	40 – 3000″	200 – 1200″
Valid in patients with reduced acuity †	Yes — larger target elements remain resolvable when acuity is reduced in one eye, enabling valid stereo measurement and treatment monitoring in mild to moderate amblyopia — not just screening for its presence	Partial — fine dot patterns may not resolve at low acuity	Partial — fine dot patterns may not resolve at low acuity	Partial — coarser contours help, but monocular cues remain a concern	Partial — fine lenticular pattern may not resolve at low acuity; Lang sensitivity aids detection of amblyopia but does not confirm binocular vision is intact
Repeat testing reliability ‡	Yes — real depth target can be repositioned; patients cannot memorise or predict the correct response on repeat testing	No — fixed printed stimulus; prior exposure risks learned response	No — fixed printed stimulus; prior exposure risks learned response	No — fixed printed stimulus; prior exposure risks learned response	No — fixed lenticular positions; prior exposure risks learned response
Detects binocular vision anomalies	High specificity — reliable confirmatory tool with very few false positives	Moderate specificity	Highest sensitivity among card tests	Low — monocular cues allow guessing	High specificity; good for infant screening
Research & clinical trial use	Widely used as reference standard in clinical trials internationally	Common in US clinical trials	Research use in some settings	Rarely used — monocular cue concern	Screening studies
Equipment dependence	Fully standalone — no lane equipment needed	Commonly bundled with lane systems	Standalone card	Often bundled with lane systems	Standalone card
Clinician survey rating (UK / US / CA)	1st — rated best practice*	Widely used in US clinics	2nd in surveys	Declining use	Preferred for infants

Green = advantage Red = limitation Amber = partial / context-dependent Highlighted row = key Frisby design feature

* Rated best-practice stereotest by the majority of respondents in peer-reviewed surveys of clinicians across the UK, United States, and Canada: Read et al. (2020) ‘Which Stereotest Do You Use?’ Ophthalmic and Physiological Optics, PMC7510382.

† The Frisby test uses larger triangular target elements by design, so the stereo stimulus remains resolvable even when acuity is reduced in one eye — enabling valid binocular vision measurement and treatment monitoring in patients with mild to moderate amblyopia. This is distinct from a test’s ability to screen for or detect amblyopia: tests with high sensitivity (such as Lang and TNO) flag cases well but may not yield valid stereo measurements once amblyopia is present.

‡ Because the Frisby target is a real physical object whose position can be varied by the clinician between trials, patients cannot memorise or predict the correct response — making it uniquely suited to longitudinal monitoring and reassessment. Printed and lenticular tests present a fixed stimulus whose location is unchanged between encounters; a patient who has previously seen the answer, or been shown it, may pass on memory rather than stereopsis.

RDS = random dot stereogram. ‘Detects binocular vision anomalies’ reflects specificity and sensitivity characteristics from comparative field studies (Hatt et al.; Greenberg et al.; Simons et al.). High specificity (few false positives) and high sensitivity (proportion of true cases detected) are distinct and both clinically valuable properties. This table covers near-vision card tests only; distance stereotests and digital/tablet-based tests are not included. All clinical decisions should be based on current peer-reviewed evidence.

Request a demonstration unit — we offer complimentary demo units to optometry educators and some clinical research programmes. Contact us at sales@frisbystereotest.co.uk or visit our contact page.