Why Screen for Stereo Vision?

True stereopsis is determined by both of a patient’s eyes working in unison to synthesize a cohesive three-dimensional mental image. While depth perception is heavily dictated by the degree of biological stereopsis, the human visual system also relies on alternative monocular cues to process space.

In an extreme clinical example where a patient has only one properly functioning eye, that individual will exhibit zero stereopsis. However, they will retain basic depth perception through alternative monocular observations. Well-developed stereo vision assists immensely in everyday functional tasks, like safely crossing a busy street or walking down a flight of stairs without the risks of distance misjudgment.³

Key Examples of Monocular Cues:

• Image Size Disparity: Objects positioned further away naturally appear smaller to the retina.
• Motion Parallax: Elements located deep in the background appear to translate across the visual field much slower than closer objects.
• Interposition / Blocking: If an object partially obscures the sightline of another, the mind automatically determines that the blocking element is in front.

The Original Stereo Fly Test

The Stereo Fly Test has established itself globally as an exceptionally reliable and straightforward standard for assessing stereoscopic vision across all patient demographics. By introducing structured spatial challenges, it empowers practitioners to rapidly diagnose developmental defects including amblyopia, spatial suppression, and strabismus.

• Gross Stereopsis Isolation: Accurately measures levels spanning from 355 down to 700 seconds of arc.
• Graded Circle Sequence: Refines assessment down to ultra-precise margins ranging from 800 to 40 seconds of arc.
• Integrated Children's Section: Features stylized animal indicators graded from 400 down to 100 seconds of arc to maintain pediatric engagement.

Standard polarized Stereo Fly screening setup.

Randot® geometric shape assessment matrix.

Randot® Stereotest

Engineered principally for advanced adult diagnostics while integrating pediatric modules, the Randot® Stereotest asks mature patients to discern six distinct geometric forms embedded in complex random-dot backgrounds. This protocol rigorously assesses deep-field perception alongside normal operational stereo vision.

• Random Dot Background Evaluation: Evaluates gross stereopsis metrics at specific 500 and 250 seconds of arc milestones using geometric matrices.
• Graded Circle Tests: Maps a detailed performance curve from 400 down to 20 seconds of arc.
• Pediatric Target Ranges: Measures child responses reliably between 400 and 100 seconds of arc.

Butterfly Stereotest

The Stereo Butterfly provides highly accurate, randomized assessments targeting gross stereopsis (2500 to 1200 seconds of arc) alongside fine depth acuity. A key security feature distinguishing the Butterfly test from legacy formats is that its diagnostic figures remain completely invisible unless viewed through polarized glasses, effectively eliminating patient guesswork.

• Graded Circle Sequencing: Ranges seamlessly from 800 down to 40 seconds of arc.
• Pediatric Optimization: Standardized animal symbols map vision acuity from 400 to 100 seconds of arc.

Stereo Butterfly random dot stereopsis booklet.

Bernell FBAT™ non-verbal evaluation format.

Bernell Functional Binocular Assessment Test Booklet (FBAT™)

Co-developed in direct partnership with leading clinical specialists Dr. Gregory Kitchener and Dr. Paul Harris, the portable Bernell FBAT™ uses precise anaglyph target filters to examine binocular mechanics across varied populations. It is an exceptional diagnostic choice for testing older infants, toddlers, and non-verbal patients.

Because these cohorts will reflexively reach into the air to grasp the highly isolated 3D figures emerging from the page planes, examiners can confirm both functional stereopsis and localization simultaneously. Built-in variation of peripheral fusion locks and central references helps clinicians accurately categorize strabismic performance.

Random Dot “E” Stereotest

Formally recommended by both the American Academy of Ophthalmology (AAO) and the American Academy of Pediatrics (AAP), this test is engineered specifically to screen toddlers and children from age three upward.

The pediatric patient is asked to successfully differentiate between a clear stereoscopic "raised E" target and a non-stereo card blank. Because the letter forms are entirely indistinguishable to the naked eye without specialized polarization viewing glasses, guessing artifacts are completely removed from the screening documentation.

Random Dot "E" card testing set with polarized glasses.

Lenticular glasses-free dinosaur screening card.

Bernell Evaluation of Stereopsis Test (BEST) - Dinosaur Version

This highly popular, glasses-free depth perception tool leverages high-grade lenticular printing technology to produce deep, brilliant 3D target visuals without demanding the use of cumbersome polarized or red/green glasses. This makes it an ideal screening option for highly sensitive pediatric patient groups.

• Plate 1 (Gross Stereopsis): Features a central, high-contrast Dinosaur figure optimized for immediate macro depth verification.
• Plate 2 (Fine Depth Perception Matrix): Split into two distinct diagnostic sub-tests containing rows of graded shapes progressing from 400" down to a highly fine 40" of arc.

Lang-Stereotest® I-R

The Lang-Stereotest® I-R stands as a premier, highly sensitive orthoptic instrument for the professional screening of complex binocular vision disorders in both adult and young pediatric cohorts. By combining a precise random-dot matrix layer natively over fine lenticular lenses, no specialized screening glasses are required during examination.

This glasses-free configuration provides a tremendous clinical advantage, allowing the attending specialist to monitor and evaluate a patient's natural compensatory eye movements directly during testing.

Standardized 3D Targets & Disparities:

Lang-Stereotest® I-R magnetic diagnostic panel.