Titmus Stereopsis Test: Animal and Circles Components
Test Components and Structure
The Titmus stereopsis test consists of two main quantitative components: the Circles test (measuring stereoacuity from 800 to 40 seconds of arc) and the Animal figures (measuring stereoacuity at 100-400 seconds of arc), plus a qualitative House Fly component for gross stereopsis screening. 1, 2
Circles Component
- Measures fine stereoacuity ranging from 800 seconds of arc down to 40 seconds of arc 2
- Consists of nine diamond-shaped patterns, each containing four circles 2
- Patient identifies which circle appears elevated or closer in each pattern 2
- Normal stereoacuity threshold is 80 seconds of arc (6/9 circles correct) 3
- Uses polarized glasses to present disparate images to each eye 1
Animal Component
- Assesses intermediate levels of stereopsis at 100-400 seconds of arc 1
- Contains three animals (typically cat, rabbit, and monkey) presented at different disparity levels 1
- Patient identifies which animal appears to stand out or be closer 1
- Serves as a bridge between gross stereopsis (fly) and fine stereoacuity (circles) 1
Clinical Application for Depth Perception Assessment
Testing Sequence
- Begin with the House Fly for gross stereopsis screening, then progress to Animals for intermediate levels, and finally Circles for fine stereoacuity 4
- Maintain standard testing distance of 40 cm 1
- Ensure proper polarized glasses alignment 1
Critical Limitations to Recognize
Both Circles and Animals contain monocular form cues that can produce false-positive results, particularly in patients with binocular vision disorders: 2
- Stereoacuity scores worse than 160 seconds of arc (>2.2 log seconds of arc) should be interpreted with extreme caution as monocular cues increasingly invalidate results beyond this threshold 2
- Patients with small-angle strabismus who have been repeatedly exposed to the test are particularly vulnerable to overestimation of stereoacuity 4
- The Titmus Fly test has only 26% specificity due to high false-positive rates, despite 79% sensitivity 4
Avoiding Common Pitfalls
- Modify the Fly test presentation by varying the angle or covering portions to reduce false positives in patients with childhood-onset strabismus 4
- When testing patients with known binocular disorders, consider supplementing with random-dot stereotests that lack monocular cues 2
- In strabismic patients, recognize that static stereopsis tests (including Titmus) may not capture motion-in-depth perception abilities 5
- For patients with suspected chiasmal lesions who maintain good visual acuity and orthophoria, failure on Titmus Circles (unable to achieve 6/9 correct) may indicate compression of decussating fibers affecting the fixation point 3