Test retest variability in stereoacuity measurements

Area of Science:

• Ophthalmology
• Vision Science
• Clinical Measurement

Background:

• Clinician's choice of stereotest relies on measurement robustness, including sensitivity, specificity, and test-retest variability.
• Limited data exist on the test-retest variability of newer stereotests compared to established ones.
• Understanding test-retest variability is crucial for accurate clinical assessment of stereoacuity.

Purpose of the Study:

• To determine the test-retest variability of four stereotests: TNO, Frisby, Lang Stereopad, and Asteroid (Accurate STEReotest On a mobIle Device).
• To compare stereoacuity measurements between these tests in an adult population.
• To provide data for clinicians selecting reliable stereotests.

Main Methods:

• Stereoacuity was measured twice in adult participants (≥18 years) with normal vision using TNO, Frisby, Lang Stereopad, and Asteroid.
• Participants had best-corrected visual acuity ≥0.3 logMAR and interocular difference <0.2 logMAR.
• Bland-Altman analysis assessed agreement within and between tests; Wilcoxon signed-rank tests compared stereo thresholds.

Main Results:

• Fifty-four adults participated. Test-retest variability was clinically insignificant for TNO, Frisby, and Asteroid (mean bias ≤0.06 log seconds of arc).
• The Asteroid test exhibited the smallest variation between repeated measures (mean bias: -0.01 log seconds of arc).
• The Frisby and Lang Stereopad tests showed the narrowest and widest limits of agreement, respectively. Significant mean bias was found between Frisby and Lang Stereopad.

Conclusions:

• TNO and Frisby tests demonstrate good reliability but cover a narrower stereoacuity range.
• The Asteroid test offers less variation on repeated testing and a wider testing range.
• Further research is needed to assess variability in individuals with reduced stereoacuity.