Novel Glasses-Free Distance Stereotest Using Eye Tracking: Evaluation of Sensitivity, Validity, Reliability, and Monocular Cue Masking.

Objective: This study assessed the sensitivity, validity, reliability, and monocular cue masking of a novel glasses-free distance random-dot stereotest system (GFDRDSS) compared with the established Distance Randot stereotest in youth with normal vision.

Methods: A total of 185 participants (17-20 years) with normal uncorrected visual acuity and eye alignment were enrolled. Distance stereoacuity was measured by GFDRDSS at 5 m and Distance Randot at 3 m. Among 38 participants, stereoacuity was measured under normal and induced monocular blur conditions using Bangerter filters for blurring. Test-retest data were gathered from 58 additional participants. Thirty-eight normal participants were tested with both methods to compare the sensitivity of the two stereopsis acuity tests. The same 38 participants had their monocular vision blurred to suppress stereopsis, followed by testing with the two methods mentioned above to evaluate their effectiveness. Additionally, 58 participants underwent repeated testing with a one-day interval to compare the stability of both methods, 89 participants used one eye to identify stereograms in revised GFDRDSS, GFDRDSS, and DR, and compared the monocular cues present in the three methods.

Results: Among the 38 participants, 81.58% achieved 60 arcsec stereoacuity with GFDRDSS and 100% reached 100 arcsec, while 47.37% achieved 60 arcsec and 97.37% 100 arcsec with Distance Randot (P = 0.58×10^-3). With monocular blur, stereoacuity in 89.47% (34/38) of participants fell to ≥ 200 arcsec with both stereotests (P = 0.115). Test-retest data indicated identical stereoacuity in 70.69% (41/58) of participants for GFDRDSS and 79.31% (46/58) for Distance Randot. Using both GFDRDSS and Distance Randot tests, 5.62% (5/89) of the participants were able to correctly perceive stereoscopic images with a disparity of ≤200 arcsec using only one eye. Under revised GFDRDSS conditions, only one participant was able to correctly perceive stereoscopic images at the 800 arcsec level using only one eye.

Conclusion: GFDRDSS demonstrates greater sensitivity and comparable validity and reliability to the Distance Randot stereotest. Improving the design of stereoscopic random-dot patterns can effectively eliminate monocular cues, supporting its potential in clinical stereotesting.