Overestimation of stereo thresholds by the TNO stereotest is not due to global stereopsis

Abstract

PurposeIt has been repeatedly shown that the TNO stereotest overestimates stereo threshold compared to other clinical stereotests. In the current study, we test whether this overestimation can be attributed to a distinction between ‘global’ (or ‘cyclopean’) and ‘local’ (feature or contour‐based) stereopsis.MethodsWe compared stereo thresholds of a global (TNO) and a local clinical stereotest (Randot Circles). In addition, a global and a local psychophysical stereotest were added to the design. One hundred and forty‐nine children between 4 and 16 years old were included in the study.ResultsStereo threshold estimates with TNO were a factor of two higher than with any of the other stereotests. No significant differences were found between the other tests. Bland‐Altman analyses also indicated low agreement between TNO and the other stereotests, especially for higher stereo threshold estimates. Simulations indicated that the TNO test protocol and test disparities can account for part of this effect.DiscussionThe results indicate that the global – local distinction is an unlikely explanation for the overestimated thresholds of TNO. Test protocol and disparities are one contributing factor. Potential additional factors include the nature of the task (TNO requires depth discrimination rather than detection) and the use of anaglyph red/green 3D glasses rather than polarizing filters, which may reduce binocular fusion.

Which Stereotest do You Use? A Survey Research Study in the British Isles, the United States and Canada

“…Clearly, an ideal test would avoid non-stereo artefacts, such as the motion artefacts visible monocularly in both the Frisby and Lang stereotests if the patient moves their head. It also seems desirable to avoid the interocular colour differences introduced with anaglyph glasses, which may be responsible for the poorer stereo thresholds obtained with the TNO stereotest (Vancleef et al, 2017). However, the question of which stereotest is "best" is complicated by the fact that, as indicated in the Introduction, different tests measure different aspects of stereopsis.…”

Evaluation of vision screening in five‐ to eight‐year‐old children living in Region Västra Götaland, Sweden – a prospective multicentre study

“…Ocular motility was tested with a penlight, and binocular function was tested with the TNO test (Vancleef et al. ).…”

Accommodation and stereopsis in adults with traumatic brain injury

“…This discrepancy may be caused by the measurement tool, because the TNO stereotest was found to overestimate the stereo thresholds compared to the randot stereotest. 24 Additionally, the severity of the conditions of the patients included 50 per cent mild and 50 per cent severe TBI in this study (as shown in Table 1) which may explain the elevated stereoacuity thresholds. 22 Nevertheless, all the studies reported elevated stereoacuity thresholds in TBI patients compared with control subjects.…”

“…Near stereoacuity was assessed using the TNO stereopsis test (Lameris Ootech BV Ede, 18th edition), previously described. 24 ACCOMMODATION TESTS Amplitude of accommodation was measured monocularly and binocularly using the Push-Up method. Expected amplitude of accommodation was calculated according to the Hofstetter formula.…”