Effect of TNO red-green glasses on local stereoacuity

Local stereoacuity was reduced when red-green anaglyph glasses were worn. Glasses were from the TNO stereotest. Without these glasses, all 15 subjects had good or almost good local stereoacuity. With the glasses, all stereoacuities were reduced but one subject still had a good stereoacuity of 8 sec arc. Reductions with the TNO anaglyph glasses ranged from 2 to 34 sec arc. The TNO test was also performed to see if there was a difference between local and global stereoacuity while wearing the glasses. Results were similar for 6 subjects, all of whom had the best TNO stereoacuity of 15 sec arc. Global (TNO) stereoacuity was worse than local stereoacuity for the other subjects with the most extreme difference being 464 sec arc. If aniseikonia was induced by the red-green glasses, this could not have contributed to a reduction in either local or global stereoacuity.