Purpose: Although there have been studies in the past of the difference between distance and near stereopsis in intermittent exotropia, no such comparisons have been studied and/or reported for other forms of strabismus, nor for strabismic functional amblyopia, or for refractive functional amblyopia.
Methods: The study was prospective: Sixty-eight consecutive patients, ages 6-76 years, with either childhood onset strabismus and no amblyopia, childhood onset strabismus and amblyopia, or refractive amblyopia and no strabismus, had their stereopsis measured. Distance stereopsis was determined on the Mentor BVAT with Random Dot E Test (global stereopsis) and the Circle Test (contour stereopsis). Near stereopsis was determined with the Circle Test of the Randot Stereotest. The data were tabulated and analyzed statistically.
Results: Of the 26 strabismus/no amblyopia cases, 14 (54%) appreciated distance stereopsis. Of these, 12/14 were intermittent, and other 2 who were constant had deviations of 8 PD or less. Only 4 of the 14 appreciated global stereopsis at distance (mean = 90 sec. of arc), but all 14 appreciated contour stereopsis at distance (mean = 125 sec. of arc). Of all 26, 21 (81%) had near stereopsis (mean = 137 sec. of arc). For the 21 strabismic amblyopes, only one appreciated global stereopsis at distance (120 sec of arc), and 2 (10%) contour stereopsis at distance (mean = 210 sec. of arc). These two and 4 others (total 29%) had near stereopsis (mean = 162 sec. of arc). For the 21 refractive amblyopes, 3 appreciated global stereopsis at distance (mean = 220 sec. of arc), 11 in all, (52%) contour stereopsis at distance (mean = 121 sec. of arc) and 20 (95%) had near stereopsis (mean = 78 sec. of arc). The percentages of patients in all categories capable of appreciating distance stereopsis were "statistically significantly" (P<.05) or clinically/medically significantly different from (less than) the percentages having near stereopsis.
Conclusions: distance stereopsis is more likely to be reduced or absent than near stereopsis in strabismus, strabismic amblyopia and refractive amblyopia and thus appears to be more sensitive to, and better screening for, binocular vision disorders and a stronger and better outcome standard for treatment of binocular vision disorders than near stereopsis.