Second Generation Binocular Polaroid Test

Spatial perception in normal and strabismic subjects: role of stereopsis and monocular clues

PURPOSE

To evaluate the roles of binocular vision, monocular clues, and experience in spatial perception in a prospective, nonrandomized, case-control study.

METHODS

A test was created consisting of three wood blocks arranged along the frontal plane inside Panum area. To produce some degrees of horizontal disparity, blocks were moved along a sagittal plane. Thirteen normal subjects (control group) and 13 nonamblyopic strabismic subjects (study group) were asked to identify, both under binocular and monocular vision, the position of the blocks in a series of 12 randomized presentations (phase 1). In phase II of the trial, a letter E in three different sizes, acting as a monocular clue, marked the three blocks. In both phases, the number of correct answers to the test during binocular and monocular vision was recorded.

RESULTS

Binocular normal responses appeared greater than monocular normal responses and strabismic binocular responses in both phases (p < 0.001). Binocular strabismic responses and monocular answers of both groups appeared similar.

CONCLUSIONS

In our experimental model, spatial orientation of strabismic subjects in binocular vision is substantially identical to that of normal subjects in monocular vision. Monocular clues were used in the same manner in both groups of subjects, and experience seemed to play no role in spatial localization of visual objects.

Screening for suppression in young children: the polaroid suppression test

BACKGROUND

Assessment of monocular visual impairment during screening of young children is often hampered by lack of cooperation. Because strabismus, amblyopia, or anisometropia may lead to monocular suppression during binocular viewing conditions, a test was developed to screen for suppression in young children.

METHODS

Children were invited to look through two polaroid filters of different polarization direction at two pictures covered with polaroid filters of opposite polarization direction. In this way, each eye could only see one of the two pictures. In cases of suppression, only one picture would be visible. Acuity measurements in 201 5-year-old children were compared with the Polaroid Suppresion test (PST) results.

RESULTS

The PST had a high success rate (99.5%) and testing time was under 1 minute. Specificity of the PST for acuity impairments was 91%. The low sensitivity of 60% was caused mainly by the fact that some children with binocular acuity impairments were not detected with the PST. However, the PST was highly sensitive for significant interocular acuity differences.

CONCLUSION

The PST has been found to be a useful screening method for amblyogenic factors in young children. The test can be carried out without occlusion of one eye. The apparatus is portable, the test duration is short, and the costs are low. The results indicate that the PST is a very promising tool to use in clinical conditions and for screening large numbers of young children.