Resistance to occlusion: sensitivity to induced blur in 6- to 12-month-old infants.

BACKGROUND

Resistance to occlusion and fix and follow are often used to make inferences about the acuity of young children. In this study, the acuity of 6- to 12-month-old infants was degraded monocularly to elicit resistance to occlusion or loss of fixation.

METHODS

Occlusion foils and optical blur were used to simulate monocular acuity reduction. Two different targets, a mechanical rabbit and a "flickering" light were used for fixation.

RESULTS

More infants resisted occlusion when viewing the rabbit than the light. Resistance to occlusion was observed in the majority of infants when acuity was degraded to the level expected for 6 to 12-month-old infants (20/80-20/300).

CONCLUSIONS

The sensitivity of resistance to occlusion is influenced by the test target and if an interesting target is used, resistance to occlusion may be a useful tool for detecting interocular acuity differences in 6- to 12-month-old infants.