An Assessment of Stereovision Acquired in Adulthood

Comparison of Depth-Related Visuomotor Task Performance in Uniocular Individuals and in Binocular Controls With and Without Temporary Monocular Occlusion

Purpose

Do one-eyed (uniocular) humans use monocular depth cues differently from those with intact binocularity to perform depth-related visuomotor tasks that emulate complex activities of daily living? If so, does performance depend on the participant's age, duration of uniocularity and head movements?

Methods

Forty-five uniocular cases (age range 6-37 years; 2.4 months-31.0 years of uniocularity) and 46 age-similar binocular controls performed a task that required them to pass a hoop around an electrified wire convoluted in depth multiple times, while avoiding contact as indicated by auditory feedback. The task was performed with and without head restraint, in random order. The error rate and speed were calculated from the frequency of contact between the hoop and wire and the total task duration (adjusting for error time), respectively, all determined from video recordings of the task. Head movements were analyzed from the videos using face-tracking software.

Results

Error rate decreased with age (P < 0.001) until the late teen years while speed revealed no such trend. Across all ages, the error rate increased and speed decreased in the absence of binocularity (P < 0.001). There was no additional error reduction with duration of uniocularity (P = 0.16). Head movements provided no advantage to task performance, despite generating parallax disparities comparable to binocular viewing.

Conclusions

Performance in a dynamic, depth-related visuomotor task is reduced in the absence of binocular viewing, independent of age-related performance level. This study finds no evidence for a prolonged experience with monocular depth cues being advantageous for such tasks over transient loss of binocularity.

A Lifetime of Double Vision: A Case Report and Literature Review of Chronic Strabismus

Strabismus is a condition preventing foveal alignment in normal gaze. Its effects can have long-standing impacts on physical, psychological, and social health. Multiple treatment options exist for strabismus such as surgery, optical correction, and vision therapy, however, treatment efficacy remains variable with little consensus on long-term impacts. Diplopia is a common side effect of the ocular misalignment secondary to strabismus and its treatment. When defining long-term success of treating strabismus, it is essential that visual sensory perception and binocular fusion has been integrated and remedied. Strabismus is complex and can be challenging to manage. To illustrate this, we report a 67-year-old female who presented with complications from long-term treatment of infantile strabismus. This case highlights differences in historical and contemporary strabismus treatments.