*4.3. Stereopsis Di*ff*erences between Slow and Fast Gross Motor Development*

Stereopsis allocates depth calculations based on the binocular disparity between the images of an object in the left and right eyes [62]. Toddler stereopsis determination allows rapid detection of visual disturbances, mainly cases of amblyopia with a history of strabismus [63]. Previous studies concluded that toddlers with deficient stereopsis have developmental disorders [20]. Other studies showed that stereopsis is associated with higher performance of certain fine motor tasks at very young ages [21]. We also found studies that showed that many toddlers perform well on manual skill assessments even with poor stereopsis [64]. Previous research demonstrated that toddlers who underwent strabismus surgery showed postoperative improvements in motor performance that were not correlated with stereopsis improvements [65]. Our stereopsis findings were similar in the toddlers' fine and gross motor development. This was probably because the toddlers in the sample did not present any type of visual alterations. Stereopsis was positive in both groups, with a slight non-statistically significant difference in the fast-gross motor development group (282.35 ± 131.35) second arc, compared to the slow gross motor development group (303.89 ± 143.67) second arc with P = 0.45.

### *4.4. Future Research and Limitations*

Future research could be assessed by visual and therapy programs. Visual therapy has been shown to be a useful treatment option in subjects with visual disturbances [66,67] and assesses how it affects motor development quotients. We also proposed the reverse option, conducting an intervention to promote and enhance motor development in toddlers with slow gross motor development to ascertain how it affects binocular vision development. Within the limitations, sample follow-up was missing because this was a cross-sectional study. Future research should include longitudinal gross and fine motor development changes in this sample. The toddlers enrolled were in their last year of nursery school. This issue could limit sample follow-up.
