Background In recent years, vision problems in children have attracted more and more attention from their parents and the whole society, and children with intermittent exotropia are commonly seen in hospitals. However, related studies in China and globally mainly focus on the effect of surgery and postoperative training.
Objective To measure the changes of simultaneous vision (coincidence points), fusion range, and distance stereoacuity in children with intermittent exotropia by using synoptophore, and analyze the features of triple visual function in both eyes, so as to provide evidences for early diagnosis and timely surgical treatment.
Methods A retrospective analysis was performed for the clinical data about 103 children who visited the ophthalmic clinic for oblique amblyopia in the First Medical Center of Chinese PLA General Hospital from May 1, 2019 to May 10, 2020. Of the 103 cases, 55 children had basic-type intermittent exotropia served as intermittent exotropia group, and the other 48 children with normal vision who attended the hospital during the same period were enrolled as normal control group. The L-2510B synoptophore manufactured by Inami, Japan, was used for the examination to all the children, and the children with refractive error underwent this examination after correction. Simultaneous vision, fusion vision, and distance stereoacuity of both eyes were recorded to analyze related features. For the intermittent exotropia group, distance stereoacuity was compared between the children with different refractive status, ages, strabismus angles, and collective fusions.
Results Compared with the normal control group, the intermittent exotropia group had a significant outward shift of simultaneous vision (coincidence points) (−11.89° ± 3.20° vs −0.24° ± 1.97°, P＜0.05). Diffuse fusion was consistent between the intermittent exotropia group and the normal control group (−4.37° ± 1.39° vs −4.81° ± 1.13°, P＞0.05). Compared with the normal control group, the intermittent exotropia group had a significant reduction in collective fusion (4.40° ± 3.02° vs 12.22° ± 4.63°, P＜0.05), a significantly smaller fusion range (8.77° ± 3.16° vs 17.03° ± 4.79°, P＜0.05), and a significantly lower positive rate of distance stereoacuity 60% (33/55) vs 100% (48/48), P＜0.05. For the children with intermittent exotropia, the children with a large strabismus angle had a significantly higher loss rate of distance stereoacuity than those with a small strabismus angle (58.33% vs 20.00%, P＜0.05); the children with a small range of collective fusion had a significantly higher loss rate of distance stereoacuity than those with a large range of collective fusion (48.84% vs 8.33%, P＜0.05); however, age and refractive status had little influence on distance stereoacuity (P＞0.05).
Conclusion There are characteristic changes in the results of visual function parameters in patients with intermittent exotropia, i.e., significant outward shift of simultaneous vision (coincidence points), significant reductions in the absolute values of collective fusion and fusion range, and a significant increase in the loss rate of distance stereoacuity. The ability of collective fusion and the function of distance stereoacuity tend to get worse with the increase in strabismus angle.
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