Correlations of fusional convergence with suppression depth in control of exotropia
Reviewed by Fiona Rowe

This study was undertaken to investigate the differences in fusional convergence during refusion in patients with intermittent exotropia based on suppression depth and exotropia control. This was a cross-sectional study of 25 patients; 15 female and 10 male aged mean 10.8 ±3.4 years (range 6–18). Eleven had a dominant right eye. Mean angle of deviation was 34.4 ±15.6PD at 4m distance and 40.6 ±17.2PD at near. Fourteen were basic type exotropia and 11 convergence insufficiency type. There were no cases of divergence excess type. Mean control score was 30 ±1.8 at 4m distance and 1.9 ±2.1 at near. There was a trend to higher control scores for basic type exotropia. There was no agreement between control score and types of intermittent exotropia. Mean contribution rate to fusional convergence was 1.08 ±0.49 log10% in the dominant eye and 1.35 ±0.51 in the non-dominant eye. Mean suppression depth was -0.65 ±1.82 log10% in the dominant eye and -1.18 ±1.76 in the non-dominant eye. Mean phoria maintenance values were 1.43 V0.65 log10% in the dominant eye and 1.59 ±0.58 in the non-dominant eye. Overall contribution rate to fusional convergence was not significantly correlated with suppression depth for either eye. However, on subtype analysis of suppression depth, there was a significant correlation in the dominant eye for those with shallow suppression. There was no significant correlation for deep suppression and none for phoria maintenance. The authors speculate that progression of suppression affects fusional convergence between dominant and non-dominant eyes and the asymmetric fusional convergence leads to a decrease in fusional control. They acknowledge the need to test these measures in larger numbers, in adults and in all types of intermittent exotropia.

Relationships between fusional convergence, suppression depth and exotropia control in intermittent exotropia.
Kakene K, Mihara M, Ataka H, et al.
STRABISMUS
2024;32(3):139–48.