Fusion vergence measures
Reviewed by Fiona Rowe

The purpose of this study was to compare fusional vergence measurements between orthophoria, esophoria and exophoria and determine the strength of correlation between fusional vergence and angle of deviation. This was a cross-section study of 530 children aged six to 14 years with a mean of 7.66±1.2 years. Of these, 52.8% were female and there were 181 cases of exophoria. The overall angle of deviation was 1.81±2.63 (0-10) at near and 0.13±0.661 (0-4) at distance fixation. The median angle of deviation was -4 (2-10) at near and -4 (2-4) for distance fixation in exophoria; 6 (2-10) for near and 4 for distance fixation in esophoria. There were no cases of vertical phoria. Mean near point of convergence was 6.04±0.38cms (six to 11) and mean near accommodative point was 19.74±1.19D (10-20). The overall prism fusion positive range was 20.23±5.04 at near and 13.08±3.19 at distance fixation; negative range was 9.71±1.99 at near and 6.98±1.81 at distance fixation. Mean fusion reserve ratios were 4.45±2.56 (1-17.5) at near and 4.24±1.72 (1.5-7) at distance fixation. Prism fusion range positive range values differed for exophoria being smaller than those of orthophoria and esophoria. There was a significant inverse correlation for small convergence amplitude with large deviation angles. Recommendations from this study are for consistent target size and measurement methods for assessment over time. In eso deviations, negative fusion ranges should be considered first and, for exo deviations, positive fusion ranges should be considered first. 

Variability of fusion vergence measurements in heterophoria.
Costa Lanca C, Rowe FJ.
STRABISMUS
2016;24(2):63-9.