This study reports the changes to angle of deviation following prism adaptation in a group of 58 patients with convergence excess esotropia and their surgical outcomes. Age at prism adaptation was 7.2 (SD1.82) years. One child refused prisms and two discarded prisms after regaining control of their deviations. Six did not have sufficient measurements. Forty-nine children remained for analysis. On correction of the near deviation with prisms, nine developed exotropia at six metres. After one-hour adaptation, four had reverted to esophoria, one exophoria, one intermittent esotropia, one intermittent exotropia and three constant exotropia. The median prism was 30PD. Twenty-eight needed a change in prism strength during the adaptation process; 22 increased. Data was available for 55 children after surgery; nine had residual esotropia and 46 were fully binocular (31 fully accommodative esotropia, 13 esophoria, one microtropia and one orthophoria). The author concludes that prism adaptation reveals an otherwise masked angle in most cases with median increase of 20PD at near and distance. The distant angle frequently approaches the near angle measurement. About 84% of cases became fully binocular after one operation following prism adaptation. 

The effect of prism adaptation on the angle of deviation in convergence excess esotropia and possible consequences for surgical planning.
Garretty T.
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Fiona Rowe (Prof)

Institute of Population Health, University of Liverpool, UK.

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