The purpose of this study was to evaluate the effects of varied testing distance and order of testing on fusion amplitudes in subjects with normal eye examinations, along with impact of examination encouragement and subject level of alertness. Average age of 99 subjects was 38 years with a 4:1 F:M ratio. A modified cross-over design was used to alter the order of testing. All measured heterophoria was incorporated into the final value of fusional amplitude. Break and recovery points for divergence were significantly affected when assessed after convergence. Measurements at near were significantly higher for convergence and divergence than at distance. A significant negative correlation was found for age and convergence break and recovery points. Encouragement significantly affected convergence break and recovery points but there was no significant association with alertness. The author recommends a standardised testing approach to enable more accurate comparisons of measures.

Fusional amplitudes: developing testing standards.
Fray KJ.
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Fiona Rowe (Prof)

Institute of Population Health, University of Liverpool, UK.

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