Can prism adaptation for acquired esotropia be accomplished in a shorter time frame?

Results of the Prism Adaptation Study (PAS) indicated that surgical success rates were highest when augmented surgery was performed for the increased angle of deviation in the prism adaptation responders who underwent surgery for the prism-determined angle of esotropia. The purpose of this study was to see if the prism adaptation response process could be performed in a shorter time span than dictated in the PAS protocol (minimum, 4-7 days).

After the prescription of appropriate spectacles, patients with acquired stable esotropia were prism adapted and then reexamined and readapted if necessary at 24 hours and 4 to 7 days. The 4- to 7-day visit was the determining visit in the PAS. The question in this study was whether the 24-hour visit would provide the same end point and allow adaptation in a shorter period of time. In addition, a motor end point was used in this study, whereas in the PAS, the end point was both motor and sensory.

Thirty-two patients met the entry criteria. Nineteen of the 32 patients built up their entry angle during the prism adaptation process. Thirty of the 32 patients who left the office stable at the 24-hour visit remained stable at the 4- to 7-day visit.

If the 4- to 7-day visit is used as the "gold" standard, 94% of the patients in this study would not have benefited from a longer (beyond 24 hours) wear time of prisms. With the use of motor stability, prism adaptation can be carried out in a reproducible and timely fashion.