The purpose of this study was to evaluate the effect of the prism adaptation test (PAT) on angle and distance-near-deviation (DND) in intermittent exotropia (IXT), and determine the frequency of responders and non-responders to PAT. This was a single-centre study of 100 patients; 46% male. Mean age at surgery was 31.9 ±17.1 years. Preoperative angle was -33.6 ±13.3 prism dioptres (PD) for distance and -34.4 ±15.5PD for near. Bagolini response was positive for 53 patients. After PAT, the angle was -32.7 ±12.4PD for distance and -34.6 ±12.9PD for near. Responses were grouped further to (1) D>N angle with DND of ≤3PD (n=24), (2) D=N ±2PD (n=37), and (3) N>D angle with DND of ≥3PD (n=39). Surgery involved unilateral medial rectus plication and lateral rectus recession for 94 cases; unilateral lateral rectus recession for 6 cases. Postoperative angle was -4.3 ±6.6PD for distance and -6.9 ±8.1PD for near. Positive Bagolini was in 58 cases, suppression in 29 and diplopia in 9 cases at distance. At near, 78 had positive Bagolini, 14 with suppression and 4 with diplopia. Postoperative angle measurements were significant lower for group 1. Overall, 19 cases were overcorrected at distance and 11 at near. Fewest overcorrections were in group 2. Results were worst for group 3. The results suggest PAT is helpful in establishing the largest angle preoperatively to guide surgical dose, whilst also testing for binocular vision potential and postoperative diplopia. A limitation of the study was the short follow-up period.
Prism adaptation responses for variable distance-near deviation in intermittent exotropia
Reviewed by Fiona Rowe
Impact of prism adaptation test on distance-near-deviation (DND) before strabismus surgery in patients with intermittent exotropia.
CONTRIBUTOR
Fiona Rowe (Prof)
Institute of Population Health, University of Liverpool, UK.
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