[Diplopia after sub-Tenon's anesthesia for cataract surgery].

PURPOSE To study the clinical signs, treatment and prognosis of strabismus after sub-Tenon's anesthesia for cataract surgery. METHODS Eight patients without previous strabismus developed incomitant diplopia immediately after cataract surgery; the left eye was affected in five patients and the right eye in three. Restrictive strabismus was diagnosed with the cover test, prisms, and active and passive ductions in all cases. In seven cases the deviation was vertical and in one patient it was horizontal. The average deviation was 17.5 S.D. 9.84 (range 5-35) prismatic dioptres in primary position. The deviation increased looking upward in seven cases, and looking sideways to the left in the other. It was considered to be a good result if the diplopia disappeared after treatment. RESULTS Botulinum toxin was the first treatment applied in four patients, but only one showed a good response and required no further therapy. Strabismus surgery was required in four cases, and prisms were adapted in three. Three patients required two strabismus operations. A good result was achieved in all cases, with the average time interval being 10.12 (SD 5.5) months. CONCLUSIONS Sub-Tenon's anesthesia may result in restrictive strabismus and incomitant diplopia which does not resolve spontaneously. The inferior rectus is the most commonly affected muscle. Strabismus surgery is required to resolve the diplopia in half of the cases. Good results have been achieved in all patients.