Diplopia as a complication of laser in situ keratomileusis surgery

A case is presented of a patient with high myopia who developed vertical bi nocular diplopia after decentred laser in situ keratomileusis (LASIK) surge ry with associated decompensation of pre-existing exophoria into an exotrop ia. A 40-year-old man underwent LASIK surgery for high myopia in his right eye. Preoperatively, he was approximately -26.00/-2.00 x 35 degrees with vi sual acuity of 6/12(-2) in that eye. He also had an asymptomatic exophoria. After LASIK surgery, he achieved a refraction of -3.25/-0.50 x 80 degrees with 6/21 best-corrected visual acuity. He also developed binocular diplopi a. The ablation zone had been decentred upwards and there was also an exo- and hypo-deviation of his right eye. He was able to superimpose the two ima ges in free space with vertical and horizontal prisms. A hard contact lens also resulted in superimposition of the two images. Vertical decentration o f the ablation zone can induce a vertical prism effect after LASIK surgery and result in vertical diplopia. This together with abnormal optics also ca used loss of best-corrected vision and decompensation of his pre-existing e xophoria into an exotropia.