To consider the etiology of surprise intraocular lens (IOL) power after non-complicated cataract surgery and evaluate the outcomes of secondary piggyback IOL implantation in these unsatisfied patients.

This prospective case series included 11 pseudophakic eyes of 11 patients, who had residual myopia or hyperopia after cataract surgery. Demographic information was recorded and uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and spherical equivalents (SE) of absolute residual refractive error (ARRE) were evaluated before and after surgery. In addition, the type and power of the secondary piggyback IOL were calculated.

Eleven patients with mean age of 36.8±29.63 years (range: 6months - 71 years) were operated. Causes for secondary piggy back IOL implantation were myopic shift in 3 eyes and hyperopia in 8 eyes. The causes of IOL surprise were miscalculation or mis-selection of IOL power in hyperopic eyes and myopic shift after childhood cataract surgery in 3 subjects with myopia. SE of ARRE had changed from 7.2 D preoperatively to 0.50 D after surgery. Postoperative target refraction was Plano except for three children that their IOL power was adjusted for age and management of aniometropia. One month after piggyback implantation all eyes were within +/-0.5 D from target refractions. Seventy eight percent of eyes were within +/- 0.5D from target refraction 6 months after piggyback IOL implantation, but all 8 adult subjects with hyperopia had stable refractions from the first to sixth months after surgery. No intraoperative or postoperative complications were observed during follow up period.

Secondary piggy back IOL is an effective and safe technique to correct residual ametropia, especially in extreme hyperopia and children with significant anisometropia.