Intraocular lens power calculations in a patient with posterior keratoconus

Purpose: We describe a patient with posterior keratoconus accompanied by hyperopia and a cataract, which were successfully treated by cataract surgery and secondary piggyback intraocular lens (IOL) implantation. Methods: Case report. Results: A 47-year-old woman presented to our clinic with low vision in her right eye. Uncorrected distant visual acuity was 20/400 in the right eye with a manifest refraction of +11.5 diopters. On the slit-lamp examination, localized posterior keratoconus and lens opacity were noted in the right eye. First, we performed phacoemulsification and posterior chamber IOL implantation. Postoperatively, hyperopic shift was noted because localized posterior elevation of the cornea is not considered in the conventional IOL power calculation. After secondary piggyback IOL implantation in the sulcus, her refractive error was finally properly corrected and uncorrected distant visual acuity improved to 20/50. Conclusions: In patients with posterior keratoconus, IOL power calculation from conventional keratometry may be inaccurate, and secondary piggyback IOL procedure may be needed after cataract surgery.