Editor,—The goal of cataract surgery is the rapid attainment of good visual acuity, ideally unaided for the intended focal distance and this is dependent on accurate intraocular lens (IOL) power calculation. Refractive prediction errors, if substantial, can be problematic for the patient.

If the problem is one of symmetrical ametropia, spectacle correction is usually successful. Contact lens fitting may be necessary for those patients with anisometropia in whom spectacle wear would induce significant and intolerable aniseikonia. IOL exchange as a secondary procedure may have to be considered in cases refractory to these measures.

In our study, we aimed to ascertain whether objective refraction at the end of surgery was feasible and if so, to determine how this refraction related to the final refraction at 4–7 weeks postoperatively with a view to suggesting guidelines for immediate exchange of implant in cases of gross refractive prediction errors.