CATARACT Orbscan II and double-K method for IOL calculation after refractive surgery Sérgio Kwitko & Diane R. Marinho & Samuel Rymer & Norton Severo & Carlos G. Arce Received: 30 October 2011 / Revised: 13 February 2012 / Accepted: 16 February 2012 / Published online: 29 March 2012 # Springer-Verlag 2012 Abstract Background Precise IOL calculation in post-refractive sur- gery patients is still a challenge for the cataract surgeon. The purpose of this study is to test whether adding Orbscan II values into the double-K method improves IOL calculation in this group of patients. Methods A prospective study with 43 eyes previously sub- mitted to refractive surgery that underwent cataract extrac- tion. IOL calculation was performed with double-K method. Post-K value was derived from Orbscan total-mean power map. The average corneal curvature of the general popula- tion (43.8D) was used as the pre-K value. Refraction results 30 days after surgery were compared with refraction that would be obtained if we used: (1) post-K values from keratometry, (2) post-K values from topography, and (3) pre-K values from Orbscan total-mean power. Anterior chamber depth measures obtained with the IOL Master and Orbscan II were compared. Results Mean postoperative spherical equivalent (SE) was -0.25±1.10 D in eyes submitted to radial keratotomy , – 1.04±1.42 D in eyes previously submitted to myopic Lasik, and +0.05±1.76 D in those submitted to hyperopic surger- ies. Had we inputted post-K values derived from keratom- eter and from topography, we would have obtained significantly higher postoperative refractive errors in eyes previously submitted to myopic refractive surgery (p <0.05). Refractions using pre-K derived from the central 8 mm Orbscan instead of 43.8 D were similar in all studied groups (p >0.05). Anterior chamber depth measured with IOL Master or Orbscan were similar. Conclusions Orbscan measurements used as the post-K val- ues into the double-K method provide a precise IOL calcula- tion, especially in post myopic refractive surgery patients. Keywords IOL calculation post-refractive surgery . Cataract surgery after radial keratotomy . Cataract surgery after excimer laser surgery Introduction One of the great challenges in performing cataract surgery in post-refractive surgery patients is obtaining an accurate re- fractive outcome, especially in previously myopic patients. Intraocular lens (IOL) calculation is less reliable in these cases, generally inducing hyperopic errors after cataract surgery [1–3]. The two main sources of biometric errors are the IOL formulas and the inaccuracy of post-refractive surgery central corneal curvature measurements [4]. The authors do not have any financial interest. S. Kwitko : D. R. Marinho (*) : S. Rymer : N. Severo Department of Ophthalmology, Hospital de Clínicas de Porto Alegre, Federal University of Rio Grande do Sul, Av. Dr. Nilo Peçanha, 724/401, ZIP: 90.470-000, São Paulo, Brazil e-mail: diane@portoweb.com.br S. Kwitko e-mail: sergio@oftalmocentro.com.br S. Rymer e-mail: samrymer@terra.com.br N. Severo e-mail: norton_severo@yahoo.com.br S. Kwitko : D. R. Marinho OftalmoCentro, Porto Alegre, Brazil C. G. Arce Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil e-mail: cgarce@terra.com.br Graefes Arch Clin Exp Ophthalmol (2012) 250:1029–1034 DOI 10.1007/s00417-012-1974-z