Orbscan II and double-K method for IOL calculation after refractive surgery

• Published in: Graefe's archive for clinical and experimental ophthalmology 2012-07, Vol.250 (7), p.1029-1034
• Main Authors: Kwitko, Sérgio, Marinho, Diane R., Rymer, Samuel, Severo, Norton, Arce, Carlos G.
• Format: Article
• Language: English
• Subjects: Aged; Cataract; Cataract Extraction; Corneal Topography - methods; Humans; Hyperopia - surgery; Keratomileusis, Laser In Situ; Keratotomy, Radial; Lenses, Intraocular; Medicine; Medicine & Public Health; Middle Aged; Myopia - surgery; Ophthalmology; Optics and Photonics; Photorefractive Keratectomy; Prospective Studies; Refraction, Ocular - physiology; Refractive Surgical Procedures
• ISSN: 0721-832X; 1435-702X
• DOI: 10.1007/s00417-012-1974-z

Background Precise IOL calculation in post-refractive surgery 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 submitted to refractive surgery that underwent cataract extraction. 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 population (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 surgeries. Had we inputted post-K values derived from keratometer and from topography, we would have obtained significantly higher postoperative refractive errors in eyes previously submitted to myopic refractive surgery ( p   0.05). Anterior chamber depth measured with IOL Master or Orbscan were similar. Conclusions Orbscan measurements used as the post-K values into the double-K method provide a precise IOL calculation, especially in post myopic refractive surgery patients.