1. Orbscan II and double-K method for IOL calculation after refractive surgery
- Author
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Diane Ruschel Marinho, Samuel Rymer, Sergio Kwitko, Nórton Souto Severo, and Carlos G. Arce
- Subjects
Optics and Photonics ,medicine.medical_specialty ,genetic structures ,medicine.medical_treatment ,Keratomileusis, Laser In Situ ,Cataract Extraction ,Refraction, Ocular ,Photorefractive Keratectomy ,Cellular and Molecular Neuroscience ,Ophthalmology ,Refractive surgery ,Myopia ,medicine ,Humans ,Prospective Studies ,Orbscan ii ,Aged ,Keratotomy, Radial ,Lenses, Intraocular ,business.industry ,Corneal Topography ,Middle Aged ,eye diseases ,Sensory Systems ,Refractive Surgical Procedures ,Hyperopia ,Optometry ,sense organs ,business - Abstract
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.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.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). 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.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.
- Published
- 2012