Accuracy of different topographic instruments in calculating corneal power after myopic photorefractive keratectomy

Purpose: to compare the corneal power measurements obtained using different topographic instruments after myopic photorefractive keratectomy (prk). methods: patients with myopia who were candidates for corneal refractive surgery were sequentially included. pre-prk and six months post-prk corneal powers were measured using javal manual keratometer,orbscan ii,galilei,tomey tms4,and eyesys 2000 topographers. measured values were compared with those obtained using the clinical history method (chm). results: this study included 66 eyes of 33 patients. the lowest keratometric measurements were obtained using the galilei topographer (42.98 ± 1.69 diopters,d) and the highest measurements were obtained using the javal manual keratometer (43.96 ± 1.54 d) preoperatively. the same order was observed postoperatively. effective refractive power (effrp) measured using eyesys was most similar to the values obtained using chm (icc,intraclass correlation coefficient = 0.951),followed by the total corneal power measured using the galilei system (icc = 0.943). the values obtained using the adjusted effrp formula (effrp - 0.015∗δ refraction - 0.05) were more consistent with the values obtained using chm (icc = 0.954) compared to those obtained with the adjusted average central corneal power formula measured using the tomey system (icc = 0.919). conclusion: post-prk corneal powers measured using the adjusted effrp formula were the most similar to values obtained using chm. baradaran-rafii alireza 1 oculartissue engineering research center; labbafinejad medical center,shahid beheshti university of medical sciences,tehran fekri sahba 2 labbafinejad medical center; ophthalmic research center,shahid beheshti university of medical sciences,tehran rezaie mohammad 3 ophthalmic research center,shahid beheshti university of medical sciences,tehran salehi-rad shahram 4 ophthalmic research center,shahid beheshti university of medical sciences,tehran moradi ali 5 ophthalmic research center,shahid beheshti university of medical sciences,tehran motevasseli tahmineh 6 ophthalmic research center,shahid beheshti university of medical sciences,tehran kalantarion masumeh 7 department of medical education,school of medical education,shahid beheshti university of medical sciences,tehran waring go,durrie ds. emerging trends for procedure selection in contemporary refractive surgery: consecutive review of 200 cases from a single center. j refract surg 2008;24:s419-23. rajan ms,jaycock p,o'brart d,nystrom hh,marshall j. a long-term study of photorefractive keratectomy; 12-year follow-up. ophthalmology 2004;111:1813-24. rosa n. standards for reporting results of refractive surgery. j refract surg 2001;17:473-4. rosa n,capasso l,lanza m,romano a. axial eye length evaluation before and after myopic photorefractive keratectomy. j refract surg 2005;21:281-7. de bernardo m,capasso l,rosa n. algorithm for the estimation of the corneal power in eyes with previous myopic laser refractive surgery. cornea 2014;33:e2. cennamo g,rosa n,la rana a,bianco s,sebastiani a. non-contact tonometry in patients that underwent photorefractive keratectomy. ophthalmologica 1997;211:341-3. rosa n,cennamo g. goldmann applanation tonometry after prk and lasik. cornea 2001;20:905-6. rosa n,furgiuele d,lanza m,capasso l,romano a. correlation of changes in refraction and corneal topography after photorefractive keratectomy. j refract surg 2004;20:478-83. rosa n,lanza m,capasso l,lucci m,polito b,romano a. anterior chamber depth measurement before and after photorefractive keratectomy: comparison between iol master and orbscan ii. ophthalmology 2006;113:962-9. rosa n,capasso l,lanza m. power calculation after laser refractive surgery. © 2017 journal of ophthalmic and vision research published by wolters kluwer - medknow.