مقایسه‌ی کراتومتری پنتاکم وکراتومتری IOL Master در محاسبه‌ی لنز داخل چشمی افراد با قرنیه‌ی طبیعی

Background and Objective: Proper method and machine for corneal evaluation is an important factor in many anterior segment interventions. This study was performed to compare the mean keratometry (K) readings obtained with an IOL Master and Pentacam for intraocular lens power calculation in normal subjects with no history of refractive surgery. Materials and Methods: Mean K values were obtained with the automated (IOL Master) and Scheimpflug keratometer. Scheimpflug readings obtained from simulated K (SIMK) and Holladay equivalent K (EKR) were analysed. Specific formula for a defined intraocular lens was considered according to the IOL Master, Pentacam SIMK and EKR data. Results: 100 eyes undergoing PRK were evaluated. The mean age of patients was 27 ± 4.3 year old. The mean corneal power by IOL Master, SIMK and the EKR was 44.52 D ± 1.54, 44.08 D ± 1.46 and 44.25 D ± 1.48, respectively. The mean intraocular lens power by these three machines was 17.15 D ± 2.14 and 17.6D ± 2.2 and 17.53 D ± 2.14, respectively. There was a statistically significant correlation between IOL Master and SIMK and EKR corneal power and intraocular lens power calculated by the three aforementioned techniques (P < 0.001). There was a statistically significant difference between mean corneal power by IOL Master, SIMK and EKR and intraocular lens power calculated by IOL Master, SIMK and EKR. (P < 0.001) Conclusion: Despite the high correlation between the mean corneal power of automated keratometry, SIMK and EKR, also indicated a high correlation between intraocular lens power calculated by automated keratometry, SIMK and EKR. There was a statistically significant difference between them and the values were not interchangeable. References 1- Elie Saad, Maya C, Shammas H, John Shammas. Scheimpflug corneal power measurements for intraocular lens power calculation in cataract surgery. Am J Ophthalmol. 2013 156: 460-67. 2- J Santodomingo-Rubido, EAH Mallen, B Gilmartin, JS Wolffsohn. A new non-contact optical device for ocular biometry. Br J Ophthalmol. 2002 86: 458-62. 3- Olsen T. Improved accuracy of intraocular lens power calculation with Zeiss IOLMaster. Acta Ophthalmol Scand. 2007 85: 84-87. 4- Richard J Symes, MRCOphth, Paul G. Ursell, FRC Ophth. Automated keratometry in routine cataract surgery: comparison of scheimpflugand conventional values. J Cataract Refract Surg. 2011 37: 295-301. 5- Borasio E, Stevens J, Smith GT. Estimation of true corneal power after keratorefractive surgery in eyes requiring cataract surgery: BESSt formula. J Cataract Refract Surg. 2006 32: 2004-14. 6- Kawamorita T, Uozato H, Kamiya K, et al. Repeatability, reproducibility, and agreement characteristics of rotating scheimpflug photography and scanning-slit corneal topography for corneal power measurement. J Cataract Refract Surg. 2009 35: 127-33. 7- Visser N, Berendschot T, Verbakel F, Brabander P, Nuijts R. Comparability and repeatability of corneal astigmatism measurements using different measurement technologies. J Cataract Refract Surg. 2012 38: 1764-70. 8- Richard J, Symes MR, Miranda J, Say MS, Paul G, Ursell FR. Scheimpflugkeratometry versus conventional automated keratometry in routine cataract surgery. J Cataract Refract Surg. 2010 36: 1107-14. 9- Neuhann T. Pentacam system’s overview: understanding its benefits. Highlights of Ophthalmology. 2007 35: 1-3. 10- Woodmass J, Rocha G. A comparison of scheimpflug imaging simulated and holladay equivalent keratometry values with partial coherence interferometry keratometry measurements in phakic eyes. Can J Ophthalmol. 2009 44: 700-4. 11- Giacomo Savini, Piero Barboni, Michele Carbonelli, Kenneth J. Accuracy of scheimpflug corneal power measurements for intraocular lens power calculation. J Cataract Refract Surg. 2009 35: 1193-97. 12- Barkana Y, Gerber Y, Avni I, Zadoc D. Comparison of different techniques of anterior chamber depth and keratometric measurements. Am J Ophthalmol. 2007 143: 48-53. 13- Shirayama M, Wang L, Weikert MP, Koch DD. Comparison of corneal powers obtained from 4 different devices. Am J Ophthalmol. 2009 148: 528-35. 14- Fledelius HC, Stubgaard M. Changes in refraction and corneal curvature during growth and adult life. A cross-sectional study. Acta Ophthalmol. 1986 64: 487-91. 15- Lam AK, Douthwaite WA. The ageing effect on the central posterior corneal radius. Ophthalmic Physiol Opt. 2000 20: 63-69.