Purchase this article with an account.
K.L. Masselam, J. Wong, D. Jardim, D. Pettinelli, B. Soloway, C. Starr; Nomogram for the Pre–Operative Prediction of Ablation Depth With CustomCornea Refractive Surgery . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4377.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To develop a novel nomogram for predicting the ablation depth of corneal–based refractive surgery (LASIK and Epi–LASIK) using Alcon’s LadarWave CustomCornea platform. Methods: In this retrospective study, a ratio of ablation depth in microns (u) perDiopter (D) of either spherical equivalent (SE), sphere only (SO), or sphere plus cylinder (SC) was established in 45 eyes which underwent either CustomCornea LASIK or Epi–LASIK. Average SE, SO, and SC were calculated and then divided into the average ablation depth for all 45 eyes to determine three ratios (u/D). A sub–analysis compared the ratios of ablation depth per diopter (SE, SO, SC) in 19 eyes with pre–op higher order aberrations (HOA) > 0.4u versus 26 eyes with pre–op HOA < 0.4u. Higher order aberrations were assessed using the iTrace Aberrometer (Tracey Inc., Houston, TX). Results:The average predicted ablation depth for all (45) eyes was 77. 1 u. Average SE, SO, and SC in all 45 eyes was –4.35 D, – 3.97 D, and –4.57 D, respectively. The ratio of ablation depth per diopter of SE, SO, and SC was 17.7 u/D, 19.4 u/D and 16.9 u/D, respectively. The eyes were then sub–analyzed based on HOA, 19 eyes with HOA > 0.4u (average 0.59u) and 26 eyes with HOA < 0.4u (average 0.25u). For 19 eyes with HOA > 0.4u, average ablation depth was 89.8 u and for 26 eyes with HOA< 0.4u was 67.9 u. Average SE, SO, and SC for the increased HOA group were –5.08D, –4.61 D, and –5.58 D, respectively. Average SE, SO, and SC for the lower HOA group were –3.94 D, –3.64 D, and –4.25 D, respectively. Therefore, for the increased HOA group, the ratio of ablation depth per diopter of SE, SO, and SC was 17.7 u/D, 19.5 u/D and 16.1 u/D, respectively, and for the lower HOA group the ratio of ablation depth per diopter of SE, SO, and SC was 17.2 u/D, 18.6 u/D and 16.0 u/D, respectively. Conclusions: A novel nomogram can be used in the office setting to predict ablation depth prior to customized refractive surgery using Alcon’s LadarWave platform. The ratio of ablation depth per diopter ranged from 16.9 –19.4 u/D (average of 18.1 u/D) for all eyes. We found no significant difference between the ratio of ablation depth per diopter between the increased HOA group (16.1 – 19.5 u/D) and the lower HOA group (16.0 – 18.6 u/D). Using a nomogram of 18 microns of ablation per diopter of spherical equivalent, the refractive surgeon can accurately predict the amount of corneal tissue to be removed at the time of surgery and avoid post–operative complications including corneal ectasia.
This PDF is available to Subscribers Only