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Effect of Intraoperative Aberrometry on the Rate of Postoperative Enhancement: Retrospective Study

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Effect of Intraoperative Aberrometry on the Rate of Postoperative Enhancement: Retrospective Study ARTICLE Effect of intraoperative aberrometry on the rate of postoperative enhancement: Retrospective study Mark Packer, MD PURPOSE: To determine whether the use of intraoperative wavefront aberrometry reduces the fre- quency of postoperative laser enhancements over the rate in cases in which aberrometry was not used. SETTING: Private surgical center and private practice, Eugene, Oregon, USA. METHODS: This was a retrospective case-control chart review of patients who chose to have correction of preexisting corneal astigmatism by limbal relaxing incisions (LRIs) at the time of cataract surgery or refractive lens exchange. In the aberrometry group, an ORange wavefront aberrometer was used intraoperatively to measure total ocular refractive cylinder after intraocular lens implantation and to guide LRI enhancement. A group in which the aberrometer was not used served as the control. RESULTS: The control group had 37 eyes and the aberrometry group, 30 eyes. The excimer laser enhancement rate was 3.3% in the aberrometry group and 16.2% in the control group. The mean postoperative cylinder was 0.48 diopter (D) in the control group and 0.37 D in the aberrometry group. Residual cylindrical refractive error, not sphere, determined the patients’ decision to have enhancement. CONCLUSION: The use of intraoperative wavefront aberrometry to measure and enhance the effect of LRIs produced a nonsignificant trend that led to a 5.7-fold reduction in the odds ratio of subse- quent excimer laser enhancement. Financial Disclosure: Dr. Packer is a paid consultant to WaveTec Vision Systems, Inc. J Cataract Refract Surg 2010; 36:747–755 Q 2010 ASCRS and ESCRS Supplemental material available at www.jcrsjournal.org. An astigmatically neutral postoperative result is a ma- intraocular lenses (IOLs) to treat higher levels of pre- jor goal of modern small-incision phacoemulsification operative astigmatism have contributed toward and refractive lens surgery. Careful planning of inci- achieving that goal.9–11 Limbal relaxing incisions are sion location, addition of limbal relaxing incisions widely used for low dioptric corrections.12 They pre- (LRIs) intraoperatively,1–8 and implantation of toric serve the optical qualities of the cornea, are easy to per- form, do not cause significant patient discomfort, and are sufficiently effective for lower levels of astigma- Submitted: September 27, 2009. tism. The limbal location of these incisions results in Final revision submitted: November 24, 2009. 13 Accepted: November 27, 2009. a consistent 1:1 coupling ratio that causes little change in spherical equivalent (SE) and eliminates From a Private surgical center and private practice, Eugene, the need to change IOL power. Osher14 and Gills1 Oregon, USA. were early advocates of LRIs. Supported by WaveTec, Inc., Aliso Viejo, California, USA. Successfully placed LRIs reduce cylinder without overcorrection or axis shift. Determining the exact lo- Presented in part at the XXVII Congress of European Society of Cat- cation of the cylinder, however, is often challenging. aract & Refractive Surgeons, Barcelona, Spain, September 2009. Keratometry, refraction, and corneal topography Corresponding author: Mark Packer, MD, Oregon Eye Associates, may not correlate. Of these, corneal topography has 1550 Oak Street, Suite 5, Eugene, Oregon 97401-7700, USA. been the most helpful and is most often used to guide E-mail: [email protected]. the surgical plan and evaluate postoperative results. Q 2010 ASCRS and ESCRS 0886-3350/10/$dsee front matter 747 Published by Elsevier Inc. doi:10.1016/j.jcrs.2009.11.029 748 INTRAOPERATIVE ABERROMETRY AND POSTOPERATIVE ENHANCEMENT RATES However, real-time information about the refractive 5 seconds. It has a dynamic range of À5.00 to C20.00 diop- status during cataract surgery could aid in the correct ters (D). placement of LRIs and prevent the need for postoper- ative enhancement surgery; it might also be able to au- Patient Counseling tomatically take into account surgically induced All suitable candidates were counseled about the expected astigmatism from clear corneal incisions (CCIs). benefits and potential risks of LRIs to correct preexisting Patients who opt to have astigmatism correction at astigmatism and the potential for reduced spectacle depen- the time of cataract surgery, with or without dence postoperatively. Patients were also counseled about toric IOLs; patients who chose this option were not included presbyopia-correcting IOL implantation, may not be in this review. Patients were also informed of the availability satisfied with the results if they continue to require of presbyopia-correcting IOLs, including the multifocal and spectacle correction because of a residual refractive er- accommodative designs that became available during the re- ror. These patients may seek further refinement of view period. The informed consent process included several their refractive status through an enhancement proce- informational videos about the general risks and benefits of cataract surgery as well as specific video presentations re- dure. Enhancement procedures for residual myopia, lated to several IOL options. hyperopia, or astigmatism are often performed with Patients were fully informed of the additional charges for the excimer laser. Although generally effective, en- the services associated with these procedures, which are not hancements incur tangible and intangible costs to the covered by Medicare or commercial health insurers in the patient and the surgeon. This study was performed United States. With the integration of the intraoperative aberrometer into the LRI procedure, the increased facility to determine whether use of an intraoperative wave- fee the surgical center charged for LRIs was carried through front aberrometer reduced the frequency of postoper- to cover the additional costs. Patients were also told that if an ative enhancements over that in cases in which the enhancement procedure was indicated to correct residual re- aberrometer was not used. fractive error after the initial refractive RLE or cataract sur- gery, there would be an additional charge for the enhancement that would equal the amount the facility PATIENTS AND METHODS charged the surgeon for performing the procedure. This retrospective case-control chart review comprised pa- tients who opted to have correction of preexisting corneal Biometry and Intraocular Lens Power Calculation astigmatism by LRIs at the time of cataract surgery or refrac- Throughout the study period, a single standardized ap- tive lens exchange (RLE) by the same surgeon (M.P.) be- proach was used for biometry and IOL power calculation. tween May 2007 and June 2009. The nature of the The IOLMaster partial coherence interferometry device procedure was explained to all participating patients, and (Carl Zeiss Meditec) was used for axial length, anterior they all signed informed consent forms before having the chamber depth, and corneal white-to-white measure- procedure. Exclusion criteria were ocular disease other 17 ments. Along with these measurements, simulated kera- than cataract, previous eye surgery including keratorefrac- tometry values from the EyeSys corneal topography tive surgery, abnormal corneal topography, and intraopera- system (Tracey Technologies) were input into the Holladay tive or postoperative complications that might limit visual 18 IOL Consultant software program. The Holladay 2 formula acuity. A standardized surgical LRI technique was used was used to calculate IOL power. throughout the study period. The patients were divided into 2 groups. The control group comprised patients who had LRIs but no wavefront Surgical Technique measurements. The aberrometry group consisted of patients The surgical technique was standardized throughout the treated with LRIs who had intraoperative wavefront mea- study period. surements and therefore may or may not have had an intra- operative LRI extension based on the wavefront Phacoemulsification Phacoemulsification was performed measurements. using a previously described biaxial microincision tech- nique.19 Briefly, 2 trapezoidal CCIs (1.4 mm) were con- Wavefront Aberrometry Device structed temporally, allowing introduction of a 20-gauge, 30-degree beveled phaco tip and an irrigating chopper. The Beginning in August 2008, the ORange intraoperative location of the 2 incisions varied depending on the antici- wavefront aberrometer (WaveTec Vision Systems, Inc.) pated location of the LRIs. In all cases, the capsulorhexis was used to measure total ocular refractive cylinder after was designed to be round, centered, and smaller in diameter IOL implantation and to guide LRI enhancement; a few cases than the IOL optic. Phacoemulsification proceeded with did not have intraoperative aberrometry because the device a vertical chop technique. The IOL was inserted through was not available. The aberrometer uses Talbot moire´inter- a third temporal trapezoidal CCI; the CCI diameter was 2.2 ferometry,15,16 which is based on 2 transmission grids spaced to 2.8 mm depending on the size required for IOL a specific distance apart and rotated relative to each other. implantation. The spectacle correction in an aberrated ocular wavefront is determined using Fourier transform calculation and is rep- Limbal Relaxing Incisions Axial maps obtained from resented in the resulting interferogram. The aberrometer at- the corneal topography system served as the basis for plan- taches to the surgical microscope and gives on-demand ning the incisions. The extent and
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