Eyeworld

EW RESIDENTS 74 September 2018 EyeWorld journal club by Mary Kate Russell, MD, Alexander Knezevic, MD, Lauren May, MD, and Dmitry Pyatetsky, MD They also reported an "Index of Success," which is the ratio of DV to TIA. Both procedures undercor- rected the astigmatism on average (SIA < TIA). Manual LRI corrected significantly less cylinder than FS- AK (p=0.02): 48% of the measured astigmatism versus 73%, respective- ly. When using a goal of <0.5 D of residual cylinder, 20% of the manual LRI group met the goal versus 44% of the FS-AK group. When the goal was set at <1 D postoperative cylinder, 44% of manual LRI cases were successful compared to 74% of FS-AK cases. Despite multiple param- eters revealing statistically signifi- cant differences favoring FS-AK, the "Index of Success," which factors in the preoperative criteria, was not sta- tistically significant between the two groups (p=0.07). In addition, both groups achieved similar visual acuity outcomes with approximately 60% of patients in each group not need- ing additional refractive correction. Neither group had a misalignment Four hundred patients with >0.9 D of cylinder were randomized. Paired LRIs were done prior to cataract surgery with a 600-micron guard- ed diamond knife. Donnenfeld's nomogram was used for LRI calcula- tions, aiming to correct 100% of the astigmatism. All of the FS-AK cases used the Day et al. nomogram, 6 which is intended to correct up to 70%, but for calculation simplicity, Roberts et al.'s study had a goal of 100% correction. The authors recorded postoper- ative visual acuity, refraction, and corneal topography (Pentacam, Oculus, Wetzlar, Germany). Postop- erative astigmatism was compared to the preoperative measurements using the Alpins method. The Alpins method is commonly used in refrac- tive surgery, comparing the ideal outcome, target-induced astigma- tism (TIA), to the actual outcome, surgical-induced astigmatism (SIA). The difference between these values is the difference vector (DV). Each value has a magnitude and an axis. 7 conjunction with standard cataract surgery. Limbal relaxing incisions have been performed for nearly 20 years. The typical procedure involves mak- ing a single or paired 600-micron (within 50 microns of full thickness) incision along the steep axis, parallel to the limbus. 4 FS-AK is a newer addition to this genre of procedures, and typically involves arcuate incisions at 95% depth along the steep meridian of the midperipheral cornea or as in Roberts et al.'s study, non-penetrat- ing intrastromal arcuate corneal laser cuts. 5 To our knowledge, a direct com- parison of outcomes between manu- al LRIs and the use of FS-AK in rou- tine cataract surgery has not been published. In Roberts et al.'s study, each procedure was performed in conjunction with cataract surgery (phacoemulsification with Infiniti vs. LenSx femtosecond laser-assisted cataract surgery, Alcon, Fort Worth, Texas) at a single surgery center. A stigmatism is a common component of refractive error. A study of 24,000 preoperative cataract patients showed that 30% of patients had >1 D of cylin- der on biometry, with the average being 0.98 D. 1 Patients increasingly expect spectacle independence after cataract surgery. Thus, the manage- ment of astigmatism during cataract surgery is of utmost importance. Today, many surgeons push for <0.5 D, as this is considered the threshold of success in studies of astigmatic correction. 2,3 Common treatments for astigmatism include manual limbal relaxing incisions (LRIs), femtosec- ond laser astigmatic keratotomies (FS-AK), and toric IOLs. Roberts et al.'s study "Refractive outcomes after limbal relaxing incision or femtosec- ond laser-assisted astigmatic keratot- omy in the management of corneal astigmatism at the time of cataract surgery" investigates the correction of mild to moderate astigmatism in Review of "Refractive outcomes after limbal relaxing keratotomy in the management of corneal astigmatism Dmitry Pyatetsky, MD, ophthalmology residency program director, Northwestern University Feinberg School of Medicine Given the cost differences, the pau- city of studies comparing manual and femtosecond laser astigmatic keratotomy is surprising. I invited the Northwestern residents to review this comparison study that appears in the August issue of JCRS. —David F. Chang, MD, EyeWorld journal club editor From left: Alex Knezevic, MD, Dmitry Pyatetsky, MD, Mary Kate Russell, MD, and Lauren May, MD Source: Northwestern University

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