Eyeworld

EW NEWS & OPINION 20 No healthcare employee connection found W hen it comes to me- thicillin-resistant Staphylococcus aureus (MRSA), new evidence suggests that non- healthcare workers are just as likely to be affected as those employed in the industry, according to Randall J. Olson, M.D., professor and chair- man, John A. Moran Eye Center, University of Utah, Salt Lake City. Results published in the December 2010 issue of Clinical Ophthalmology May 2011 by Maxine Lipner Senior EyeWorld Contributing Editor MRSA superbugs flying high for general public In-the-bag capsular te nsion ring/intraocular lens subluxation or dislocation: Pathological evaluation of 20 cases Liliana Werner, M.D., Brian Zaugg, B.S., Tobias Neuhann, M.D., Michael Burrow, Manfred Tetz, M.D. Findings of 86 cases of in-the-bag intraocular lens (IOL) subluxation/dislocation sent for pathologi- cal analyses at the John A. Moran Eye Center have recently been described. None of the speci- mens contained a capsular tension ring (CTR), which indirectly suggested the efficacy of this de- vice in completely preventing this complication. However, since then, we had the opportunity to analyze 20 IOL/capsular bag specimens with a CTR. The patients were aged 76.36+/–8.59 years at explantation, performed 72.11+/–32.33 months after implantation (58+/–37.25 in cases with capsulorhexis phimosis). Different foldable IOLs were represented in this series. The most im- portant associated condition was pseudoexfolia- tion. Late post-op subluxation/dislocation of the CTR-IOL-capsular bag complex is a risk for pa- tients with severe or progressive zonulopathy. It occurred approximately 6 years after implanta- tion in this series. Analysis of long-term data re- lated to CTR complications may help define the degree of zonular insufficiency that can be stabi- lized with the CTR alone and the degree that re- quires further support. Dose-response for mitomycin-C in prevention of haze in photorefractive keratectomy for high myopia: Twelve-month outcomes Elizabeth M. Hofmeister, Frank M. Bishop, David J. Tanzer, Sandor Kaupp, Steven C. Schallhorn Background: Mitomycin-C is widely used for the prevention of haze following PRK, but its safety and efficacy have not been documented in a ran- domized prospective fashion. Purpose: To investigate the safety and efficacy of mitomycin-C (MMC) 0.1 mg/ml in preventing haze formation following WFG PRK for high my- opia. Three different dose durations were studied: 1 minute, 30 seconds, and 15 seconds. Methods: This was a double-masked, random- ized, prospective trial comparing three dosing regimens of MMC 0.1 mg/ml for highly myopic patients undergoing WFG PRK (treatment mean MRSE= –6.43 D, range from –4.8 to –8.8 D): 1 minute, 30 seconds, and 15 seconds. One eye of the patient received MMC on a 6 mm diameter surgical sponge while the other eye received placebo. Endothelial cell counts, haze scores, acuities and contrast acuities, manifest refrac- tions were measured pre-operatively and at 1, 3, 6, and 12 months. Outcomes were analyzed by repeated measures (post-op exams over time) MANOVA. Results: 28 subjects were enrolled: 10 in the 1 min. group, 9 in the 30 sec. group, 9 in the 15 sec. group. No eye developed more than trace haze. There was a significant difference in haze scores between treated and untreated eyes at the 1-month visit (p=0.034), but there was no differ- ence at the 3, 6, and 12-month visit. By 12 months, all haze scores were zero. Endothelial cell counts decreased slightly in both the MMC and the placebo eye in all three groups at 1 month post-op, but returned to baseline by 6 months. There was no difference in photopic or mesopic contrast acuity, uncorrected acuity, or BCVA between the MMC and the placebo eye in any group. Conclusion: The 15-second application of MMC 0.1 mg/ml appears to be just as effective in pre- venting haze. There was no significant difference in haze formation between eyes that received MMC and those that did not at any dose, and MMC had no adverse effect on endothelial cell counts. Optical modeling of negative dysphotopsia: ray tracing analysis S Masket, M.D., and NR Fram, M.D., X Hong, Ph.D., Y Liu, Ph.D., and M Karakelle, Ph.D. Negative dysphotopsia (ND) is a clinical condi- tion characterized by the subjective perception of a temporal dark crescent. ND occurs only with in-the-bag IOLs. There are no clinical tests to evaluate ND and no beneficial medical therapy; however, piggy- back IOLs, reverse optic capture (ROC), and sul- cus placement are helpful. The current ray tracing study was conducted to test the authors' hypothesis that the capsu- lorhexis-IOL interface is the source of ND. Zemax NSC ray-tracing analysis was em- ployed and the image detector discerned photic structures from the optic, edges, surfaces, and capsulotomy. Capsulorhexis size, pupil diameter, the ef- fects of ROC, and piggyback IOL implantation were evaluated. For the capsulorhexis and pupil size, 3 mm and 6 mm were chosen as extremes. Larger capsulorhexis size and ROC reduced photic structures, corroborating clinical impres- sions. This study confirms that ND is reduced if the optic overlies the capsulotomy and the capsu- lorhexis/optic interface is the likely source for ND. The contribution of posterior corneal astigmatism to total corneal astigmatism MP Weikert, DD Koch, M Shirayama, L Wang This retrospective study compared the contribu- tion of posterior corneal astigmatism to total corneal astigmatism as measured by a device that combines Placido and dual-camera Scheimpflug imaging. Posterior corneal astigmatism was calcu- lated using vector analysis in 137 eyes of 81 pa- tients by subtracting the astigmatism measured on the anterior surface axial map from the total corneal astigmatism measured by ray tracing. The mean posterior astigmatism vector had a magni- tude of 0.25 D±0.16 D, with 93% of eyes having a magnitude ≤0.5 D. The steep meridian was ori- ented vertically in 89% of eyes on the posterior surface, but only in 57% of eyes on the anterior surface. In younger patients, posterior surface astigmatism tended to partially compensate for astigmatism on the anterior surface. However, in older patients the contribution of posterior corneal astigmatism tended to be additive to the total corneal astigmatism. Therefore in certain patients, calculating total corneal astigmatism based only on anterior surface measurements may lead to incorrect estimations, which may be significant in clinical situations such as toric IOL implantation. Olson said. While this is monitored over time, investigators here thought that it would be of particu- lar importance to ophthalmologists to determine the bacterial milieu of the eye at the time of cataract sur- gery. "A lot of people don't use any- thing before surgery, so we thought indicated that patient age, not field of employment, may be the link here. "The big problem is that methi- cillin-resistant Staph is becoming an increasing problem, and if it's methi- cillin-resistant then more and more, it's also multi-drug resistant," Dr. At the ASCRS•ASOA Symposium and Congress, the Best Paper of Session is selected by the moderator and panel for each free paper symposium. In the next several issues of EyeWorld, the medical editors will be highlighting some of these best papers by inviting the authors to submit a brief summary or abstract. David F. Chang, M.D., chief medical editor

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