Eyeworld

EW REFRACTIVE SURGERY 52 by Maxine Lipner Senior EyeWorld Contributing Editor Out of the darkness: Comparing the Visian toric ICL to conventional PRK Night driving simulation outcome favors ICL T he Visian toric ICL (im- plantable contact lens, STAAR Surgical, Monrovia, Calif.) outperformed con- ventional PRK in night driving simulator testing in a recent study published in the May 2010 issue of the Journal of Refractive Sur- gery. Results from the study indi- cated that for identification tasks during night driving simulation, the toric ICL performed better than con- ventional PRK, according to Capt. (Ret.) Steven C. Schallhorn, M.D., San Diego, and medical director, Op- tical Express, London. "There is a subset of patients who would not meet the indications for LASIK and for whom we would be faced with the options of either implanting a phakic intraocular lens or possibly considering a surface procedure," Dr. Schallhorn said. In- vestigators hoped that this study would help to clarify which proce- dure would be preferable here. Night driving simulation In this prospective, randomized study involving patients with mod- erate to high myopic astigmatism, the toric ICL was implanted in 43 eyes while another 45 eyes under- went conventional PRK with appli- cation of mitomycin C. As a sub study, 27 of the toric ICL patients and 21 of the PRK patients were tested using a night driving simula- tor. "The night driving simulator is a very unique device because it meas- ures the visual essence of night driv- ing—the ability to detect and identify targets like pedestrian haz- ards, road signs, and business signs," Dr. Schallhorn said. "That's a lot of the essence of the vision require- ments of night driving." While the simulator measures these elements, it does not require the skills of night driving, he stressed. Investigators felt that testing driving was an excellent way to dis- cern visual performance. "We chose night driving because patients who have quality-of-vision problems after surgery often complain of night driving issues such as glare and halos," Dr. Schallhorn said. "Also, night driving is a very strenuous task because it involves low light but high intensity potential glare sources, it requires skill, and it's commonly performed by people." During the simulation, patients sat in a car with a road scene image projected in front of them. Investi- gators then noted how many feet away they could detect hazards or road signs and at what point they could actually identify them. Dr. Schallhorn sees the way the training took place as very sophisticated. "We would have a training period where the subjects were trained in what they were looking for and how they were supposed to respond," he said. "Then we tested their detection and identification ability repeat- edly." Investigators then looked at the learning curve and identified the point at which the patients' per- formance peaked; it was these results that were included in the study. Detecting driving hazards Results from the night driving simu- lator indicated that the ICL per- formed better than the conventional PRK. While there was no difference in the distances needed to detect signs or hazards, identification tasks were another story. With such tasks, patients would be asked to deter- mine, for example, whether a pedes- trian was walking into or away from the road. With such identification tasks, those in the toric ICL group performed significantly better than their PRK counterparts. Investigators found that both with and without glare, ICL patients were better able to identify pedestrian hazards as well as business and road signs. Dr. Schallhorn theorized that the difference was in the aberrations that were likely induced by PRK dur- ing the conventional treatment. De- spite the fact that the optics favored the ICL, Dr. Schallhorn was a little surprised at how well the lens fared overall. "I think that the most sur- prising thing was that the ICL per- formed better," he said. "The levels of P values were really significant for the identification tasks, but across the board the ICL performance was quite superior." He hopes that others come away from the study with a better under- standing of the quality of vision the lens can offer patients compared to a conventional laser approach. "The visual quality of this phakic intraoc- ular lens is superior and should be considered for the high visual qual- ity as compared to conventional ex- cimer laser," Dr. Schallhorn said. "I think that it compares very favor- ably to a conventional excimer laser procedure." Overall, Dr. Schallhorn thinks that the biggest strength of the study is that a real task was per- formed here. "This is significant be- cause it has intrinsic meaning," he said. "We tested night driving, so that adds an element of importance to this type of work—this is task- based analysis and that is very rarely done in ophthalmology." EW Editors' note: Dr. Schallhorn has finan- cial interests with Abbott Medical Op- tics (Santa Ana, Calif.). Contact information Schallhorn: 619-920-9031, scschallhorn@yahoo.com Visian toric ICL Source: STAAR Surgical Early vitrectomy effective for Norrie disease R esearchers out of Tucson, Ariz., discovered that an early vitrectomy may be effective in treating Norrie disease, a rare condition that causes hearing loss, mental retardation, and blindness in males. The physicians reviewed the medical records of all patients seen in their pediatric retinal practice over a 10-year period who had the potential to de- velop the disease by examining clinical findings and genetics and/or family history. The review revealed 14 boys diagnosed with Norrie disease. Thirteen of those patients had the disease gene mutations noted through genetic testing and four of those patients had the gene mutations and/or appropriate family history. All patients had vitrectomy with or without lensectomy in at least one eye before their first birthday. "Of the 14 boys with definite Norrie disease, seven maintained at least light perception visual acuity in one eye and three had no light perception vi- sual acuity bilaterally," the researchers wrote. "Historically, no treatment has been offered to mitigate the dismal natural history of Norrie disease. We rec- ommend consideration of early vitrectomy in Norrie disease." The findings were published in the Archives of Ophthalmology (2010, 128, 456-460). February 2011

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