EyeWorld Asia-Pacific September 2011 Issue

September 2011 15 EW FEATURE Multifocals are contraindicated in patients who have any type of maculopathy, corneal disease, or opacification of the cornea. They would not do well in patients who have conditions that might affect the transmission or processing of light back to the brain—for example, a stroke, some type of atrophy from glaucoma, or a type of genetic disorder that affected the retina, optic nerve, or the brain, Dr. Logan said. “That is why we have to have a brilliant relationship with the primary care doctor, so that we know what the patient’s medical condition is.” Dr. Logan said the utilization of multifocal lenses is low because surgeons don’t believe that they can achieve as good vision as with the monofocal approach. “The whole goal now is to have doctors educate their patients on the fact that lens technology has improved significantly, to the point where we’re getting results comparable to monofocal lenses. That wasn’t the case with the first generation of these lenses,” he said. Focusing on monovision For his part, Graham D. Barrett, FRANZCO, clinical professor, Lions Eye Institute, Perth, Australia, andSir Charles Gairdner Hospital, Perth, said he has several reasons for preferring monovision. First and foremost, it offers the option of reversal. “At any time, patients can put on their spectacles and get full binocular vision with no compromise,” Prof. Barrett said. Vision can be adjusted with a refractive procedure such as LASIK, he added. “If you have an unhappy multifocal patient, explantation is sometimes required because there’s no way you can correct multifocal vision,” Prof. Barrett said. Vision with monofocal lenses is more robust, and the procedure is easier to explain to patients, he said. “Monovision will tolerate astigmatic defocus much better than a multifocal lens,” he said. As for the patients, “Monovision is something patients can easily comprehend. You can demonstrate the type of vision they’re going to get. It makes the whole exchange easier and faster.” Patient satisfaction after the procedure is a benefit. “It is rare to experience an unhappy patient,” Prof. Barrett said. He added that he was pleased to have this thought backed up in Dr. Zhang’s study, which showed the overall satisfaction score is higher in monofocal patients. “I wasn’t surprised to see [the results], but it was nice to see a head-to-head comparison,” he said. “This is a good study because it’s a prospective group, and, overall, it’s a well-conducted study. There were a lot of parameters across a broad range of features.” While traditional monovision aims for –2 D of myopic defocus, which offers excellent near vision, Prof. Barrett warned that some patients might not tolerate this amount of separation. He prefers, instead, to target about 1.25 D of myopia. “At that level, you can be almost certain that a patient will not experience problems of disassociation between the two eyes,” Prof. Barrett said. Lower levels of myopic defocus will also preserve contrast sensitivity and stereoacuity. “However, at that lower level, you don’t get quite the same ability to read up close,” Prof. Barrett said. “That patient will require, in some cases, spectacle correction for reading a book for prolonged periods. It’s a small percentage of the time because intermediate vision is so good. The trade-off is that you can be much more certain of patient acceptance.” With the smaller levels of myopic defocus being used, some could contest the use of the term monovision, Prof. Barrett said. “It’s a poor description because patients have binocular vision and it doesn’t describe the situation very well,” he said. “The two eyes are used synergistically.” J.E. “Jay” McDonald II, MD, Fayetteville, Ark., USA, said he prefers monovision because it preserves the complete visual pathway and signals. “The issue is that when you use a multifocal lens you decrease the energy level of light by about 18%, and on each retina you have continued on page 17