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Managing Dysphotopsia in Multifocal IOL Patients
By Tony Hampton
There are three types of post-cataract surgery dysphotopsia: positive dysphotopsia, in which patients experience bright arcs, rings, halos or streaks of light in the visual field; negative dysphotopsia, in which patients perceive an arc of darkness in the temporal region; and a third type—limited to patients with multifocal IOLs—that causes patients to experience split images and halos or rings around lights.
The frequency and severity of these symptoms in multifocal IOL patients is unclear. The authors of a multicenter European study of Alcon’s AcrySof ReSTOR multifocal lens reported in the journal Ophthalmology in 2006 that 8.5 percent of patients reported “severe” glare and 4.2 percent reported “severe” halos.1 A broad review of studies of Abbott Medical Optics’ Tecnis multifocal lens reported varying but roughly similar levels of unwanted photic phenomena.2
Adaption to multifocal IOLs
Robert M. Kershner, MD, president and CEO of Eye Laser Consulting in Palm Beach, Fla., and professor and chairman of the department of ophthalmic medical technology at Palm Beach State College in Lake Worth, Fla., notes that neuroadaptation to multifocal lenses depends on the individual.
“Some patients adapt fairly readily, some will adapt if given sufficient time to tolerate an imperfect situation, and others, not at all,” he said. “Patients have to be willing to give it the time required.”3-8
Dr. Kershner adds that dysphotopsia isn’t the only issue with multifocal IOLs: “By definition, when we split light to create multiple focal points, we cause image degradation that will show itself in a number of ways, including reduced visual acuity and a drop in contrast sensitivity. When you add this to the dysphotopsia that is also inherent in multifocal lenses, it’s a lot for the brain to cope with, and some individuals haven’t the patience or neuroadaptive capacity to deal with it.”
Cataract surgeon Samuel Masket, MD, founding partner of Advanced Vision Care and clinical professor of ophthalmology at the Jules Stein Eye Institute, both in Los Angeles, sees the options for patients as ultimately binary: “If there is no specific problem that can be found and addressed, the patient must either adapt to the lens, or the lens must be explanted and replaced.”
Dr. Masket notes that any photic side effects of the multifocal IOL will be magnified by residual ametropia. But if the patient is close to emmetropia, and if the implant is properly centered on the visual axis, there is little that can be done for patients who cannot neuroadapt.
Dr. Masket believes that some multifocal lens failures can be prevented through patient selection. Patients whose vision is compromised by other factors , such as dry eye, blepharitis, epithelial basement membrane dystrophy, must be treated prior to surgery. A pristine cornea increases the chance of success with multifocal lenses.
Other factors that can degrade multifocal vision include zonular instability and very large or eccentric pupils. In addition, any significant optic neuropathy or maculopathy is likely to reduce vision quality and increase the impact of undesired images.
Dr. Masket sums up these conditions as the five “opathies”: keratopathy, pupilopathy, zonulopathy, optic neuropathy, and maculopathy. To this he adds that some patients have psychological issues that can interfere with adaptation, which he terms “psychopathy.” Candidates for multifocal lenses should be essentially free of all of these “opathies.”
To help patients form realistic expectations, Dr. Masket introduces the issues of vision quality and photic phenomena well in advance of surgery: “I generally show patients with my hands, like a balance beam, saying, ‘On the one side is the convenience of reduced need for glasses. On the other side is quality of vision. As one goes up, the other goes down—like a seesaw.’ I make sure that when my patients choose multifocal lenses, they expect to see halos around lights at night, and maybe some streaks of light.”
When it doesn’t work
“For the great bulk of patients, photic symptoms either disappear or become easily tolerable,” Dr. Masket notes. “But even patients who have been prepared to expect quality of vision issues may complain in the early postoperative period of a variety of undesired images and poor quality vision.”
At that point, Dr. Masket looks for any ametropia or evidence of compromise with the implanted lens. If there is no treatable condition, the next step is hand-holding: “I'll ask the patient to tell me what the issues are, and I will see them often to determine whether the problems are improving. If there is improvement, I encourage the patient to have surgery for the fellow eye soon, as multifocal lenses in both eyes can speed adaptation.
“But if the patient is unhappy and becoming less tolerant, I have no hesitation suggesting a lens exchange within six to eight weeks after surgery. If a patient’s brain can’t accept multifocality, the best thing is to explant the lens, and to do it sooner rather than later.”
Realistic expectations are critical
For Dr. Kershner, expectations and personality are critical issues in multifocal patient selection. The ideal patient must be willing to accept compromise. “The patient has to be just that: patient,” Dr. Kershner says.
He notes that, given enough time, most patients will adapt. “The question is how much time can you wait before the patient goes somewhere else, disgruntled and tells all his friends how unhappy he is with what you did?” he asks. “This is why it is critical to establish open lines of communication with the patient prior to surgery, because if you don’t have that, trying to explain to them what they’re going through after surgery will be futile.”
In Dr. Kershner’s view, a patient’s ability to adapt to multifocality is a function of the lens,the patient’s age, sex, visual status and potential acuity, and the ability of the patient’s brain to neuroadapt.
“How much time the patient will actually allow for neuroadaptation is a function of the patient’s personality, his or her expectations, and the type of rapport the surgeon establishes prior to surgery,” he adds.
Dr. Kershner describes neuroadaptation as the process by which the brain modifies its sensory input to enable it to cope with a constantly changing environment. He states that, to a limited degree, preoperative training may make it possible to predict and even enhance some patients’ ability to neuroadapt.
“The adult nervous system is remarkably plastic,” he says. “Just how the brain recruits the neurons to make this happen is a mystery but new data is shedding light on the subject. Every processing point along the visual pathway contributes to the final perceived visual image. Thus, any interruption in the smooth flow of information can become problematic. Until they reach the sixth-order neurons, the images from the retina are monocular. At the lateral geniculate bodies, the images begin to fuse. If these centers are flooded with retinal signals from multiple images, the deep centers of the brain that need to make sense of the chaos begin to fail. But they can learn.”
Because neuroadaptation can occur over a period of weeks to months and even years shows that complex neurogenesis is at work. It takes time to make new neural connections and suppress old ones,” Dr. Kershner says. “There is data to suggest that surgeons may be able to get superior outcomes if they train the patient prior to surgery.”9
Visual training can give patients an advance idea of what they will experience following surgery and gauge how quickly they will adapt, he says. However, he is cautious.
“It’s not absolute, but some studies suggest that if you take the extra time to pre-train the patient, adaption may occur more readily or at the least, you may be able to screen out a patient to whom this optical choice is not suited,” he says.
Use of digital aids to facilitate neuroadaptation can also be started postoperatively, but Dr. Kershner notes that neuroadaptive training devices will have greater credibility and patient acceptance if they are introduced prior to surgery: “I don’t personally use them for everybody,” he says. “But the fact is they have been shown to be of some benefit.”
Dr. Kershner has no financial interests to disclose. Dr. Masket is a consultant to Alcon.
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