“At a mad tea party with a post-LASIK cataract patient, who received a Tecnis monofocal IOL following phacoemulsification and who was suffering from glare and halos”
Phacoland: At a glance
• Cataract patients who have previously had LASIK present a real challenge • Challenges include calculating IOL power and determining lens type • Type of spherical aberration relates to kind of LASIK performed • Be sure to evaluate topography before performing cataract surgery
“Into the rabbit hole with the case of a Salzmann’s nodule patient scheduled to undergo cataract surgery.”
Peering through the
looking glass at curious post-cataract cases
Patient aberrometry before enhancements and after cataract surgery Source: Eric Donnenfeld, M.D.
Salzmann’s nodular degeneration, an unusual disorder that may lead to less-than-perfect outcomes after phaco if undetected Source: Edward J. Holland, M.D.
They’re cases that you just can’t seem to forget that may stump you at first but which ultimately leave you grinning like a Cheshire cat. During this year’s 2010 ASCRS Winter Update, held in Riviera Maya, Mexico, practitioners shared a host of such memorable cases. Here are two of these curious cases to consider. Would you have taken the same tact as practitioners here or would you ultimately have gone another way?
A pool of tears for a
Eric D. Donnenfeld, M.D., co-chairman, Cornea, Nassau University Medical Center, East Meadow, N.Y., brought to light a type of case that is becoming more and more common—the post-LASIK cataract patient who is unhappy following phacoemulsification. The case involved a 68-year-old patient who had undergone phacoemulsification in 2008 with a Tecnis monofocal IOL (Abbott Medical Optics, Santa Ana, Calif.). Following the surgery the patient was complaining bitterly of glare and halos. His ophthalmic history showed that he had a conventional PRK done in 2002 and that he subsequently came back for an enhancement the following year when the technology changed. His original manifest refraction showed that he had a lot of cylinder and was hyperopic. His corneas were fairly steep. He also had a Q value of –0.29. It is important to note that this patient had a negative spherical aberration of the cornea caused by the hyperopic ablation.
Such cataract patients who have previously undergone LASIK many practitioners are finding to be a real challenge. “The number one problem is in calculating your IOL power,” Dr. Donnenfeld said. “ASCRS has the best Web site for doing that and I think that it’s a great place to start.” New technology may also be helpful here. “I firmly believe that the new wavefront intraoperative aberrometry is going to be the answer,” Dr. Donnenfeld said. “I don’t calculate the lens [power] anymore. I just go take it in the [operating room] and I take my reading light there.” He finds that this always gives him a great result within 0.5 D of his target.
The second issue is in determining what type of lens to choose. “Understanding the aberrations of the lenses that we use now are important,” Dr. Donnenfeld said. “Spherical aberration is really the only aberration that you have to worry about—90% of all problems in refractive and cataract surgery are spherical aberration.” Different types of spherical aberration have varying effects. “Positive spherical aberration creates halo, and too much negative spherical aberration can also create halos,” Dr. Donnenfeld said. “A little bit of negative spherical aberration, however, is good since that increases depth of focus.”
The type of spherical aberration usually relates to the kind of LASIK performed. “If you had a patient who had a myopic ablation that type of patient almost always has positive spherical aberration,” Dr. Donnenfeld said. Likewise, those who have undergone hyperopic LASIK often have negative spherical aberration.
Indeed, in this case, the patient’s wavefront from his original treatment showed negative spherical aberration. This was also present on his WaveScan. “The patient has negative spherical aberration from the previous hyperopic LASIK,” Dr. Donnenfeld said. “What type of IOL do you want to put in here?” he asked the panel. Alan S. Crandall, M.D., professor and senior vice chair, Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, pointed out that there are several Food and Drug Administration-approved aspheric lenses available. “Two of these lenses add further negative spherical aberration,” he said. “The Alcon SNW [Fort Worth, Texas] adds –0.2 D and the Tecnis if it’s an aspheric one adds –0.27 D.” He points out that using one of these here would be a prescription for trouble. “If you already have –0.2 D and you’re adding –0.27 and both of those have square edges so you have the potential for dysphotopsia anyway depending upon the centration,” he said. While other aspheric IOLs don’t add any spherical aberration, Dr. Crandall himself would opt to use a spherical, not an aspheric, lens here.
Dr. Donnenfeld agrees that neutralizing the spherical aberration is essential here. Before the cataract surgery the patient already had spherical aberration and after undergoing the cataract surgery this was compounded. “Here is the same patient after the cataract surgery. They’ve added two scoops of negative spherical aberration and that why the patient has glare and halo,” Dr. Donnenfeld said. He sees the options as using a lens that adds positive spherical aberration, or using one that adds no spherical aberration. Dr. Donnenfeld himself would opt to use a lens with zero spherical aberration such as the Akreos AO (Bausch & Lomb, Rochester, N.Y.) or the SofPort AO (Bausch & Lomb). That was what was done here. “We replaced the lens with a Bausch and Lomb SofPort AO with zero spherical aberration,” he said. “The patient became very happy and did very well.”
One pearl that Dr. Donnenfeld offered up here was to consider the topography in such cases. “One of the rules if you’re going to be putting these lenses in is to look at the topography on these patients before you do cataract surgery because that will help you determine what to do,” he said. “If an ablation is well centered it opens up all types of opportunities for you.” He finds that a well-centered ablation really allows him to consider a variety of lenses. “I personally am doing a lot of multifocal IOLs on patients after LASIK as long as they meet certain caveats,” he said. “They have to have well-centered, large modern ablations—not the really old oblate ablations.” Also they cannot have high myopia. However, if a patient was initially –3 or a –4 D myope Dr. Donnenfeld finds that such multifocal lenses in post-LASIK patients can work well.
Also, an accommodating lens can still be a good choice as well. “Just because someone has had previous LASIK or PRK does not mean that they can’t have a refractive IOL and have had very good results, with one caveat,” Dr. Donnenfeld said. “I tell them that their risk of enhancement is much higher than in a conventional case.”
Adventures in Salzmann’s nodule land
At the symposium, Edward J. Holland, M.D., professor of ophthalmology, University of Cincinnati, and director of Cornea Service, Cincinnati Eye Institute, offered up a case involving a patient who had been referred for a cataract evaluation. The patient’s topography had come back as abnormal and the referring practitioner couldn’t get a good reading. It appeared as if the patient had a high degree of irregular astigmatism. “Actually, the original referring clinician forgot to raise the lid and really wanted to know why there was abnormal topography,” Dr. Holland said. “There was in fact a large Salzmann’s nodule in the cornea.” Salzmann’s nodule degeneration is something that Dr. Holland finds is actually very common in his practice and that can create challenges for surgeons. The question Dr. Holland posed for attendees was whether to first remove the nodule with a superficial keratectomy technique, let the cornea heal and ultimately then do the phacoemulsification, or whether to instead remove the nodule in concert with phacoemulsification. The majority of attendees, 64%, claimed that if they were presented with such a case they would opt to remove the lesion and let the cornea heal first, but another 29% said that they would go ahead and do the phacoemulsification at the same time as nodule removal.
Jonathan B. Rubenstein, M.D., vice chairman and Deutsch Family Professor of Ophthalmology, Rush University Medical Center, Chicago, recommended doing the procedures separately. “I strongly agree with treating the cornea first and allowing it to become smooth for two reasons,” he said. “Number one, it’s going to help you to be a more accurate cataract surgeon because you’re going to be able to assess the true power of the cornea.” He points out that it can be difficult to get keratometry readings in such cases, making IOL calculations at times in these patients who have a Salzmann’s nodule or a basement membrane dystrophy at times vexing. “Any time you don’t have a good corneal topography corneal surface it’s going to affect your accuracy of measurements,” he said.
The number two issue, he finds in such cases is the induced astigmatism. “Of course visually these patients aren’t going to see as well if they have something inducing an irregular astigmatism,” Dr. Rubenstein said. So, he recommends smoothing the cornea and allowing a better assessment of corneal power and also of what their visual acuity would be like without the nodule interference. Removing these nodules Dr. Holland finds is fairly straightforward. “To take these off you’ll typically find a plane and if they’re small enough you can actually do it at the slit lamp,” Dr. Holland said. “If you think that the nodule is going to be up toward the limbus, if you’re worried about a little bleeding it’s more comfortable for patients to do it in a minor room – you use a 64 or a 69 blade, scrape the epithelium and catch the edge of the nodule and frequently there will be a lamellar plane and the lesion will peel off almost in one sheet.”
Dr. Donnenfeld points out that a case such as this one overwhelmingly has meibomium gland diseases or lid margin diseases as the ideology of the Salzmann’s nodule. “Whatever you decide to do the real issue here is don’t let it recur,” he said. “To do that, you really have to treat the disease very aggressively.” He stresses the need for good meibomium gland and or blepharitis therapy in such cases, with use of hot compresses, lid hygiene, nutritional supplements and possibly some steroid use as well.
Dr. Holland agrees. “Most of these patients have external disease—they have dry eye and/or blepharitis, 90 to 95% are women, and you do get recurrence,” he said. Sometimes to help prevent this he uses mitomycin C (MMC). “If it’s a small paracentral one I’ll take it off without mitomycin,” he said. “But in a lesion like this which is large and close to the limbus I think the risk of recurrence is high so I apply mitomycin (.04%) for a short time, just 10 seconds and I do think that it dramatically reduces the recurrence rate.”
Editor’s note: None of the presenting physicians have financial interests related to their presentations.
Crandall: 801-581-2352, firstname.lastname@example.org
Donnenfeld: 516-446-3525, email@example.com
Holland: 859-331-9000, firstname.lastname@example.org
Rubenstein: 312-563-2305, email@example.com