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ASCRS survey shows new technologies are impacting surgical preferences
This year’s meeting was centered on wavefront-guided ablation and IOLs for cataract and refractive surgery.
SAN DIEGO – Almost three quarters of ophthalmic surgeons responding to a survey said they used clear corneal cataract incisions in 2003. Bimanual phacoemulsification was used regularly by 16.5% of respondents, and 20% more said they intend to adopt the technique in the coming year.
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![David V. Leaming, MD [photo]](/~/media/images/news/print/ocular-surgery-news-europe-asia-edition/2004/01_january/leaming_245_175_6785.jpg)
These were some of the trends identified by David V. Leaming, MD, in his annual survey of U.S. members of the American Society of Cataract and Refractive Surgery. About 1,000 ASCRS members participated in the 2003 survey, Dr. Leaming said here during the opening session of the ASCRS meeting.
In refractive surgery, the number of LASIK procedures in 2003 declined from its peak in 2000 and has “sort of leveled off,” Dr. Leaming said. But meanwhile the number of surgeons performing clear lens exchange has grown, he said.
Last year’s growth rate in cataract surgery was 14% more than in the 2002 survey, but it still showed a gradual decline from the late 1990s, Dr. Leaming said.
“Cataract surgeons are dropping out primarily due to the rapid rise of LASIK,” he said.
In 2002, more ophthalmic surgeries were performed in ambulatory surgery centers than in the hospital setting for the first time, the survey found.
Regarding anesthetic choice, “topical is done predominantly now, retrobulbar is second at 24% and periocular is around 17%,” Dr. Leaming said. “Of those doing topical, a majority are doing it with intracameral, about 22% are doing topical only and a very small percentage are using topical plus subconjunctival.”
More than half of cataract surgeons responding (53%) said they still favor the four-quadrant nucleofractis technique. Chopping was the second most favored choice. Of survey respondents who use a chopping technique, 60% said they use the stop-and-chop method.
In 2003, use of clear corneal incisions was reported by 73% of survey respondents. The type of blade used is still predominantly a metal blade, Dr. Leaming said.
Regular use of bimanual phaco-emulsification was reported by 16.5% of respondents, and 20% said they plan to switch to that technique during 2004.
In patients with bilateral cataract, almost half of respondents said they perform cataract surgery in the second eye within 3 weeks, and most said they perform the second surgery within a month of the first.
The most preferred optic material continued to be acrylic, Dr. Leaming said, and for the first time last year preference for a one-piece foldable IOL overtook preference for a three-piece foldable.
“When asked what IOL respondents felt held the most promise for small-incision surgery, the acrylic was No. 1, injectable was No. 2, ThinOptX was third and silicone was fourth,” Dr. Leaming said.
Looking ahead to new technologies, 100% of those polled said they were interested in the accommodating IOL; second was an injectable IOL.
The Leaming survey, now in its 20th year, tracks practice styles and preferences of the U.S. ASCRS membership. For the 2003 survey, about 15% of the 6,350 surveys were returned for analysis.
Long-term corneal stability still a challenge
With the advent of customized ablation, many ophthalmologists believe they have found the holy grail of refractive surgery. But the promise of wavefront-guided laser ablation will not be fully realized until researchers gain a more complete understanding of corneal biomechanics, according to a pioneer of excimer laser corneal research.
John Marshall, PhD, of London, delivered the Charles D. Kelman, MD, Innovator’s Lecture on the topic of “Wavefronts and Biomechanics.”
Dr. Marshall recalled that pioneers of laser refractive surgery faced questions about how much corneal tissue could be removed before corneal instability occurred. Early work in photorefractive keratectomy (PRK) resulted in variability of outcomes, which were only improved with the introduction of corneal topography and the refinement of laser beam and spot sizes, he said.
Dr. Marshall, one of the organizers of the First International Workshop on Laser Corneal Surgery, noted that the introduction of LASIK also marked a major breakthrough in reducing, and sometimes eliminating, postoperative pain and haze.
But the biomechanics of LASIK, in comparison to PRK, suggest that the microkeratome-based procedure causes more corneal weakening, he said.
The cornea is made up of collagen filaments arranged in grids not unlike the steel skeleton of a building or car tire, according to Dr. Marshall. When tissue is removed in PRK, he said, the surgeon cuts through 5 million of those fibers. In LASIK, by comparison, 232 million fibers are disrupted, he said.
The mechanical system of the cornea is weakened by the microkeratome cut even before the laser ablation, which induces its own micro abrasions, Dr. Marshall noted.
“Certainly, at the moment, it seems that LASIK is less stable over the long term than surface procedures,” he said. “This is a major problem if we think we’re really going to use wavefront to the level we want to use it.”
The real benefit of wavefront technology to date has been to enhance or correct previous surgeries, he added.
He challenged future innovators to make sure that “wavefront technology has [not] gotten ahead of the biology.”
| 2004 ASCRS film awards
Source: ASCRS/ASOA |
Topography study suggests corneal role in accommodation
Contraction of the ciliary muscle causes an increase in corneal power that may play a role in accommodation, according to a study presented here.
In the first part of a two-part study, Akihiro Yasuda, MD, and colleagues in Tokyo compared corneal topographies of 18 eyes of nine volunteers before and 45 minutes after the administration of topical pilocarpine. In a presentation at ASCRS, Dr. Yasuda said the researchers found a “small but statistically significant” increase in both corneal steepening and mean ring power within 45 minutes of administering pilocarpine.
In the second part of the study, Dr. Yasuda and colleagues compared the corneal topographies of two groups, each with 14 eyes of seven patients. One group received topical pilocarpine and the other received balanced salt solution. A statistically significant change was seen in the pilocarpine group, but not in the control eyes receiving balanced salt solution, he said.
Dr. Yasuda speculated that ciliary muscle contractions may aid in accommodation by exerting pressure on surrounding ocular structures, namely the scleral spur and the trabecular meshwork, which in turn may cause the cornea to steepen.
Posterior chamber IOL shows promise
A posterior chamber accommodating IOL “shows promise as an effective means of providing useful accommodation following refractive lens exchange,” according to early study results.
Deepak K. Chitkara, MD, FRCS, of Manchester, England, presented results of the Kellan LH1000 posterior accommodating IOL by Lenstec.
In the study, 6-month results in pseudophakic eyes showed distance-corrected near visual acuity of J3 or better in 40% of eyes and J5 or better in 60% of eyes, Dr. Chitkara said. Uncorrected distance vision was 20/40 or better in 83% of eyes and 20/25 or better in 67% of eyes, he said.
“This lens shows stability at up to 6 months,” Dr. Chitkara said. Further study is warranted, he added.
Vitreous loss affects IOP control
Even though surgeons have moved to less invasive cataract procedures, vitreous loss during cataract surgery continues to adversely influence postoperative IOP in glaucoma patients.
Abhay R. Vasavada, MS, FRCS, an Ocular Surgery News Europe/Asia-Pacific Edition editorial board member from Ahmedabad, India, addressed new microsurgical techniques, which had not been previously considered in the literature.
In a retrospective study, patients with primary open angle glaucoma from several hospitals in the United Kingdom were divided into three groups; group 1 included eyes with complicated phacoemulsification (ie, posterior capsular tear with vitreous loss), group 2 included the fellow eyes of those patients, and group 3 was eyes with uncomplicated phaco.
At the 12 month follow-up, investigators found no difference in IOP across the groups, according to Dr. Vasavada. However, when investigators considered the number of glaucoma medications per eye, they saw a significant increase in the mean number of medications used in group 1.
When phacoemulsification caused vitreous loss, 61% of patients required a greater number of glaucoma medications postop. Eyes in group 1 increased their number of medications by a mean of 0.78, and eyes in group 2 also showed a slow disease progression.
Eyes in group 3, in contrast, decreased their mean number of medications used postop, leading Dr. Vasavada to conclude that the surgical event itself – and specifically the vitreous loss – adversely affected glaucoma. Uncomplicated phaco, meanwhile, actually improved IOP control, he noted.
Dual-optic accommodative IOL shows good functional results
Early experience with a dual-optic accommodative IOL shows “good functional results and reliable refractive outcome,” according to a researcher speaking here.
Gerd Auffarth, MD, of Heidelberg, Germany, presented results of 1- to 2-month follow-up in six patients who were implanted with the dual-optic Synchrony IOL from Visiogen. The capsulorrhexis size in each eye was less than 5 mm.
Results showed a mean uncorrected distance acuity of 0.61 ±0.36 (range 0.2 to 1.0) and a mean best corrected distance acuity of 0.97 ±0.36 (range 0.4 to 1.6). The distance-corrected near acuity was an average of 0.37 ±0.15 (range 0.2 to 0.6), according to Dr. Auffarth.
“A dual-optic system may have more accommodative power” than a single-optic lens, he said.
Pupils dilate more quickly after LASIK, study finds
Pupils in eyes that have undergone LASIK dilate significantly faster than they did before refractive surgical correction, said Hak Sung Chung, MD, with the Indiana University School of Medicine.
Nineteen eyes of 10 patients were prospectively enrolled in a study to determine pupil dilation rates after LASIK surgery compared to the rates before surgery. Time to dilate to 6 mm after instillation of tropicamide 1% was determined preoperatively and at 3 months postop. Pupil size was measured at 5-minute time increments until the 35-minute mark.
The researchers found that mean central corneal thickness went from 564 um preoperatively to 514 um postop. The mean age of patients was 40 years. Five patients had blue irides, one had hazel and four had brown.
Preoperatively, the pupils took a mean 14.4 minutes to dilate to 6 mm; postoperatively they dilated in 11.5 minutes.
Dr. Chung speculated that “the enhancement of corneal drug penetration resulted from stromal thinning and not from surgery.”
Mitomycin may prevent post-LASEK corneal haze
Use of mitomycin-C during laser epithelial keratomileusis may help prevent postoperative corneal haze, according to a presentation here.
A trend toward better visual acuity results was also seen in patients who underwent LASEK with antimetabolites, said Maria Jose Cosentino, MD.
Dr. Cosentino reported on a study in which she colleagues performed LASEK in two groups of 30 eyes. In group the eyes were treated with 0.02% mitomycin for 60 to 75 seconds and then washed profusely with Ringer’s solution before the flap was replaced. The other group was not treated with mitomycin.
With 10 months of follow-up, Dr. Cosentino reported a trend toward better visual acuity and significantly reduced corneal haze in eyes that had undergone LASEK with the antimetabolite.
None of the test group patients experienced corneal haze; 16.7% of the control group patients noticed trace haze. In addition, the control group included one case each of grades 1, 2 and 3 haze.
Dr. Cosentino noted that no toxic effects were observed from the mitomycin during the follow-up period. However, mitomycin did cause some delay in healing (4.07 days vs. 3.91 days), perhaps because of its antifibrotic properties.
She added that she now uses mitomycin routinely in LASEK patients.
Interocular axial length differences affect eyes
Interocular differences in the axial length of pediatric eyes undergoing cataract surgery can affect postoperative changes in those eyes, a study presented here suggests.
Rupal H. Trivedi, MS, of Salt Lake City, U.S.A., advised surgeons to consider interocular axial length differences in planning IOL power in pediatric cataract surgery. She said the growth of these eyes after surgery seems to be related to differences in axial length between eyes.
She described a study of pediatric patients undergoing cataract surgery which found that in patients with more than 0.5 mm difference in axial length between eyes, shorter eyes tend to have greater growth, normal eyes tend to grow normally and longer eyes have less growth.
Dr. Trivedi and colleagues reviewed the charts of 58 pediatric eyes with an average age of 3.2 years. Mean follow-up was 3.3 years.
Cause of foldable IOL explantation
Surgeon mistakes, including improper IOL power calculations, are the leading causes mandating explantation of foldable IOLs, regardless of lens material, said Nick Mamalis, MD, in a presentation here.
Dr. Mamalis reported on the annual joint survey of members of the American Society of Cataract and Refractive Surgery and the European Society of Cataract and Refractive Surgeons.
“The complications vary depending upon the type of foldable IOL used,” Dr. Mamalis said. “Some complications are particular to a particular type of lens material.”
Incorrect lens power, glare or visual aberrations, and dislocation or decentration were the most common reasons for removal of three-piece silicone IOLs, three-piece acrylic IOLs and one-piece acrylic IOLs, he said.
For one-piece silicone IOLs, dislocation and decentration were the most common reasons for explantation, Dr. Mamalis said. Hydrophilic acrylic IOLs were most commonly removed due to postoperative calcification.
Multifocal silicone IOLs were most often explanted because of glare or optical aberrations, he said.
Postoperatively, however, good visual results were obtained in all patients, Dr. Mamalis noted.
Excellent surgical technique is mandatory to lower the explantation rate, he stressed.
“The most common reason for removing these lenses is us,” he said. “Surgeons need to have good loading technique, good insertion technique, accurate IOL measurements and proper patient selection.”