November 01, 2009
6 min read

New femtosecond laser has applications in cataract surgery

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OSN NY 2009 meeting logo

NEW YORK – A new femtosecond laser is showing good clinical results in applications for cataract surgery, according to a presenter here at the OSN NY 2009 meeting.

“What I am going to show you today is something that was mostly science fiction 5 years ago,” Richard L. Lindstrom, MD, Ocular Surgery News Chief Medical Editor and Primary Care Optometry News Editorial Board member, said.

Richard L. Lindstrom, MD
Richard L. Lindstrom

“Reproducibility of cataract surgery is still an issue surgeon-to-surgeon and case-to-case,” Dr. Lindstrom said. Applying femtosecond laser technology to cataract surgery can help improve that reproducibility, he said.

While there are several companies working on this technology, Dr. Lindstrom spoke specifically about the LenSx femtosecond laser technology.

He told attendees that this femtosecond laser can be used to liquefy, soften or chop the lens, create a perfectly centered and sized capsulotomy, create perfect dimensions and architecture of all surgical incisions and correct astigmatism with precise corneal incisions.

Intracorneal inlay improves near vision in presbyopic patients

An intracorneal inlay has been shown in European studies to improve near vision in patients with presbyopia. It functions on the same principle as a camera aperture, blocking unfocused light with a centrally located hole, which increases depth of focus.

Jason E. Stahl, MD
Jason E. Stahl

“With the AcuFocus inlay, by increasing the depth of field, we can decrease this blur circle that can improve near vision,” Jason E. Stahl, MD, said as he presented study results.

The AcuFocus corneal inlay has been implanted in 343 eyes worldwide. In an ongoing European study, 70 patients have received the inlay, and 57 have completed 1-year follow-up. Results so far show a mean uncorrected distance acuity of 20/20 and uncorrected near acuity of J1, Dr. Stahl said.

“There’s no significant loss of distance vision,” he said. Ongoing U.S. study results “mirror what we’re seeing internationally.”

The inlay is 5 µm to 10 µm thick, with a 3.8 mm diameter and a 1.6 mm aperture. It is made of a lightweight biocompatible polyvinylidene fluoride material, with a flexible cup shape to match corneal curvature.

“We use a femtosecond laser to make a pocket and, within the pocket, implant the inlay,” Dr. Stahl said. Cornea shape is maintained, and there is minimal tissue disruption, leading to a rapid recovery, he said.

Tiny randomly placed holes in the inlay decrease nighttime visual issues, Dr. Stahl said. Nutrients flow through the holes to keep the cornea healthy.

The inlay is virtually undetectable, even in blue eyes. “If you’re looking directly at the patient, you can’t really see it,” he said.

Keratoconus screening can improve refractive surgery outcomes

Effective screening for keratoconus using topography and pachymetry can help clinicians predict risk factors and outcomes of refractive surgery.

Risk factors for ectasia after refractive surgery include abnormal topography, high myopia, reduced preoperative corneal thickness, reduced residual stromal bed after laser ablation and advanced age, Stephen D. Klyce, PhD, said.

“The highest risk factor for the development of ectasia after refractive surgery is still abnormal corneal topography,” he said. “It is something you need to be able to recognize using standardized procedures.”

Use axial power when screening, he said, to note subtle changes consistent in keratoconus suspects. Using instantaneous scales can be confusing, Dr. Klyce said. “There’s too much noise, and it’s hard to differentiate what’s a bad cornea from the other components in that display.”

The truncated bow tie shape, shown on topography, is “one of the faces of keratoconus that you need to recognize,” he said. Also, an asymmetrical “lazy eight” bow tie shape in which the radial axes are skewed is another sign of keratoconus.

For best outcomes, “evaluate thickness carefully, use a thick standard scale and axial diopters in screening, learn how to estimate the [inferior-superior] value in lieu of a screening program and learn the different features of keratoconus,” Dr. Klyce said.

Screening strategy key to reducing corneal ectasia after LASIK

Abnormal topography is the most common risk factor for eyes developing corneal ectasia after LASIK, so topographic screening is important, a surgeon said.

“Using a screening strategy that employs analysis of the multiple risk factors that we can identify should help us prevent ectasia,” Helen K. Wu, MD, said. “Can we predict it? Not 100% of the time. But further research into corneal biomechanics and ectasia should continue to improve our knowledge base.”

Dr. Wu presented data from a retrospective chart review study that she and colleagues conducted on the safety and efficacy of LASIK in 1,510 eyes. Of those, 193 eyes of 137 patients were selected. Those eyes had high-risk criteria including elevated posterior float, thin cornea, high myopia and against-the-rule astigmatism.

A total of 50 eyes met strict forme fruste keratoconus criteria. Follow-up was at least 6 months.

Two eyes of one patient developed ectasia in the study, Dr. Wu said.

She said the study showed that just one high-risk factor did not lead to development of ectasia. Identifying a combination of risk factors is the most likely way to prevent the condition, she said.

Clinicians assisted by array of techniques to manage corneal ectasia

Keen awareness, strict screening criteria and increased use of penetrating keratoplasty have reduced the incidence of corneal ectasia, according to a physician, and options for managing the condition continue to expand.

“Ectasia, as we become more careful about our selection for patients having corneal refractive surgery, is less common because of the increased awareness and tighter criteria for screening, as well as increased use of PRK and femtosecond laser,” David R. Hardten, MD, said.

Some patients with borderline ectasia do well with LASIK, and some do poorly and develop progressive ectasia leading to vision loss.

“Our need for ectasia management around the time of refractive surgery, as well as in naturally occurring keratoconus or pellucid patients … we need to have those options before us,” Dr. Hardten said. “Our options continue to expand.”

Management options include glasses, contact lenses, collagen cross-linking, Intacs implants (Addition Technology) with conductive keratoplasty, lamellar corneal transplantation and PK, Dr. Hardten said.

Cross-linking, widely used outside the United States, involves the absorption of riboflavin into the corneal stroma with the aid of ultraviolet light to stiffen the cornea.

“It’s fairly simple and straightforward as long as you take off the endothelium and make sure that you saturate the corneal stroma and appropriately focus the light source on the cornea with the appropriate energy,” Dr. Hardten said.

U.S. clinical trials for cross-linking have shown positive results, he said.

Intacs implants with CK stabilize ectasia in some patients, but other patients need lamellar keratoplasty or PK, he said.

Above all, ectasia is not completely preventable.

“How do we prevent ectasia?” Dr. Hardten said. “I think it’s impossible to totally prevent ectasia, but we should be looking for those patients at higher risk: unstable refractive error, unusual topography, posterior elevation abnormalities. Asymmetry between the eyes is a real risk factor.”

John A. Hovanesian, MD, FACS
John A. Hovanesian

John A. Hovanesian, MD, FACS, a member of the PCON Editorial Board and the OSN Cornea/External Disease Board, commented on Dr. Hardten’s report.

“Ectasia continues to be the most feared complication of keratorefractive surgery, but advances in treatment have and will greatly reduce the impact of this still rare problem,” he told OSN. “Deep anterior lamellar keratoplasty (DALK) offers the benefit of maintaining a patient’s own endothelium in a near-full-thickness procedure. Collagen cross-linking, while still a ‘young’ procedure, allows us to halt and sometimes reverse progression in a minimally invasive way.”

PresbyLASIK shows good results, satisfaction

Hyperopic presbyopic patients who underwent multifocal corneal ablations had good visual acuity, maintained spectacle independence and reported satisfaction with results, a clinician reported.

“At 1 year, 100% of the subjects achieved the zone of happiness, both 20/25 distance and J3 near or better, and 88% achieved 20/25 and J1, which is comparable to the data you saw [in a presentation] this morning for multifocal and accommodating IOLs,” Marguerite B. McDonald, MD, FACS, said.

Dr. McDonald presented 1-year results of 82 eyes of 49 hyperopic presbyopic patients who underwent presbyLASIK. The majority of patients in the study group had bilateral treatments, and patients answered questionnaires before and after surgery.

The study found that at 6 months, 73% of eyes were within ±0.5 D of emmetropia; at 1 year, 80% of eyes were within ±0.5 D of emmetropia. In addition, contrast sensitivity loss was within normal limits, she said.

Dr. McDonald said results in the ongoing study are showing that while the technique is evolving, multifocal treatments of hyperopic presbyopic patients are a safe and effective treatment option “together with refractive correction.”

Discuss cataract surgery risks with patients who have compromised corneas

In patients with compromised corneas, the secret to a successful cataract surgery outcome is spending an ample amount of time talking with the patient, preparation and a careful surgical technique, Dr. Hovanesian reported at the meeting.

He shared pearls for cataract surgery in the compromised cornea. “Patients with endothelial disease deserve some special attention,” he said.

Dr. Hovanesian said it is important to discuss in detail all risks involved and why the patient with a compromised cornea has those risks.

“The patient undoubtedly will be asking themselves, ‘Well, all of my friends had perfectly simple cataract surgery. Why is this doctor telling me this? Doesn’t this doctor know how to do this surgery?’ and we have to explain this to them,” he said.

“I have found that it’s helpful is to give patients a percentage chance,” Dr. Hovanesian said. “People like to hear what the likelihood is that they’re going to have complications. Of course there’s some guesswork in that. I tend to overestimate the chance.”

Dr. Hovanesian also recommended a return visit with the patient to discuss the challenges again. He encourages patients to visit, where they can get into discussions with other patients in similar situations.

“If you tell the patient about it ahead of time, whether it’s endothelial cell count or something else, they think of you as a genius,” he said. “If you tell them afterward, you’re making excuses, which is something I got from David Bogorad, MD, who was one of my mentors.”