ULTRAFAST LASERS/BIOMEDICAL IMAGING: Laser cataract surgery: Clearly advanced

Cataracts—the clouding of the lens that helps to focus light on the retina—affect nearly 22 million Americans age 40 and older, according to the American Academy of Ophthalmology (AAO). "Cataract surgery is the most common surgical procedure that we perform in ophthalmology," Richard L. Lindstrom, MD, of Minnesota Eye Consultants (Bloomington, MN), told BioOptics World. About 3.2 million such procedures are performed each year in the United States, with nearly 18 million annually worldwide. Lindstrom adds: "What the femtosecond laser promises to do is to enhance refractive outcomes and make them more accurate."

Think for a moment about Lindstrom's comments in relation to refractive corneal surgery (that is, LASIK and its ilk), and the impact laser technology has had on that procedure. Yes, he's saying that this newer application of lasers ultimately has the potential to impact ophthalmology in a bigger way.

The fact that femtosecond lasers are not the only optical technology required for laser cataract surgery amplifies the implications for the biophotonics industry. The approach "requires advanced 3D imaging in addition to the laser delivery system. You have to know where the front and back of the cornea is, and where the front and back of the natural lens is," explains Lindstrom. "In conjunction with an integrated imaging and optical system, accurate and reproducible treatment in the lens can be conducted without fear of rupturing the lens capsule," says Mark Packer, MD, FACS, CPI, of Oregon Health and Sciences University (Portland, OR).

Current developers of laser cataract surgical systems include Alcon (Fort Worth, TX), which offers LenSx, and OptiMedica (Santa Clara, CA), producer of Catalys—the only two companies to have received U.S. Food and Drug Administration (FDA) approval. Others are LensAR (Orlando, FL), which in March 2012 announced $24 million in private financing to fund the first commercial shipments of its system, and Technolas (Munich, Germany). Suppliers of lasers for this application include Abbott Medical Optics (AMO; Santa Ana, CA) and Bausch & Lomb (Rochester, NY).

LensAR's imaging system, based on Scheimpflug technology, "allows the surgeon access to precise mapping of the tissues and automated image-guided laser placement," says Packer, who is affiliated with the company. William W. Culbertson, MD, Professor of Ophthalmology, Bascom Palmer Eye Institute (Miami, FL), notes that OptiMedica's proprietary imaging approach uses spectral-domain optical coherence tomography (SD-OCT) to deliver the femtosecond pulses "safely and precisely" to the intended location. Lindstrom (who consults for LenSx, Bausch & Lomb, and Abbott Medical Optics, and holds a small equity position in LensAR) explained that most surgical systems developers are using OCT—which is advancing continually. But, he says, "I don't think any of us knows for sure whether one or the other will turn out to be better."

Game on

Femtosecond lasers have been used by ophthalmologists for years, but not until 2009 did the FDA approve a femtosecond laser able to reach deep enough into the eye to be used in cataract removal. (The awardee was LenSx, a company purchased about a year later by Alcon for $361.5 million.) The first laser cataract surgery in the U.S. was performed in March 2010; since then, the FDA has issued other approvals related to the procedure. At the 115th Annual Meeting of the American Academy of Ophthalmology (held in October 2011), laser cataract surgery was "one of the hottest topics" of the conference, according to the AAO. So, "it's no longer 'is it going to happen?'" says Lindstrom. "It's happening!"

Jay C. Grochmal, MD, says the aging baby-boomer population has brought an influx of patients needing vision correction for cataracts and other age-related conditions. Lindstrom quantifies: In America, 78 million baby-boomers are coming into the cataract age, "and most of them can afford, once in a lifetime, to spend $2,000," a ballpark figure he is basing on the cost of LASIK. "The way I put it sometimes is that it's cheaper than one artificial tooth to enhance your vision for a lifetime." Lindstrom notes that currently, cataract surgery patients have a life expectancy of about 18 years. "When I first started in ophthalmology about 30 years ago, their life expectancy was on average about 5 years. Now we're operating younger and people are living longer. So they're living with the vision that they get for a long time, and that has a big impact on the last 20 years of your life."

Steadier than a steady hand

Traditional cataract surgery requires the steady hand of a surgeon to make an incision in the eye and remove a disc from the capsule surrounding the eye's lens (a procedure known as capsulorhexis). The surgeon uses an ultrasound probe to break up the lens, which is then suctioned out. Into the space that's left, the surgeon inserts a replacement intraocular lens (IOL) made of plastic.

Research headed by the Stanford University School of Medicine compared the traditional method with laser-based "capsulotomy," and found that a femtosecond laser-based system safely cut 12 times more precisely than the traditional method, and left edges twice as strong in the remaining lens capsule. The clinical trial portion of the research, involving 39 patients, showed that the laser method also came much closer to producing the intended size of the capsular disc (within 25 μm vs. 305 μm in the manual procedure), and cut a more perfect circle (making a better fit for the intraocular lens). This research revealed no significant adverse events.¹ The work was commissioned by OptiMedica, in which the researchers have equity interest, but the results have implications across the board for laser-based cataract surgery.

Femtosecond lasers and their application to cataract surgery constitute a major innovation in modern ophthalmic surgery, according to Alio and Herndandez.² These lasers offer several advantages over conventional lasers: An ability to penetrate deep into the anterior segment of the eye-into the transparent and even opaque cornea, short pulse duration, and micro-precision. "Femtosecond lasers have ultra-short pulse widths, which provide precise cutting without significant collateral damage to adjacent tissues," explains Packer. These lasers operate in the near-infrared (1030 nm).

Goals and future applications

Lindstrom says that beyond producing more precise and accurate outcome goals, the hope for laser cataract surgery is to "improve predictability from one patient to another, and from one surgeon to another." That's basically what laser technology did for refractive corneal surgery.

The launch of LenSx, "I think by anyone's standards, was significantly more successful than had been anticipated," Lindstrom notes. But for the technology to reach its full potential, he explains, "we'll need two to three strong competitors." The competition should reduce the cost of instruments as well as the per-procedure cost. And, he adds, "more science needs to evolve." When growth happens in terms of numbers of surgeons, lasers, and procedures, we'll get an "explosion of knowledge and understanding."

Lindstrom hopes for a move to less-expensive solid-state laser technologies and, because procedure times are "still higher than ideal," faster laser operation. "We saw this in refractive corneal surgery: It used to take us a minute and a half to create a flap, and now we can do it in 20 or 30 seconds. We'd like to be able to do it in 5 seconds," he explains. He notes that nuclear fragmentation now takes 60 to 90 seconds—and reducing that time would make things easier on the patient. He'd also like to be able to know how dense the lens is.

"So there's a tremendous amount of laser physics and engineering opportunity for advancement," says Lindstrom, "in the imaging, in the delivery systems, and the rate with which lasers fire, and so on." The laser-assisted procedure is "good for patients and difficult for doctors," concludes a recent paper by Lawless and Hodge—who explained that the laser approach is more technically demanding and lengthy than standard cataract surgery.³

Culbertson imagines that, due to the procedure's precision and predictability, an application beyond the clinic will be for research "to launch many years of clinical studies aimed at further improving vision for patients around the world."

Packer notes additional indications such as the treatment of astigmatism make the ability to pass-through costs to the patient easier and the financial model more secure—in the U.S., at least. As more safety and effectiveness data is made available, there is an increasingly cogent argument for the benefits of laser cataract surgery, he says.

Lindstrom further imagines systems able to do both refractive corneal and refractive cataract surgery. He says the technology could also be suited to corneal transplants and glaucoma surgeries.

REFERENCES

1. D.V. Palanker et al., Sci. Transl. Med., 2, 58, 58–85 (2010).
2. J.L. Alio and M. Hernandez, Saudi J. Ophthalmol., 25, 3, 219–223 (2011).
3. M. Lawless and C. Hodge, Asia-Pac. J. Ophthalmol., 1, 1, 5–10 (2012).