Laser Cataract Extraction: Has Its Time Finally Come?
Here's the latest information on the advantages and limitations of the technology at this point in its development.
By Mark Packer, M.D., I. Howard Fine, M.D., and Richard S. Hoffman, M.D., Eugene, Ore.

The newest laser phacoemulsification technology offers many potential advantages for the cataract surgeon, including nonthermal extraction of cataract material, increased endothelial protection and smaller incision size. Here, we'd like to share some of our experience working with these systems and provide a brief update on their advantages and limitations -- at least at this point in their development.

Upcoming laser options

Currently, two cataract extraction systems employing laser energy are under investigation. A third system -- the Dodick Q-switched Neodymium:YAG laser (from ARC GmbH, in Jona, Switzerland) -- was recently approved by the FDA for use in the United States.

The approved Dodick Neodymium:YAG laser (1064 nm) system uses plasma formation technology and shock wave generation to produce photolysis of lens material. Laser pulses are transmitted via a fiber and focused on a titanium target within the tip. The laser pulses produce plasma, generating an acoustic wave that emulsifies the cataract.

The two systems still under investigation are:

• The Neodymium:YAG Photon Laser PhacoLysis System, from Paradigm Medical in Salt Lake City. This system's probe has a ski-shaped distal tip that intercepts laser light emitted from the optical fiber. The cataract is broken down by photofragmentation and removed by aspiration.
• The Erbium:YAG Phacolase, from Asclepion-Meditec, in Jena, Germany. This 2940-nm laser delivers its energy via a fiber inside the aspiration port that's placed flush with the tip. The surgeon brings the tip into contact with the lens material, occluding the tip; a vacuum holds the material in place as it's evaporated and aspirated. The energy of this laser is well absorbed by tissues with high water content. It has a penetration depth of less than one micron.

System efficiency

New technology for phacoemulsification raises concerns about two key efficiency issues: the energy required to remove a cataract, and the time required to perform surgery.

• Energy expenditure during surgery. This is important because decreased energy expenditure in the eye correlates with faster healing and improved visual rehabilitation.
  So far, laser phacoemulsification compares favorably with the latest ultrasound techniques:
  • Recently, Helmut Hoh published data showing an average energy expenditure of about 60 Joules for phacoemulsification performed with the Erbium:YAG.
  • In the February, 2001 issue of the Journal of Cataract & Refractive Surgery, Werner Huetz and Berthold Eckhardt published a study indicating that phacoemulsification can be performed with the Dodick-ARC laser using less than 10 Joules.

  For comparison, in that same issue of the Journal of Cataract & Refractive Surgery, we published the results of a recent study in which we showed that it's possible to perform ultrasound phacoemulsification using less than 10 Joules of energy.
  Of course, we've made vast improvements in our application of ultrasound technology in recent years; this is orders of magnitude less than the benchmarks set by DeBray and Olson in their 1998 publication comparing the divide-and-conquer technique (3264 Joules) to phaco chop (782 Joules). Similar reductions in energy expenditure may be in store for the new laser-based cataract extraction systems, as surgeons develop new and improved techniques during the upcoming years.

• Length of surgery. Another key efficiency issue -- especially in this era of ambulatory surgical centers -- is how long it takes to perform surgery using a given technology.
  So far, in our experience, cataract removal with the laser systems takes longer than cataract removal with ultrasound. (This agrees with the published results of other investigators.) However, we attribute this, in part, to the novelty of the technology. As our familiarity with these devices grows, we're certain to develop new techniques that will take better advantage of their unique characteristics and permit more rapid surgery.

Safety issues

Laser-based systems are potentially safer for the patient than ultrasound systems:

• Absence of heat. A key safety feature of all three laser systems is the absence of thermal energy. (Corneal wound burns during ultrasonic phacoemulsification can be devastating, sometimes even requiring penetrating keratoplasty.)
  The Phacolase and Photon handpieces currently employ the familiar design of ultrasound phacoemulsification tips, with the irrigation sleeve over the tip. However, because the lasers don't produce vibration, no heat is created at the tip.
  In fact, the absence of thermal energy allows the separation of irrigation from the application of laser energy and aspiration. For that reason, future application of these devices will likely involve a bimanual technique, and that will permit an even smaller incision than is used with ultrasound technology. This decrease in incision size will become more important as intraocular lens design changes over the coming years, especially if injectable IOL material becomes clinically available.
• Endothelial cell loss. One of the advantages of laser systems is an apparent decrease in loss of endothelial cells. Hoh's pilot study, using the Erbium:YAG laser from Phacolase, showed an endothelial cell loss of only 0.96%, compared with 2.9% when using ultrasound.

Other issues

As with any new technology, many issues remain to be worked out:

• Grade of nuclei. At present, the laser devices appear to be most useful for the lower grades of nuclear sclerosis:
  • The Photon Laser Phase II trial includes cataracts of grade 1+ to 2+ nuclear sclerosis.
  • The Phacolase trial includes grades 1+ to 3+.
  • Huetz and Eckhardt studied lenses up to and including 3+ nuclear sclerosis, as discussed in their article on the Dodick-ARC laser. Given the increased time needed to complete a case and the concurrent use of topical anesthesia, it appears best to limit our current use of these systems to softer nuclei.
• Irrigation/aspiration. Both the Phacolase and the Dodick-ARC systems have been combined with the Geuder Megatron unit, a peristaltic irrigation/aspiration pump. The Megatron features a bidirectional foot pedal with independent control of aspiration and laser power. (The Dodick laser has also been combined with a Venturi aspiration pump and pressurized irrigation system.) The Photon laser has been combined with the Mentor SIStem, a peristaltic design.
• Technique. Despite the short (1 micron) penetration of the Erbium:YAG laser, it appears possible that evaporation bubbles can line up at the tip when using certain application frequencies. This can create cavities up to 3 mm in length.
  This penetration distance must be taken into account when working in the endocapsular space. Because of the generous endothelial safety profile of the Erbium:YAG laser and the potential for capsular disruption, it may be prudent to perform laser evaporation of lens material in the iris plane rather than deep in the bag.
  In contrast, the design of the Photon Neodymium:YAG laser makes damage to the capsule or iris unlikely. You can actually place the capsule in the direct line of the laser energy and fire the laser without disrupting the capsule.

The future looks bright

This new laser technology will undoubtedly come to enjoy a wider role in cataract surgery. Given the excellent safety profile of these devices and their applicability to softer nuclei, they may also develop an important role in lens-based refractive surgical modalities, including clear lens replacement. 

Mark Packer, M.D., I. Howard Fine, M.D., and Richard S. Hoffman, M.D., are professors at the Casey Eye Institute at Oregon Health Sciences University. Dr. Packer is clinical assistant professor of ophthalmology; Dr. Fine is clinical associate professor of ophthalmology; and Dr. Hoffman is clinical instructor of ophthalmology. All three are in private practice in Eugene, Ore. They have no financial interest in the products mentioned.