Intraoperative aberrometry may help refractive cataract surgery reach the next level

Issue: December 25, 2010

ByRichard L. Lindstrom, MD

Richard L. Lindstrom

Many ophthalmologists agree that the greatest unmet need in IOL surgery is a way to improve postoperative refractive outcomes. Especially with advanced-technology IOLs such as toric, multifocal and accommodating implants, for which patients are paying a premium to achieve a refractive outcome goal to enhance their lifestyle and quality of life, hitting the target refractive goal is a critical need.

Going back 25 years, while serving as chief medical officer of 3M Vision Care, I was studying the outcomes of the first-generation diffractive multifocal IOL, and one fact became abundantly clear: Refractive outcome was the critical success factor. We performed comprehensive subjective and objective outcomes analysis and evaluated patient-reported outcomes and satisfaction in detail, including intense psychological profiling. While many teach that proper patient selection in regards to personality is critical in achieving a high success rate in terms of patient satisfaction, we did not find this to be the case. In the end, the only thing that correlated with patient satisfaction was the refractive outcome achieved. If the patients were emmetropic, even with this early-generation multifocal IOL, they were happy. If they had significant residual defocus or astigmatism, they were not. It did not matter if they were engineers with six colored pens in their pocket or laid-back retired housewives from small-town America. If we hit our refractive outcome goal, they were happy, and if we did not, they were not.

That prompted me to adopt and start teaching refractive cataract surgery skills in 1985, and I have been at it ever since. Sadly, even with major advances in our IOLs, with rare exceptions we are still doing miserably as cataract surgeons in regards to achieving the desired refractive outcome goal. We now have enough data to know that a residual defocus or astigmatism of more than 0.5 D results in a major reduction of quality of vision with any IOL. Accommodating IOLs seem especially sensitive to defocus, which reduces their accommodative amplitude or quality of vision, depending on the model used. Multifocal IOLs are especially sensitive to astigmatism, and 1 D of astigmatism is devastating to image quality in the multifocal IOL.

Data from Guy Kezirian’s DataLink suggest that the best surgeons in America with currently available technology achieve a refractive outcome goal within 0.5 D of target in less than 50% of cases — 42%, to be exact, in his last report of more than 45,000 eyes. The most commonly performed corneal refractive procedure, LASIK, achieves this goal in well more than 95% of patients, with an enhancement rate under 3%. We have a long way to go to make refractive cataract surgery outcomes as predictable as refractive corneal surgery outcomes, but that must be the goal.

Actually, with LASIK in low to moderate myopia today, we make most patients see better without correction than they did preop with spectacles and/or soft contact lenses. It took 25 years to get there with LASIK, but today’s refractive outcomes are within 0.1 D of emmetropia for low to moderate myopes, and we are programming corrections to 0.01 D and now targeting the treatment of higher-order aberrations with a goal of zero. This is where we need to go with refractive cataract surgery.

Several new technologies are likely to help. Femtosecond laser refractive cataract surgery, which we have discussed in other commentaries, is one promising technology now launching that should improve refractive outcomes and reduce enhancement rates. Intraoperative aberrometry is another technology that is very promising. The ability to accurately measure phakic, aphakic and pseudophakic refractive error in real time in the operating room has been a surgeon’s dream for decades. The WaveTec ORange device is the first commercially available surgical microscope-mounted instrument that is capable of giving us these measurements. There are more to come.

Both the femtosecond laser alone and intraoperative aberrometry alone in innovative surgeon hands are showing they are capable of enhancing postoperative refractive outcome predictability. I predict the two together will be synergistic. The combination of femtosecond laser refractive cataract surgery with intraoperative aberrometry can be anticipated to take us into a new era in refractive outcome predictability. This will increase patient and surgeon satisfaction and drive strong growth in refractive cataract surgery. The femtosecond laser may also allow access to a minimally invasive enhancement strategy that is more easily adopted by the typical cataract surgeon than excimer laser corneal surgery or incisional refractive keratotomy.

Finally, as we move into the 2011 to 2020 decade, we cataract surgeons seem poised to truly embrace as a realistic goal providing our patients with refractive outcomes similar to those enjoyed by our corneal refractive surgery patients with a reasonable enhancement rate. A goal of 90% with 20/20 vision, perhaps at all distances with next-generation accommodating IOLs, without correction and less than 0.5 D residual defocus and astigmatism by 2020 is achievable with a single procedure. Two very promising synergistic technologies are now launching: femtosecond laser refractive cataract surgery and intraoperative aberrometry. This next decade is the time for we cataract surgeons to make a commitment to adopt them and deliver the outcomes our patients desire. I believe those of us who do so will not only survive the external challenges looming, but also prosper.