Implementing new technology for biometry and IOL power calculation represents an important investment for the surgeon.
The advent of an accommodating IOL has the potential to alter the landscape of cataract and refractive lens surgery significantly. We now have more than 4 years' experience with the accommodating posterior chamber IOL (Crystalens/model AT-45, eyeonics Inc.), both in the FDA-monitored investigation and in the new post-approval environment, and we would like to share our experience from the perspective of practice management.
One point of clear agreement among users and critics of accommodative lens technology is the need for precise biometry and IOL power calculation. This requirement represents one of the important reasons that eyeonics requires surgeons to attend a full-day workshop and learn to implement the lens systematically in practice. Currently, the workshop carries a price tag of $2,000.
In the FDA study, investigators used either partial coherence interferometry (IOL Master, Carl Zeiss Meditec) or immersion ultrasound (Axis II, Quantel Medical). There was a slight trend, not statistically significant, toward better results with immersion, but our study published in the Journal of Cataract and Refractive Surgery showed a correlation between these modalities of 0.997.1
The FDA protocol called for manual keratometry, but we have had good success using the autokeratometry from the IOL Master, supplemented by simulated keratometry values from the EyeSys Corneal Topographer (Tracey Technologies) or the Humphrey Atlas (Carl Zeiss Meditec). We use topography if we are going to correct pre-existing corneal astigmatism, or if the autokeratometry does not agree with the refractive cylinder (irregular astigmatism).
In patients who have had previous incisional keratorefractive surgery, we use the Effective Refractive Power (EffRP) from the Holladay Diagnostic Summary of the EyeSys. Our results with this method appeared in the Journal of Cataract and Refractive Surgery and demonstrated a frequency distribution of postoperative spherical equivalent within ±0.5 D in 80% of eyes.2
So far, we have limited experience with post-LASIK eyes, and for these we adjust the EffRP according to a method worked out by Doug Koch, MD, of Houston-subtracting 16% of the refractive correction after myopic LASIK and adding 15% of the refractive correction after hyperopic LASIK.
Once we have obtained accurate keratometry and axial length, we use the Holladay IOL Consultant to determine the IOL power. The Holladay II formula is the only widely available formula in the United States that allows in-house regression analysis and continual improvement. The formula is more accurate because it takes into account seven variables to determine the effective lens position. Implementing Holladay II does require technician time to input the outcomes data; however, it is well worth the extra time and the price.
A serious commitment Implementing new technology for biometry and IOL power calculation represents an important investment for the surgeon who is serious about refractive lens surgery. Given the premium price our client-patients will be paying for these procedures, we must examine the quality of our work continually and seek improvements that will enhance our outcomes. We think the results justify the extra effort.
With the IOL power calculation in hand, one now needs the IOL itself. Currently eyeonics requires surgeons to purchase a consignment of 20 IOLs at a price of $16,000 to get started. Perhaps more than any other single factor, this price represents the greatest influence that eyeonics is having on the cataract and refractive surgery marketplace.
Surgeons are being challenged to think critically about the value of the procedures they offer and to figure out a reasonable price. It is in this situation that the somewhat blurry line between cataract and refractive surgery becomes crucial. The way finances are handled for refractive patients differs markedly from the way they are handled with private insurers. Medicare patients with cataract represent yet a third group.