Our current IOL calculation methods have been improving steadily for the past few decades. When the original SRK formula came out, it worked reasonably well for most average eyes, but not so well for others. The SRK II helped to address those other eyes, but it was the emergence of the theoretical formulae such as Holladay 1, SRK/T and Hoffer Q that really improved IOL calculation accuracy.
These theoretical formulae use the keratometry (K) and axial length (AL) measurements to determine the effective lens position (ELP) and thus aid in the calculation of optimal IOL power for the eye and desired refractive goal. Other more complex formulae such as the Holladay 2 and Haigis can incorporate other biometric data such as anterior chamber depth or white-to-white size to further enhance accuracy of determining ELP. More recently, the Barrett Universal and Olsen formulae have been purported to have great results.
And then we have extreme eyes such as high myopes with long axial lengths in which yet another calculation, the Wang-Koch axial length modification, is required to get more accurate results. To add yet more complexity, we have rules of thumb such as using the Hoffer Q for short eyes, the Holladay 1 for average eyes, and the SRK/T for longer eyes except if they have unusual Ks, in which case the SRK/T may be thrown off. And in post-refractive eyes, we can use the Aramberri double-K method so that the measured K can be used for the power calculation but then a standardized K can be used for the ELP calculation.
This is too much! There has to be a better way. And John Ladas, MD, PhD, and his colleagues have come up with the ultimate solution.
What if we could represent all current formulae and all future formulae in one “Super Formula” and then represent it all with one 3-D “Super Surface?” This Super Formula would even be dynamic in that data from actual prior calculations and surgeries could be used to further refine the results. In an initial test of 100 eyes, the Super Formula localized to the correct portion of the Super Surface 100% of the time and chose the best IOL power 100% of the time. The individual formulae didn’t fare as well with 70% for Hoffer Q, 84% for Holladay 1, 78% for Holladay 1 with Wang-Koch adjustment, 76% for SRK/T and 52% for Haigis.
This concept of the Super Surface and Super Formula may very well revolutionize IOL power calculations for your cataract surgery patients.
An original article was published in JAMA Ophthalmology on Oct. 15: http://archopht.jamanetwork.com/article.aspx?articleid=2451647
Disclosure: Dr. Devgan has no relevant financial disclosures.