Cataract/Anterior Segment, Comprehensive Ophthalmology, Refractive Mgmt/Intervention
Without an accurate method of predicting IOL power calculations in post-keratorefractive eyes, a tsunami is threatening to wash over ophthalmology in the near future, says ONE Cataract Editor Warren Hill,MD. Refractive surgeons need to throw out the standard practice of destroying medical records after seven years. Keep your refractive surgery records indefinitely, he says, or give your patients a card with their pre-LASIK keratometry.
According to Marketscope, 1.4 million people underwent LASIK in 2008 for the reduction of myopia and hyperopia in the United States. A dramatic downturn in the economy notwithstanding, approximately 1 million people still elected to undergo LASIK in 2009. Add to these numbers the many millions of patients who had radial keratotomy beginning more than 25 years ago, and the number of post-keratorefractive eyes that will undergo cataract surgery in the near future begins to look like a tsunami, soon to wash over ophthalmology.
In 2010, we remain faced with three fundamental problems regarding IOL power calculations for the post-keratorefractive eye. First, following myopic LASIK an instrument that can correctly determine the central corneal refractive power remains elusive. Second, the central corneal power correction algorithms that have been developed for all forms of keratorefractive surgery provide only estimations rather than something exact. And lastly, traditional IOL power calculation formulas often come to the wrong conclusions in the presence of the artifact of a very steep or very flat central corneal power. These formulas then require additional internal and external manipulations based on historical information in order to approximate the correct IOL power. Regrettably, the current level of technology for estimating the central corneal power of the post-keratorefractive eye remains an estimation, based on an algorithm, adjusted by prior experience. Hardly something exact.
In spite of these many limitations, patient expectations remain high, making a lack of accuracy all the more disturbing to both the physician charged with the responsibility for the IOL power calculation and the patient who has already made a significant investment in a desired refractive result.
When a mathematical exercise lacks precision, one helpful strategy for improving the likelihood of an acceptable outcome is to approach it from multiple, independent directions, looking for agreement. For IOL power calculations after LASIK, this comes down to comparing one or more calculation methods based, in part, on historical information, such as the modified Masket method, with those that rely on purely objective information, such as the innovative Haigis-L formula.
An emerging and increasingly troubling issue is that many LASIK surgeons continue the practice of destroying medical records after seven years. Because several of the more accurate calculation methodologies rely on both historical information and objective measurements, when historical information is lacking, this important, confirmatory piece of the mathematical puzzle is missing.
The creation of millions and millions of post-LASIK patients in the United States alone has lead to a unique circumstance in ophthalmology whereby the usual and customary rules regarding medical record keeping simply do not apply. LASIK has created an ethical dilemma with regards to IOL power calculation that extends far beyond the procedure itself and renders meaningless the current statutory requirement for medical records keeping.
With advancing technology often comes a new level of responsibility. Before record keeping takes the form of patient-driven state or federal legislation, LASIK surgeons everywhere should make it their goal to maintain their refractive surgery records indefinitely, or give to their patients, at the very minimum, a card with the pre-LASIK cycloplegic refraction, pre-LASIK keratometry and a post-LASIK manifest refraction from four to six months after LASIK. Four to six months after LASIK is long enough for the refractive outcome to stabilize, yet soon enough so that lens-induced myopia does not play a role prior to cataract formation.
Next year, at least another million people in the United States will undergo LASIK. It should be our responsibility as ophthalmologists to do all we can so that the inherent inaccuracy of IOL power calculations for these patients is not rendered even more problematic by a simple lack of information.
The Academy developed a "K-card" to be given to patients by their LASIK surgeons, which captures a patient's preoperative keratometry readings and refraction. It is often difficult to track down this critical data years later, when the patient is need of cataract surgery or additional eye care. Find it here
Dr. Hill is a consultant to Alcon, Carl Zeiss Meditec, Santen and Oculus. He also receives lecture fees from Alcon, Carl Zeiss Meditec and Oculus.