About the Calculator
Formula
The FemtoAK calculator was developed in 2019 to improve the correction of astigmatism at the time of cataract surgery. Corneal astigmatism may be corrected with either toric intraocular lenses (IOLs), limbal relaxing incisions (LRIs), or femtosecond laser-assisted astigmatic keratotomies (FLAK). While toric IOLs are widely regarded as a more accurate method of astigmatism correction, there is still a place for LRIs and FLAKs, especially at lower levels of astigmatism. The FemtoAK nomogram calculates planned arcuate incisions based on patient age, anterior and empirically derived posterior corneal astigmatism, as well as surgeon-entered surgically induced astigmatism (SIA).
Clinical Results
The FemtoAK calculator has been used since 2019 on thousands of eyes. Some subjects (69 eyes from 54 patients) have enrolled in a prospective clinical trial to evaluate the efficacy of the nomogram for the correction of astigmatism. In this trial, pre-operative biometry values were collected, FLAK was planned using the FemtoAK calculator, and post-operative biometry, corneal hysteresis and manifest refraction was collected 1 month after surgery. The corneal correction index [CI: defined as the ratio of surgically induced astigmatism (SIA) to target induced astigmatism (TIA)] for all eyes was 0.85 (where a CI of 1.0 is ideal). The refractive correction index revealed an over-correction (1.69) in WTR and under-correction (0.90) in ATR eyes. The proportion of eyes with less than 0.5 and 1.0 D of keratometric astigmatism increased from 0% and 51% preoperatively to 54% and 90% postoperatively.
The results of this work were presented, in part, at the 2021 American Academy of Ophthalmology Annual Meeting and at the 2022 American Society of Cataract and Refractive Surgery meeting. Publication is pending.
About the Creators of FemtoAK
Seth Pantanelli, MD, MS
Seth Pantanelli, MD, MS is a Professor of Ophthalmology and Vice-Chair for Clinical Research at the Penn State College of Medicine in Hershey, PA. He received his undergraduate and master’s degrees in biomedical engineering from the University of Rochester, and his medical degree from the University of Rochester School of Medicine & Dentistry. He completed an ophthalmology residency at the University of Rochester Medical Center’s Flaum Eye Institute and a fellowship in cornea, external disease, and refractive surgery at the Bascom Palmer Eye Institute. He is a member of the Cornea Society, the American Society of Cataract and Refractive Surgery, and is a fellow of the American Academy of Ophthalmology. Dr. Pantanelli has authored or co-authored more than 40 peer-reviewed articles, as well as multiple book chapters. His research interests lie in the correction of astigmatism and IOL power calculations.
Brett Ernst, MD
Brett Ernst, MD is a graduate of Wayne State Medical School. He completed his ophthalmology residency at the Cleveland Clinic and is a board-certified ophthalmologist. He moved to Harrisburg with his wife Mariann and daughters Alexandra and Victoria in 1993. Dr. Ernst is Chief of Ophthalmology for Pinnacle Health Systems and is also Assistant Clinical Professor at Penn State College of Medicine. Dr. Ernst is a member of the Pennsylvania Academy of Ophthalmology, the American Academy of Ophthalmology and a Fellow of the American Society of Cataract Surgeons. Dr. Ernst has been named a Top 50 Surgeon by Sightpath Medical. He is also the President of Schein Ernst Mishra Eye in Harrisburg, PA. His practice was instrumental in the clinical trial and continued use of the FemtoAK nomogram.
Gautam Mishra, MD
Gautam Mishra, M.D., was brought up in Syracuse, New York, where he received his primary education. He then completed his bachelor’s degree at Boston College and went on to graduate from Jefferson Medical College in Philadelphia. Dr. Mishra served as Chief Resident during his residency in Ophthalmology at Wake Forest University, North Carolina. He received his training in cornea and refractive surgery at Albany Medical Center and joined Schein Ernst Mishra Eye in 2006. Dr. Mishra is board certified in ophthalmology and is also a Clinical Assistant Professor of Ophthalmology in the Penn State College of Medicine. He lives in Harrisburg with his wife Mridula and daughter Anjali.
Dr. Mishra has performed thousands of surgeries since he began operating in 2004 and joined Schein Ernst Mishra Eye in 2006, where he now serves as Vice President of the company. Dr. Mishra is passionate about restoring sight to patients and improving their way of life. In his free time, you can find him traveling internationally with family, learning new technologies or practicing yoga.
Contributions
We are also grateful for the contributions and effort put forth by medical students and staff of the Penn State College of Medicine and Schein Ernst Mishra Eye to move this project forward. These individuals include Catherine Seeger, Ashley Sun, Nguyen Truong, Amy Longenecker, Charla Ferchow, among others.
This work was made possible through generous support from the Pennsylvania Lions Sight Conservation and Eye Research Foundation, Inc.