Outcomes in toric iols
Adjustable lenses could render many current technologies obsolete
David F Chang MD
Many technological advances have emerged that can improve toric IOL outcomes, David F Chang MD told the American Academy of Ophthalmology 2017 Annual Meeting in New Orleans, USA. Dr Chang generally prefers toric IOLs over limbal-relaxing incisions because they produce more predictable outcomes. “However, toric IOLs require proper selection of the cylindrical power and axis, and accurate surgical alignment that is maintained postoperatively”, he said.
Accurate preoperative measurement of corneal astigmatism continues to be critical. Newer biometry platforms such as the Lenstar LS 900 (Haag-Streit) and the IOLMaster 700 (ZEISS) have improved keratometry accuracy compared to their predecessors. One study found that these systems were more accurate in measuring corneal curvature than topography (Abulafia A et al., J Cataract Refract Surg 2015; 41:936-944). However, topography still provides important information regarding the corneal surface, regularity of astigmatism and possible ectasia.
Dr Chang regularly looks at corneal wavefront aberrometry with all premium IOL patients. “Diagnosing corneal abnormalities preoperatively will generally rule out diffractive multifocal IOLs, and allows me to counsel patients regarding issues that will likely impair their vision following surgery,” he said.
We have also learned about the importance and impact of posterior corneal curvature (Koch DD et al., J Cataract Refract Surg 2012; 38:2080-2087; Koch DD et al., J Cataract Refract Surg 2013; 39:1803-1809), and there are several devices to measure it preoperatively. However, Dr Chang highlighted a study showing that the Barrett toric IOL formula was as good for predicting toric IOL power as for directly measuring the posterior corneal surface (Ferreira T et al., J Cataract Refract Surg 2017; 43:340-347).
Digital overlay systems incorporated into the microscope, such as the Callisto (ZEISS) and Verion (Alcon), help us to align toric IOLs more accurately, Dr Chang said. “Intraoperative aberrometry enables fine-tuning of the toric IOL alignment – particularly when different corneal measurements suggest different axes.” He added: “One study shows that the majority of any postoperative toric IOL rotation occurs within the first hour after surgery” (Inoue Y et al., Ophthalmology 2017; 124(9):1424-1425).
“These many advances in technology are giving us better toric IOL outcomes than ever before,” said Dr Chang. “But once we get adjustable lenses, many of these same technologies may become superfluous, because we will just be treating the stable post-op refraction after surgery.” The light-adjustable IOL from RxSight (formerly Calhoun Vision) was FDA approved one week following the conclusion of the AAO meeting.
The utility of lenses that can be adjusted after surgery was recently demonstrated in a randomised prospective clinical trial comparing the RxLAL (RxSight) with a non-adjustable toric lens implanted in 371 astigmatic patients. Mean residual refractive error was two-fold less in the RxLAL group, resulting in 70% of patients achieving 20/20 uncorrected visual acuity compared with 40% in the non-adjustable toric IOL group.
Dr Chang is a consultant for ZEISS, J&J Vision and RxSight.
David F Chang: email@example.com