Precision in optics points to predictability

Take-Home

Among the most important advances in laser cataract surgery toward achieving improved outcomes are:

• Better predictability of the effective lens position.

• More accurate and producible incisions to correct astigmatism.

• Better visual outcomes.

By Lynda Charters; Reviewed by Zoltan Z. Nagy, MD, PhD, DSc

Budapest, Hungary-Advances in laser cataract surgery are resulting in a safer and more predictable procedure for patients.

The most important advances toward achieving improved outcomes are better predictability of the effective lens position (ELP), more accurate and producible incisions to correct astigmatism, and better visual outcomes.

“The modern requirements for an improved refractive cataract surgery are a perfect ELP and predictability,” said Zoltan Z. Nagy, MD, PhD, DSc, clinical professor of ophthalmology, Department of Ophthalmology, Semmelweis University, Budapest, Hungary.

“Therefore, we need a uniform shape and size of the capsulotomy, control of the preoperative corneal astigmatism with reproducible corneal entry and arcuate incisions, and better early vision postoperatively via reduced phaco power and corneal edema,” he said.

A uniform capsulotomy is of utmost importance. Studies have reported that about 10% of implanted lenses are decentered by more than 0.5 mm or tilted by more than 5º, both of which can induce changes in the effective IOL power. In patients with multifocal IOLs, even smaller changes can induce higher-order aberrations and decreased best-corrected visual acuity, according to Dr. Nagy.

Key factors associated with the laser capsulotomy are uniform shape and position, which facilitate perfect centering of the IOL. The reproducible size of the capsulotomy achieves a predictable axial position of the IOL.

“These factors will allow us to achieve a reproducible IOL power and effects,” he said.

Laser fragmentation is another important factor. Efficient segmentation can reduce the phaco power, corneal edema, and the effective phaco time-resulting in better early vision postoperatively, Dr. Nagy noted.

Refractive accuracy

The refractive accuracy is another issue in cataract surgery. A comparison of a femtosecond laser (LenSx, Alcon Laboratories) with ultrasound phacoemulsification indicted that at all visual acuity levels the femtosecond laser achieved better outcomes (e.g., 20/16 was achieved by 5% of patients treated with the femtosecond laser compared with 0% treated with ultrasound phacoemulsification). The results for 20/20 or better, 20/25 or better, and 20/40 or better, respectively, were 52% and 44%, 81% and 57%, and 94% and 87%, Dr. Nagy noted.

When considering the intended correction, a comparison of the femtosecond laser correction with ultrasound phacoemulsification showed that 18% achieved plano compared with 4%, respectively. Targets of ±0.25 D or less, ±0.5 D or less, ±0.75 D or less, ±1 D or less, and ±1.5 D or less, respectively, were 57% and 50%, 81% and 79%, 98% and 89%, 100% and 93%, and 100% and 100%.

“The femtosecond laser-treated eyes achieved much better accuracy in the targeted correction,” he said.

Use of laser arcuate incisions allows the surgeon to control the depth of the incision from 80% to 90%. A prospective multicenter study of 39 eyes found that 77% of the eyes were within 0.5 D of the targeted astigmatic result, Dr. Nagy noted.

“Laser cataract technology continues to advance rapidly, making cataract surgery a safer and more predictable procedure for our patients,” Dr. Nagy concluded. “A rapidly growing body of clinical data is showing better predictability of the ELP, more accurate and reproducible corneal incisions for astigmatic correction, and better visual outcomes.”

fyi

Zoltan Z. Nagy, MD, PhD, DSc

E: zoltan.nagy100@gmail.com

Dr. Nagy is a consultant to Alcon Europe and Alcon/LenSx. This article is based on Dr. Nagy’s presentation during Refractive Surgery 2012 at the annual meeting of the annual meeting of the American Academy of Ophthalmology.