Improved toric adhesive capabilities minimize rotational instability

The rotational and refractive stability of a toric IOL is enhanced by the haptic design and adhesive biomaterial.

Edward J. Holland

A study has suggested that an improved haptic design and adhesive biomaterial in a toric IOL work together to treat cataracts and corneal astigmatism, offering favorable rotational stability and distance vision spectacle freedom.

In the study, published in Ophthalmology, the AcrySof toric IOL (Alcon) showed a significantly lower incidence of rotational stability than that of first-generation IOLs.

Patients implanted with more customary spherical monofocal IOLs sometimes require spectacles or supplementary corneal refractive procedures to achieve optimal visual acuity. Toric IOLs were designed to decrease and possibly eliminate the need for these enhancements, but they have been associated with postoperative rotational instability, the study authors wrote.

“The AcrySof toric IOL haptic design and acrylic material create improved adhesive capabilities that prevent rotation when the IOL is inserted into the posterior capsular bag,” Edward J. Holland, MD, lead author of the study and an OSN Cornea/External Disease Board Member, said in an e-mail interview with Ocular Surgery News.

The haptics enhance stability by attaching the IOL to the capsule, and the new biomaterial adheres to the capsular bag.

Methods and limitations

This randomized, subject-masked, multicenter study included 517 patients and was conducted over the course of 1 year; 256 subjects experienced unilateral implantation of an AcrySof SA60T3, SA60T4 or SA60T5 toric IOL, and 261 received an AcrySof SA60AT spherical IOL (Alcon).

To maximize the comparability of results in the multicenter study, only temporal incisions were used. The authors acknowledged this to be a limitation of the study.

“Each surgeon has a surgically induced astigmatism factor depending on his or her wound construction. By moving the incision toward or away from the steep axis, a surgeon can further enhance patient outcomes,” Dr. Holland said. “The results of this study were excellent, but individual surgeons may produce even better results by changing the incision location.”

Study authors also discussed the possibility that even lower IOL rotational values may be reported by researchers who use more advanced assessment technologies.

“A study by Weinland et al demonstrated less rotation than our study primarily because digital photography was used. This is more sophisticated technique of assessing rotation,” Dr. Holland noted.

Study results

The AcrySof toric IOL showed a significantly lower incidence of rotational stability than first-generation IOLs. Rotation incidence was 15· or greater in 1.2% of cases, as opposed to the 16% to 50% observed in spherical IOLs.

“Rotational stability of the AcrySof toric IOL has been established,” Dr. Holland said. “Future studies will look at the safety and efficacy of using lower and higher astigmatic powers in the AcrySof line.”

One year after surgery, 77.7% of eyes in the toric IOL group had best corrected distance visual acuity of 20/20 or greater, compared with 69.2% of eyes in the control IOL group; 40.7% of toric IOL eyes vs. 19.4% of control IOL eyes had uncorrected distance visual acuity of 20/20 or better.

The mean absolute residual refractive cylinder for toric IOL eyes was 0.59 D, while eyes in the control IOL group had a mean refractive error of 1.22 D. Six months after surgery, 61% of patients with toric IOLs were spectacle-free vs. 36.4% of patients with control IOLs.

“We would encourage surgeons who have not yet utilized AcrySof toric IOLs to become familiar with this technology in order to offer patients their best options,” Dr. Holland said.– by Michelle Pagnani

Reference:

• Holland E, Lane S, Horn JD, Ernest P, Arleo R, Miller KM. The AcrySof toric intraocular lens in subjects with cataracts and corneal astigmatism. Ophthalmology. 2010;117(11):2104-2111.

• Edward J. Holland, MD, can be reached at the Cincinnati Eye Institute, 580 South Loop Road, Edgewood, KY 41017; 859-331-9000; e-mail: eholland@holprovision.com.
• Disclosure: Dr. Holland is a consultant for Alcon.

This study demonstrates the efficacy and safety of using the AcrySof toric IOL in patients who have both cataracts and corneal astigmatism. The results reflect what we observe in the clinic, that patients are extremely happy with their vision following implantation of the toric IOL. Patients often experience spectacle independence and have very stable postop refraction. Limbal relaxing incisions are reported to be less predictable and more subject to the effects of corneal wound healing, which can reduce their efficacy. The take-home message here is that the AcrySof toric IOL is an effective, safe, predictable option for patients with cataracts and astigmatism who wish to be less dependent on eyewear for their distance correction.

– Y. Ralph Chu, MD
Bloomington, Minn.
Disclosure: Dr. Chu has no financial interest to disclose.