All About Cataracts

Implantation of a popular multifocal intraocular lens (IOL) during cataract surgery provides clear and stable visual acuity — both for distance vision tasks such as driving and for near vision tasks such as computer work and reading.

Tecnis Multifocal IOL (Image: Abbott Medical Optics)

That’s the finding of a new study published this month in Journal of Cataract & Refractive Surgery.

Researchers in Japan conducted a retrospective study of 72 eyes (of 41 patients) that were implanted with the Array Multifocal IOL (Abbott Medical Optics, Santa Ana, Calif.) after cataract extraction.

The mean age of patients in the study was 48.7 years (range: 18 to 71 years) and all participants were followed for a period of four years after surgery.

Among the results:

• At one month after surgery, mean uncorrected distance visual acuity (VA) was between 20/20 and 20/25, and mean uncorrected near VA was between 20/30 and 20/40.
• Visual acuity remained stable for the four-year study period, but patient satisfaction with near vision decreased at two years after surgery.
• A follow-up laser eye surgery — laser capsulotomy — was performed on 48 eyes (66.7 percent) due to formation of posterior capsular opacification (PCO).

PCO is a clouding of the posterior portion of the lens capsule — the normally clear sac-like structure that holds the eye’s natural lens in place — that is intentionally left in place during cataract removal to prevent certain cataract surgery complications.

Laser capsulotomy is a brief outpatient procedure that uses a special laser (called an Nd:YAG laser) to create a central opening in the lens capsule to restore vision.

The mean time for laser capsulotomy surgery was approximately two years after cataract surgery.

The researchers concluded that the Array Multifocal IOL provided good and stable distance and near visual acuities over the four-year follow-up, despite a significant percentage of eyes receiving the lens implant experiencing posterior capsule opacification that affected near vision and required subsequent surgical treatment.

Ed. note: The Array Multifocal IOL, which was the first FDA-approved multifocal IOL, is no longer available. Abbott Medical Optics has replaced the Array IOL with two new multifocal IOLs: the ReZoom and Tecnis Multifocal IOL. Ask your cataract surgeon for details.

Posterior capsule opacification (PCO) is one of the most common cataract surgery complications. It can occur relatively quickly after cataract surgery or months later.

The natural lens inside the eye is surrounded by a clear, membrane-like capsule. The front portion of this capsule is removed during cataract surgery to gain access to the cloudy natural lens and remove it. The posterior portion of the lens capsule is left intact to prevent loss of the gel-like fluid behind it, which would increase the risk of a detached retina from cataract surgery.

Posterior capsule opacification is thought to be caused by lens epithelial cells remaining in the eye after the cloudy lens is removed during cataract surgery. These cells can migrate onto the surface of the posterior capsule, where they undergo cellular changes and form an opaque membrane that decreases vision.

PCO can be successfully treated with a non-invasive outpatient procedure called a neodymium:YAG (Nd:YAG) laser capsulotomy. The procedure uses laser energy to obliterate the opacity, restoring vision.

Researchers at Storm Eye Institute, Medical University of South Carolina (Charleston, SC) recently conducted a retrospective study of 225 eyes that underwent cataract surgery with intraocular lens (IOL) implantation to investigate whether the type of IOL used in the surgery has an effect on the rate of PCO occurrence.

The eyes in the study received one of three IOLs: AcrySof ReSTOR SN60D3 (a spherical multifocal IOL), AcrySof Natural SN60AT (a spherical monofocal IOL), or AcrySof IQ SN60WF (an aspheric monofocal IOL).

All three IOLs are manufactured and marketed by the same company (Alcon, Inc.). Each lens was implanted in 75 study eyes, and mean follow-up time after surgery was 15.9 months.

The researchers found the rate of posterior capsule opacification after surgery was:

• 42.7 percent among eyes receiving the spherical multifocal IOL (ReSTOR)
• 28.0 percent among eyes receiving the spherical monofocal IOL (Natural)
• 14.7 percent among eyes receiving the aspheric monofocal IOL (IQ)

The Nd:YAG laser capsulotomy rate for eyes receiving the IOLs was 25.3 percent, 17.3 percent and 4.0 percent, respectively.

The researchers concluded that IOL design affects the rate of posterior capsule opacification occurring after cataract surgery.

Also, based on the rates of laser capsulotomy procedures performed, PCO appears to be less visually significant in eyes receiving the AcrySof IQ aspheric monofocal IOL, compared with eyes receiving the spherical multifocal IOL (AcrySof ReSTOR) and the spherical monofocal IOL (AcrySof Natural). 

The study was supported in part by Research to Prevent Blindness and the National Institutes of Health.

Source: Comparison of the incidence and visual significance of posterior capsule opacification between multifocal spherical, monofocal spherical, and monofocal aspheric intraocular lenses. Journal of Cataract & Refractive Surgery. July 2009.