Baltimore?Cataract surgeons and their patients now have three multifocal IOLs to choose from, depending on the patient's needs and interests as well as the physician's preference for and experience with a particular lens.
Lenses on the market include the ReZoom (Advanced Medical Optics/AMO), the AcrySof ReSTOR (Alcon Laboratories), and the crystalens (eyeonics).
"There are very distinct differences among the three commonly used multifocal lenses on the market," explained Satish S. Modi, MD, FRCS, in private practice in Poughkeepsie and Fishkill, NY. Dr. Modi discussed the merits of the lenses here at the Current Concepts in Ophthalmology meeting, which was sponsored by the Johns Hopkins University School of Medicine, Baltimore, and Ophthalmology Times.
The ReZoom is a redesign of the first multifocal lens to receive FDA approval, AMO's Array, a refractive silicone IOL introduced in 1997. The Array did not attain wide popularity among physicians because of problems such as a high incidence of halos, poor contrast sensitivity, and poor vision in mesopic light, Dr. Modi said, adding that the lens had an approximate 2% explantation rate, according to AMO's own records.
AMO's newer ReZoom acrylic IOL was built on the Array platform but has a refractive, distant-dominant optimized multifocal optic. It was made commerically available last spring.
"However, if you look at the amount of light transmission for near tasks, with a small 2-mm pupil, you see it is close to zero; this translates to poor near vision for anyone with small pupils, such as a non-Caucasian patient," Dr. Modi said.
The crystalens, the only accommodating multifocal lens on the market, received FDA approval in November 2003. This is a hinged lens that moves backward and forward within the eye, so that patients can ideally achieve good vision at all distances. The motion is about one-third of a millimeter, in Dr. Modi's experience.
According to Dr. Modi, the silicone material from which this lens is made is a drawback.
"Patients have problems with posterior capsular opacification (PCO) very early with this lens," he said. "Everyone ends up needing a YAG capsulotomy within 9 months."
Also, the hinges on the haptics of the implant can be affected by the irregular contraction of the capsular bag, which seems to happen more frequently and more severely with silicone lenses. This can cause the lens to have "Z syndrome," in which one haptic goes forward and the other goes backward, leading to tilting of the optic, induced astigmatism, and very poor vision, Dr. Modi said.
He also noted that because of the limited movement of the lens, his patients achieve an average maximum of only 1 to 1.5 D of accommodation.
"A full 75% to 80% of my patients with this lens implanted need glasses to read, especially fine print, which is not what they signed up for," he said.
To compensate, surgeons typically operate first on the nondominant eye, aiming for a small amount of myopia (0.5 to 0.75 D), so that in combination with the accommodation patients should be able to read better, Dr. Modi said.
However, patients often end up complaining of a disparity in distance vision, he continued.
"It's a less than satisfactory situation with the crystalens," said Dr. Modi, who has implanted about 80 of these IOLs.