Advances in Cataract Surgery

Majed Alkharashi; Walter J Stark; Yassine J Daoud

Disclosures

Expert Rev Ophthalmol. 2013;8(5):447-456. 

In This Article

Intraocular Lenses for Presbyopia Correction

Presbyopia remains one of the most challenging optical problems in cataract and refractive surgery. Different approaches to treat presbyopia have been studied in recent years. These include scleral remodeling (scleral expansion and sclerotomy techniques);[25] corneal procedures (presbyLASIK,[26] corneal inlays[27] and conductive keratoplasty[28]); and monovision techniques.[28] Each of these techniques has limitations, advantages and disadvantages. There has been increasing interest in correcting presbyopia at the time of cataract surgery by using presbyopia-correcting IOLs. The two major presbyopia-correcting IOL designs are the accommodating and the multifocal IOLs.

The first presbyopia-correcting IOL to be FDA-approved was the Array (Advanced Medical Optics, Santa Ana, CA, USA and USA) in 1997. The Array is a refractive multifocal lens with five progressive concentric zones on its anterior surface. Zones one, three and five are distance-dominant, whereas zones two and four are near-dominant. In some of the first studies, 72% of the eyes implanted with the Array could see both 20/40 for distance and J3 for near compared with 48% with a monofocal lens.[29]

In 2005, the FDA approved two new multifocal designs, the refractive Rezoom IOL (Advanced Medical Optics, Inc.) and the diffractive Acrysof Restor IOL® (Alcon Laboratories, Inc.). The Rezoom represents new engineering of the Array platform, including a hydrophobic acrylic material and a shift of the zonal progression. Aspheric transitions between the zones offer intermediate vision. The near-dominant zones provide +3.50 D of add power at the IOL's plane for near vision, yielding approximately +2.57 D of add power in the spectacle plane. The Rezoom has been shown to provide spectacle independence in 93.4, 92.6 and 81.4% for distance, intermediate and near vision, respectively.[102] The major drawbacks of the Rezoom are its moderate dependence on spectacles for near tasks and the increased incidence of photic phenomena compared to other multifocal lenses.[30]

The AcrySof® ReSTOR® IOL employs a central 3.6 mm diffractive zone. This area comprises 12 concentric steps of gradually decreasing (1.3–0.2 microns) heights, the farther from the center. These steps allocate energy based on lighting conditions and activity to create a range of vision. The ReSTOR has been shown to yield high rates of spectacle freedom with uncorrected distance visual acuity of 20/30 or better in 93.8% eyes and an uncorrected near visual acuity of 20/30 or better in 75.0% of eyes.[31,32] Glare and halos have been reported as the main complication of this type of lens. Moderate glare was reported by 21.3% of the patients compared to 7.1% for a monofocal IOL.

In 2007, the FDA approved the aspheric version of the ReSTOR (AcrySof IQ ReSTOR), which has a negative asphericity, while maintaining its apodization, diffractive and refractive components. The AcrySof IQ ReSTOR IOL + 3.0 D (SN6AD1) incorporates a +3.0 diopter correction at the lenticular plane (~+2.5 D at the spectacle plane). It also has nine concentric steps (three less steps than the original IOL) farther apart to improve intermediate vision over the AcrySof IQ ReSTOR IOL +4.0 D (SN6AD3), with similar near and distance visual acuity. Halos and glare are still common complaints of patients implanted with these lenses. Patients implanted with the SN6AD1 noticed more glare and patients implanted with SN6AD3 noticed more halos.[33,34] The ReSTOR Toric is the newest addition to this lens design. It provides a single platform to correct astigmatism and improve near and intermediate vision. This lens is currently available in Europe and Canada, but is not yet available in the United States.

In 2009, another diffractive IOL was approved, the Tecnis multifocal (Advanced Medical Optics, Inc. Santa Ana, California). The newer version is a single-piece acrylic (ZMB00) and has a full diffractive posterior surface that makes it pupil independent. It has an aspheric anterior surface with +4 D near add (+3.0 D at the spectacle plane). A retrospective study on the earlier version of this IOL found an uncorrected distance visual acuity of 20/30 in 85% of eyes and an uncorrected near visual acuity of J1 in 93.7% of 2500 eyes, 3 years postoperatively.[35] Glare and halos were reported as severe by 6.1 and 2.12% of patients, respectively.

Multifocal lenses have the persistent drawback of the potential for patients to see glare or halos for few weeks or months following surgery. Indeed, it has been shown that multifocal lenses have greater incidence of glare and halos than monofocal IOLs.[36] However, it has been shown that glare and halos symptoms decrease as most people learn to disregard them with time.[37] Another drawback of multifocal IOLs is the potential for decreased contrast sensitivity especially in dim lights. However, contrast sensitivity with multifocal IOLs improves over time and may approximate the levels found with spherical monofocal lenses by 6 months postoperatively.[38] Patient selection for multifocal IOL is critical. Patients with high expectations, or those with significant astigmatism, ocular surface disease (e.g., epithelial basement membrane disease and severe dry eye), zonular weakness (e.g., pseudoexfoliation ) or patients with retinal diseases (e.g., macular degeneration and epiretinal membrane) may not be good candidates.

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