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Refractive lens exchange with diffractive multifocal IOL yields good contrast sensitivity
J Cataract Refract Surg. 2008;34(12):2043-2048.
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Patients who underwent refractive lens exchange with a diffractive multifocal IOL had contrast sensitivity comparable with that of preoperative levels under photopic and mesopic lighting conditions.
"The best way to assess the in vivo visual performance of multifocal IOLs is to compare the [contrast sensitivity function] before and after implantation," the study authors said.
The study included 30 eyes of 15 hyperopic patients who were 50 to 60 years old. Patients underwent phacoemulsification and bilateral implantation of the AcrySof ReSTOR SN60D3 multifocal IOL (Alcon). At 6 months after surgery, mean residual spherical equivalent refractive error was 0.21 D. Best corrected distance and near visual acuity were comparable with preoperative levels.
A loss of retinal image contrast after diffractive IOL implantation may be expected, but contrast sensitivity was not affected.
"We propose this is because our patients had a high degree of contrast-reducing scatter before surgery (with natural lens), producing a reduced [contrast sensitivity function] compared with that in normal young eyes," the study authors said
This paper supports my clinical experience that quality of vision is good following refractive lens exchange and placement of a diffractive multifocal IOL. An individual’s quality of vision as measured by photopic and mesopic contrast sensitivity declines steadily with age as the natural lens matures. Before a lens opacity significant enough to reduce best corrected Snellen visual acuity develops, there is an increase in higher-order aberrations and light scatter that reduce quality of vision. Therefore, the typical presbyopic patient over the age of 45 who presents for refractive lens exchange has a compromised quality of vision. This study suggests that the visual function compromise secondary to natural lens aging seems to be similar to the reduced quality of vision caused by a multifocal IOL in regards to contrast sensitivity in photopic and mesopic conditions. So the typical 45- to 65- year-old will not perceive a reduction in quality of vision with a multifocal lens as compared to their vision with their aging lens, which is actually an incipient cataract.
– Richard L. Lindstrom, MD
OSN Chief Medical Editor