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The most recent results from the 2008 American Society of Cataract and Refractive Surgery/European Society of Cataract and Refractive Surgeons survey on foldable IOLs requiring removal or other secondary intervention highlight changes over time in the complications associated with various lens types.
The 2008 survey represents the 11th year of data collection for this project conducted by Dr. Mamalis and colleagues at the Intermountain Ocular Research Center, University of Utah, in conjunction with the ASCRS Cataract Clinical Committee.
Incorrect lens power no longer ranked as one of the top two leading causes for IOL explantation/exchange/secondary intervention as it did in prior years. Instead, dislocation/decentration was by far the most common reported complication, followed by glare/optical aberrations. Variations, however, were seen in subset analyses that tabulated results for lenses categorized by style and material.
The survey asks surgeons to provide data about preoperative visual acuity, patient signs and symptoms, and complications requiring IOL removal. Lens category subgroups:
The distribution of lens types within the series reflected the pattern of IOL usage in the community, with three-piece hydrophobic acrylic, three-piece silicone, and one-piece hydrophobic acrylic with haptics each accounting for about 25% of the entire group.
When data were analyzed for the various IOL categories, dislocation/decentration followed by glare/optical aberrations were the first and second most common complications leading to explantation/secondary intervention for each of those top three IOL groups. Within each of these three lens categories, dislocation/decentration accounted for 30% to 35% of surgical interventions, and glare/optical aberrations was the underlying cause for 20% to 25% of secondary procedures.
Dislocation/decentration was the most common reason for explantation/secondary intervention for silicone one-piece plate haptic IOLs, but for this type of lens, dislocation/decentration accounted for more than 70% of the procedures, whereas calcification/opacification and cystoid macular edema were responsible for the rest.
The data on hydrophilic acrylic (hydrogel) and multifocal IOLs diverged from the overall trends. For the hydrogel IOLs, calcification/opacification accounted for all explantations.
"A lot of the lenses in this category that have been the culprits in cases of calcification have been withdrawn. However, the average time to onset of this complication is 2 years after implantation, and there are still a lot of patients with an implanted hydrogel IOL that can develop calcification in the future," Dr. Mamalis said.
Considering acrylic multifocal IOLs, which are the most common type of multifocal IOLs removed, glare/optical aberrations accounted for all of the underlying complications.
"We are now seeing an increasing number of multifocal IOLs being explanted, probably because these types of lenses are being implanted more frequently and not because they have any greater propensity to be associated with problems," he said. "The importance of optical aberrations and glare as a reason for multifocal IOL explantation speaks to the importance of proper patient selection and thorough preoperative counseling when implanting these lenses."
Regarding trends over the past 11 years of the survey, for the three-piece silicone IOLs, incorrect lens power accounted for 50% of complications in the first year of the survey, but its role has steadily decreased, and it was identified as the reason for intervention only 10% of the time in the 2008 survey. The prevalence of dislocation/decentration has fluctuated over the years, although it has remained an important complication over time for the three-piece silicone IOLs.
For the three-piece acrylic IOLs, incorrect lens power accounted for 40% and 60% of complications during the first 2 years of the survey, but it also was reported for only about 10% of the three-piece acrylic IOLs in the 2008 survey. With this type of IOL, problems with dislocation/decentration have shown an increasing trend over time.
For the one-piece silicone plate IOLs, dislocation/decentration was the primary reason for intervention during the first year of the survey and the situation has not changed over time.
Forms for the foldable IOL survey are available online at http://www.ascrs.org/.