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ASCRS/ESCRS survey shows variety of reasons for foldable IOL explantation
CALCIFICATION, decentration and incorrect lens power lead the list of problems leading to explantation of foldable IOLs, according to the latest ASCRS/ESCRS member survey. Nick Mamalis MD reported the results of the fifth annual survey at the XXI Congress of the ESCRS. The survey asks members to provide data on each foldable lens that required removal or secondary surgical intervention. The respondents provide information on the IOL material and design, signs and symptoms, pre- and post-op visual acuity and other relevant clinical information.The current report compiled responses from ASCRS and ESCRS members during 2002. The data collected by the survey is cross-referenced by IOL material and design. Materials used to make the lenses include silicone, hydrophobic acrylic, hydrophilic acrylic (hydrogel) and collamer, a hybrid material. Design categories include one-piece plate IOLs, one-piece IOLs with haptics, three-piece IOLs and multifocal IOLs. "Over the past 15 years we've seen an increase in the use small incision cataract surgery, and with this has come an
increase in use of foldable IOLs. With this increase we've also seen an associated rise in the incidence of complications. We're not saying one lens is better than another. Rather, we're saying that a particular type of complication may be seen if you use a particular type of lens," Dr Mamalis told EuroTimes. Dislocation or decentration was the most common reason for explantation of the three-piece silicone foldable IOLs. Incorrect lens power was another common reason. Less common complications included optical aberrations and cracked lenses. Decentration or dislocation was also the primary problem associated with the removal or adjustment of one-piece plate-type silicone lenses. Less common complications included damaged lenses and corneal oedema. Incorrect lens power was the leading reason for explantation of three-piece acrylic IOLs, followed by glare and other visual aberrations and dislocation/decentration. The incidence of glare and visual aberrations declined slightly from the year before. Incorrect lens power also accounted for most cases of explanation of one-piece acrylic lenses with haptics. Dislocation/decentration and problems with glare and optical aberrations also accounted for some re-interventions. The most common problem reported for collamer lenses was damage or cracking during insertion. However, the numbers explanted were small, so conclusions are difficult to reach regarding that category of lens. The findings with hydrogel IOLs were distinct from those of other lens types. Calcification was the leading cause of explantation for one-piece hydrogel lenses with haptics as well as for three-piece hydrogels. Glare or optical aberrations were also cited as reasons in a few cases. "In the hydrogels or hydrophilic acrylic IOLs, we really saw a different complication rate. The calcification problem is complicated. We find different types of calcification occur with different lens types. There are many types of hydrogels with different water contents and different additives, such as UV blockers. We want to be careful not to lump them all together," he stressed. There were few overall differences between the complications for the different lens types reported by US and European surgeons. However, calcification was reported more often by Europeans, a fact that Dr Mamalis attributed to the wider availability of hydrogel IOLs in that region. Bausch and Lomb initially delayed the launch of its Hydroview hydrogel IOL in 1999 following reports of calcification in some international markets. The company traced the problem to the product packaging and subsequently launched the Hydroview with different packaging. No cases of calcification were reported with this lens in the current survey. The survey also gathered information on multifocal foldable IOLs. As expected, glare and other visual aberrations accounted for most cases of lens removal in that category. Incorrect lens power was also cited as a reason for lens removal. "Our survey indicates that complications do vary depending on the type of intraocular lens. And there are some complications unique to particular types of lenses. We've seen some trends continue over the past five years, but we have also seen new types of complications showing up that we didn't see earlier on," One positive trend was a significant decrease in the incidence of explantation of three-piece silicone lenses due to breakage. Dr Mamalis attributed this to the fact that surgeons have learned how to implant the lenses. The survey suggests that the learning curve is also improving with multifocal IOLs, as demonstrated by a reduction in complications of glare and visual aberrations. He attributed this to better patient selection, based on a better understanding of who might benefit from this lens choice.There were a wide variety of post-explant complications including corneal oedema, bullous keratopathy, cystoid macular oedema and retinal problems, but no trends were apparent. On the positive side, most patients ended up with quite good visual acuity.Overall, incorrect lens power continued to be the most common complication, with dislocation/decentration a close second. Optical aberration and calcification are also not uncommon problems. "Incorrect lens power still remains a significant problem. The solution, at least in part, will come with better biometry. New laser interferometry systems such as the IOL Master are helping in this regard. Immersion A-scan ultrasound is also very good, but it does require an experienced technician." Dr Mamalis emphasised that good surgical technique remains the key to minimising complications. This includes performing a capsulorhexis, putting the lens in the bag and folding the IOL properly. It is also crucial to be vigilant when implanting IOLs made of new materials to make sure that new complications are not occurring, he stressed. Nick Mamalis MD
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