Dislocation found to be main cause of IOL explantation

Incorrect lens power calculation, opacification and neuroadaptation failure also led to explantation.

Issue: November 2012

A multicenter study conducted in Spain demonstrated that the main cause for IOL explantation was dislocation, followed by incorrect lens power calculation and opacification.

An overall IOL explantation rate of 0.59% was found for a 6-year period between 2004 and 2010.

“Multifocal lenses were the fourth cause of explantation, due to neuroadaptation problems. The lenses were perfectly centered, but patients were unable to adapt,” study co-author Roberto Fernández-Buenaga, MD, said.

Explantation is a rare but important complication of cataract surgery, as it may be associated with severe sequelae. Understanding the causes of explantation is key to improving surgical techniques and lens manufacturing.

Fernández-Buenaga noted that studies on this topic are rare in Europe despite the high number of cataract surgeries, approaching 5 million per year, with a ratio of 63 cataract surgeries per 10,000 people. Spain has the highest ratio at 99 surgeries per 10,000 people and approximately 400,000 cataract surgeries performed.

“We follow up with IOLs for a certain period of time. We see their refractive outcomes, lens stability, how they behave inside the eye, but we don’t check what happens in the long term. And yet most of the complications of IOLs are late complications,” he said. “Our study, which involved 15 centers in Spain, is the largest to my knowledge.”

Roberto Fernández-Buenaga

Dislocation issues

A total of 257 explanted IOLs were studied. Surgeries were performed in different locations throughout Spain in both public and private practices.

The main cause of explantation was lens dislocation, which occurred in 145 eyes (56.3%). In almost all cases, dislocation occurred after successful, uneventful cataract surgery and was neither surgeon-related nor lens-related.

“It occurred as a consequence of zonular failure in patients with predisposing risk factors such as high myopia, uveitis or pseudoexfoliation,” Fernández-Buenaga said.

Dislocation turned out to be a frequent cause for explantation, occurring on average 5 years after cataract surgery.

“Ten years ago there was no literature on this topic, but in the last 5 years, publications have been many. Cases are going to grow exponentially in future years. Because of the longer lifespan, there will be a huge increase in the population of pseudophakes,” Fernández-Buenaga said.

No specific lens was found to be more often involved with dislocation. The lenses that were more frequently explanted were also the lenses that were more frequently implanted, he said.

Incorrect lens power calculation

Incorrect lens power calculation was the second cause of explantation, accounting for 33 cases (12.8%) in the study. It occurred earlier, a few months after implantation, because patients were dissatisfied with their vision.

“Incorrect lens power was the first cause of explantation in previous years. The surveys of the ESCRS and ASCRS and other papers report an even higher rate of explantation due to this reason, close to 16% of the cases,” Fernández-Buenaga said.

Advances in the methods for lens power calculation have improved accuracy, but more cataract surgeries are going to be performed in future years in patients who have previously had LASIK, and this may produce more refractive surprises.

“After LASIK, IOL power calculation is more difficult. There is a chance that incorrect lens power in these patients may become a too frequent issue in the future,” he said.

Opacification, neuroadaptation failure

IOL opacification was the third cause, occurring in 29 eyes (11.3%), at an interval of more than 5 years from primary surgery.

The role that lens material plays in this complication is still unclear, Fernández-Buenaga said. The acrylic hydrophilic material was previously thought to be the cause, and several cases occurred in the past with hydrogel lenses. However, researchers found that opacification was not due to the material itself but a defect in the manufacturing process.

“Now we have hydrophilic lenses that do not opacify,” he said.

Like all the other groups in the study, the opacification group will undergo further research to determine why this complication occurred.

The fourth and final cause for explantation was neuroadaptation failure with multifocal lenses, which occurred in 16 cases (6.2%). The interval between lens implantation and removal was also short in these cases.

“These patients had a perfect refractive outcome and a perfectly centered lens but were uncomfortable because of photic phenomena,” Fernández-Buenaga said.

Most patients are happy with multifocal IOLs, but a subjective intolerance to multifocal vision cannot be excluded, he said. Patient selection is vital to improve the success rate and avoid explantation.

“You need time to take into account the personality as well as the baseline refraction of the patient. We know now that hyperopes do better than myopes. In the past, we used to implant multifocal IOLs with fewer criteria and we had more problems. Now the number of unhappy patients has definitely dropped,” he said.

The study noted the dramatic change in the causes for explantation in comparison to the 1990s, when the most common causes were complications such as pseudophakic bullous keratopathy and cystoid macular edema. Thanks to refinements in phaco technique and IOL technology, these complications are now rare, Fernández-Buenaga said.

Further study with a more specific analysis of the causes of explantation will be undertaken in order to identify possible preventive measures and improve the outcomes in the growing population of pseudophakic patients. – by Michela Cimberle

For more information:

Fernández-Buenaga R, Alió JL, Muñoz-Negrete FJ, Barraquer Compte RI, Alio-Del Barrio JL. Causes of IOL explantation in Spain. Eur J Ophthalmol. 2012;22(5):762-768.

Roberto Fernández-Buenaga, MD, can be reached at Vissum Corporation, Avenida de Denia, 03016 Alicante, Spain; email: rfernandezbuenaga@gmail.com.

Disclosure: Fernández-Buenaga has no relevant financial disclosures.