Options for drug-delivering IOLs vary by advantages, drawbacks
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Researchers who reviewed various drug-loaded IOLs for preventive treatment after cataract surgery wrote that they are a promising alternative to current therapies.
“A great effort has been made to achieve IOLs that can be used as drug delivery devices in the prophylaxis of postcataract surgery complications,” Ana Topete, from the Instituto Superior Técnico in Portugal, and colleagues wrote in a study published in the International Journal of Pharmaceutics. “The advantages of drug loaded IOLs for the prevention of [posterior capsule opacification (PCO)] can be even greater, since this is the most common postcataract surgery complication, and no effective solution is available at present.”
Topete and colleagues noted that one of the challenges for drug-loaded IOLs is achieving sustained and controlled drug release that meet therapeutic needs.
Following a literature review, the researchers addressed the advantages and disadvantages of the most common strategies for drug delivery, including soaking in drug solution, superficial fluid technology, surface modifications and attachment of drug reservoirs to the IOL.
Topete and colleagues noted that soaking in drug solution was the most widely used method and would be easily implemented. However, the technique is highly dependent on the water content of the hydrogel and would work best with hydrophilic IOLs.
Superficial fluid technology can be applied to both hydrophilic or hydrophobic IOLs, and the device behavior can be optimized by tuning pressure, temperature and solvent. The disadvantages of this method come from the cost and complexity of the required impregnation apparatus.
Modification of the IOL surface includes options such as layer-by-layer deposition, spray-coating, spin-coating, grafting or attachment of nanoparticles.
“In this case, the drug incorporation is independent of the nature of the IOL material, but the amount of loaded drug is limited by the thickness of the coating, which cannot compromise the optical properties of the lens,” Topete and colleagues wrote.
Finally, they addressed the attachment of drug reservoirs to the IOL. They wrote that this method was often a less popular strategy because attachment of the reservoirs may be difficult, and their presence could raise concern at the time of IOL insertion.
“Overall, the successful results of many research works reported in the review demonstrate that drug loaded IOLs are a promising alternative to the therapies in use,” the researchers concluded. “However, more validation studies are still needed before the drug loaded IOLs may be used in clinical practice.”
Perspective
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Imagine a world in which the potential adverse effects of cataract extraction are mitigated by the very device that provides visual rehabilitation. Current research aims to bring us that reality. The use of IOLs to deliver drugs would maximize compliance and decrease infection, inflammation and PCO formation following cataract surgery, thereby simplifying postoperative management. Researchers are investigating many methods to achieve this goal, from simply soaking the IOL in the drug to incorporating medications into the structure of the lens during manufacturing. Some notable barriers to success include maintenance of drug delivery, changes to IOL optics due to drug impregnation, degradation of drugs as a result of common sterilization techniques and cost. With the volume of research currently underway in this area, there is little doubt that eye doctors will see a time when postoperative administration of medications by topical or injectable routes is a thing of the past. However, with no current clinical trials in process, that time is likely many years away.
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