Polymer-coated lenses could help prevent a common cataract surgery complication

Cataracts are one of the leading causes of blindness worldwide. They can be easily corrected by replacing the opaque natural lens with an artificial one. But one common complication of this surgery, called posterior capsule opacification (PCO), is formation of cloudy scar tissue behind the implanted lens, which can cause blurry, hazy vision. Researchers have now figured out a simple way to avoid this by coating part of the artificial lens with a polymer that can be heated up by shining infrared light on it (ACS Appl. Bio Mater. 2021, DOI: 10.1021/acsabm.1c00089).

During cataract surgery, a doctor removes the natural lens and leaves a tissue membrane called the lens capsule to keep the implanted lens in place. PCO happens when cells in the capsule grow abnormally and move to cover the back of the lens. A laser method can treat PCO by burning a small hole in the capsule to let light through, but the high-powered lasers used may lead to side effects such as lens damage, retinal detachment, and glaucoma.

So Ke Yao of Zhejiang University and colleagues came up with an alternative method. They deposited a thin, two-layer coating of polyethylenimine on polydopamine around the edges of the replacement lens, leaving an uncoated area in the center. The coating is photothermal, absorbing light and heating up when an infrared laser shines on it.

The IR laser increases the temperature of the coating by up to 40 ºC, while the uncoated area remains at room temperature. This heating stops migration of the cells, preventing PCO, Yao says.

The team tested coated and uncoated lenses in rabbits by shining the IR laser on the implanted lenses a few times over 28 days, for 10 min at a time. This proved that the lens capsule was clearer for coated lenses compared with uncoated lenses. Both polyethylenimine and polydopamine are common, widely used biomedical polymers, Yao says, and the team found no significant cytotoxicity in experiments with cells or in rabbits.

“The coating concept is not new,” says Hao Wang of the National Center for Nanoscience and Technology, China, who was not part of the research. “However, modifying the lens with a photothermal agent is quite useful for preventing PCO.” More research will have to be done on its biosafety, though, before clinical use, he adds.