Scientists develop technique to reduce 'halo' effect caused by lenses

16 Apr 2015

Presbyopia sufferers could have a clearer view for night-driving, reading with "smoothed" lenses.

Scientists from Bar-Ilan University in Israel have presented a new technique that significantly reduces the “halo effect” that is generated when a person uses multifocal (contact and intra-ocular) lenses when looking at bright point sources in dark conditions. The team's work has been published in Optics Communications.

The medical condition known as Presbyopia is a result of natural aging of the eye and stems from a gradual thickening and decrease in elasticity of the lens inside the eye. Conventional corrective lenses used to address Presbyopia can often lead to a halo effect.

This manifests itself as a glow or color light pattern observed by the subject when looking at a bright source of light in front of a dark background. It is mostly experienced at night when people see such halos around street lamps and car headlights, and it can make driving at night unsafe or even impossible in extreme cases.

Co-author of the paper, Prof. Zeev Zalevsky, head of the Electro-Optics study program of the Faculty of Engineering at Bar-Ilan, explains, "Our solution involves smoothing the surface structure of a contact lens or an intra-ocular lens that has extended depth of focus or multifocal capabilities.

”The smoothing does not complicate the fabrication complexity of the lens and yet yields the same optical performance in treating presbyopia and assisting people after cataract surgery, but with about one order of magnitude smaller. This allows people that use such lenses to be able to use them also at night."

More and more commercial ophthalmic products incorporate EDOF (extended depth of focus) and multifocal technologies in contact and intra-ocular lenses to solve presbyopia. Until now, such lenses were very problematic when used in dark illumination conditions. The researchers say their proposed concept can resolve the above difficulties and make the existing products even more applicable and useful.

Conclusion

The paper in Optics Communication by the Zalevsky group concludes: “We have demonstrated a new concept to reduce the halo effect occurring in dark illumination conditions in various ophthalmic lenses such as IOLs and contact lenses. Our solution involves smoothing the surface structure yielding the extended depth of focus. The proposed lens designs were fabricated and successfully tested numerically and experimentally including via preliminary in-vivo trials.”

About the Author

Matthew Peach is contributing editor to optics.org.