A New Era in

Wavefront-Optimized

Contact Lenses

Len Zheleznyak, PhD

Presbyopia correction with contact lenses is challenging. Conventional multifocal contact lenses suffer from poor image quality, resulting in frustrated patients and clinicians. In some ways, this is unavoidable. To increase the eye’s depth of focus for intermediate and near vision is to inherently sacrifice some image quality at distance. However, there are better and worse ways to make this trade-off. Conventional multifocal contact lenses have been limited to “refractive multifocal” optical designs (e.g. “center-near,” “center-distance”), which primarily comprise the asphericities in the lens surface and subsequent spherical aberrations.

Over the last 20 years, multifocal intraocular lenses (IOLs) have undergone a revolution: transitioning from refractiveto diffractive multifocal designs to optimize the trade-off between distance vision and near visual benefit. The advantage of diffractive multifocals is that they use the entire optical zone to contribute to both far and near vision. This makes them less susceptible to changes in lighting conditions, resulting in higher patient satisfaction [1, 2].

So what’s stopping diffractive contact lenses? The surface. Diffractive structures on the surface of a contact lens are untenable due to tear film dynamics and debris accumulation. Alternatively, IOLs don’t suffer from these issues because they are implanted within the eye. Similarly, it is proposed to place the diffractive wavefront within the contact lens and to retain the smooth contact lens surfaces.

To that end, laser-induced refractive index change (LIRIC) uses a femtosecond laser to embed the diffractive wavefront within the contact lens [3-5]. The figure below shows frontal and cross-sectional views of a LIRIC diffractive contact lens imaged with phase contrast microscopy. Note the internal gradient refractive index diffractive lens in the cross-section image. The key to localizing the wavefront to a thin, internal region is nonlinear absorption of the laser energy, similar to multiphoton microscopy. The laser is scanned throughout the optical zone of the contact lens while simultaneously adjusting pulse energy, resulting in the desired wavefront.

LIRIC contact lenses are the world’s first diffractive multifocals with a uniform thickness profile, enabling the benefits of diffractive multifocals in soft contact lenses. Those benefits include excellent image quality and a well-defined add power, avoiding the ambiguity that makes fitting conventional multifocals difficult.

In addition to presbyopia correction, diffractive LIRIC contact lenses have implications for single-vision correction. Decoupling sphero-cylindrical power from shape enables uniform thickness, improving on-eye stability and providing consistent oxygen permeability and comfort across all dioptric corrections. LIRIC also has applications in test-driving a surgical technique (e.g. multifocal intraocular lenses or LIRIC corneal treatment), myopia control, customized higher-order aberration correction, prism for patients with macular degeneration, and even streamlining virtual and augmented reality devices. In addition, Clerio Vision is using a  hydrogel material designed to provide outstanding all-day comfort as a platform for its novel LIRIC optics.

With all of these technological advancements, the future is bright for contact lenses. As the population ages, the need for high-quality presbyopia correction is ever more important. Despite the drawbacks of aging vision, perhaps comfortable lenses with improved optics can give us all something to look forward to.

Disclosures: LZ is employed by and has a financial interest in Clerio Vision, Inc.

References:

[1] Chang, David F. "Prospective functional and clinical comparison of bilateral ReZoom and ReSTOR intraocular lenses in patients 70 years or younger." Journal of Cataract & Refractive Surgery 34.6 (2008): 934-941.

[2] Choi, Junoh, and Jim Schwiegerling. "Optical performance measurement and night driving simulation of ReSTOR, ReZoom, and Tecnis multifocal intraocular lenses in a model eye." Journal of Refractive Surgery 24.3 (2008): 218-222.

[3] Knox, Wayne H. "Inventing a New Way to See Clearly: Non-invasive Vision Correction with Femtosecond Lasers." Technology and Innovation 20.4 (2019): 385-398.

[4] Xu, Lisen, and Wayne H. Knox. "Lateral gradient index microlenses written in ophthalmic hydrogel polymers by femtosecond laser micromachining." Optical Materials Express 1.8 (2011): 1416-1424.

[5] Butler, Sam C., et al. "Next generation diffractive multifocal contact lenses for presbyopia correction using LIRIC." Investigative Ophthalmology & Visual Science 60.9 (2019): 3723-3723.

Len Zheleznyak is Vice President of Vision Science at Clerio Vision. He is currently developing non-invasive methods of correcting refractive error in the human eye using ultrafast laser phenomena to modify refractive index.

Len’s previous research interests included presbyopia correction, intraocular lens design and developing adaptive optics systems to study the visual system. He completed his PhD in Optics from the University of Rochester in 2014.

Prior to his doctoral work, he developed photonic devices for optical inspection of pharmaceuticals at Ometric Corporation, a start-up company spun out of the University of South Carolina, subsequently acquired by Halliburton Energy Services. Len has authored numerous peer-reviewed journal articles, book chapters and patents relating to vision and optical science.