Article

EXTENDED DEPTH OF FOCUS LENSES

HOW EDOF LENSES WORK AND HOW THEY MAY SERVE YOUR PATIENTS

The following article appears in Optometric Management's January 2018 special “Contact Lens” editorial section.

EXTENDED DEPTH of focus (EDOF) IOLs and contact lenses are designed to provide continuous vision across multiple distances. As such, both relatively new lens types could provide vision solutions for presbyopic patients.

Also featured in this issue:

The FDA approved the TECNIS Symfony, the only EDOF IOL currently on the market, in 2016 and provided 510(k) clearance to technology from Brien Holden Vision Institute for an EDOF contact lens in 2015, though no EDOF contact lenses are currently on the market.

So, how, specifically, does each lens work, and how may they serve your patients? Here, several eye care providers answer these questions.

Nominal power profiles of EDOF prototype contact lenses aimed to serve emerging, early and established presbyopes.
Courtesy of Brien Holden Vision Institute

EDOF IOL

This IOL utilizes proprietary diffractive echelettes, or reflective grating, at variable distances and alterations in chromatic aberrations, to elongate the IOL’s focus and provide a continuous range of vision from intermediate to distance, says Preeya K. Gupta, M.D., associate professor of ophthalmology at Duke Eye Center.

In comparison, a monofocal IOL provides clarity for a single focal point, often distance vision, while the patient utilizes a spectacle refraction for near vision. A multifocal IOL utilizes two zones on the lens to provide clarity at distance and near.

For the EDOF IOL, Dr. Gupta says intermediate vision occurs at about 22 inches from the face. To provide a real-life example, Dr. Gupta says patients can typically see their dashboard or computer, but may need readers for small, up-close things. Research shows spectacle independence was high among study participants for the EDOF IOL, at about 85%, with 14.4% of patients reporting that they required reading spectacles frequently, according to the Journal of Cataract & Refractive Surgery.

The diffractive echelette pattern across the entire surface of the lens works as a unit to provide this extended depth of focus technology, says Dr. Daniel H. Chang, M.D., of Empire Eye and Laser Center.

The IOL maximizes image quality by correcting the chromatic aberration that can degrade vision and occurs whenever a wave of light passes through an optical system, including the patient’s own lens and cornea.

Specifically, the diffractive technology, combined with the use of a material that has low inherent chromatic aberration properties (UV-blocking hydrophobic acrylic, according to Johnson & Johnson Vision) actively corrects and focuses the colors of light closer together, thus reducing the effects of chromatic aberration on the eye and improving quality of vision, says Dr. Chang.

“By first improving the overall image quality, you can then extend your depth of focus from a single point to a range — and still end up with visual quality comparable to a monofocal,” he explains.

Some patients may experience night vision symptoms, specifically starbursts or halos. In the same study in the Journal of Cataract & Refractive Surgery, more than 90% of patients reported no or mild halos, glare or starbursts.

In Dr. Gupta’s clinical experience, patients in this IOL complain less about halos, as compared with a multifocal IOL. However, they more often describe starbursts, which are generally less visually distracting, rather than halos.

Serving patients. Dr. Gupta says anyone interested in presbyopia correction is a candidate for the IOL. Specifically, Dr. Gupta named those who have an active lifestyle and would like to reduce their dependence on eyewear as ideal candidates. She takes a cautious approach with patients, however, telling then that while the IOL will decrease dependence on readers, it may not eliminate the need for them.

Co-management of Extended Depth of Focus IOLs

In describing the IOL to her patients, Dr. Huggins says she counsels that the EDOF IOL most closely simulates their natural vision by providing a continuous range of vision.

Clearly setting out patient expectations is an important step in counseling these patients. She says there are two points to emphasize:

  1. The patient may still need low-powered readers for small, detailed up-close work.
  2. There may be a trade off in some night vision symptoms. (See article.)

“Patients always seem very excited when they hear about this kind of technology,” she says. “For them, it’s like having refractive surgery and cataract surgery in one procedure.”

Follow-up care for these patients includes: next day, one week, one month and three to six months, Dr. Huggins says.

In continuing care of these patients, Dr. Huggins says O.D.s should be aware of managing any residual refractive errors. She also cautions not to rely solely on an autorefraction for these patients, as the tool may provide an over minus reading. As a result, she recommends starting at a refraction that is over plussed. She recommends beginning at 20/40 and working the patients down the chart. Be careful not to prescribe more than they need, she says.

Another tip: Gain an understanding of the defocus curve and how the lens works to aid in managing these patients. A clear understanding of this curve will provide guidance in addressing any residual refractive error and the effects it will have on the patient’s vision.

Laura Huggins, O.D., Empire Eye and Laser Center, says she expects VA of 20/32 at near, with some patients achieving 20/20 or better. This near VA is similar to what one would expect from a patient with a multifocal IOL.

Setting expectations at the outset and gauging the wants of the patient is important to achieving patient satisfaction with this IOL. (See “Co-management of EDOF IOLs,” above.) Also, Dr. Gupta says to ensure success, assess several key parameters: health of the ocular surface, retina and healthy optic nerve (i.e. no signs of AMD or glaucoma). In addition, she says she avoids implanting presbyopia-correction technology in eyes that have aberrated corneas.

Dr. Chang says he offers the EDOF IOL to help patients to reduce their dependence on spectacle wear. However, he says the optics and quality of vision of the IOL allow for him to offer the lens to a broader range of patients than he could with multifocal IOLs. For example, because the lens is more tolerant to refractive error, he can consider it for someone who has undergone LASIK. And because the quality of vision is comparable to that of a monofocal, he says he can consider it for patients who have other ocular pathologies, such as dry eyes, anterior basement membrane dystrophy or mild retinal pathologies.

CONTACT LENS

Researchers from the Brien Holden Vision Institute have been working to create EDOF technology for use in the contact lens market. Head of Research and Development Ravi C. Bakaraju, BOptom, Ph.D., F.A.A.O., says that through manipulation of higher-order aberrations, an EDOF contact lens can provide continuous vision from distance to near.

Through experimentation, the researchers at the Institute, led by Dr. Bakaraju, looked to create the ideal lens; one that would perform at all distances, offer performance relatively insensitive to pupil changes, lens decentration and inherent ocular aberrations. This work resulted in the development of non-diffractive, non-monotonic, aperiodic refractive profiles that yield a retinal image quality that is stable over distances.

To create this lens, the Institute’s proprietary software manipulates higher-order aberration profiles that are then converted into power profiles and transcribed onto the contact lens, after taking into account geometrical attributes of the lens, Dr. Bakaraju says. Put in another way: Use of the EDOF optics redistributes the incoming light energy on and before the retina, which would facilitate uninterrupted visual correction from distance to near viewing distances.

Do Your Research

Several studies have been published on extended depth of focus contact lenses and their performance:

  1. Tilia D, Bakaraju RC, Chung J, et al. Short-term visual performance of novel extended depth-of-focus contact lenses. Optom Vis Sci. 2016;93(4):435-444.
    http://bit.ly/2j5882g
  2. Tilia D, Munro A, Chung J, et al. Short-term comparison between extended depth-of-focus prototype contact lenses and a commercially available center-near multifocal. J Optom. 2017;10:14-25.
    http://bit.ly/2j2SC6U
  3. Sha J, Tilia D, Kho D, et al. Comparison of extended depth-of-focus prototype contact lenses with the 1-Day ACUVUE MOIST MULTIFOCAL after one week of wear. Eye Contact Lens. 2017; Epub ahead of print.
    http://bit.ly/2j1b5Rk
  4. Bakaraju RC, Ehrmann K, Ho A. Extended depth of focus contact lenses vs. two commercial multifocals: Part 1 Optical performance evaluation via computed through-focus retinal image quality metrics. J Optom. 2017; Epub ahead of print.
    http://bit.ly/2j1OxzR
  5. Bakaraju RC, Tilia D, Sha J, et al. Extended depth of focus contact lenses vs. two commercial multifocals: Part 2 Visual performance after 1 week of lens wear. J Optom. 2017; Epub ahead of print.
    http://bit.ly/2j3hg7n

In clinical studies, respondents to questionnaires have indicated overall visual satisfaction of about 7.5 out of 10 with the EDOF lens. (See “Do Your Research,” above.)

Serving patients. Clinical studies have indicated that this contact lens works equally well across both myopic and hyperopic presbyopes and all presbyopic add groups, Dr. Bakaraju says.

The Institute has not developed a toric option yet. However, participants in clinical studies with up to 1.00DC of astigmatism were fitted with spherical equivalent correction and were quite happy with the visual performance. OM