Article Date: 6/1/2007

Individualized High Definition Vision

Individualized High Definition Vision

Thanks to wavefront technology, O.D.s can create unique spectacle lenses for their patients. Here's how these O.D.s are using this technology in the lane.

Paul M. Karpecki, O.D., F.A.A.O. (Moderator): A new ophthalmic dispensing aberrometer generates prescriptions that are unique to each patient and provides crisp vision. This innovation is made possible by measuring light wave aberrations and developing new ophthalmic lenses that address imperfections in vision that were once imperceptible.

Today, we'll discuss how to introduce this technology to your practice. We'll identify the ideal candidates for this technology and discuss several applications, including refractions, which is one of the most significant. Let's begin with an overview.

How the technology works

Daniel E. Quon, O.D.: To grasp how this new technology functions, we should remember we've always used ophthalmic lenses to correct lower-order aberrations (classified as first to second aberrations by order of complexity), such as myopia, hyperopia and astigmatism. Higher-order aberrations, ranging from an order of third to sixth, include coma, spherical aberration and trefoil.

Point spread function and retinal image of a perfect eye compared with eyes that have higher-order aberrations, such as coma, spherical aberration and quadrefoil.

These higher-order aberrations — which can cause compromised night vision, glare, halos, blurring, diplopia and starbursts — are created by irregularities of the tear film, cornea, vitreous humor, aqueous humor and crystalline lens, including cataracts. We can discern higher-order aberrations by passing a wavefront of light through the eye and measuring the distortion of the reflected wavefront that returns from the retina and exits the cornea.

Of course, this technology has been used for several years now to achieve customized ablations in LASIK surgery. So what's new about wavefront technology that has us so excited? We now have a small, exam-lane-compatible instrument that enables us to use the same wavefront technology at a fraction of the cost to analyze distorted light pathways. Then, we can formulate findings to develop a highly specific correction that produces a unique ophthalmic lens for each eye.

Dr. Karpecki: Two types of lenses have been designed with wavefront technology: the Varilux Physio 360° by Essilor of America and the iZon lens by Ophthonix. The Physio 360° uses wavefront technology to address aberrations that cause distortions of the lens, while the iZon lens addresses vision problems caused by higher-order aberrations of the eye. Today, we'll discuss primarily the iZon lenses, which are produced in a special offsite laboratory, using a patented process in which the unique iZonik™ photopolymer is sandwiched between two lens blanks. These lenses are created with prescriptions generated by the instrument Dr. Quon described, the Z-View Aberrometer. We have a few other terms to discuss, such as iPrint and iZon PAL, which clinicians should become familiar with if they're thinking about using this technology in their practices.

The iZon lens is customized based upon the optical fingerprint, or iPrint, which is measured by the Z-View Aberrometer. The lenses are produced using a patented process in which the iZonik photopolymer is sandwiched between two lens blanks.

Stuart A. Gindoff, O.D., M.B.A., F.A.A.O.: The iPrint is the data that's compiled from the Z-View Aberrometer measurements. The data is equivalent to obtaining a fingerprint of the eye; each eye is different. An iZon lens is the lens that's driven by the iPrint, and the iZon PAL lens is merely the progressive addition that Ophthonix puts into the iZon lens.

We now have a small, exam-lane compatible instrument that enables us to use the same wavefront technology at a fraction of the cost to analyze distorted light pathways.
Daniel E. Quon, O.D.

Higher-order aberrations

Dr. Karpecki: How important are higher-order aberrations? Overall, do they significantly affect vision?

Pamela A. Lowe, O.D., F.A.A.O.: Current literature in wavefront aberrometry states that higher-order aberrations account for about 17% to 20% of a patient's visual deficiency. So, higher-order aberrations are very important, representing up to 20% of uncorrected refractive error. Conventional lenses don't address this. What's exciting about this technology is that it returns us to our optometric roots, improving considerably on a technique that is as old as our profession.

Dr. Gindoff: In our practice, where our surgeons perform LASIK and multifocal implants, some patients just aren't satisfied with their overall vision after these procedures, no matter what we do. With the Z-View Aberrometer, not only can we see what patients are talking about, but we can actually neutralize the problem, or at least help them get through the prolonged healing process.

Dr. Quon: I use the iZon lenses for many patients who had LASIK before custom procedures were available. They're experiencing glare and seeing halos around headlights at night.

Just as everyone's fingerprint is unique, so is each of your patient's eyes. In fact, their eyes have their own optical fingerprint. The iZon® High Resolution Lens is customized based upon the optical fingerprint, or iPrint™, which is measured by the Ophthonix Z-View® Aberrometer. The iZon brand is the only spectacle lens based upon the patient's iPrint.
The iPrint contains all second to sixth order aberrations of the eye, and the iZon Lens addresses the vision problems commonly associated with these aberrations. Halos around lights caused by spherical aberrations, starbursts from trefoil and comets from coma are examples of such vision problems. Ophthonix has found that 96% of myopic patients have pronounced levels of higher-order aberrations (HOA); 77% of emmetropic patients have pronounced levels of HOAs (Source: Ophthonix clinical investigations).
The iZon lens provides patients with generally sharp visual acuity, improved night-driving vision, better contrast acuity, greater depth perception and the ability to see colors with greater richness and intensity (Sources: iZon patient feedback questionnaire. Clinical investigations at the U.S. Navy Refractive Surgery Center in San Diego and the University of Illinois-Chicago, Ophthalmology & Vision Sciences).

A comparison of vision quality with and without wavefront-guided lenses. The wavefront-guided iZon lenses can address imperfections in vision that were once imperceptible.

Jacqueline Campisi, O.D.: I've practiced optometry for 16 years with a special interest in developmental vision and vision therapy. When a patient complains about light sensitivity, often I look for binocular vision disorders. This technology has really helped me better determine if a patient has Fuchs' dystrophy or perhaps binocular vision problems. If they do have convergence insufficiency and glare, I prescribe the iZon lenses with a little base-in prism, and I can feel confident these patients won't go anywhere else to get their next pair of eyeglasses.

A 37-year-old patient presented with complaints about her correction even though her distance visual acuity was 20/20 OU (OD was 20/25+; OS was 20/20). Her residual refractive error was less than -0.50D. Nonetheless, she felt debilitated. For 5 years, she was unable to drive at night. She said that headlights of oncoming cars looked like one huge halo, and that her poor depth perception made lane changes extremely difficult. Conventional eyeglasses couldn't solve her problem. I prescribed iZon lenses for her, and she started driving at night immediately.
An 81-year-old patient had failed his eye test at the department of motor vehicles, despite the fact his visual acuity was 20/50, slightly worse than the 20/40 minimum requirement. He'd worn trifocals for 40 years and now had inoperable cataracts due to multiple systemic conditions.
Generally, I don't switch long-term trifocal wearers to progressives. But we discussed the iZon lenses, and he was willing to give them a try. Turns out, he passed his eye test and was able to switch from trifocals to the iZon progressives without any problems.
Daniel E. Quon, O.D.

Personal experience

Dr. Gindoff: The best way to evaluate the iZon lenses is to try them yourself. I'm a contact lens wearer who has never felt comfortable in progressive addition lenses — until I tried the Physio 360° and got used to wearing them. Then I tried the iZon lenses and, after 2 minutes of adjusting to the even more incredible vision clarity, I became a believer.

Dr. Quon: I had a positive experience wearing the Physio 360° lenses as well, mostly because of the great distance vision they provide. The iZon progressives made my vision seem almost three-dimensional. Within a day or two, I adjusted to the lenses and everything looked much clearer and normal spatially.

Also, as innovative optometrists, you have to think outside the box. I prescribe short corridor lenses for shorter people and, sometimes, depending on their working distance, I'll decrease their add by a quarter diopter. A taller person doesn't want a short corridor lens generally because objects in their inferior field of view will appear blurrier, especially when standing. By using this creative prescribing technique and the iZon PALs, I've found patients who couldn't wear progressive lenses before now can do so successfully.

Dr. Campisi: As a visual therapy specialist who's had to defend my practice in an ophthalmology-dominated community, I introduced the Optomap (Optos) retinal exam with its enhanced capabilities 3 years ago to set myself apart from other practices in southeastern Connecticut and Rhode Island. Now I've introduced the iZon, and it's having the same effect. Patients say, "I've never seen anything like it." And that's become my slogan to print on my cards and use on all my marketing materials. I've never seen anything like the iZon lenses.

Dr. Karpecki: All of this personal insight has been helpful. We'll continue to discuss other important issues, such as how to introduce this new technology to your practice — and your patients. OM

Optometric Management, Issue: June 2007