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Why, When and How to Prescribe the Ocutech Falcon Autofocus Bioptic

femaile doctor talking with patient

Patti Fuhr, OD, PhD, FAAO
Chief, Advanced Low Vision Section, Hefner VA Healthcare System, Salisbury, NC
Henry Greene, OD, FAAO
Co-founder, President, Ocutech, Inc., Professor and Director (retired), Low Vision Service, UNC Department of Ophthalmology, Chapel Hill, NC

WHY?

Distance vision supports both our social and environmental engagement. We use it to make eye contact, read body language, and feel connected to the world around us. Distance vision helps us to derive information from our surroundings—to read signs, see signals, recognize faces and see environmental features that support independent travel. Lack of distance vision has been associated with an increased academic challenge in children, fewer vocational opportunities for working-age adults, as well as feelings of isolation leading to depression and cognitive decline in seniors.

Persons who lack central vision, generally have ample peripheral vision to avoid obstacles, enabling them to move about safely. But they lack sufficient central visual clarity to resolve details—hampering their ability to derive meaningful cues from their environment. Reduced central vision not only impacts distance seeing, but also near and midrange activities. Seeing store signs while shopping; reading labels, bills, menus, books, and newspapers; preparing medications; using the computer; performing tabletop activities at home, school and work; watching TV, and engaging in social activities all require adequate central vision resolution.

We are all creatures of habit—we tend to want to do things the way we always have.  We have muscle memory for the distances at which we normally engage in those activities.  For those born with reduced central vision, holding things close or viewing with the preferred remaining part of their retina (eccentric viewing) develops naturally over the years and becomes the individual’s habitual behavior.  But for those who enjoyed normal vision for most of their lives, adaptation to a different way of seeing can be challenging. Using sight enhancement devices, needing closer than normal working distances, or experiencing the constraints of the narrower fields of view and shallower depths of field of low vision devices can all be burdensome.

Eyecare providers organize our visual world into 3 “activity ranges”—distance (~6 feet {2 m} or beyond); midrange (~1.5-6 feet {50 cm to 2 m}); and near (~1.5 feet {50 cm}or closer).  Each range is likely to involve different types of visual engagement.  For example, we travel using distance vision; we use computers, shop, cook, eat, and play tabletop games at midrange; we read and write at near distances. And, we will often integrate several different ranges continuously such as in the classroom, at work, while shopping and even at home.

The goal in developing sight enhancing technology is to best support the user’s visual activity needs while interfering the least with their normal, habitual behavior. The more natural the device’s functioning, and the less the user needs to engage with the device, the more effective and efficient the user will be.

Ocutech’s new Falcon Autofocus bioptic has been designed to address the challenges inherent in conventional telescopic vision enhancing devices. Bioptics are miniature telescopes usually mounted toward the top of the eyeglass frame so as to not interfere with the user’s regular line of sight. This allows the user to conveniently switch their view between the regular eyeglass lens (carrier) and the telescopic view with just a slight downward head tilt. Bioptics are a convenient way to magnify objects at normal working distances. They are most frequently prescribed to support distance and midrange visual activities for individuals with best-corrected visual acuity in the 20/70 to 20/300 range.

Bioptic telescopes need to be refocused when the user looks at different distances, requiring the user to continually manipulate the device. This is especially relevant with the shallower depths of field encountered at closer distances and with higher magnification power devices. The benefit of the Falcon Autofocus is that the image is in focus immediately at virtually any distance. No manipulation of the device is required. All the user has to do is look at the object of interest, making the Falcon’s user experience as close as possible to natural vision. And, as an additional benefit, as the user moves closer to an object, the image size will increase clearly and seamlessly, providing a helpful zoom effect.

When an individual needs to looks at a fixed near distance for an extended period of time (i.e.: the computer screen) one might assume that there would be no benefit from an autofocusing device. However, since the telescope’s depth of field is most shallow at near distances, even a slight postural change could be sufficient to blur the image. As a result the user would be forced to maintain a fixed posture to maintain image focus resulting in fatigue, lowered efficiency, and ultimately undermining the device’s long-term acceptance. As a result, autofocusing for activities at near distances can provide a more natural visual experience, lessening the user’s physical demands, lessening fatigue and increasing their performance.

When viewing objects solely beyond 20 feet (6m) (for bioptic driving perhaps), most optical telescopes used by the visually impaired will be at infinity focus.  No additional focusing for viewing beyond that distance would be required.  So, if the sole goal of the device is to support vision at 20 feet or further, an autofocusing device would offer no additional benefit. However, if the device is intended to also be used for a range of other distances, an autofocusing device may still be a compelling option.

WHEN?

Autofocusing bioptics are ideal for individuals needing enhanced vision at multiple viewing distances, for those with hands-free needs such as playing music or using the computer keyboard, and for mid-range and tabletop activities. They have been found effective for individuals with dexterity challenges and for those with mild to moderate cognitive deficits, where their ability to manipulate a manual focus device is undermined.

When traveling on public transit or at the airport, individuals will benefit greatly from the ability to see any object of interest at a glance. This visual necessity becomes less burdensome when the focus is automatic and hands-free. The classroom requires distance, intermediate, and near visual tasks all day long, as such, students can benefit tremendously from the convenience of an autofocusing device, and they are usually eager and quick adopters of such technology.

The emotional benefit of seeing a loved one’s face and expressions cannot be overstated. As mentioned in the introduction, a growing body of research demonstrates that the lack of distance vision can undermine socialization, can lead to feelings of isolation, and ultimately to depression and cognitive decline in seniors.  Efforts to support distance seeing for the visually impaired should go beyond specific task-related activities to also consider their emotional and social well-being.

HOW?

When prescribing any device, we must consider how it will be used. If intended primarily for distance-seeing, positioning the Falcon in the ‘bioptic position’ is usually the most practical option, as it will not interfere with vision through the carrier lenses for walking and other non-visually demanding activities. Individuals who intend to use it mostly for near or midrange, or in more sedentary distance activities, will likely find the straight-ahead ‘full diameter position’ to be more comfortable such as when viewing TV, movies, the computer screen or tabletop. The Falcon can be positioned at the top of the frame (bioptic position) using Ocutech’s K or U frames, or in the straight-ahead position (full diameter) using the Ocutech Sleek frame. 

The Falcon instructional videos and fitting guides will take you step-by-step through the fitting process. Designed to be easy to use, you’ll soon find just how convenient it is to demonstrate, fit and prescribe the Falcon Autofocus bioptic.

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A discussion about refraction for visually impaired individuals.

I’m often asked how I manage eyeglass prescriptions for my low vision patients, so I thought I’d spend a little time exploring this issue. I’ve presented this discussion in many talks I’ve given, but thought perhaps it was time to put it in writing.

Hope you’ll find this helpful.

Henry Greene

eyeglasses in front of an eye chart

Refraction, of course, is the optometrist’s mainstay. If we can make a sufficient improvement in acuity by refraction, (usually a two-line improvement is required for the patient to experience a functional gain), than obviously that would be our first and most convenient option. A brief retinoscopy through the current eyeglasses (if any) can be valuable to see how close to neutral the reflex is as well as its quality. (Only perform retinoscopy briefly. If you spend too much time you’ll bleach the retina, which will often delay and undermine your exam.) If the reflex is dull due to media issues, consider therapeutic options that might improve it. No amount of lens power will impact acuity if there are significant media opacities. If the patient is post cataract surgery with IOLs, it is unlikely that they will have a significant refractive error. If they do, there is often an astigmatic component.

Generally, by the time a patient gets to a low vision practitioner, if a new refraction would have been of value, it would have already been prescribed. Remember, small changes don’t make big differences! If a patient sees 20/400 a half diopter or 10-degree axis change will be of little value. Changes in refraction will have more potential impact when acuity is 20/80 or better as a modest change might yield 20/60 and that can be helpful. Improving acuity from 20/400 to 20/300 is unlikely to impact the patient’s functional life. So, as a result I will spend more time refining a refraction when acuity is 20/80 or better. I find keratometry can be a very valuable tool. The character of the mires as well as cylinder can often be missed and this data can sometimes make a difference in better-seeing individuals.

I always use a trial frame; I find it more reliable and it allows for a better rapport with the patient. Trial frames are especially important with high cylinders, because it lets the patient maintain their normal posture rather than an unnatural one induced by the phoropter, which can avoid a host of cylinder axis hassles.

Remember to make a sufficient enough power change for the patient to notice. If they can’t notice a half-diopter change, try one diopter changes. There’s no use in making changes smaller than what the patient can reliably respond to- everyone will just get frustrated and you’ll not make any progress.

Remember also that the high-contrast acuity chart is a poor determiner of functional value. After I’ve determined the best refraction, I find it helpful for the patient to look at a low contrast target such someone’s face at the furthest distance that they can normally see it. If the patient can notice a difference, then the Rx change is likely to be of functional value. If they don’t notice a difference than I don’t pursue it further. Keep in mind also that acuity will fluctuate as fixation varies. Don’t let a fleeting acuity improvement fool you into thinking it’s the refraction change that’s helping—it’s more likely a PRL issue. The prescription change has to be enough to make a “real” difference! Remember that if the patient can “almost see something” they still can’t see it!

When refraction is the best you can achieve and acuity remains inadequate for the patient’s goals, than there’s only one option left to further enhance distance vision- make it bigger! And, of course, we have only two ways to do that—walk up close enough to see it, or, make it closer optically (with telescopes!).

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The In’s and Out’s of Telescopes for Low Vision: Achieving a Balance between Acuity and Field of View in Prescribing.

As we know, patients often explain that they cannot see far enough away to perform whatever activity they have in mind. They must move closer in order to see it adequately—which they may or may not be able to do, or feel comfortable doing! Patients with 20/40 vision, however, rarely complain of difficulty seeing. Individuals are licensed to drive without restrictions with 20/40 acuity, and children are unencumbered in the classroom with that level of vision.

It is reasonable to assume then, that if we can provide 20/40 acuity through the telescope, most patients should be reasonably satisfied with the functional benefit it provides. So, if the goal is 20/40, a 2x device should be adequate for an individual with 20/80 acuity, 4x for 20/160, and 6x for 20/320. If we prescribe higher magnification to achieve better acuity it will be at the expense of a narrower field of view, which is the major complaint of telescope users. Also, the higher the magnification, the greater the image motion due to head movement that may actually undermine the benefit of the higher power device.

Clinically we find that users have increasing difficulty finding what they’re looking for when fields of view become narrower than about 10 degrees. So we always need to balance adequate acuity with field of view. Personally, I prescribe Galilean telescopes for powers 2.2x and lower, and Keplerian at 3x and higher.

I have found that patients respond most well to telescopic low vision aids when their acuities are 20/200 (6/60) or better. Keplerian telescopes in 4x and 5x can readily provide 20/40 and the telescope fields of view are greater than 10 degrees. I like to tell my ophthalmology colleagues that their goal is to keep their patient’s vision 20/200 or better. Now with the wonderful success of Anti VegF treatments, many patients have acuity much better than that, making their response to low vision aids even more robust.