If you’re fitting presbyopes with progressive addition lenses (PALs), then you already know how challenging it can be to resolve ocular discomfort. Montés-Micó’s one-year study in a non-presbyopic sample of 1,679 subjects aged 18-38 years old established that 56% presented symptoms of binocular dysfunction, 61% displayed accommodation disorders, and 38% had symptoms of vergence disorders.1 These conditions are likely to be even more prevalent in presbyopes wearing PALs.
In fact, this situation may be all too common in your practice:
A patient in her mid-40’s is in your chair complaining of eyestrain, headaches, and fatigue with her readers. You prescribe a pair of PALs but she is back in your chair a week later because she can’t get used to them. You recheck her spectacle prescription and your initial instincts and measurements are validated—so you tell her honestly that she might just need to give herself more time to adapt or that maybe PALs aren’t for her—and she breaks down in frustration. Maybe she admits that she can’t drive, her PALs make her seasick, or she is becoming anxious about being less productive at work. Maybe she’s angry about aging or even the quality of her eyecare. Maybe her discomfort is so severe she gives up and leaves your practice.
Looking at another scenario, there’s the patient who comes to your practice each year and says that something seems off with their vision. They think they aren’t seeing as well as they could, but maybe it’s them? When you check their prescription, it’s the same. In the chair, they are seeing 20/20 in each eye. So you tell them they are in the best prescription for their eyes and that you hope a minor adjustment will do the trick.
Each patient has unique visual needs
It can be easy to chalk up a patient’s discomfort to a progressive lens non-adapt or assume the patient isn’t giving the lenses enough time. But the truth is that every patient has unique visual needs. I have patients who come into my exam lane and say they can’t see a thing—and yet they read the bottom line perfectly. And then I have patients who say they see perfectly but when you do an exam, you are shocked at how far they are from 20/20 vision without correction—and you definitely want to get them seeing better.
It's important to understand that 20/20 visual acuity and visual comfort are separate components—and that they tend to require equal consideration when determining a patient’s prescription.
What is the “Clarity Content” philosophy?
While it would make our professional lives easier, optimal vision doesn’t automatically occur after treating the refractive error of each eye. Instead, it’s a more complex process, due to the fact that we were dealt the evolutionary hand of binocular vision. What this means is that both eyes must work together harmoniously to ensure clear, comfortable vision. Just to be clear, “comfort” doesn’t just refer to a lack of a headache. While the side effects of a visual imbalance can be frustrating, a patient can have a decreased quality of life (QoL) which may not allow them to be fully active with their daily activities or not be as productive in their work environments.
Even if you optimize a patient’s prescription for 20/20 in each eye, a modest difference in prescriptions between the eyes (anisometropia) means that light passing through each lens will be refracted differently. Therefore, the prismatic effect of each lens will be different. Depending on the patient, the result may be a visual imbalance that can cause complaints such as blurred vision, tired and burning eyes, nausea, a “swimming sensation,” and/or headaches.
“Clarity Content” doesn’t mean we should have to compromise and offer a patient either acuity or comfort or even a half-measure of each. Instead, it refers to the fact that the ocular system can pose varying complexities. Our role as optometrists compels us to put our best foot forward when assessing and treating a patient’s refractive error, while also taking into account any potential side effects that could be prohibitive to them wearing their glasses.
What is Binocular Harmonization Technology?
HOYA’s Binocular Harmonization Technology™ (BHT) is a proven and field-tested innovation in lens technology that can meet the unique visual needs of today’s progressive lens wearers. Unlike other PALs, HOYA lens designs are optimized to ensure both eyes have balanced support and comfortable vision, even if each eye has a different prescription.
HOYA lenses with BHT technology can relieve symptoms of disharmony by taking the prescriptions of both eyes into consideration and adjusting the power distribution and lens curvatures to allow an equal balance of binocularity. As a result, patients receive accommodative support as both eyes rotate through the corridor powers. This technology can allow patients to adapt with ease to their glasses and resolve any accommodative struggles between the two eyes.
The Binocular Eye Model
Hoya’s patented Binocular Harmonization Technology (BHT) considers the prescription for the right and left eyes as individual components to calculate the optimal binocular lens design, ensuring that the power distribution and progressive corridor of each lens is exact according to the needs of the eyes working together. The result is: perfect and effortless focusing, constant stability and excellent depth of vision.
How can progressive lenses contribute to an imbalance in binocular vision?
When looking through the center of a single vision lens, the image is typically crisp and clear. However, most PALs force the wearer to look through different segments of the lens, including distance (top), intermediate (middle), and near (bottom).
Because each viewing area of a PAL may have unique powers, light rays can exit the progressive lens in different positions, causing a prismatic effect. For some patients, looking off to the edge or periphery of the lens can cause images to be blurry or distorted as you might expect from looking through a certain angle of a prism. This distortion can interfere with the eyes’ ability to balance together.
As eyecare professionals, we are typically trained to evaluate visual acuity by having a patient cover one eye at a time to determine the prescription of the other. Yet, how many times have you measured visual acuity as 20/20 with each eye individually—and your patient still complains about blurry vision or other unpleasant effects?
These symptoms may be due to an imbalance in accommodative harmonization—which can affect all patients, but can be more common in presbyopes dealing with anisometropia and prismatic effects of progressive lenses.
What does anisometropia have to do with binocular vision?
The majority of presbyopes are also dealing with anisometropia—which is any refractive differential between each eye. This condition affects about 7 out of 10 presbyopic patients2 (and anecdotal evidence points to more).
While clinical studies demonstrate a decline in binocular function with increasing levels of anisometropia, even relatively low degrees of the condition can cause significant issues in high-grade binocular visual function in adults.3 The imbalance between the eyes combined with the different prismatic effect of each lens (due to a different prescription in each eye) can lead to asthenopic complaints of pain around the eyes and an inability to wear PALs—even if they are optimized for 20/20 visual acuity in each eye.
HOYA’s unique 5-step evaluation program takes into account:
- Accommodative difference
- Convergence difference
- Magnification difference
- Prismatic difference
- Clearness index mapping
Which patients are candidates for HOYA Binocular Harmonization Technology?
BHT can be ideal for all patients to improve adaptation and patient satisfaction. Even if a patient presents with equal refractive errors in each eye, BHT could still enhance the quality of vision by taking into account lifestyle activities and the position wear measurements.
I go to binocular harmonization technology because it’s the high-end technology that also considers the daily activities of my patients as well as the position wear measurement—which includes how the glasses are sitting on the face. If I know how the frames are tilted, how much they are wrapped, and how far away they are from the eyes, then by taking those measurements I can enhance the quality of the lens design by almost up to 20% depending on the prescription. Since the personalized measurements of pantoscopic tilt, wrap, and vertex distance are incorporated into the lens design, a broader and more balanced near corridor is created.
As anisometropia increases and the prescriptions become more unequal between the eyes, the more of an impact BHT could have, as it allows for both enhanced binocular balance and adaptation. For the patient, this translates into improved comfort and clarity. Even a small amount of anisometropia can be benefited by BHT.
BHT, on the other hand, can further promote accommodative balance, especially at near, when working on the computer or reading. As a result, you’ll likely experience less office remakes and fewer repeat visits—contributing to greater efficiency in your practice.
What are clues that a patient may have issues with accommodative balance?
A telltale sign of a failed progressive lens wearer is when they come in with two pairs of glasses: one for distance and one for reading. Some have had very difficult times with their glasses. For example, they may say, “I see great out of my left eye and great out of my right eye, but when I look out of both eyes, it’s hard. It’s weird.” They tell me they’ve tried progressives in the past and they’ve never been able to adjust to them. As a result, these patients may no longer be as productive at work or participate in activities they love, so it’s even more than side effects—which are extremely uncomfortable—but their lack of accommodative balance can seriously impact their quality of life.
Alternatively, I may have patients whose visual acuity will be clear when looking through the center of their lenses. It’s when they move their head or start to engage in their daily activities where they are transitioning from near to far that they are going to have problems. When any of these patient types present, I know they will benefit from BHT.The majority of those patients generally turn out to also be anisometropes. Once I explain to them that their difficulties stem from the fact that their two eyes are having a hard time working together, they are relieved to know there is a solution.
Best practices for HOYA’s Binocular Harmonization Technology
Binocular Harmonization Technology is beneficial for all patients wearing progressive or workstyle lenses. Even when a patient presents with equal refractive errors, BHT will still enhance the quality of vision by utilizing the position of wear measurements. With the personalized measurements of pantoscopic tilt, wrap and vertex distance being incorporated into the lens design, a larger and more balanced near corridor is created. As the anisometropia increases and the prescriptions separate between the eyes, the more important BHT becomes.
With over 70% of the world’s population having a different prescription between the two eyes, BHT becomes more relevant allowing for greater comfort with clarity, better binocular balance and greater adaptation. Even a small amount of anisometropia can be benefited by BHT, but when your patients present with 1.00-2.00 diopters of difference between the two eyes, BHT really stands out allowing the two eyes to work together in accommodative balance, especially when working on a computer or reading. This visual harmonization leads to greater success for patient adaptation and less office remakes.
I have found BHT to benefit my patients needs when utilizing progressive or workstyle lenses, even those patients with extreme anisometropia. I remember a patient that to incorporate “slab off” due to his four diopters of difference between his two eyes. He felt insecure in the way the slab off looked and was never really comfortable with his vision. I explained BHT and the benefits it could bring to his wearing comfort. He ordered the glasses and I was excited to hear his opinion the next saw him. A couple weeks after he picked the glasses up he came back to the office just to inform me that this was the best pair of glasses he has ever had and that he was thankful I put him in Binocular Harmonization Technology.
Pro Tip: Questions you should be asking your presbyopes
- How much time do you spend on a device? Which kind of devices do you use most commonly?
- How many monitors do you use at work? How far away from them do you sit?
- If I could improve your comfort at work, would that be of interest to you?
- Are many hours a day are you on your phone?
- What are your hobbies? Could those be more enjoyable if your vision was more comfortable?
- What are your activities?
- How much time are you outside?
I can’t recall a scenario where BHT didn’t perform up to my expectations. Overall, BHT has helped pretty much all of my non-adaptive patients. Some of these patients didn’t even know they had an issue with accommodative balance, while my more extreme cases gave up hope of ever being able to be comfortable wearing spectacles. This is such a huge reward for me, because there is nothing worse than having a patient come back in and not being able to wear their progressives when the prescription checks out fine.
I’m sure you’ve had the experience where you look at the progressives and everything marks up, and everything's sitting on their face correctly. And you're just scratching your head, asking yourself what’s going on?
BHT might be the solution you have been waiting for to tap into to potentially deliver visual clarity as well as visual comfort.
For those patients who have tried and struggled with progressives and have said “never again”—BHT could be an opportunity to explore these new lens designs. They can see well, they don’t have side effects, they can wear just one pair of glasses without any hassle, they work more efficiently, and they can receive more enjoyment from their daily activities. Invariably, these patients end up very happy with their new lenses, which is always my goal as their doctor.
What technologies do iD Lifestyle 3 lenses harness?
iD Free Form Design Technology
Commonly, progressive lens designs are based on one surface technology. However science shows that there are benefits of having some progressive elements on the front and some progressive elements on the back. Hoya’s patented iD technology distributes the add power over two surfaces. Image recalculation allows for decreased peripheral distortion and wider, more stable fields of view.
Advantages of positioning the vertical progressive component on the front surface of the lens include minimized vertical eye movement and fast interaction between near and far. The effects of positioning the horizontal progressive component on the back surface of the lens include less impact to peripheral vision (because the closer distortion is to the eye, the less it impacts peripheral vision), the usable corrective surface is enlarged, and a wider, clear visual field at all distances is created regardless of prescription.
What does this mean for patients? With a non-harmonized progressive lens, objects are distorted in the lower periphery of the lens, resulting in a swaying feeling. With iD Free Form Design calculation, the lens surface can be modified to control image distortion through mathematical computation to create less of a swim sensation.
Supporting Technologies
View Xpansion Technology
View Xpansion Technology improves the lens optics from edge to edge for wider fields of distortion free vision. Standard progressive lenses usually offer a sharp image through the central zone when looking straight ahead. The eye encounters distortion and lens aberration as the gaze rotates toward the lens periphery or edges. This can lead to blurred peripheral vision and head turning. View Xpansion Technology decreases aberrations. This results in ease of focus at all viewing angles.
Stable View Enhancer
Stable View Enhancer reduces distortion of the view. Standard progressive wearers often notice distortion when going up and down stairs, which can make the wearer feel unsteady and uncomfortable. The problem is dramatically reduced with Stable View Enhancer, a digital evaluation method, which corrects dynamic distortion.
