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Addressing presbyopia & anisometropia with Binocular Harmonization Technology in progressive lenses

A new wave of presbyopes (difficulty seeing objects up close) are coming, as millennials are already hitting their 40s. On top of that, more than 70% of all presbyopes have different prescriptions in each eye.1 With how much time we spend on devices daily and reading/working up close, this leads to a frustrating amount of strain for people with presbyopia. 


Warren Modlin, HOYA Vision Care’s VP of Product Technology was recently quoted in Vision Monday. He explained that, “If the eyes are looking through different prescriptions, you’ve got different amounts of magnification. If you’re spending hours in front of a computer with different images, the brain is going to fatigue, experience migraines or headaches or dryness that often is not recognized as being the result of two eyes trying to work together in order to harmonize an image.” 


Let’s talk about presbyopia and anisometropic (differing) prescriptions in each eye – as well as the technology and lens designs needed to address it. 


Single vision lenses vs. progressive lenses for presbyopia


Your patients may not understand why their single vision lenses aren’t right for their needs.  


Sure, single vision lenses create less strain because the wearer can adjust objects for near vision using the central position of the lens. However, these lenses are only addressing vision for one distance at a time, one vision problem at a time.  


When you have presbyopia, along with a different prescription in each eye, single vision lenses just aren’t enough. Presbyopes benefit more from progressive lenses because they utilize different areas of the lens depending on the activity.  


This brings us to progressive lenses of today: even with the evolution of progressive lenses, we knew there was more we could do to marry disparate images for presbyopes: Binocular Harmonization Technology (BHT). 

Download the Free BHT White Paper

BHT Whitepaper Infographic



Explaining to patients: “it’s our brains that see, not our eyes”


Dr. Thomas Gosling put it in a way that patients can truly understand: “When you have a prescription for the two eyes that aren’t equal, there’s going to be a fight. It’s our brains that see, not our eyes. And the brain will tell you that it’s being challenged by showing you symptoms – headaches, eyestrain, and fluctuation in vision in our eyes.” 


Often, the patient won’t even know they’re struggling with their lenses as a result of different prescriptions in their eyes. They just know they’re experiencing symptoms, and it’s the ECP who knows to check for the binocular disparities.  


What's happening for your patients: 


Vision problem: Presbyopic patients with different prescriptions in each eye need their brain to work harder to balance the images each eye is processing.  


Eyewear problem: Their eyewear provides slightly different images when using anything but the central position on their glasses. When using anything but the central position of the lens, the light rays exit the lenses at different locations, creating a difference in image perceived by each eye. 


BHT in progressive lenses: a true binocular solution based on 5 primary elements


BHT in progressive lenses Chart



BHT takes this difference into account through 5 measurements in the Binocular Eye Model. These measures consist of: 


  • Binocular Clearness Index 
  • Convergence Difference between R/L 
  • Accommodation Demand Difference between R/L 
  • Magnification Difference between R/L 
  • Vertical Prismatic Difference between R/L 


By taking into account the difference in prescription, we can make adjustments tothe progressive lenses to correct for the variation in images perceived by each eye, helping to reduce eye strain because the wearer no longer has to self-correct.






BHT allows the ECP to offer presbyopia solutions that make a difference for patients 

Whether your patients know they are feeling strain or not, you can educate them about their binocular disparity, uncover the real discomfort they’ve been facing, and offer them this technology so they can finally see at their best and most comfortable. 


Binocular Harmonization Technology is currently available in the following HOYA Vision Products: 


  • iD MyStyle®2 
  • iD LifeStyle®3 
  • Array 2® 
  • iD SpaceTM 
  • iD ScreenTM 
  • iD ZoomTM 


Progressive Lenses with BHT


Learn more about Binocular Harmonization Technology 

To learn more about the technology behind BHT and to see the difference it makes for patients — download our comprehensive ebook Binocular Harmonization Technology & Binocular Eye Model.

Download the Free BHT White Paper


1Hoya data in file. European progressive lens orders 2007-2013