5 Things to Know When Considering Electronic Glasses for the Visually Impaired People

RevoSight Wearable Augmented Reality Glasses - Zoomax

What's the most important things to consider when choosing electronic glasses for the visually impaired?


Augmented Reality (AR) technology has been positively impacting many cutting cutting-edge fields around the world, including wearable assistive technology for people who are visually impaired. While many solutions for people with visual impairments remain quite expensive, the benefits to independence and productivity are significant.


While there is awareness about traditional solutions for low vision such as optical magnifiers and electronic video magnifiers, the same is not true for the emerging wearable solutions. Specialists knowledgeable about electronic wearable solutions are few, which means many potential users may need to conduct more research on their own. 


In the face of the technical specifications of an electronic glasses, a prospective user may have the following questions:

• What do all these specifications mean?

• Does a particular feature or product work for my eye condition?

• Will I notice the types of benefits describe in the brochure or video? 


No two people are the same, which is why it's so important to consider personal eye conditions as part of the overall decision-making process. Let's review five of things you should consider before investing in a electronic glasses solution, and when comparing different solutions. 


Field of View

Field of View (FOV) determines how much perspective you can see. 


With normal vision, the human eye probably has a 150-degree FOV. By contrast, one of the more popular Virtual Reality (VR) game devices is closer to a FOV of 100 or 110 degrees.


Typical FOV Comparison, based on scenes from video game

Fig. 1: Typical FOV Comparison based on scenes from video game.


A large FOV is very beneficial for eye conditions such as Age-Related Macular Degeneration (AMD), that are affected in the center of vision. It is not so beneficial for those with narrow vision conditions such as Retinitis Pigmentosa (RP) or Glaucoma. Individuals with a narrow field of vision do better when a larger scene is presented in areas where remaining vision still exists.


A video game player simulated his vision on gamespot.com. He believed that by adjusting the ratio from 4:3 to 16:9, he could address his FOV problem, even though it made the world smaller.


A visual perspective of a visually impaired game player of Overwatch

Fig. 2: A visual perspective of a visually impaired game player of Overwatch


It should be noted that extremely large FOVs may produce vertigo, though there is no need to worry about this issue affective assistive technology users at this time. FOV in mainstream devices is between 20 and 40 degrees.


RevoSight delivers a FOV of 45 degrees per eye. To date, no reports of dizziness have been received.


Refresh Rate

When images on a screen change, the screen refreshes several times per second, to ensure a smooth transition as things change. With computer screens and similar types of devices, this is referred to as refresh rate. Most people tend to think of refresh rate in terms of display speed, or delay.


While refresh rate is related to delay, it is not by itself a parameter that describes delay. The parameter describing the delay is something called Motion-to-Photon Latency. In the VR/AR domain, this means the lag between the instant you move the head to the moment that the display responds to that movement. A high motion-to-photon latency results in a poor experience, similar to motion sickness and nausea.


There is a conversion between refresh rate and motion-to-photon latency:


Latency (ms) = 1000 ms / refresh rate (Hz)


This is to say that the higher the refresh rate is, the less motion-to-photon latency will occur. Ideally, latency should be less than 20ms, though it's possible that latency up to 25ms may be adequate. This translates to a refresh rate between 40-50 Hz.


Taking RevoSight's 60Hz as an example, the latency will be 1000/60=16.67ms.


Many VR/AR game consoles have motion blur and movement prediction functions to simulate a natural visual delay because the human eye behaves in much the same way, but generally the current wearable visual aids cannot make it happen. What is clear is that the higher the refresh rate, the better.


Frame Rate

Frame rate is also a common parameter, and some wearable aids developers use it to replace the frame rate. The difference between refresh rate and frame rate is this: the refresh rate is how many frames your CPU is producing or drawing, while the refresh rate is how many times the monitor is refreshing the image on the screen.


What's an ideal frame rate? As long as you have a good CPU, a higher frame rate will be better. In terms of using a VR device to watch video, the minimum frame rate is 30 fps, with many people pushing for 50–60 for hyper-realistic videos.


Fig. 3: Frame rate comparison

Fig. 3: Frame rate comparison


Display

Although the high refresh rate is important, there are few products that can achieve 60 Hz. Most products on the market have a refresh rate mostly between 30-45 Hz.


Which brings us to another aspect you should consider: the display. Displays can be divided into enclosed and open display.


In the case of an enclosed display, the discomfort caused by low refresh rate is more noticeable. Many a promising VR product has fizzled because the immersive experience viewed through enclosed headgear can cause dizziness and nausea.


Various open-display wearables allow people to see the real ground through they own eyes, though it should be noted that one of the causes of nausea is the ground simulation in the vision.


An open display delivers relatively better experience since the wearer has the opportunity to perceive the environment through the part that is not completely occluded, and this part of the perception can compensate for the delayed picture.


Ideally, to keep vertigo away, the best combination of display is high refresh rate and an open display.


Presentation

High-contrast and zoom-in are common features of these types of products, whose design reference comes mainly from traditional visual aids including the daily gadgets with vibrant colors, and high contrast colors settings.


Intense color contrast has been proven to be very helpful when it comes to improving visual acuity in people with visual impairment. In non-high contrast mode, some products also emphasize modification of normal mode, such as brightness/contrast enhancement for real-time scenes.


Chart showing color preference of children with Cortical Visual Impairment (CVI)

Fig. 4: Chart showing color preference of children with Cortical Visual Impairment (CVI)


In a study titled "What is the minimum field of view required for efficient navigation? ", the researchers found that the subjects performing in high image contrast conditions could pass the virtual forest to the target tree without hitting any obstacles in smaller FOV. Research section is summarized as follows:


“The critical points for efficient navigation were FOVs of 32.1°, 18.4°, and 10.9° (diam.) for low, medium, and high image contrast levels, respectively, highlighting the importance of contrast on the size of the FOV required for efficient navigation.”


Of course, there are products that do not emphasize high contrast. These products may focus on other functions, such as depth of field presentation, or specifically designed for people who are color blind.


Contours and compensation are two innovative ways of presenting.

- The outline algorithm presents the image in the form of outlines.

- The compensation is to project the missing portion of the visual field to the remaining visual field after measuring the vision loss area.


Presentation simulation of RevoSight outline function

Fig. 5: Presentation simulation of RevoSight outline function


The current version of RevoSight is equipped with 12 high-contrast color settings, zoom-in and zoom-out, and outline function (contours). The compensation will be added in later versions.

Future Plans

The Strength of the Brand

Imagine having encountered a product problem a couple of years after purchase, only to discover that you cannot reach customer service because the company is no longer in business. Strong companies demonstrate fiscal responsibility, while investing in ongoing development to ensure that their products are updated. We believe this is more likely to provide sustainable service.

Proven Track Record

When investing in an AR solution, ask questions about the path forward. Is the product upgradeable if new technology becomes available in the future? Does the manufacturer have a reputation for innovation? Is there evidence of the manufacturer's commitment based on other products they make? Technology moves quickly, which means products can become outdated if they are not being updated along the way.


Next Steps?

Okay, so you have completed your preliminary research on electronic glasses that sound like they might work for you and your eye condition.

Try Them Out

Investing in technology like electronic Glasses is not an impulsive decision. Much like buying a motor vehicle, a test drive is recommended to make sure things truly work for you. In a research paper published by the Royal National Institute for the Blind (RNIB) in the U.K., there is a clear statement indicating the variation in individual experience:


"The results also show that two people with similar characteristics, for example, age, gender, visual field, visual acuity or sight loss condition, may not have the same experience when using the Smart Glasses."


Plan to try more than one solution to help you make an informed decision.

Compare the Important Things

With the information learned from this article, we know to ask about and compare the following things:

1. Field of View

2. Refresh Rate

3. Frame Rate

4. Display

5. Presentation


Not all companies publish the full specifications for their solution, or they provide only basic information. You will need to ask.


For example:

- What is the Field of View (FOV)?

- Why is not always fully displayed? (Answer: the display of FOV is limited by the presentation)

- Does the FOV refer to the camera or the device? (Comment: The FOV of the device is the important one)

- What is the Refresh rate? (Ideal Answer: 60 hz; faster refresh rate is always best)

- What is the Frame rate?

- Is the Display Enclosed or Open? (Ideal Answer: Open, because Enclosed Displays can cause feelings of nausea or dizziness)

- What are some of the ways information is Presented? (Observation: Zooming in and out and changing colors should be considered basic level functionality. Ideally, the electronic Glasses will also provide alternative viewing modes, including outlining of edges or high contrast image)

An example of how display FOV limits the camera FOV via Reddit

Fig. 6: An example of how display FOV limits the camera FOV via Reddit


Generally, you won't find these two kinds of FOV indicated, and it's not important if both can make you see better when you try two wearable devices. However, you need to pay attention to the one which claims a larger FOV yet doesn't deliver larger vision in effect.


Be an informed consumer. Ask questions. Request a trial. Make the right choice!



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