Are all eyeglasses created equal?  The answer is no – especially when it comes to performance lenses.  They may look the same as “regular glasses,” but how they work and the way they can improve your vision is very different.Before we examine performance lenses, let’s take a look at the eyeglasses typically prescribed by optometrists: compensating or corrective lenses.

Typical vision screenings assess visual acuity, or whether vision is 20/20. When vision is not 20/20, refractive conditions such as nearsightedness, farsightedness and/or astigmatism may be the cause. In these cases, doctors prescribe compensating or corrective lenses to address the refractive condition.

However, having good vision is more than just seeing 20/20. Visual skills such as eye teaming, tracking and focusing are part of your functional vision, and should also be assessed.

In addition to corrective lenses, developmental optometrists prescribe performance lenses to help with functional vision.  These lenses can help with signs and symptoms of poor eye teaming, tracking and focusing.

The difference between compensating lenses and performance lenses is in the purpose of the lens. Compensating lenses primarily address visual acuity, whereas performance lenses address the person’s visual function. Instead of just making things more clear, performance lenses are prescribed to improve a person’s functional vision.

Functional Vision in Action

Functional vision involves how you perceive an object in space.  For example, if a football is thrown to you through the air, your brain uses all of your visual skills (eye teaming, focusing and tracking) to judge how far away it is and when it will arrive. 

In addressing functional vision problems, performance lenses work in a fundamentally different way than compensating lenses.

“Most eyeglasses compensate for some kind of problem,” said Dr. Kellye Knueppel.  “For example, if you're nearsighted, you can only see a certain distance.  A typical pair of lens will suddenly help you see far away.” That’s referred to as compensation, thus the term compensating lenses.

Dr. Knueppel notes that the goal of performance lenses is to aid functional vision, and actually help it improve.  “It’s a shift to the positive,” Dr. Knueppel said. “Using the lens, in conjunction with vision therapy, can help patients improve their visual skills.”

Why do New Glasses “Feel” Funny?

The concept of performance lenses is a departure from how many optometrists think about vision.  “When optometrists prescribe typical glasses, they tend to think more about the light coming into the lens,” Dr. Knueppel said.

Remember, vision is an active process, and involves your perception of where things are in the world.  As you walk down a hallway, for example, you’re actively looking around you, using your vision to judge distances and draw conclusions.  It’s not passive; it involves people looking out through the lens.

When you consider vision as active, it explains why any new glasses, performance lens or otherwise, require an adjustment period for the user. 

Putting on a new pair of glasses is not as simple as adjusting the focus on a camera.  Your entire visual system must adjust.  

For example, new lenses with compensation for astigmatism may cause you to see the world a little "crooked."  “Your brain has to adjust to the new lens,” Dr. Knueppel said.

Dr. Knueppel notes that everyone who gets new glasses experiences an adjustment period. However, if you have a visual system that’s functioning properly, you’ll adapt faster.  If it's not functioning properly, your glasses will give you problems.  

Could a Pair of “Typical” Glasses be Harmful?

Dr. Knueppel notes many occurrences of people with glasses who need to take them off in specific situations.  For example, a person who is nearsighted and has a functional vision problem might keep his or her glasses on to copy something from the board, but take them off to read.

“The teacher might think they should wear them more, but there’s a reason they keep taking them off.”

If you see the child repeatedly taking off their glasses, you may want to ask why he or she is doing that.  The student might answer, “I don’t know” or “I see better when I read.”  

In that case, you may want to consider having a Functional Vision Test to see if there are problems with vision.  It may be a case where performance lens prescription can be blended with a regular prescription or the result may be bifocals.

What do Performance Lens Look Like?

Performance lenses look just like any other pair of glasses.  However, because they tend to have a prescription with a small power, they’re not thick.  

It is essential that performance lenses be made correctly.  There are standards in place for the accuracy of a compensating lens prescription, but with performance lenses smaller changes in power can make a big difference in function.  Therefore, they often require a higher level of accuracy.

In addition to being made correctly, it is important to use a lens material that offers the best optics for the lens. High index lenses are often recommended to ensure optimal comfort and function.

How do I Know if I Need Performance Lens?

A standard eye screening may not detect functional vision problems.  Instead, you’ll need a Functional Vision Test, which can be given by a developmental optometrist.

Performance lenses are becoming more common as people spend more and more time with near point tasks on computers, tablets and smart phones.

For an example of performance lenses in action, check out our previous post on Computer Eye Strain Leads to 21st Century Reading Glasses.