The Great Myth About Eyeglass Lenses

My Dad used to say that any job could be done if you only had the right tool.  This too can be said for eyeglasses.   Many of our patients when they come to our office are under the impression that a lens is a lens when it comes to eyeglasses.  But in fact, there are many factors that affect visual clarity and visual comfort.  Let’s take a look at 5 key factors that affect the quality of your vision when it comes to eyeglass lenses.

 

1. The Rx – Your eyeglass Prescription

The foundation of good vision is having the correct prescription, written by your eye doctor, put into your glasses. Prescriptions change.  For children and adults in their 40’s, vision often changes annually, and sometimes more often than that.  Vision can also change with habits.  A change in career, a change in school or workload, and a change in health are all things that can affect an eyeglass prescription.   Eyeglass prescriptions when carefully measured, account for the power that puts each eye into focus AND that allows both eyes to work together as a team.  In fact, a significant amount of eyestrain can result from poor teamwork between the muscles that work to keep both eyes in alignment.  Your eye doctor is trained to evaluate this and to prescribe lenses to address any issues with misalignment.

2. Eyeglass Material

Are you old enough to remember when convertible windows were not made of glass, but rather were made of plastic that wasn’t all that clear? Or maybe recently you’ve peered through a plexiglass sneeze guard and observed the lack of clarity in this “clear material?”  Not all materials transmit light the same way, and this variation in transmission has an impact on the optics of a lens.  The most cost effective lens material is plastic, specifically CR39.  Arguably more popular however, due to its shatter-resistant properties and thin profile is polycarbonate.  Unfortunately, while polycarbonate is a low cost option with many positive attributes, crisp optics is not one of them.  It’s a less than ideal option especially for far-sighted patients with plus-powered lenses.  Alternatively, high index lens materials are thin, lightweight and provide superior optics and more comfortable vision.  It’s also important not to overlook the impact that the weight of a lens can have on comfort:  heavy glasses make for sore noses and sore ears at the end of the day.

3. Lens Treatments

Light can either pass through a lens or reflect off the surface of it. You need some amount of light otherwise you would have no vision, but visual comfort and clarity is a matter of controlling which light makes it through an eyeglass lens to focus on the retina inside the eye.  Anti-reflective treatments reflect light off the lens.  They can selectively reflect specific wavelengths of light, enabling a knowledgeable optician to customize a pair of eyeglass lenses for a patient’s lifestyle or a specific task.  One type of lens treatment is one that reflects blue wavelengths of light.  These shorter wavelengths of light are emitted from digital devices like cell phones and computer screens.  To enter the eye, light must pass through the pupil, a window to the eye formed by the colored part of the eye called the iris.  The muscle fibers in the iris contract and relax to control the amount of light that enters the eye.  Just like the muscles in the rest of your body, these muscles get tired.  Long hours on the computer can lead to tired eyes and an anti-reflective treatment that reflects blue light away from the eye limits the amount of work these muscles must do, preventing eye fatigue.  Just as you can reflect light, you can also absorb it, using a filter to limit specific wavelengths of light from reaching the retina.   These blue light lens filters and anti-reflective treatments have become especially popular at a time when computer use for virtual employees and students is at an all time high.

4. Eyeglass Lens Design

For most young patients, a single power in an eyeglass lens provides clear vision at distance and near. However, for adults over the age of 40 and for some young adults and children, one power does not make things clear at all distances.  When patients require more than one prescription they may opt for a multifocal lens design.  In recent years, lens designs have become available that provide additional help for near tasks like ipad and cell phone use.  These designs are called anti-fatigue lenses and they can provide significant relief for those who spend a lot of time using digital devices.  The design isn’t obvious; in fact it takes a trained optician to examine a lens to determine if the lens features an anti-fatigue design.  It is however obvious to a patient who has been wearing an anti-fatigue lens if this feature is omitted in his next pair of glasses.

Perhaps the greatest mistake we see the patients in our office make on a regular basis is the use of the wrong lens design for the wrong task.  For patients who require a different prescription to see far than they do to see close, many opt for progressive addition lenses.  These lenses incorporate all of the prescriptions a patient may need to see at every distance into a single convenient pair of glasses.  Progressive lenses are designed with the distance prescription at the top of the lens and gradually “progress” through the computer prescription, located just below eye level in the lenses, down to the reading prescription at the bottom of the lenses.   If a patient is wearing progressive lenses and looking straight ahead at a desktop monitor, he is looking through his distance prescription, not his computer prescription.   And so the patient is looking through the wrong prescription for the wrong task and this will inevitably result in tired eyes, blurred vision, and a sore neck.  A better lens design in this scenario is a computer-specific lens design that allows for clear comfortable vision on the computer and when reading.  The options are endless for different designs made by different manufacturers.  This is why it’s imperative to rely on a knowledgeable optician with access to the latest technology to select the best lens design for a patient’s unique visual needs.

5. Eyeglass Measurements

Do you know the distance between your eyes? How about the distance between your right eye and your nose or between your left eye and your nose?  Did you know one can be different from the other?   Your optician knows this and will incorporate these measurements into your eyeglass prescription to insure that you will have clear, comfortable vision with your new glasses.  Where progressive lenses are concerned, how high in the lens does your eye sit?  This will be impacted by the way the frame sits on your nose and the size of the frame.  This measurement affects the alignment of the various prescriptions that will go into the lens, and it most certainly will affect the clarity and comfort of the vision you will have in your glasses.

There is a lot to consider when it comes to selecting eyeglass lenses.  Fortunately our patients don’t have to be experts in lens design to leave with great vision and visual comfort.  As it turns out, a lens is definitely not just a lens and there are a lot of things that contribute to great vision.  At SeaView Eyecare, our knowledgeable staff is here to provide you with years of expertise, the latest technology, and great customer service with the goal of selecting the right tools to give you the fantastic vision you deserve!

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