Everyone has heard saying “you get what you pay for,” this could not be more true than about eyewear. Whether it is spending money on frames or lenses, if you find the cheapest pair glasses you can, chances are the frame will break quickly and your vision won't be its clearest. Choosing a quality lens is a good first step to ensuring your best vision.
After choosing your perfect frame, making the decision of which lens to put in it is a big deal. If the wrong lens design is used you may find it difficult to use your glasses. For instance, what if a progressive (no line bifocal) lens is prescribed by the doctor and a transition lens (lens that darken in the sun) is put in your glasses instead. You will pick them up expecting to be able to read, but you will be unable to. It is important to communicate clearly about what lenses you want to avoid miscommunication.
Some lens problems have nothing to do with communication, but have everything to do with the expertise of the optician. When it comes to taking measurements for glasses being accurate with the measurements is key to the lenses working to the best of their ability. There are a couple key measurements that always should be taken. The first measurements that should always be taken are the pupillary distance (PD) for both distance vision and near vision. This measurement ensures the optical center of the prescription is aligned with the eye horizontally. If this measurement is incorrect or not measured at all, the lab will place the optical center in the center of the lens. When the PD is incorrect it can cause everything from double vision, to blurred vision or cause the wearer to feel the need to turn their head to the left or the right to see clearly. These symptoms can be amplified with stronger prescriptions. The cause of these symptoms is the horizontally induced prism from the measurements being incorrect. Induced prism causes images to be seen in a shifted location causing the brain to have trouble fusing the image. The further off the measurement the worse the symptoms.
This brings us to the next key measurement, optical center height (OCHT). The OCHT is the location of the eye vertically in the lens. This is important for reasons similar to the PD measurement, but if this measurement is off it causes induced prism vertically instead of horizontally. Vertically induced prism will cause images to “jump” up or down depending on the prescription and where the eye sits in the lens. The OCHT is an interesting measurement in today's online based glasses business, as it is a measurement that can NOT be measured without the frame. So, with companies like Warby Parker operating online, many individuals are not getting their best vision due to the inability to measure the OCHT.
On a related note, a Seg height measurement which is used to measure where the eye sits in a progressive lens can have similar troubles to a mis-measured OCHT if not measured correctly. However, unlike the OCHT, the seg height is responsible for determining where the progression starts. If incorrect, a progressive lens wearer may feel like they have to dip their chin to see distance or tilt their head back to be able to read. This makes you think, with so many people hearing horror stories about progressive lenses, how many of these horror stories could have been avoided with correct measurements.
With all the talk about measurements, when someone actually has prism in their prescription, these measurements become all the more important. Prism is commonly used to treat double vision in many patients. Some may have seen advertisements for digital measurements and how digital measurements are more accurate than traditional methods of measuring for lenses. This can be correct, however digital measurements are only as good as the optician who is taking the measurements.
Aside from the measurements, vision through your new glasses can also be impacted by the lens materials and lens coating. For instance an anti-glare coating can improve vision by removing glare from your lenses to allow you to see whats in front of you and not the glare of the lenses. Anti-glare coatings become increasingly important as prescriptions increase and thinner lens materials are utilized. When high-index lenses are used glare can become more apparent and cause vision to become compromised if an anti-glare coating is not used.
Lens styles can be just as important as the measurements. In progressive lenses, the style of progressive is just as important as the measurements. In traditional progressives the corridor can be very narrow and make it very difficult to use the lenses. Choosing a free-form digital progressive will give a wider field of vision and make use of the lens easier.
How can you avoid these lens complications? The easiest ways to avoid complications with your new glasses are to first make sure your optician adjusts your frames to fit the way you would like them to fit before any measurements are taken. This will ensure the measurements are made where your eyes will be positioned in the lenses. Digital measurements, when done correctly, can add the additional customization to a digitally surfaced lens to deliver the clearest vision possible. The second thing to do is make sure to discuss what you will be using your glasses for and your doctor or optician will be able to make recommendations based on your lifestyle and use of your glasses.
Stop by either of our locations and we can help recommend lenses and find you a frame that will fit your lifestyle.