At the end of your eye exam, you might be given a glasses prescription. Once you finally narrowed it down to the perfect glasses frame, then it’s time to talk about lenses. Single vision, bifocal, multifocal, progressive, coatings… Were you overwhelmed by the lens and coating options available? Let me break it down for you.
Single vision lenses have only one power, meaning that you can only see well at one distance, unless your eyes can accommodate (those who are before their 40’s). We can prescribe specific power for single vision lenses to help you see distance for driving or near for reading.
Bifocal lenses have a line and a window at the bottom. These lenses have two powers, helping you see both distance and near. There are mainly two disadvantages with bifocal. First, the line and the little window are not found to be cosmetically appealing. Second, there are only two focal points, and no power available for the intermediate distance.
Progressive lenses are commonly referred to as no-line bifocal, but technically they are multifocal. Progressive lenses have power that changes from distance to near progressively. There are infinite numbers of focal points from infinity to your reading distance. The advantage of progressive lenses is that you have one pair of glasses that takes care of the different visual demands. Now, not all progressive lenses are created equal. As you shop around, you would find a wide price range that reflects the quality of the progressive lenses. There are two things that distinguish a good progressive from a poor progressive. 1) The amount of distortion in the periphery and 2) the ability to customized the lenses to your lifestyle. With progressive lenses, there will always be some degree of distortion on the side. However, by minimizing the amount of distortion and customizing to your specific visual needs, you get a larger and more usable viewing area. In turn, it is much easier to get used to the lenses for the first time wearer and more comfortable for the seasoned wearer.
There are different kinds of coatings, which may be included in your lenses or sold as add-on products. Just like how there are different quality of progressive lenses, the quality of lens coatings varies.
Anti-reflective coat decreases the amount of reflection off your lenses. This feature is important for glasses wearer especially for night driving and computer work. In both situations, a light source is shining at you, creating reflections on your lenses that can degrade your vision. Cosmetic is also a concern because others would often see a reflection off your lenses instead of your eyes. For that reason, anti-reflective coating is highly important for public speaking and camera appearances.
Hard coat makes the surface of the lenses tougher making them more scratch resistant. When the industry first introduced plastic lenses to replace glass, many people were frustrated by how plastic get scratched so easily. Nowadays, there are premium coatings that have better scratch resistance than glass.
Blue blocker limits amount of blue light entering your eyes. Research has shown that blue light causes retinal cell death which may lead to retinal disease like macular degeneration. Where do we see blue light? Computer screens, compact fluorescent lamps and even the sun emit a high level of blue light. Fluorescent lamps emit 25% of harmful blue light while computer screens emit 35% of harmful blue light. With technology all around us, our exposure to blue light is inevitable, so blue blocker is recommended for most people and especially for those who spend a significant amount of time in front of smartphones, tablets or computer screens.