Shopping for Prescription Eyewear 101

Shopping for prescription eyewear is often very confusing. Its like shopping for a custom suit -- there are different fits and cuts that will fit people differently for various reasons. Additionally, like a custom suit, these are items that you should NOT be shopping for online -- always a good idea to be able to try on frames and have someone take specific measurements for you.
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We'll try to break things down to the simple nuts and bolts of things so the next time you go into an optical boutique or your optometrists' office, you'll be prepared.
​(If you would like to chat about the physics of lens and go into detail, come chat with us!)

1. Get an Annual Eye Exam
To prepare for your shopping trip, its best to get an annual eye exam from your optometrist to ensure that everything is working properly, and get an updated prescription. Opticians cannot fill prescriptions that are expired or go off of your glasses that you've been wearing for "x" amount of years, which you feel are just "fine" for you now -- both for legal reasons, and because your eyes have most likely changed since you got those glasses filled. 

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2. Understanding Your Prescription
If you don't need corrective lenses, things will come into focus for you directly on your retina (the red-orange part on the eyeball diagrams below) and you'll see at all distances pretty well. Similar to a camera, our eyes flip the images upside down on the retina. Images are sent from here directly to your brain, via the optic nerve, where the brain interprets the image and you see what was snapped for you by your eyes. Light allows us to see things -- the way light enters our eyes, the shape of your eyeball, and where light displaces with respect to our retina tells us if you need lenses and what type lenses you'll need.

If you need corrective lenses, you'll typically you'll see your prescription laid out with some numbers along a sort of table:

• SPH = your sphere power
• A "+" in front of it means you have hyperopia
  • Difficulty seeing up close
  • Light comes into focus behind your retina
• A "-" in front means you have myopia
  • Difficulty seeing far away
  • Light comes into focus in front of your retina

CYL = your astigmatic power

• This means that light is being scattered inside your eye 

AXIS = the axis for your astigmatic power

• Astigmatism is axis specific and corrective lenses with astigmatism will correct at the axis you are experiencing your astigmatism. 

​OD = ocular dextrus -- aka. right eye
OS = ocular sinister -- aka. left eye

ADD = your add power when you enter presbyopia

• This is a naturally occurring vision change as we age where the lenses in your eyes start to lose elasticity, making it hard for you to focus on things up close. ​

3. Your Prescription and Lenses Materials
The higher the sphere/cylinder powers, the thicker the lenses you will need to correct your vision. However, there are different lens materials which will help make thinner lenses. Typical lens materials we work with are polycarbonate, CR-39, mid-index 1.56, high indexes in 1.60/1.67/1.74, or trivex. The higher the index [of refraction], the thinner the lenses will be. There are many other characteristics of each lens which are of more concern to some patients, but typically, thickness and lightness of lenses is the main factor patients have when picking out lenses. 

Lenses that correct for hyperopia will be convex in nature, being thicker in the center than at the sides -- this helps bring the images you're seeing into focus on the retina. Vice versa of this is also true -- myopia corrective lenses are concave, being thicker at the sides of the lens than the center. Lenses that correct for astigmatism are cylindrical, with the power of the lens being effective at the axis called for. 

When powers are over -4.50 or +2.00 in the sphere, we'll bring up the option to go to a high/mid index lens. Polycarbonate is the staple lens choice for standard prescriptions, those that are usually under -6.00 or +4.00 in sphere. In California, children under 18 must wear polycarbonate lenses since its considered a safety lenses and virtually indestructible. If your sphere powers are higher than +3.50, you may also choose a mid-index lens as it will help shave off some center thickness.

4. Frame Shapes for your Prescription
If your prescription calls for relatively low powers, we like to say below -4.00 or +2.00 ranges in sphere, you have free reign over what shapes you would like to pick out. Go for the large frames or the small frames -- your lenses shouldn't be too heavy. Of course, if you go for the large frames, lens will be larger and heavier than if you went with a small frame, but shouldn't be too bad. It comes down to personal preference at that point. 

When your powers are upwards of the -4.00 sphere, think about choosing frames that are smaller in shape than others to shave off some of the thickness of the lenses. Round frames are typically great options to go with if you call for a high prescription -- this results in evenly shaving off the thicker edges of the lens. 

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5. Lens Options
There are lots of lens options to choose from to customize your lenses to fit your lifestyle, for fashion statements, or more practically, to protect you from harmful UV light or blue light.

ANTI-REFLECTIVE COATING
The one option everyone SHOULD be getting on their lenses is some sort of anti-reflective (AR) coating! Whether it is a standard AR coating or a premium coating, it will be a night and day experience for you if you've never had it on your lenses. An AR coating reflects light so you wont see the reflections you otherwise experience on a lens. Not only will it be cosmetically more appealing (i.e. when you're taking photos there wont be a glare from your lenses and your friends can actually see your eyes and not their reflections in your lenses), it helps to filter light coming into your eyes. This is super helpful at night if you have astigmatism, cutting down the glare you experience from oncoming headlights or street lamps. 

TRANSITIONS
Transitions are photochromatic lenses that activate and darken in the presence of UV light. They block UV, while filtering the light coming into your eyes -- this not only protects your eyes, it helps with bright light outdoors. These lenses are great everyday lenses, especially if you're out running errands and don't want to fuss with swapping between clear lenses and some type of UV blocking/polarized sunglasses. 
HOWEVER, it is worth mentioning that they are NOT meant to be a replacement for sunglasses! There are multiple types of Transitions lenses with different features and benefits:

• Signature/Generation 8: does not activate in the car (unless you are driving a convertible, since there's not much UV in a car) 
  • Completely clear indoors
  • Activated by UV light
• XTRActive: has a slight tint indoors while getting darker outdoors
  • Mild activation behind the windshield
  • Activates when hit with visible light as well as UV rays.
• Vantage: offers variable polarization -- meaning that it becomes polarized when activated
  • Does not activate behind a windshield
  • Activated by UV light

​POLARIZED SUNGLASSES
Sunglasses with polarized lenses are especially important in places where there's lots of sun (ie. our sunshine state of CA)! Sunlight is scattered in all directions and when it bounces off a flat surface, it often creates blinding glare -- which not only makes it hard to see things, but prolonged exposure could temporarily leave blinding effects. Polarized lenses have a filter that blocks out this glare, making it easier to see things more clearly!

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​This can still seem like a lot of info, which is what your local opticians are here for. Similar to the custom tailored suit analogy in the beginning of the post, it will be hard building a custom suit on your own; custom prescription eyewear is no exception -- opticians are the tailors for your eyes and happy to help you build out a great eyewear wardrobe!