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updated = "2018"
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# How to order glasses online

## My measurements

SIZE =
- frame width: medium (135mm-139mm -- ~136mm) // 141mm?
- bridge width: small (17-18mm -- ~17mm) // 18mm
- lens width: medium (52-54mm -- ~53mm) // 52mm
- lens height: medium (33-40mm -- ~35mm) // 32mm??
- temple arm: medium (135-144mm -- ~140mm) // 145mm?

PD =
- Single: 65mm (64.5mm)
- Dual: ~32.5mm right / ~32.5mm left? 33/32? 32/33?

PRESCRIPTION = Single Vision
```
     SPH     CYL AXIS
OD -6.50   -0.75   30
OS -5.75   -0.75  170
```
------------------------------

## NOTES:

### Abbe numbers
- Abbe value measures color dispersion.
- Higher Abbe means less chromatic aberration.
- glass is the best, low-index plastics are close, polycarbonates suck
- Crown glass = 59
- CR-39 Plastic = 58
- Trivex = 43
- Polycarbonate = 30

### Clarity, peripheral vision, chromatic aberration
- look for a high abbe value if you want
  - more clarity,
  - better peripheral vision,
  - and less chroma aberration.
- consequently, the index actually doesn't matter for clarity; it only really matters for thickness! a high-index lens will typically lower the abbe value and therefore reduce clarity.

### Aspheric lens
- aspheric designs will change curvature gradually, leading to flatter lens and better peripheral clarity. many high-index plastics might have aspheric designs to counteract the thicker edges.
  
### Distortion
- i ordered one trivex and one 1.67 high-index from zenni but both glasses had distortion at edges.
- i think that's normal but i personally can't live with it, so i returned them and will be saving money to buy something with a better material.
  - lenscrafters advertises this as "hd lenses", which is also a manufacturing process-based technique. if that's anything like what i did in amman, then an eye scan will be required. the digital scan of your eyes is used to carve out much more precise lenses up to 0.01D instead of 0.25D increments.
  
### UV / Blue Light
- UV protection coating is kinda bullshit, the lens material will typically block <380nm anyway
- Blue light filters are even more bullshit, and can actively cause color shifts!

------------------------------

## RESOURCES:

- https://www.visioncareproducts.com/high-index-lens-materials-past-present-future/
- http://www.mastereyeassociates.com/eyeglass-lens-materials
- http://www.trivexspecialist.com/blog/slimming-down-are-high-index-lenses-always-the-answer/
- https://www.allaboutvision.com/lenses/how-to-choose.htm