1. Diopters are inverse meters (remember 100cm = 1m)

```
````D = 1 / Meters; Conversely Meters = 1 / D`

2. Point of refraction and *guideline for differential strength* (still depends on distance/some people are exceptions)

https://youtu.be/9z2jjT_Gm7o s= distance to object (for distance just put in large number)(meters) s'= distance to point of refraction (for myopes how far can see clear) (meters)(put in as negative) f= focal length of lens (meters) P= power of lens (Diopters) 1/f = (1/s) + (1/s') 1/f = P

3. Visual acuity equation (consistent units)

(Font height / distance to sign)(180/60pi) = arcminutes = a Note: 5Arcminutes = 20/20 Set up proportion a/(20/x) = 5/ (20/20)

3a. Visual acuity (mm/meters)

```
````(Font height {mm}/distance to sign{m}) * 13.75 = denominator x of 20/x`

3b. Visual acuity (in/feet)

```
````(Font height {in}/distance to sign{ft.}) * 1146 = denominator x of 20/x`

^^Thank you to Val (what is last name?) for this impromptu Snellen equation. Reminder from Jake: With text that we are familiar the brain may clear up that text more than our vision actually operates at.^^

4. Average axial length accomodation/rate of change

Typical emmetropic eye = 25mm = 25,000microns {change} in axial length of 1mm = 3D If someone with typical eyes wanted to adapt say 20/20 to .25 less normalized within 3-4 months would need to decrease axial length 0.083mm about 0.92microns/day - 0.69microns/day average* Credit: Mark Podowski