Calcualtions
Coming from a biomedical engineering background, details are important to me, especially when designing medical devices. From designing biometric controlled robotic prosthesis to eye charts, I have taken great care to make sure that each transistor is in order and each letter is the correct size for measuring visual acuity. I have done this by analyzing pixel sizing to give accurate letter sizes. Everything you see here has been taught to you in your optics and visual psychophysics classes. I am just adding a digital component to it to interface with a monitor and coding it in java.
Optotypes
First we need to find the size of a 20/20 or 6/6 that is 20 feet away or 6 meters away respectively.
Pixels
Now we need to figure out how to display a 8.73mm letter on our screen. We do this by looking at the smallest unit to display light which is called a pixel.
Housekeeping
As you can see we are unable to form an exact 20/20 letter as we cannot display a fraction of a pixel. However the difference comes in a such a small amount that it should not make much of a difference when trying to judge VA.
