Focal Point and Vision range

Hello,

If I would like to see 80cm, that will convert to 1/8 = -1.25 Dipoter for myopic person, Now Focal point would be the optimal vision for the person. What would be the  the focal point in this case and with that focal point, what would be the vision range person should expect with that focal point ?

-Thanks,

[John C Hagan III, MD, FACS, FAAO]

First of all the eye is not a perfect optical system like lens on a optical bench. Thus it is not possible to 100% guarentee a post op refraction of -1.25; second a focal point for a lens is a single point at a single distance. Anthing further or nearer is somewhat out of focus. What you are referring to is "depth of focus" and that can be changed somewhat by pupil size with smaller pupils giving a larger depth of focus just like in photography.

So exact calculations applicable to the human eye is not possible. Most of my patients with -1.25 refractive error post op can read regular size GOOD print in GOOD LIGHT, shop, use computer, see dashboard without glasses assuming rest of eye normal and pupil works.

JCH MD