I have been coming across school nurses using a Spot conversion chart to convert refraction state to visual acuity.
Apparently this is being distributed and encourage by the company that promotes the spot vision screener.
I found this link to the conversion chart on line
Refractive error can not directly be converted into visual acuity. A person with the same visual acuity may have different prescriptions. The units used by schools are screening autorefractors meant to screen for the precursors to amblyopia and should only be recorded as a pass or fail by school nurses.
To my knowledge, the only screening autorefractor that test visual acuity is the Plusoptix unit and this is ONLY done through a second test using HOTV.
Please feel free to contact me with any questions you might have.