This near vision (40 cm / 16 inch) hand-held testing chart is two sided and features a different optotype per side.
On the first side are Sloan optotypes which were developed from the idea of Snellen optotypes. However, Sloan optotypes do not feature any serifs, making distinguishing optotypes slightly easier. Also, Sloan optotypes were chosen for their equal difficulty along with the amount of space they occupy in the Snellen 5×5 grid. Sloan letters adhere to the principles set for Snellen optotypes, but also take in new principles of total equality and difficulty.
Side two features PV Numbers optotypes and are calibrated comparatively to our Patti Pics series charts: on the basis of the 5×5 Snellen grid and calibrated for equal recognizably against Sloan letters. Even illiterate adults can often recognize numbers. Deaf or mute adults can indicate the number seen with simple finger signs.
The two islands on either side reduce memorization when testing OD, OS, and OU (Oculus Dexter, Oculus Sinister and Oculus Uterque).
Constructed with the same precision, accuracy, and methodology as traditional ETDRS charts. Lines are of equal difficulty. Geometric progression in letter size from line to line. Letter size is only variable.
Click additional information to the above for more specifications.