The Sharp VA v4 & v5 software works best with the following screen/monitor sizes and working distances.
Please see the possible optical viewing distances below:

15" Standard Monitor: 6.5 to 18.5 feet.

17" Standard Monitor: 8 to 20 feet.

19" Standard Monitor: 8 to 20 feet.

17" Widescreen Monitor: 7 to 21 feet.

19" Widescreen Monitor: 8 to 23 feet.

21.5" Widescreen Monitor: 9 to 24 feet.

20" Widescreen Monitor: 9 to 24 feet.

22" Widescreen Monitor: 10 to 26.5 feet.

23" Widescreen Monitor: 10 to 26.5 feet.

24" Widescreen Monitor: 10.5 to 28 feet.

32" Widescreen Monitor: 13 to 30 feet.

Currently, you can calibrate the Sharp VA v4 and v5 software for the above effective viewing distances in both Mirror and Direct views (6" increments).
Please note, if your monitor is not on this list, a clinically accurate calibration may still be obtainable. Please inquire prior to purchase.

Why do monitor sizes have different calibration ranges?
Monitor size limitations have been imposed to protect the quality and accuracy of our system. We have done extensive research on our software, and the effects of different monitor sizes and working distances. We found that with certain patient types (corneal issues, cataracts, amblyopia), too much blank white space on a screen can induce visual acuity reducing glare. For example, if you have a very small exam room, then there will be an upper limit on the monitor size you can use. This limit has been imposed to prevent veiling glare in certain patient populations. At the same rate, a very small monitor with a large working distance may be too small to present larger optotypes.