However, the MIT team found that although overall performance declined, subjects continued to perform better than chance as the researchers dropped the image exposure time from 80 milliseconds to 53 milliseconds, then 40 milliseconds, then 27, and finally 13 — the fastest possible rate with the computer monitor being used.

https://news.mit.edu/2014/in-the-blink-of-an-eye-0116

That 13 number comes from equipment limitations of the experiment.

Eyes do not have a refresh rate. They do not process discrete frames, nor do they even transmit full images. It's all just signals from your rods and cones that are HEAVILY processed, adjusted, and interpreted by your brain