TL;DR: during lucid REM sleep, patients with extra EEG probes around the eye socket can make detectable left to right eye movements that can be repeated to communicate numerical values (e.g. 2) in response to verbal questions like “eight minus six”.
The dreamer has indeed been able to signal to instrumentation via eye movements during lucid dreaming for some time. Do you have any links about two-way communication being used for decades?