There are no specific medical restrictions placed on drone pilots in the US, however the pilot should not have reason to believe their state of health (physical and/or mental) will affect the flight:
§ 107.17 Medical condition.
No person may manipulate the flight controls of a small unmanned
aircraft system or act as a remote pilot in command, visual observer,
or direct participant in the operation of the small unmanned aircraft
if he or she knows or has reason to know that he or she has a physical
or mental condition that would interfere with the safe operation of
the small unmanned aircraft system.
Source: eCFR 14.I.F.107.B.17