Hello,
I can recommand to you to add another custom field let explain this :
1° Create a new custom field, a radio button type (Yes/No), with as a label, a question, in your case something as :
"Do you have a current prescription ?"
2° Use this new custom field to create a condition to display or not, as you can see on my screenshot :
Here, this current custom field, will
only be displayed if the Test custom field have the value : Yes
And so, you can imagine that in your other custom field, you will do the same settings except that is displaying condition
will be on the No value.
Your user will just have to complete the question to see the required custom field.
Hope this will fit your needs.
Regards