Deduction under section 80dd

As per Section 80D(4) , teh deduction shall be allowed on the basis of the copy of the Certificate issued by the medical authority in the prescribed form. 

So you can allow deduction on the basis of photocopy, no other docs will be requried.  Given below is the extract of sub-section 4 :

(4) The assessee, claiming a deduction under this section, shall furnish a copy of the certificate issued by the medical authority in the prescribed form and manner²⁴, along with the return of income under section 139, in respect of the assessment year for which the deduction is claimed: