"In every vendor-payment action brought before this Court, it is the vendor's burden initially to allege in its complaint documented proof that Illinois Department of Public Aid had determined its patient to be a recipient, with respect to the date or dates on which the vendor furnished the goods or services which are the subject of its proposed claim". Mercy Hospital & Medical Center v. State (1988), 40 Ill. Ct. Cl. 269. Certain optical goods and services are " Medical Assistance Program -covered" and thus eligible for payment by Illinois Department of Public Aid, while others are not; the scope of Medical Assistance Program coverage is explained in Illinois Department of Public Aid Rules 140.416 and 140.417 (89 Ill. Admin. Code 140.416, 140.417), and in Handbook Topics 0--220, et seq. Similarly, certain goods or services may be "covered" (and thus eligible for Medical Assistance Program payment) only if the optometrist has first obtained the Illinois Department of Public Aid professional staff's prior approval of a specified product or service (in response to a DPA form 1409 request), in light of a particular recipient's established need therefor. (Illinois Department of Public Aid Rule 140.417(e), and Handbook Topics 0--230, et seq.; and see generally Canlas v. State (1987), 39 Ill. Ct. Cl. 150, 152; Krakora v. State (1987), 40 Ill. Ct. Cl. 233, 235; Simon v. State (1987), 40 Ill. Ct. Cl. 246, 248-49.)