The paper presents general aspects concerning the content and way of preparation of collyria used in ophthalmology for diagnosis and treatment. The collyria contain, beside the active substance, a preservative having the role of bactericide and fungicide. An essential condition for its use is sterility. The possibility of contaminating the collyria with different pathogenic germs mentioned in the specialty literature requires some prevention measures. They have to be prepared in the hospital pharmacy and sterilized in autoclave.