HELP.. Filling Second DropDownList based on parameters of selection in another DropDown List.

I have First DropDownList as a selection of a Lens Material.  Based upon that material selection, a second list fills with lenses available in that material.  The problem is,,,  when you do click the submit buttom, the information written to the database is not correct for the second dropdown list.  It chooses the first item in the list rather than the selected item and writes that info to the db.   I am NOT well versed on coding or development so I need all of the help I can get.
Thank all for any and all input.  Below is the routine for filling the dropdownlists

SqlConnection conn;
        SqlCommand comm;
        SqlDataReader reader;

        //  Read the connection string from Web.Config

        string connectionString =
   &n ...