JOINT FILING ------------ Douglas Williams Family Limited Partnership, Brodersen-Williams Eye Institute, P.C. and Douglas P. Williams, M.D. hereby agree that the Schedule 13G to which this Agreement is attached is being filed on behalf of each of...

CUSIP No. 66986W 10 8                                        Page 13 of 13 Pages


                                   EXHIBIT 1

                                 JOINT FILING
                                 ------------

     Xxxxxxx Xxxxxxxx Family Limited Partnership, Xxxxxxxxx-Xxxxxxxx Eye
Institute, P.C. and Xxxxxxx X. Xxxxxxxx, M.D. hereby agree that the Schedule 13G
to which this Agreement is attached is being filed on behalf of each of Xxxxxxx
Xxxxxxxx Family Limited Partnership, Xxxxxxxxx-Xxxxxxxx Eye Institute, P.C. and
Xxxxxxx X. Xxxxxxxx, M.D.

Date:  February 11, 2000

                              XXXXXXX XXXXXXXX FAMILY LIMITED PARTNERSHIP


                              By:  Xxxxxxxxx-Xxxxxxxx Eye Institute, P.C.,
                                   its General Partner


                                   By:  /s/ XXXXXXX X. XXXXXXXX, M.D.
                                        -----------------------------
                                   Its: President


                              XXXXXXXXX-XXXXXXXX EYE INSTITUTE, P.C.


                              By:  /s/ XXXXXXX X. XXXXXXXX, M.D.
                                   -----------------------------
                              Its: President


                              /s/ XXXXXXX X. XXXXXXXX, M.D.
                              -----------------------------
                              Xxxxxxx X. Xxxxxxxx, M.D.