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                                                                    EXHIBIT 4.3


                              SECOND AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT




                  This Second Amendment to Amended and Restated Registration
Rights Agreement (the "Amendment") amends that certain Amended and Restated
Registration Rights Agreement dated as of October 21, 1996, as amended pursuant
to that certain First Amendment to Amended and Restated Registration Rights
Agreement dated November 30, 1999, (the "Agreement") by and among SPECTRX,
INC., a Delaware corporation (the "Company") and the holders of Registrable
Securities (as such term is defined in the Agreement).



                              W I T N E S S E T H:

                  WHEREAS, the Company has determined to issue and sell to
George F. Landegger, a resident of the State of Connecticut, The Whittemore
Collection, Ltd., a corporation and T. Brown Badgett, a resident of the State
of Kentucky (collectively, the "Purchasers", and individually each a
"Purchaser") a total of 500,000 shares of common stock, par value $.001 per
share, of the Company ("Common Stock"), and as a condition to the obligation of
Purchasers to purchase shares of Company Stock, the Company and Purchasers
desire to effect an amendment to the Agreement to provide Purchasers with
registration rights in respect of shares of Common Stock to be issued to
Purchasers by the Company;

                  WHEREAS, the holders of at least a majority of the
Registrable Securities for the benefit of the Company have agreed, to induce
Purchasers to purchase the 500,000 shares of Common Stock referenced above, to
amend the Agreement by entering into this Amendment;

                  NOW, THEREFORE, in consideration of the mutual promises and
other terms and conditions set forth in the Agreement and in the agreements
pursuant to which Purchasers will acquire the Common Stock referenced above,
the parties hereto agree as follows:

                  1.       EFFECTIVENESS OF AMENDMENT. The Company and the
holders of Registrable Securities who have executed and delivered this
Amendment below acknowledge


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and agree that the Agreement is hereby amended by this Amendment pursuant to
the provisions of Section 14 of the Agreement whereby any provision of the
Agreement may be amended with the written consent of the Company and the
holders of a majority of the Registrable Securities then outstanding, and
further acknowledge and agree that such Amendment shall be binding upon each
holder of Registrable Securities then outstanding and each future holder of all
Registrable Securities of the Company.

                  2.       AMENDMENT. The parties hereto agree that the
definition of "Registrable Securities" as contained in Section 2 of the
Agreement is hereby amended and restated as follows:

         "Registrable Securities" shall mean (i) the Common Stock issued upon
         conversion of the Series A Preferred Stock, (ii) the Common Stock
         issued upon conversion of the Series A Preferred Stock issued upon
         exercise of certain warrants issued pursuant to the Note and Warrant
         Purchase Agreement dated April 6, 1994, (iii) the Common Stock issued
         upon conversion of the Series A Preferred Stock issued upon exercise
         of certain warrants issued pursuant to the Note and Warrant Purchase
         Agreement dated April 29, 1994, (iv) the Common Stock issued upon
         conversion of the Series A Preferred Stock issued upon exercise of
         certain warrants issued pursuant to the Note and Warrant Purchase
         Agreement dated June 15, 1994, (v) the Common Stock issued upon
         conversion of the Series B Preferred Stock, (vi) the Common Stock
         issued upon conversion of the Series C Preferred Stock, (vii) the
         Common Stock issuable or issued upon conversion of the Redeemable
         Convertible Preferred Stock, (viii) the Common Stock which may be
         issued to Abbott Laboratories pursuant to the Common Stock Purchase
         Agreement dated November 30, 1999, by and between the Company and
         Abbott Laboratories, (ix) the Common Stock which has been issued to
         George F. Landegger, The Whittemore Collection, Ltd., and T. Brown
         Badgett (the "Purchasers") pursuant to the Common Stock Purchase
         Agreement dated of even date herewith by and between the Company and
         the Purchasers and (x) any Common Stock or other securities issued
         with respect to such Series A Preferred Stock, Series B Preferred
         Stock, Series C Preferred Stock, Redeemable Convertible Preferred
         Stock or Common Stock; provided, however, that shares of Common Stock
         or other securities shall only be treated as Registrable Securities if
         and so long as they have not been (i) sold to or through a broker or
         dealer or underwriter in a public distribution or a public securities
         transaction or (ii) sold by a person in a transaction in which their
         rights under this Agreement are not assigned."


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                  IN WITNESS WHEREOF, the parties have caused this Agreement to
be duly executed and delivered by their proper and duly authorized officers as
of the date first above written.

                                    SPECTRX, INC.


                                    By:
                                       -----------------------------------------
                                    Title:
                                          --------------------------------------


                                    HILLMAN MEDICAL VENTURES 1993 L.P.,
                                      a Delaware limited partnership

                                    By:  Hillman/Dover Limited Partnership,
                                         general partner

                                    By:  Wilmington Securities, Inc.,
                                         its sole general partner


                                    By:
                                       -----------------------------------------
                                    Title:
                                          --------------------------------------



                                    NORO-MOSELEY PARTNERS II, L.P.,
                                      a Georgia limited partnership

                                    By:  Moseley & Company, II,
                                         general partner


                                    By:
                                       -----------------------------------------
                                       Jack R. Kelly, Jr.
                                    Title:  General Partner


                                    ABBOTT LABORATORIES


                                    By:
                                       -----------------------------------------
                                    Title:
                                          --------------------------------------


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