<PAGE>

                                                                    EXHIBIT 31.2

                                  CERTIFICATION

I, Timothy R. Maier, certify that:

     1.  I have reviewed this quarterly report on Form 10-Q of VISX,
         Incorporated;

     2.  Based on my knowledge, this report does not contain any untrue
         statement of a material fact or omit to state a material fact necessary
         to make the statements made, in light of the circumstances under which
         such statements were made, not misleading with respect to the period
         covered by this report;

     3.  Based on my knowledge, the financial statements, and other financial
         information included in this report, fairly present in all material
         respects the financial condition, results of operations and cash flows
         of the registrant as of, and for, the periods presented in this report;

     4.  The registrant's other certifying officer(s) and I are responsible for
         establishing and maintaining disclosure controls and procedures (as
         defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the
         registrant and have:

             (a) Designed such disclosure controls and procedures, or caused
             such disclosure controls and procedures to be designed under our
             supervision, to ensure that material information relating to the
             registrant, including its consolidated subsidiaries, is made known
             to us by others within those entities, particularly during the
             period in which this report is being prepared;

             (b) Evaluated the effectiveness of the registrant's disclosure
             controls and procedures and presented in this report our
             conclusions about the effectiveness of the disclosure controls and
             procedures, as of the end of the period covered by this report
             based on such evaluation; and

             (c) Disclosed in this report any change in the registrant's
             internal control over financial reporting that occurred during the
             registrant's most recent fiscal quarter (the registrant's fourth
             fiscal quarter in the case of an annual report) that has materially
             affected, or is reasonably likely to materially affect, the
             registrant's internal control over financial reporting; and

     5.  The registrant's other certifying officer(s) and I have disclosed,
         based on our most recent evaluation of internal control over financial
         reporting, to the registrant's auditors and the audit committee of the
         registrant's board of directors (or persons performing the equivalent
         functions):

             (a) All significant deficiencies and material weaknesses in the
             design or operation of internal control over financial reporting
             which are reasonably likely to adversely affect the registrant's
             ability to record, process, summarize and report financial
             information; and

             (b) Any fraud, whether or not material, that involves management or
             other employees who have a significant role in the registrant's
             internal control over financial reporting.

         /s/ Timothy R. Maier
         ------------------------------
         Timothy R. Maier
         Chief Financial Officer
         July 31, 2003