Ths artical linked below gave thorough analysis on the issue. Vitronics case is not the model case followed by most cases after Markman. It may well be the most extreme example of court opinions what minimize the value/usefulness of extrinsic evidence, as indicated by the author.

Here are some quote from this artical -

"The Markman decisions, however, did not actually prevent a party’s use of extrinsic evidence to show how the skilled artisan would construe the claims.7 Thus, the outright ban, seemingly championed by Vitronics, on extrinsic evidence where the intrinsic evidence purportedly sufficed to construe the claims, may have unwittingly gone beyond the holdings in the Markman decisions. Indeed, Federal Rule of Evidence 702 provides that expert testimony is admissible to educate the court, and the Supreme Court has cautioned against rigid rules for excluding expert testimony emphasizing that, as gatekeeper, the trial court is given broad latitude to determine how much weight should be accorded to relevant expert testimony.8 Not surprisingly, other panels of the Federal Circuit instinctively were compelled to modify Vitronics’ rigid rule of construction.9 Given that trial judges, absent guidance, are not in a position to understand how the skilled artisan would interpret contested claim terms, a rule limiting the evidence that judges may receive has not been well-received.10"

"Vitronics does not prohibit courts from examining extrinsic evidence, even when the patent document is itself clear...Moreover, Vitronics does not set forth any rules regarding the admissibility of expert testimony into evidence. Certainly, there are no prohibitions in Vitronics on courts hearing evidence from experts. Rather, Vitronics merely warned courts not to rely on extrinsic evidence in claim construction to contradict the meaning of claims discernible from thoughtful examination of the claims, the written description, and the prosecution history--the intrinsic evidence ... '[Expert] testimony [on the proper construction of a disputed claim term] may only be relied upon if the patent documents, taken as a whole, are insufficient to enable the court to construe disputed claim terms. Such instances will rarely, if ever, occur.' Thus, under Vitronics, it is entirely appropriate, perhaps even preferable, for a court to consult trustworthy extrinsic evidence to ensure that the claim construction it is tending to from the patent file is not inconsistent with clearly expressed, plainly apposite, and widely held understandings in the pertinent technical field.12"

"Extrinsic Evidence
Accordingly, if desired, extrinsic evidence should be offered to the trial judge, at least to influence the claim construction decision with the goal of ensuring that the court-ordered claim construction is not completely at odds with the understanding of the skilled artisan."