From Wikipedia:

VTR (view through rate) is an estimation of the number of impressions viewed during the advertising campaign, (as well as estimation of realized advertising contacts).

VTR = 100% * Views / Shows

It gives the subjective attraction of the advertising medium, which consists of medium and advertisement messages. Moreover VTR has direct relations with indexes:

CTR = 100% * Clicks / Shows

CTR reflects the subjective informativeness of the advertisement message (high – click, low – familiarization).

CTI = 100% * Views / Clicks

CTI reflects the subjective consumer’s interest in the advertising message.

CTR(v) = VTR + CTR

CTR(v) (contact through rate based on a view) has objective nature and lets estimate the effectiveness of capture of the consumer attention as a whole (three in one).