Japanese to English Medical Marketing / Market Research

This appears in the following sentence.
現場の本当に勉強したい先生は、少し遅れて入ってくる（地方は遅い）各製品の話題より最新の話を旬のうちにオピオン医師の話が聞きたいとの声が増えているように思います。
The context is a series of responses to an employee questionnaire carried out by a pharmaceutical company. This particular employee is complaining about the lack of resources available to drug company reps in conducting marketing aimed at doctors. He then gives some suggestions. This is one of them. I have no idea what "opion ishi" means. Any comments are appreciated.