While what photosynthesis taking place in midwinter is minimal, Tony Avent from Plant Delights cautions about doing it too early in the harsher zones, you'd be a better judge of your own weather-to-come than I would be but if it helps you:

"One of the winter chores many gardeners engage in is cutting back old hellebore foliage. While we endorse the practice, I'd caution you about doing it too early. I like to wait until the first flowers are just ready to open before removing the old foliage because despite being often tattered, the foliage serves to keep the plant cool and slow down the development of the flower buds. If the foliage is cut too early, the plant develops faster and the buds and flowers reach a size that can become damaged if the temperatures drop into the low- to mid-teens F. If you're a neat freak and have already trimmed your hellebores, a light layer of evergreen branches or pine straw will really help to protect and slow them down in the case of upcoming cold temperatures. The great thing about hellebores is even if the earliest buds are damaged, new buds will still be produced as long as the plant isn't too far along." Tony Avent

Like Mor, my climate allows for cutting back whenever the mood strikes. Personally I am beginning to heavily favor all the newer hybrid forms hitting the market these days that are caulescent and do not require regular cutting back of the foliage. Which is typically too handsome to cut back anyway :-)