Meibomian glands secrete meibum, an oily substance that prevents evaporation of the eye's tear film.

睑板腺分泌油脂，这是一种防止泪膜蒸发的油性物质。

The tear film on the front of your eyes is there all the time, not just when you cry.

眼表的泪液膜一直都在，不哭的时候也在。

" The tear film on the front of your eyes is there all the time, not just when you cry. It’s less than a tenth of the thickness of a human hair, but without it, you wouldn’t see at all" .

角膜前面的泪膜不只是当你流泪的时候才存在。其厚度仅相当于人类头发丝的十分之一，但没有它，你根本就看不到东西。"