Q A friend appeared the other night with rather stunning eye make-up, which she said was down to ‘tightlining’. Can you explain? A ‘Tightlining’ eyes refers to the technique where you line the inside of your lash rim, along the waterline, instead of outside.

If well done, it can indeed subtly enhance eyes. But it is not without risks, according to research published last year in the journal Eye and Contact Lens Science and Clinical Practice.

Researchers observed that, within a few minutes, the make-up started to move into the eye’s tear film. (They used glitter liner so they could see the particles moving.) Potential risks include redness, soreness and irritation, or - more seriously - blurring, double vision and infection if this technique is used regularly.

People who wear contact lenses are most likely to have problems as the liner may stick to the lenses. Everyone should always remove eye make up thoroughly before bed

Sarah finds having tightlining applied is a bit queasy-making since it involves pulling up your upper eyelid in order to apply the liner on the inner lid. She also tends to finish the day with pink-tinged, sore eyes. So she’s not a fan and sticks with Charlotte Tilbury Rock ‘n’ Kohl, iconic liquid eyeliner pencil, £19, smudged outside the lashline.

Jo, however, has been a fan of tightlining since Laura Mercier pioneered it some years back. She swears by Laura Mercier Tightline Cake Eye Liner, £19.50 at johnlewis.com, which she applies herself (or pops into a Laura Mercier counter if she is nearby).