In the past, I’ve been guilty of impulse-buying sunglasses – like the Celine ones that were much too heavy for my small nose to keep up, so ended up being passed on to my mum, or the multiple Accessorize and Topshop pairs that I’ve bought at airports, having forgotten to pack a single pair for a week-long beach holiday.

But the right – or wrong – pair of sunglasses can transform your face, as I found recently when I met with UK-based Robert Roope for a fitting.

Roope has been an optician for 50 years, and launched his own label of opticals and sunglasses, Black Eyewear, 15 years ago.

According to Roope, even those of us who have identified a frame shape that suits us will then overlook the little details – which prompted me to draw up a guide to navigating said details while shopping, and ending up with your perfect pair.

[What your eyes reveal about your stress level]

1. Shop by shape

Trends are all well and good, but if last year’s tiny-sunglasses trend taught us

one thing, it’s that what works for Rihanna doesn’t work for the everywoman. Those teeny pairs made all but the most sculpted of faces look inflated, and at the other end of the spectrum, supersized frames can swamp a smaller face. Consult our face-shape guide (see guide below) for a steer on what may suit, then try on as many pairs as you can – this is not a purchase to make online.

2. Consider skin tone

After identifying my preferred shape (cat eyes) I gravitated towards a black pair – my reasoning being that they’d go with everything in my wardrobe, like a black handbag or pair of shoes. But if black can be too severe in dress form, just think of how unflattering it can be on the face. Tortoiseshells are a softer wear-with-everything alternative to black: Roope steered me towards an unusual pale iteration that works with my honey blonde (from a bottle) hair and fair skin. If you’re prone to redness, avoid that colour in your frames – try blues and greens instead. And if you’re considering a bright colour, think of it in combination with the colours in your wardrobe, or even your favourite lipstick – does it complement or clash?

3. Try them outside (or at least by a window)

Since you’ll be wearing your new sunglasses in sunlight, seek out the brightest natural light you can find in store – short of climbing into the window display – for the truest preview.

4. Invest in quality

The point of sunglasses is to shield your eyes from UV rays, so make sure you buy a pair that does. Anything less is a waste of money, no matter how low the price tag.

5. Bring a hairband

If you fluctuate between wearing your hair up and down, don’t forget to try a potential new pair with it worn both ways. Hair worn down may soften a shape that’s too angular for you, but if that’s the case you’ll be able to tell once you tie your hair up.

6. Pay attention to the bridge

‘The keyhole bridge will usually make the nose look longer and wider,’ says Roope, while ‘the regular bridge is most effective when used to shorten and narrow the nose shape.’ Specialist opticians will offer both, and be able to guide you to the bridge that suits you.

7. Avoid jewellery-clash

Sunglasses are an accessory, and they should complement everything else. If you only wear silver jewellery, look for frames with silver metal finishing. If you often wear large earrings, you may want to choose a more understated pair of shades that won’t dominate an outfit.

8. Don’t hide your eyebrows

‘The position of the eyebrows in relation to the top rim of the frame is important,’ says Roope. ‘The top rim should not sit too high above the brow line as this can have the effect of making the face appear much longer.’ Instead, look for frames that sit either just above the brow line, or below – though in that case, you’ll need to look for a shape that complements your brow shape.

9. Don’t stop at one

You wouldn’t expect one pair of shoes to see you through every occasion, but many ask that of their sunglasses. After coordinating your hat to your dress, shoes and bag, why ruin the look with the wrong pair of sunglasses? Instead, you need a rotating shade-robe of options to suit every occasion.

Shopping by shape

The most flattering frames will be a pair that suits your face shape. While your features – especially your nose and brow bone – will make a difference too, here are the basic rules for getting the outline right.

• Oblong faces: Try oversized square shapes, like this season’s Seventies styles

• Heart faces: Try pointy cat eyes

• Square faces: Try round or oval frames

• Diamond faces: Try frames with an upswept curve at the top

• Pear faces: Try oversized frames that add width

• Round faces: Try square or angular frames

• Oval faces: Try rounded cat eyes