Koo Nebula glasses

The Koo Nebula sunglasses are extremely light, frameless shades with nothing to obstruct your vision. They’re secure, really comfortable and stylish – if you can afford them.

While the Nebula range starts at £170, the Photochromic Graphite Mirror lens version I tested costs £200. You can get a clear lens to swap to for £75 extra.

That puts the Nebula close to the top of the cycling sunglasses market, which I think their performance justifies.

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Much of what makes these great stems from the frameless design. The absence of material around the lens reduces weight to a scant 22g – very light both for this style and in absolute terms.

Clearly it won’t transform your climbing times, but it does make the Nebulas barely noticeable on your face. The arms gripped tenaciously to my temples without building up any pressure.

The second benefit of the frameless design is panoramic vision. Wherever I looked and whichever position I was in, including down in an aero-tuck, I found nothing obstructed my line of sight. Some of you may prefer the aesthetics of a full frame, but for low weight and great vision, frameless wins hands down.

The Zeiss toric lens is impressive. Zeiss says its nylon/polyamide lenses are lighter than polycarbonate (another common material), and they’re very clear. Impact resistance is also good thanks to the material’s flexibility.

Being slightly short-sighted I like to wear prescription inserts, but like many frameless designs the Nebulas aren’t compatible with RX inserts. However, lens clarity was so good both on and off road I felt less need for my inserts than when wearing lower grade lenses.

With the Visible Light Transmission ranging widely from 14% at the darkest end to 73% at the lightest, these took the glare out of low winter sun but still turned clear enough when the sky clouded over. Note that the other photochromic Nebula lens has a much narrower range of 10-43% VLT, so won’t be quite so suited to those dull UK days.

I found the Nebula’s anti-fogging properties flawless. While pushing hard on chilly, misty days and in the wet – conditions which often cause fogging – the lens stayed clear.

Koo supplies the Nebula with low and high nose bridges, which are easy to swap, and a soft bag. The lack of a proper protective hard case is disappointing given the price.

Value

Koo is firmly in the ‘luxury’ part of the market and consequently it’s at the upper end for price. They’re not the most expensive, however, given their specifications.

These are priced just under the now-£209 Rudy Project Astral Spheres, for instance, which are also frameless and photochromatic.

They’re cheaper than £250 POC Elicit Toric Bikes, which are frameless but not light-sensitive, and within a fiver of the £195 Scicon Aeroscope Sport Performance which have regular frames and standard lenses.

If you’re looking for performance without the premium, the £79.99 Van Rysel Cycling NXT Photochromatic Sunglasses RoadR 900 Perf is a great choice, as are the £59.99 Magicshine Rouleur Colour Photochromic Sunglasses. Both scored 9/10.

Overall

If prescription lenses are a must for you, the Nebulas are a no-go – personally I’d consider paying extra for the insert-compatible Astral Sphere. However, if you’re borderline like me, you may find the clarity of these lenses let you get away with it. Lack of RX compatibility aside, these lightweight, comfortable and light-reactive sunglasses perform brilliantly.