For its latest collection of high-end eyewear, the British brand Cutler and Gross found inspiration from an unlikely source: the circus. The muses for the London-based label—known for its bold, fashion-forward designs—were the traveling circus performers of the 1940s. The new Circus Collection (priced from $500 to $900) comprises a troupe of 12 men’s and women’s sunglasses and opticals in a variety of colors, from a gun-metal gray to a glittery ruby red. The Ringmaster, the collection’s principal men’s model, …