If you can’t see clearly then you’re not safe on your bike. A good pair of glasses or cycling goggles will improve your vision in harsh sunlight and bad weather and protect your eyes from dust and small stones that may fly up as you cycle.
When choosing protective eyewear make sure you get a quality product that can withstand some force like the Rudy Project Rydon Sunglasses Impact X Photochromic for £148.85 or the dhb Triple Lens Sunglasses for £29.99.