Compare nylon and polycarbonate lenses by Abbe value, how coatings alter finished-lens safety, and what works best for foldable sunglasses so you pick...
Pack a pocket sized kit and learn three optics safe methods, wipes, spray and microfiber, or soap and water, to keep sunglasses streak free while traveling.
Choose metal or acetate for travel. Learn when foldable metal packs best, when acetate wins on colour, and what to check for fit, allergy risk, and UV.