Cataract surgery is the most performed operation on the planet, yet no one has measured what it costs the planet. This prospective study analyzed 1,000 standalone phacoemulsification cases across two hospitals using identical surgical outcomes but radically different resource systems. The NHS produced 128.3kg CO2 per case; Bangladesh just 17.1kg, 86% less carbon and 87.8% less waste, with zero endophthalmitis and comparable patient satisfaction in both settings. The difference? Single-use instruments, continuous climate control, and underfilled sterilization cycles on the NHS side, versus reusable instruments, batch sterilization, and multi-dose medications in Bangladesh. Scaled across the UK's annual cataract volume, this gap represents +55.6 Tonnes CO2,  equivalent to 325,000 km of car travel, from the same operation. With 96% of surgeons globally saying cataract waste is excessive and 92% wanting more reusable instruments, the will is there. The method is now too, we're sharing the full Green Cataract Surgery Blueprint so any hospital in the world can measure their own.