We were interested to see an analysis of the carbon footprint of different local anaesthesia techniques for cataract surgery [1]. We agree that topical anaesthesia should be cheaper and more environmentally-friendly than sub-Tenon’s anaesthesia (STA). However, we believe that, in extrapolating data from just three STA’s in Leeds, the authors’ assumptions may not all apply at a national level.

In our unit, STA is almost never used for cataract surgery [2], though we do use STA for vitreo-retinal surgery, and some corneal and glaucoma procedures. With approval from our local clinical audit department, we recently audited our colleagues’ usage of STA. Costs were obtained from our theatre procurement team, though we were unable to assess disposal costs for disposal of non-reuseable equipment. Assumptions for the ‘lifetime’ of reusable equipment are in Table 1.