Thermal testing of ophthalmic lenses to establish environmental impact: Implications for sustainable waste management practices and training for healthcare professionals

Abstract

Clinical relevance: Healthcare professionals have a crucial role as environmental stewards, and comprehensive, accessible information is required to improve sustainable waste management practices in healthcare. Eyecare practitioners need to be cognisant of the environmental impact of their disposal practices. Background: Polymeric spectacle and contact lenses are typically discarded after a specific period of wear. Upon waste bin disposal, they are deposited in landfill sites where their decomposition rates and consequent environmental impact is currently uncertain. This study aimed to determine the onset of decomposition temperature and the subsequent thermal responses of various spectacle and contact lenses to predict the environment consequences of lens disposal and to guide eyecare practitioners with sustainable waste management practices. Method: Simultaneous thermogravimetric analysis and differential scanning calorimetry techniques were conducted on a sample of uncoated, coated, and tinted spectacle and contact lenses. Results: The lowest extrapolated onset of decomposition temperature of the lens sample was ~249°C. Heat flow results indicated exothermic behaviour during the thermal analysis. Some samples exhibited release of undetermined content, potentially attributable to moisture loss or volatile compounds. Conclusion: Spectacle and contact lenses can be considered as thermally stable as they are unlikely to encounter temperatures above 249°C upon disposal under natural landfill conditions, and therefore the study lenses are predicted to persist as solid waste. The increasing volumes of landfilled plastics pose an environmental threat due to persistence and associated methane emissions. Therefore, alternate end-of-life measures, such as lens recycling or utilisation in controlled energy recovery facilities should be considered. The findings highlight the necessity of integrating sustainable waste management into health sciences curricula and continuing education programs for healthcare practitioners. Educating healthcare professionals on the environmental impact of disposal practices and sustainable methods is essential for reducing the sector's ecological footprint and fostering environmental responsibility.