Environmental impact and end-of-life options of disposed polymeric spectacle and contact lenses

Abstract

Background: Global population growth and ageing are factors that contribute towards an anticipated increase in the usage of spectacles and contact lenses for vision correction. The subsequent disposal of polymeric vision corrective devices currently, has uncertain environmental impacts.

Aim: The purpose of this study was to explore potential environmental impacts and end-of-life (EOL) pathways of a sample of polymeric spectacle lenses and through the use of analytical chemistry processes.

Setting: Laboratory analysis of ophthalmic lenses.

Methods: Inductively coupled plasma–optical emission spectroscopy (ICP–OES), elemental analysis and calorific value investigations were conducted on a sample of spectacle lenses and contact lenses.

Results: Metal ion analysis by ICP–OES confirmed the presence of manganese in all the lenses and chromium in two of the 13 contact lenses. All of the lenses had over 42% carbon while calorific values of up to 32.40 MJ/kg and 23.31 MJ/kg were found in the spectacle lenses and contact lenses, respectively.

Conclusion: Further investigation is required regarding the presence of chromium in two of the contact lenses. In general, lenses are likely to remain as solid waste in landfills depending on the disposal conditions. Considering their calorific values, lenses would be useful in incineration with energy recovery processes however the suggested ideal EOL route would be the implementation of lens recycling, through non-toxic and green chemical processes, to retain material value and promote a circular economy.

Contribution: This study provides new information on the environmental consequences of current modes of lens disposal and suggests EOL alternatives thereof.