A study in the US has advanced understanding of how smoking damages the eye and may contribute to blindness. 

Age-related macular degeneration (AMD) is the leading global cause of visual impairment and blindness in people aged over 50. The condition leads to the malfunction of retinal pigment epithelial (RPE) cells, which protect and maintain the eye's lightreceptors, necessary for sight. People who smoke are around four times more likely to develop AMD than non-smokers. 

Researchers at Johns Hopkins Medicine examined how cigarette smoke affects RPE cells from young and aged mice after short-term exposure and after daily exposure for four months. Both acute and chronic exposure caused RPE cells to form abnormal clusters, reduced the activity of genes needed for normal eye function and limited access to chromatin, restricting the cells’ ability to switch on protective genes through epigenetic regulation.In both cases, young RPE cells activated a subset of genes that protect cells against age-related damage and survived, while older cells did not and were more likely to die.  

Analysis of RPE cells from healthy individuals and AMD patients identified 1,698 genes with similar activity changes in both mice and humans, indicating shared ageing-related mechanisms that may contribute to AMD. 

“Knowing environmental stress can interfere with the eye’s ability to produce the genes needed to stay healthy, we now want to narrow down which changes are temporary and which are permanent,” said James T. Handa, from Johns Hopkins Medicine and senior author of the study published in the Proceedings of the National Academy of Sciences.