The number of cigarettes a patient with normal-tension glaucoma smokes per day—but not the number of years they’ve been smoking—was associated with poorer visual function in this study. Photo: Getty Images.

Though the relationship between smoking and glaucoma is controversial, current evidence does suggest that tobacco smoke plays a role in the development of ischemia and oxidative alterations in ocular tissues. A recent study was conducted in Serbia to determine whether smoking patterns might be related to vision-related disability among the different subtypes of glaucoma. It found that a higher number of cigarettes smoked daily was associated with poorer visual impairment only among people with normal-tension glaucoma (NTG), but not the other subtypes.

The cross-sectional study included 283 patients with primary open-angle glaucoma, primary angle closure glaucoma, NTG and pseudo-exfoliative. Information about the duration and quantity of smoking was self-reported. To quantify vision-related impairment, each patient completed a validated Glaucoma Quality of Life-15 questionnaire.

After adjusting for nine confounding variables, including age, gender, glaucoma severity, IOP level and lifestyle, the data revealed that the number of cigarettes smoked per day was negatively correlated with vision-related quality-of-life among people with NTG subtypes. Smoking duration (in years), on the other hand, did not show the same association in NTG patients.

“It is believed that NTG is a distinctive subtype of glaucoma that is characterized by a somewhat different pathogenesis compared to other glaucoma subtypes,” the researchers wrote in their paper on the study, published in Ophthalmic Epidemiology. This unique pathogenesis may involve ocular blood flow disruption and vascular dysregulation, which also describes the suspected effect of tobacco on ocular tissue, they pointed out.

Oxidative stress may be another nicotine-dependent mechanism at the sub-cellular level that could contribute to worsening visual function. “It has been identified that tobacco smoking can induce cell inflammation and apoptosis in the eye tissue,” the researchers noted in their paper. “This finding is in accordance with the notion that, in glaucoma, retinal ganglions and cells of the trabeculum die by apoptosis.”

Regarding the lack of an association found between smoking duration and worse visual functioning in NTG patients, the researchers note that some literature describes a protective effect of nicotine on the optic nerve and suggests it may improve the structure’s blood supply. “This could potentially explain why long and moderate cigarette smoking was not found to be a risk factor for the onset of glaucoma [and] could also be the underlying reason as to why there are so many controversies when the association between tobacco and glaucoma is being assessed,” the study authors wrote.

Limitations of this study include the self-reporting of smoking habits and visual impairment, which introduces inherent bias, as well as the fact that the majority of participants were Caucasian, despite the higher prevalence of certain glaucoma subtypes in people of Asian and African descent.

In conclusion, the authors wrote, “Our findings highlight the need to examine smoking habits among people with glaucoma, especially among people with NTG, during their health checks and address the issue of smoking as a potential harmful factor that may further damage their vision-related functioning.”