Heavy smoking is associated with visual field loss in glaucoma
1. In a cohort of approximately 500 eyes with primary open-angle glaucoma (POAG), higher smoking intensity in pack-years was significantly associated with faster worsening on visual field (VF) tests.
2. Baseline smoking history of 20 or more pack-years was associated with a higher risk of VF progression over a median follow-up of 12.5 years, although light and moderate smoking history were not .
Level of evidence assessment: 2 (good)
Summary of the study: Despite the prevalence of glaucoma and the known contribution of smoking to many chronic diseases, the role of smoking as a risk factor for the onset and progression of glaucoma remains unclear. This multicenter retrospective cohort study aimed to show a clinical relationship between smoking and the progression of primary open-angle glaucoma (POAG). Over 500 eyes of approximately 350 POAG patients were followed using visual field (VF) testing for a median of 12.5 years. Subjects with a history of smoking did not have significantly different rates of VF worsening from those who did not. However, pack-year smoking intensity was significantly associated with more rapid worsening of VF over the duration of the study. In multivariate models adjusted for age, body mass index (BMI), and baseline ocular characteristics including intraocular pressure (IOP), patients who had a history of heavy smoking 20 packs -years or older at baseline were 74% more likely to progress based on VF over the study period than those who had never smoked. History of light and moderate smoking were not associated with increased risk. This is one of the first high-quality studies to show a positive association between smoking and the clinical progression of glaucoma. The analysis only included cumulative smoking history at baseline, rather than current smoking intensity or smoking cessation status, which limits the applicability of the results for counseling patients who have a history of smoking. Although several mechanisms have been proposed for the harmful effects of smoking on eyes with POAG, including increased oxidative stress and changes in microvascular blood flow, further studies are needed in order to shed light on possible therapeutic pathways. .
Relevant reading: Risk factors for onset and progression of glaucoma
In depth [ retrospective cohort]: Patients enrolled in two cohort studies at four medical centers were included. Patients received annual eye examinations. VFs were assessed using the Humphrey Field Analyzer. Smoking history and intensity in pack-years were self-reported; 42.1% of patients had ever smoked and 11.0% were defined as heavy smokers based on a history of more than 20 pack-years. Patients with at least three years of follow-up and at least five VFs were included. Patients with more than 33% false negative or false positive errors in VF testing were excluded. Glaucoma severity was classified as early or moderate based on mean deviation (MD) over 24-2 VF. Multivariate models fitted for IOP, central corneal thickness and baseline DM. Every 10 pack-years of smoking was associated with a decrease of 0.05 dB per year in MD (95% confidence interval -0.08 to -0.01 dB/year). A Kaplan-Meier survival analysis was also performed to compare rates of progression, defined as a significant negative change in DM for at least two visits, between heavy smokers and non-smokers.
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