Smoking and RNFL Thinning in POAG

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Smoking is associated with cataract and age-related macular de­generation, but its effect on glaucoma progression is still unknown. Research­ers at the Hamilton Eye Center at the University of California San Diego have moved closer to establishing a link: in a recent study, they found that smoking intensity is associated with faster rates of retinal nerve fiber layer (RNFL) thinning in patients with primary open-angle glaucoma (POAG).¹

The findings build on an earlier study by the San Diego researchers, which found that visual field progres­sion in eyes of heavy smokers was 2.2 times greater than in eyes of patients with no smoking history,² said Sasan Moghimi, MD.

“The [latest] findings support [the hypothesis] that smoking severity might add information to the assess­ment of risk of glaucoma progression,” said Dr. Moghimi. Moreover, they might be used to develop intervention strategies for this modifiable risk factor.

EVALUATING RISK. Researchers have found a direct dose-response relationship between smoking and RNFL thinning in patients with POAG.

Looking at longitudinal progres­sion. The researchers evaluated 314 patients (466 eyes) enrolled in two studies: the UCSD Diagnostic Innova­tions in Glaucoma Study (DIGS) and the multicenter African Descent and Glaucoma Evaluation Study (ADAG­ES). Patients received at least three years of follow-up and a minimum of five OCT imaging visits to measure RNFL thickness.

Smoking intensity was calculated by pack-year, a standard measure of the amount a person smokes over time. For example, a 10 pack-year is equal to smoking two packs per day for five years, or five packs for two years.

Dose response. Of the 314 patients, 118 (38%) reported a history of smok­ing, with 55 reporting 0-10 pack-year, 25 reporting 10-20 pack-year, and 38 reporting 20 or more pack-year.

There was a direct dose-response re­lationship between smoking and RNFL thinning; each 10 pack-year was associ­ated with .06 μm per year faster RNFL thinning. Overall, RNFL thinning increased significantly when smoking intensity exceeded 8 pack-year.

Race and other variables. The researchers also considered current alcohol consumption, which was self-reported by 136 patients (57.1%), and body mass index (mean, 27.9 kg/m2). Neither variable significantly affected rates of RNFL thinning.

In addition, although patients of African descent experience a dispro­portionate burden of POAG, racial differences did not emerge as a factor in the effect of smoking intensity on the rate of RNFL thinning in this study. However, as the authors pointed out, additional research is needed to clarify the interplay between race, smoking cessation, and glaucoma progression.

A modifiable risk factor. “Assess­ment of progression in the presence of risk factors for structural change may help clinicians in customizing the intensity of glaucoma therapy in high­er-risk patients,” Dr. Moghimi said. He added that clinicians can recommend smoking cessation, particularly for patients who are heavy smokers, to slow down glaucoma progression.

Going forward. Future studies are needed to evaluate the impact of heavy smoking on RNFL thinning, the authors emphasized.

—Miriam Karmel

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1 Nishida T et al. Br J Ophthalmol. Published online Sept. 13, 2022.

2 Mahmoudinezhad G et al. Ophthalmology. Published online June 23, 2022.

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Relevant financial disclosures: Dr. Moghimi—None.

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