Epidemiological studies have identified numerous factors that increase the risk for dry eye disease (DED). Classic examples include increasing age, female gender, thyroid disease, diabetes, and contact lens wear (Moss et al, 2000) as well as Asian race (Chan et al, 2017) and computer/device use (Jaiswal et al, 2019). Smoking contributes to developing chronic obstructive pulmonary disease (COPD) and lung cancer. Depending on study criteria, smoking can decrease life expectancy by 4.3 years up to as much as 9.3 years (Darden, 2018). Smoking is also a well-recognized risk factor for developing dry eye (Moss et al, 2000).

Cigarette smoke contains many components including carbon monoxide, nicotine, and a number of carcinogens including chromium, cadmium, arsenic, lead, nickel, and aldehydes (Zhang et al, 2019). Inhalation of cigarette smoke results in inflammatory cell infiltration into pulmonary mucosa, submucosa, and glandular tissue; over time, this process leads to the destruction of pulmonary matrix, blood supply shortage, and epithelial cell death (Zhang et al, 2019).

Impact on the Ocular Surface

There is ample evidence that cigarette smoke impacts the ocular surface as well. Turkish investigators evaluated 50 subjects who had smoked at least one pack (20) of cigarettes for a minimum of five years compared to 51 subjects who had never smoked (Aktaş et al, 2017). They found significantly mildly elevated tear osmolarity and significantly elevated Ocular Surface Dry Eye Index (OSDI) scores in the smokers compared to the controls.

They also noted significantly reduced goblet cell density in the smokers compared to the non-smokers. Tear film breakup time (TBUT) was reduced in 70% of smoking subjects. Smoking subjects reported foreign body sensation (32%), redness (36%), and itching (42%) compared to only one non-smoking subject (2%) who reported foreign body sensation and itching.

The authors postulate that nicotine in cigarette smoke may trigger inflammation by stimulating macrophages, thereby triggering apoptosis of conjunctival epithelial and goblet cells (Aktaş et al, 2017).

Wang et al (2016) conducted a large study involving 322 smokers who had meibomian gland dysfunction (MGD) and 2,067 non-smokers who had MGD. Subjects underwent evaluation of OSDI, TBUT, corneal fluorescein staining (CFS), Schirmer I test (SIT), meibomian gland expression (MGE), lid margin abnormality (LMA), and meibum quality.

The authors found no significant differences between the study group versus the controls in OSDI, TBUT, CFS, SIT, or MGE, but they did find significant correlation between smoking and the scores of LMA and meibum quality (Wang et al, 2016).

The Recommendation Is Clear

The long-recognized association between smoking and the development of macular degeneration compels eyecare providers to be especially diligent when evaluating smokers’ retinas (Myers et al, 2014). Given the importance of the tear film in vision and day-to-day functioning, it seems only logical for eyecare providers to also give special attention to the ocular surfaces of patients who smoke as well as to educate them regarding the multiple ocular risks and encourage them to consider cessation (Jha et al, 2013). CLS

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