The effect of smoking on ocular surface and tear film based on clinical examination and optical coherence tomography

Evaluation of Dry Eye Parameters Among Electronic Cigarette Smokers

Introduction  The emergence of electronic cigarettes as the "healthier" version of smoking has been popular, especially among young adults. However, knowledge about the potential effects of e-cigarettes on ocular structures is scarce. Objective  To compare the mean change in dry eye parameters between e-cigarette smokers and non-smokers and to correlate between dry eye parameters with device power output. Methodology A cross-sectional, single-visit study was conducted involving 85 e-cigarette smokers and 85 non-smokers. All participants were evaluated on dry eye parameters, including the Ocular Surface Disease Index (OSDI) score, tear meniscus height (TMH), tear break-up time (TBUT), cornea fluorescein staining, and Schirmer's I test. The mean change in dry eye parameters was compared between e-cigarette smokers and non-smokers. The correlation between dry eye parameters with device power output was analyzed. Results Specifically, 32.94% of e-cigarette smokers were found to have a TMH <0.2 mm, compared to only 5.88% of non-smokers (p<0.001). A significant change in mean TBUT was found between the e-cigarette smokers (10.41+2.65 seconds) and non-smokers (12.66+3.14 seconds, p<0.001). The lower mean Schirmer's I test was found among e-cigarette smokers (12.75+7.24 mm, p<0.001). No significant change in the median OSDI score and corneal fluorescein staining. The OSDI score and device power output were found to have a significant positive correlation (p=0.003). There was a significant association between dry eye signs and device power output, including TMH (p=0.047), TBUT (p=0.002), Schirmer's I test (p<0.001), and corneal fluorescein staining (p<0.001). Conclusion Electronic cigarette smokers are prone to develop dry eyes. Concern should be raised on the risk of electronic cigarette use on ocular health, and regulation on e-cigarette ban should be revisited.

Secondhand smoke exposure and ocular health: A systematic review

The toxicology of secondhand smoke (SHS), along with the harm of its exposure to human health, has been generally acknowledged; however, specific evidence is lacking on the association between SHS exposure and ocular health. In this systematic review (PROSPERO registration number: CRD42022247992), we included 55 original articles published by 12 May 2023, which dealt with SHS exposure and ocular disorders, such as eye irritation, conjunctivitis, dry eye diseases, uveitis, myopia, astigmatism, contact lens discomfort, age-related macular degeneration, glaucoma, and thyroid eye disease that addressed the ocular neurovascular structures of the macular, retinal nerve fiber layer, choroid, and corneal biomechanical parameters. We found compelling correlational evidence for eye irritation, conjunctivitis, and dry eye symptoms-supporting that SHS exposure was positively associated with inflammatory and allergic changes in the eyes. Yet, evidence about the associations between SHS exposure and other ocular disorders, structures, and parameters is still limited or controversial. Given the limitations of existing literature, more investigations with high quality and rigorous design are warranted to elucidate the potentially harmful effects of SHS exposure on ocular health.

Tobacco effects on ocular surface, meibomian glands, and corneal epithelium and the benefits of treatment with a lipid-based lubricant

PURPOSE

Our aim was to evaluate the ocular surface in chronic smokers and to assess the benefit of sodium hyaluronate (SH) versus semi-fluorinated alkane (SFA) eyedrops on tear film, meibomian glands, and corneal epithelial thickness (CET).

METHODS

This prospective randomized single-blinded study included smokers, who applied one eyedrop of Hyabak® on one eye (SH group) and one eyedrop of EvoTears® on the fellow eye (SFA group) 4 times daily for 2 months, and age-matched non-smokers. Ocular surface parameters, including tear film break-up time (TBUT) test and corneal fluorescein staining (CFS) score, lipid layer thickness (LLT), meibography (LipiView®), and CET measurements (Zeiss Cirrus HD-5000®), were assessed at baseline and after treatment.

RESULTS

Seventy-eight eyes were included in the smokers group (39 in the SH subgroup and 39 in the SFA subgroup) and 42 eyes in the control group. At baseline, the smokers group had a higher prevalence of dry eye (100% vs 0%, p < 0.001) and of meibomian gland dysfunction (MGD) and lower CET measurements than controls (p < 0.05). TBUT, CFS, and LLT (controls vs SFA group: 64.02 ± 1.87 nm vs 49.56 ± 4.33 nm, p = 0.05) improved in the SFA subgroup after treatment, but not in the SH subgroup, and became equivalent to those of controls. Prevalence of dry eye decreased in the smokers group after treatment (controls vs SH group vs SFA group: 0% vs 12.82% vs 16.26%, p > 0.05). Meibomian gland morphological parameters and CET did not improve after treatment (p < 0.05).

CONCLUSIONS

Smoking is associated with dry eye, MGD, and corneal epithelial thinning that seem to be only partially reversible with topical lubricants, preferably SFA.

Diurnal changes of noninvasive parameters of ocular surface in healthy subjects before and after continuous face mask wearing during the COVID-19 pandemic

To investigate whether diurnal changes in noninvasive ocular surface parameters and subjective symptoms occur in healthy subjects wearing face mask who were analyzed before and after 8 h of continuous use. In this prospective cross-sectional study, healthy volunteers attending the same workplace environment underwent a noninvasive ocular surface workup by means of Keratograph 5 M (Oculus, Wetzlar, Germany) in the same day at 2 different time points: (i) in the early morning before wearing face mask (T0); (ii) after 8 h of continuous face mask use (T1). Noninvasive break-up time (NIBUT), tear meniscus height (TMH), ocular redness and meibomian gland dropout were measured. All subjects were asked to complete the Ocular Surface Disease Index (OSDI) questionnaire before and after 8 h of face mask wearing. Data from 20 healthy subjects (10 males and 10 females, mean age 25.1 ± 3.9 years) were included. Mean value of TMH decreased significantly from 0.29 ± 0.07 at T0 to 0.23 ± 0.07 mm at T1 (P < 0.001); conversely, mean values of NIBUT, redness score and meibomian gland dropout did not change significantly after continuous face mask wearing (always P > 0.532). Concerning ocular discomfort symptoms, mean value of OSDI score worsened significantly at T1 compared to T0 (from 12.9 ± 12.6 to 19.4 ± 12.0; P = 0.017). Continuous face mask wearing for 8 h led to decreased TMH associated with the onset of ocular discomfort symptoms in young healthy subjects.

Association of dry eye disease with smoking: A systematic review and meta-analysis

There is conflicting evidence for the association between smoking and dry eye disease (DED). We conducted a meta-analysis to determine the true relationship between smoking and DED. A systematic literature search was performed using electronic databases, including PubMed, Embase and Cochrane Library, till August 2021 to identify observational studies with data on smoking as risk factor of DED. Quality assessment of the included studies was conducted using Joanna Briggs Institute (JBI) critical appraisal checklists. The random-effects model was used to calculate the pooled odds ratio (OR). Heterogeneity was evaluated by Cochrane Q and I² index; in addition, subgroup, sensitivity, and meta-regression analyses were performed. Publication bias was assessed using funnel plot and Egger’s regression test. A total of 22 studies (4 cohort and 18 cross-sectional studies) with 160,217 subjects met the inclusion criteria and were included in this meta-analysis. There is no statistically significant relationship between current smokers (OR_adjusted = 1.14; 95% CI: 0.95–1.36; P = 0.15; I² = 84%) and former smokers (OR_adjusted = 1.06; 95% CI: 0.93–1.20; P = 0.38; I² = 26.7%) for the risk of DED. The results remained consistent across various subgroups. No risk of publication bias was detected by funnel plot and Eggers’s test (P > 0.05). No source of heterogeneity was observed in the meta-regression analysis. Our meta-analysis suggest current or former smoking may not be involved in the risk of dry eye disease. Further studies to understand the mechanism of interaction between current smokers and formers smokers with DED are recommended.