Effect of cigarette smoking on precorneal tear film

Aim This study aimed to evaluate the effects of smoking on the ocular surface and tear film in active smokers. Patients and methods This prospective, cross-sectional, descriptive study was conducted at Kasr Al-Ainy Hospital, Cairo, Egypt on 40 regular daily smokers and 40 nonsmokers as a control group. All participants were subjected to a comprehensive ophthalmic examination, including history taking and standard clinical tests. The ocular surface assessment included the ocular surface disease index questionnaire, Schirmer’s test, and precorneal tear film evaluation using the “Mediworks D-130 Dry Eye Diagnostic System.” Results The smoking group had a significantly higher proportion of males compared with the nonsmoking group ( P <0.001). While no significant difference was observed in the overall ocular surface disease index scores between the two groups ( P >0.05), the moderate category (having 23–32% score points) showed a significantly higher percentage of smokers ( P =0.029). The clinical data revealed no significant differences between smokers and nonsmokers regarding best-corrected visual acuity or intraocular pressure ( P >0.05). Similarly, the Schirmer’s test results showed no significant difference ( P >0.05) except for the basal secretion test (test 2) in the left eye ( P =0.029). The dry eye diagnostic system indicated no significant differences in noninvasive tear film breakup time and fluorescein breakup time for both eyes ( P >0.05). The tear meniscus was significantly higher in the nonsmokers in the right eye ( P =0.025). However, the left eye showed no significant difference ( P >0.05). Additionally, the Meibomian gland loss was significantly higher in the right eye among smokers ( P =0.035), but not in the left eye ( P >0.05). Upper eyelid margin abnormalities were significantly more common in the right eye ( P =0.015) and left eye ( P =0.041), with a greater effect seen in smokers. However, the lower eyelid margins showed no significant differences ( P >0.05). No significant differences were observed between the two groups regarding eye redness or ocular surface staining. Conclusion Smoking may impact certain ocular surface and tear film parameters, including tear height, lipid layer integrity, Meibomian gland function, and upper eyelid margin structure.