Cigarette Smoking and Pachymetry and Specular Microscopy Parameters of Cornea; A Systematic Review and Meta-analysis

Purpose: To investigate the effect of smoking on corneal parameters, including Endothelial Cell Density, Central Corneal Thickness, Percent of Hexogonality, and Coefficient of Variation. Methods: This study was a systematic review and meta-analysis of published articles until the end of February 2019. To do this, the first search was done for creditable medical databases such as PubMed, and ISI (Web of Science), using an article search strategy and keywords derived from MeSH, including cigarette, smoking, tobacco, and their derivatives and relevance. They were conducted with the keywords pachymetry and corneal thickness. All English and Persian related articles were extracted by two independent researchers and by a thorough review of the articles; the articles that met the inclusion criteria for the present meta-analysis were selected for analysis. Results: Initial search of 351 articles found that information of 8 studies was selected and entered into the present meta-analysis. The total number of participants was 588 in the cigarette smoking group and 602in the non-cigarette smoking group. The mean age of the two groups was 38.9 and 40.4 years, respectively, and 21% of the participants were female. Of the studies included in the present meta-analysis, all studies reported the information needed to analyze the CCT index. For CV, ECD, HEX, and AXIAL LENGTH indices 4, 4, 4, and 5 studies reported the information required for performing the meta-analysis, respectively. The results of the meta-analysis showed that smoking had no significant effect on any of the corneal parameters, including CCT, ECD, CV, AXIAL LENGTH, HEX (P=0.543, P=0.591, P=542, P= 0.231, P=0.584, respectively). Conclusion: Smoking does not affect different parameters of the cornea. Due to the limited number of articles in this field, it is recommended to investigate the effect of cigarette smoking in more samples to compare the effect of cigarette smoking on high daily volume of corn.