The microstructural and functional changes in the macula of heavy habitual smokers

The influence of smoking on retinal ganglion cell-inner plexiform layer complex in male diabetes

PURPOSE

This study aims to evaluate the influence of smoking on ganglion cell-inner plexiform layer complex (GC-IPL) thickness and central macular thickness (CMT) measured by spectral domain optical coherence tomography (OCT) in male diabetes.

METHODS

90 smoking and 90 never-smoking male subjects were included in this study. They were divided into six groups based on the diagnostic criteria for diabetes and the Early Treatment Diabetic Retinopathy Study (ETDRS) classification: smoking healthy subjects (SH, n = 20), non-smoking healthy subjects (NSH, n = 20), smoking diabetic patients without diabetic retinopathy (SNDR, n = 40), non-smoking diabetic patients without diabetic retinopathy (NSNDR, n = 40), smoking diabetic patients with diabetic retinopathy (SDR, n = 30), and non-smoking diabetic patients with diabetic retinopathy (NSDR, n = 30). After a full ophthalmologic examination, GC-IPL thickness and central macular thickness (CMT) were measured by OCT. Statistical analysis was performed to compare GC-IPL thickness and CMT between groups. Multiple linear regression equations were constructed to explore the potential risk factors of mean GC-IPL thickness.

RESULTS

There were no significant differences in GC-IPL thickness and CMT between SH and NSH (all p > 0.05). Mean, superonasal, superior, superotemporal, inferonasal, inferior GC-IPL (p＜0.001, p＜0.001, p＜0.001, p = 0.003, p = 0.001, and p = 0.005, respectively) were thinner in the SNDR than NSNDR except for inferotemporal GC-IPL thickness and CMT (p = 0.066, p = 0.605, respectively). Mean, superonasal, superior, and inferonasal GC-IPL were thinner in the SDR than NSDR (p = 0.019, p = 0.045, p = 0.037, and p = 0.049, respectively). Multiple regression analysis demonstrated that age (β [SE], -0.141 [0.060]; p = 0.020) and smoking (β [SE], -4.470 [1.015]; p＜0.001) were the most important determinants for mean GC-IPL thickness.

CONCLUSION

Smoking is associated with reduced retinal GC-IPL thickness in male diabetes. Smoking behavior and age are important determinants of mean GC-IPL thickness.

Impact of cigarette smoking on fluorescence lifetime of ocular fundus

Cigarette smoking is known to adversely affect cellular metabolism and is a risk factor for various retinal diseases. Fluorescence lifetime imaging ophthalmoscopy (FLIO) has the potential to detect metabolic changes in the ocular fundus. Aim of this study was to analyze the influence of cigarette smoking on fluorescence lifetime (FLT) of healthy eyes using FLIO. Twenty-six non-smokers and 28 smokers aged between 20 and 37 years without systemic and ocular diseases were investigated by FLIO (excitation: 473 nm, emission: short spectral channel (SSC) 498-560 nm, long spectral channel (LSC) 560-720 nm). The FLT at the ETDRS grid regions were analyzed and compared. In SSC, the mean FLT (τ_m) of smokers was significantly longer in the ETDRS inner ring region, whereas the τ_m in LSC was significantly shorter in the outer ring. For the long component (τ₂), smokers with pack year < 7.11 showed significantly shorter τ₂ in SSC than non-smokers and the smokers with pack year ≥ 7.11. There were no significant differences in retinal thickness. The lack of obvious structural differences implies that the observed FLT changes are likely related to smoking-induced metabolic changes. These results suggest that FLIO may be useful in assessing retinal conditions related to lifestyle and systemic metabolic status.

Retinal dysfunctions in regular tobacco users: The retina as a window to the reward circuit in addictive disorders

The nicotine contained in tobacco is a neuromodulator which affects neurotransmission within the brain. The retina is an easy way to study central synaptic transmission dysfunctions in neuropsychiatric disorders. The purpose of this study is to assess the impact of regular tobacco use on retinal function using pattern (PERG), flash (fERG) and multifocal (mfERG) electroretinogram (ERG). We recorded PERG, fERG and mfERG for 24 regular tobacco users and 30 healthy non-smoking subjects. The protocol was compliant with International Society for Clinical Electrophysiology of Vision standards. The amplitudes and peak times (PT) of P50, N95 waves (PERG), a-, b- and oscillatory potentials (fERG), and N1, P1, N2 (mfERG) were evaluated. Compared to non-smokers, the results (Mann-Whitney U test, Bonferroni correction) for tobacco users suggested a significant increase of ~ 1 ms in the PT of light-adapted 3.0 fERG b-wave (p = 0.002). Using mfERG, we observed the following increases in tobacco users: in ring 3 for P1 PT of ~1,5 ms and in ring 5 for P1 PT of ~ 1 ms and for N2 PT of ~ 1 ms (p = 0.002, p = 0.002 and p = 0.006). It is our hypothesis that these results reflect the consequences of regular tobacco use on retinal synaptic transmission, and more specifically on dopaminergic and cholinergic transmission. We deduce that the retina may provide a crucial site of investigation for neurotransmission modulation of the reward circuit in regular tobacco users.

Effects of Cigarette Smoking on Retinal and Choroidal Thickness: A Systematic Review and Meta-Analysis

Background

Cigarette smoking has been regarded as a risk factor for the incidence of a wide variety of chronic illness; however, its effect on thickness of the retina or choroid is still unknown.

Methods

A consummate literature search was conducted in PubMed and Embase up to January, 2018. The quantitative synthesis was conducted by Stata 12.0.

Results

A total of 13 observational studies were included in this meta-analysis. In this meta-analysis of all available observational studies, no significant effect of tobacco smoking on retinal or choroidal thickness change was detected. However, advanced analyses showed that smoking would influence the thickness of RNFL (average: SMD, −0.332; 95% CI, −0.637 to −0.027; inferior: SMD, −0.632; 95% CI, −1.092 to −0.172; and superior: SMD, −0.720; 95% CI, −0.977 to −0.463) and GCL (superior: SMD, −0.549; 95% CI, −0.884 to −0.215; inferior: SMD, −0.602; 95% CI, −0.938 to −0.265). Meanwhile, subgroup analyses demonstrated that the results based on studies in some regions (America and Africa) and cross-sectional studies showed a reduced choroidal thickness in smokers. No publication bias was detected in this study.

Conclusion

In conclusion, no significant effect of tobacco smoking on retinal or choroidal thickness change was detected. However, smoking would influence the thickness of RNFL and GCL. Future research on this field would help in the prevention and treatment of smoking-associated disorders.