Exposure to Secondhand Smoke in Children is Associated with a Thinner Retinal Nerve Fiber Layer: The Hong Kong Children Eye Study

Does occupational radiation exposure affect retinal nerve fiber thickness?

PURPOSE

To evaluate the thickness of peripapillary nerve fibers in radiation-exposed healthcare workers.

METHODS

The study included 60 radiation-exposed healthcare workers and 60 healthy control groups. SD-OCT was used to measure mean peripapillary RNFL thickness along with peripapillary RNFL thickness in the upper, lower, nasal, and temporal quadrants.

RESULTS

The mean age of the subjects participating in the study was 37 ± 6.3 (range 25-50) in the radiation-exposed group and 38 ± 4.9 (range 26-48) in the control group. The mean duration of exposure to radiation in healthcare workers was 11 ± 5 years (range 5-27). While the mean total rim thickness was 94.25 ± 8.2 in the radiation-exposed group, it was 102.8 ± 7.4 in the control group (p < 0.001). The mean superior rim thickness was 123.93 ± 15.13 in the radiation-exposed group, while it was measured as 129.75 ± 14.64 in the control group (p = 0.34). While the mean inferior rim thickness was 110.88 ± 13.43 in the group exposed to radiation, it was 130.08 ± 13.44 in the control group (p < 0.001). The mean nasal rim thickness was 70.25 ± 9.50 in the group exposed to radiation, while it was 75.38 ± 13.77 in the control group (p = 0.46). While the mean temporal rim thickness was 71.77 ± 8.73 in the group exposed to radiation, it was measured as 75.78 ± 13.15 in the control group (p = 0.52). Significant thinning of nerve fiber thickness was found statistically significant in all and especially the inferior quadrants of the healthcare workers exposed to radiation compared to the control group.

CONCLUSION

After at least 5 years of radiation exposure, the thickness of the peripapillary retinal nerve fibers may decrease in healthcare workers.

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.

Associations of pre- and postnatal exposures with optic nerve status in young adults

PURPOSE

We aimed to explore the effect of multiple pre- and postnatal exposures on optic nerve status in young adults due to this critical period for development.

METHODS

We analysed peripapillary retinal nerve fibre layer (RNFL) status and macular thickness at age 18 years in the Copenhagen Prospective Studies on Asthma in Childhood 2000 (COPSAC2000 ) cohort in relation to several exposures.

RESULTS

Of the 269 participants (median (IQR) age, 17.6 (0.6) years; 124 boys), 60 participants whose mothers had smoked during pregnancy had a thinner RNFL: adjusted mean difference -4.6 μm (95% CI -7.7; -1.5 μm, p = 0.004) compared with participants whose mothers had not smoked during pregnancy. A total of 30 participants who were exposed to tobacco smoke both during foetal life and childhood had thinner RNFL: -9.6 μm (-13.4; -5.8 μm, p < 0.001). Smoking during pregnancy was also associated with a macular thickness deficit: -4.7 μm (-9.0; -0.4 μm, p = 0.03). Higher indoor concentrations of particulate matter 2.5 (PM2.5) was associated with thinner RNFL: -3.6 μm (-5.6; -1.6 μm, p < 0.001) and a macular deficit: -2.7 μm (-5.3; -0.1 μm, p = 0.04) in the crude analyses, but not in the adjusted analyses. No difference was found among participants who smoked at age 18 years compared with non-smokers on RNFL or macular thickness.

CONCLUSIONS

We found that exposure to smoking during early life was associated with a thinner RNFL and macula at age 18 years. The absence of an association between active smoking at 18 years suggests that the vulnerability of the optic nerve is highest during prenatal life and early childhood.

Influence of secondhand smoke exposure on the retinal vasculature of children in Hong Kong

BACKGROUND

A recent prospective demonstrated that cardiovascular risk factors in early childhood were associated with later cardiovascular events. However, the impact of secondhand smoke (SHS) on children is unclear. The aims of this study is to determine the effects of SHS exposure on the retinal vasculature of children.

METHODS

This is a population-based cross-sectional study of children aged 6 to 8 years. All participants received comprehensive ophthalmic examinations and retinal photography. Data on SHS exposure was derived from a validated questionnaire. A validated deep-learning system was used to automatically estimate retinal arteriolar and venular calibers from retinal photographs. Associations of quantitative retinal vessel caliber values with SHS exposure, number of smokers in the household, and total number of cigarettes smoked were determined by analyses of covariance (ANCOVA) after adjusting for potential confounders. Test of trend was determined by treating categorical risk factors as continuous ordinal variables.

RESULTS

Here we show children exposed to SHS have wider retinal arteriolar (CRAE 152.1 µm vs. 151.3 µm, p < 0.001) and venular (CRVE 216.7 µm vs. 215.5 µm, p < 0.001) calibers compared to those in smoke-free homes, after adjustment for different factors. Wider arteriolar and venular calibers are also associated with increasing number of smokers in the family (p trend < 0.001) and more cigarettes smoked among family smokers (p trend<0.001).

CONCLUSIONS

Exposure to SHS at home is associated with changes in retinal vasculature among children. This reinforces the adverse effect of secondhand smoking around children though further research incorporating comprehensive assessment of potential confounders is necessary.

Non-Pharmaceutical Interventions against COVID-19 Causing a Lower Trend in Age of LHON Onset

Leber hereditary optic neuropathy (LHON) is a monogenic but multifactorial disease vulnerable to environmental triggers. Little is known about how LHON onset changed during the COVID-19 pandemic and how non-pharmaceutical interventions (NPHIs) against COVID-19 impact LHON onset. One hundred and forty-seven LHON patients with the m.11778G>A mutation complaining of vision loss were involved between January 2017 and July 2022. The onset time points, age of onset, and possible risk factors were evaluated. Analyses were conducted among 96 LHON patients in the Pre-COVID-19 group and 51 in the COVID-19 group. The median (IQR) age of onset decreased significantly from 16.65 (13.739, 23.02) in pre-COVID-19 to 14.17 (8.87, 20.29) during COVID-19. Compared with the Pre-COVID-19 group, the COVID-19 group exhibited bimodal distribution with an additional peak at six; the first quarter of 2020 also witnessed a relatively denser onset, with no subsequent second spike. NPHIs against COVID-19 significantly changed patients' lifestyles, including higher secondhand smoke exposure (p < 0.001), adherence to masks (p < 0.001), reduction in time spent outdoors for leisure (p = 0.001), and prolonged screen time (p = 0.007). Multivariate logistic regression revealed that secondhand smoke exposure and mask-wearing were independent risk factors of younger LHON onset. Lower age of onset of LHON appeared after the breakout of the COVID-19 pandemic, and novel risk factors were detected, including secondhand exposure and long mask-wearing. Carriers of LHON mtDNA mutations, especially teenagers or children, should be advised to avoid secondhand smoke exposure and there are possible adverse outcomes of longer mask-wearing.

[Exogenously induced retinopathies]

Exogenously induced retinopathies can be caused by consumation of stimulating substances, systemic or ocular medications, vaccinations, light or irradiation. Some of the effects are transient, whereas other effects induce irreversible toxic reactions. Retinal damage may develop either acutely with obvious relation to the damaging cause, but often may take a long duration of repeated use of a substance or medication. External stimulants (e.g. nicotine, alcohol, poppers, methanol) are the most frequent cause of exogenously induced retinal damage. Side effects from systemic drugs (e.g. hydroxychloroquine, ethambutol, MEK-, ERK-, FLT3-, checkpoint inhibitors, didanosin, pentosanpolysulfat sodium) or intravitreally applied drugs (e.g. antibiotics, VEGF-inhibitors) are less frequent. Ocular side effects associated with vaccinations are rare. Ambient light sources induce no damaging effects on the retina. Incorrect use of technical or medical light sources (e.g. laser pointers) without adherence to safety recommendations or unshielded observation of the sun might induce permanent retinal damage. Local or external irradiation might induce retinal vascular damage resulting in radiation retinopathy.

Exogen bedingte Retinopathien

Exogen bedingte Retinopathien werden am häufigsten durch externe Stimulanzien, seltener durch unerwünschte Arzneimittelwirkungen systemisch oder intravitreal eingesetzter Medikamente und noch seltener durch Impfungen oder die Einwirkung von Lichtstrahlung verursacht. Die Kenntnis exogener Ursachen und ihre mögliche Symptomatik ist zur Prophylaxe oder zur Früherkennung schädigender Wirkungen und zur adäquaten Beratung der Patienten wichtig.

Association of SIX1-SIX6 polymorphisms with peripapillary retinal nerve fibre layer thickness in children

PURPOSE

Association of SIX1-SIX6 variants with peripapillary retinal nerve fibre layer (p-RNFL) thickness had been reported in adults. This study aimed to investigate these associations in children, with further explorations by spatial, age and sex stratifications.

METHODS

2878 school children aged between 6 and 9 years were enrolled from the Hong Kong Children Eye Study. Three single-nucleotide polymorphisms (SNPs) at the SIX1-SIX6 locus were genotyped. The association of each SNP with p-RNFL thickness (including global and sectoral thickness) were evaluated using multiple linear regression.

RESULTS

SNPs rs33912345 (p=7.7×10^-4) and rs10483727 (p=0.0013) showed significant associations with temporal-inferior p-RNFL thickness. The C allele of rs33912345 was associated with a thinner temporal-inferior p-RNFL by an average of 2.44 µm, while rs10483727-T was associated with a thinner temporal-inferior p-RNFL by 2.32 µm. The association with temporal-inferior p-RNFL was the strongest in the 8-9 year-old group for rs33912345 (p=5.2×10^-4) and rs10483727 (p=3.3×10^-4). Both SNPs were significantly associated with temporal-inferior p-RNFL thickness in boys (p<0.0017), but not in girls (p>0.05). In contrast, rs12436579-C (β=1.66; p=0.0059), but not rs33912345-C (β=1.31; p=0.052) or rs10483727-T (β=1.19; p=0.078), was nominally associated with a thicker nasal-inferior p-RNFL.

CONCLUSIONS

Both rs33912345 and rs10483727 at SIX1-SIX6 were associated with p-RNFL thickness in children, especially at the temporal-inferior sector, with age-dependent and sex-specific effects. SNP rs12436579 was associated with nasal-inferior p-RNFL thickness. Our findings suggested a role of SIX1-SIX6 in RNFL variation during neural retina development in childhood.

Evaluation of subclinical alterations in retinal layers and microvascular structures with OCT and OCTA in healthy young short-term smokers

PURPOSE

To detect the changes that can be determined with optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in young and short-term smokers.

METHOD

In this cross-sectional, observational, and comparative study, 45 "healthy" smokers and 45 healthy non-smoker control participants were included. Those with a smoking history between 1 year to 5 years and an average of 10-30 cigarettes per day were included in the study. OCT and OCTA measurements were made at least 60 min after smoking and at least 8 h after caffeine-containing beverages in order to end the effect of nicotine on systemic and retinal blood flow in the smoking group.

RESULTS

The mean smoking period was 2.2 ± 0.13 years. Mean macular thickness(MMT), retinal nerve fiber layer(RNFL), and choroidal thickness(Cht) were significantly lower in the smoker group, while ganglion cell-inner plexiform layer(GC-IPL) thickness was higher. Vessel density(VD) values were similar between groups, while perfusion density(PD) values were significantly higher in the smoker group. There were significant correlations between MMT and outer VD, outer PD, foveal avascular zone(FAZ) perimeter and circularity index. FAZ area and central VD and PD were inversely correlated. Also, FAZ circularity index and subfoveal, nasal, and temporal ChTs were positively correlated.

CONCLUSION

Despite the short-term smoking, ischemic effects were observed in retinochoroidal and vascular structures.