Association of children choroidal thickness and their exposure to second hand smoking: the Hong Kong children eye study

M.Phil.Cigarette smoking is an important risk factor of systemic and ocular vascular diseases. It is known to cause anatomical alterations of the arterial system in thickening the arterial wall atherosclerosis and affecting both the microvascular and macrovascular structures. In the eye, smoking decreases retina blood flow and choroidal thickness (CT). The choroid is a highly vascularized tissue with about 90% of total ophthalmic artery blood flow for transporting oxygen and nourishment to the retina, with effects on intraocular temperature and pressure. Choroidal anatomy and blood flow are associated with ocular diseases including age-related macular degeneration (AMD), glaucoma and ocular inflammation. About 15% to 30% of women smoke tobacco during pregnancy. Maternal smoking is known to exert adverse effects on fetal development in the central nervous system, including optic nerve and the retina which has been observed. In view of these known harmful effects of smoking, the work in this thesis aim to assess the effects of exposure to second hand smoking on children’s choroidal thickness.In this study, we recruited children and parents from the Hong Kong Children Eye Study, which is a population-based study of comprehensive ocular examination and family education for children aged 6 to 9 years old, and their parents, from all over Hong Kong. It was started in March 2015 and took place at the CUHK Eye Centre of the Chinese University of Hong Kong at the Hong Kong Eye Hospital. All study children received complete and detailed ocular examinations. Their parents were examined for visual acuity, refraction, intraocular pressure, corneal biomechanics, and axial length. Systemic physical examination was conducted to all study subjects including height, weight, and waist diameter. Questionnaires were administered to the parents to get to know their smoking habits and number of smokers in the family and living environment of the children.Choroidal thicknesses of both eyes of the children were measured by swept-source Optical Coherence (SS-OCT) in a subgroup of children. Children who had prior eye trauma, congenital malformations, and ocular diseases (except myopia and hypermetropia) were not included in the study. Those who were incapable to complete optical coherence tomography or other optical examinations were also excluded. Accordingly, among 4,389 children in the Hong Kong Children Eye Study, 1,400 children were recruited into the current study.We first investigated and confirmed the association between clinical parameters and choroidal thickness of the children, age 7.64±0.99 (mean±SD) years. There were 704 boys (50.3%) and 696 girls (49.7%). The mean ±SD of subfoveal choroidal thickness (SFCT) was 271.50 ± 56.31μm. CT was significantly associated with axial length (AL), 23.13±0.93mm, (P<0.001; Beta=-18.771), but not with age.Secondly, we investigated whether these children were exposed to smoking environment after birth. There are 941 children whose parents and other family members all were not smoker, and 459 children who have at least one or more smokers living around them. We found that children’s CT was thinned by exposure to a smoking environment and was also associated with the number of smokers in the family, the more smokers the thinner the choroidal thickness. The statistical significances were in the Center (P Value=0.008), Inner inferior (I1, P=0.019), Outer inferior (I2, P=0.022); Inner temporal (T1, P=0.03); and Outer temporal (T2, P =0.01). In each area where there was statistical difference, the choroid thicknesses of children exposed to smoking was thinner than those of children who were not exposed to smoking by about 6-8μm. There was also association between children’s choroidal thickness and the number of smokers in the family: no smoker, one smoker and two or more smokers. The choroidal thicknesses of children who had no smoker in their homes was thicker than those with smokers, regardless of the number, in the Center sector (P Value=0.009), Inner inferior (P=0.049), Inner temporal (P=0.041), Outer temporal (P=0.014). In multiple regression model, it also showed the trend that children choroidal thickness negatively correlated to the number of smoker in family (Mean CT: P Value=0.048; C: P Value=0.003; I1: P Value=0.014; I2: P Value=0.016; T1: P Value=0.013; T2: P Value=0.004). We also found that children’s choroidal thickness was mildly negatively correlated with the quantity of cigarette smoking at home in the Center sector (P=0.026) and Outer temporal area (T2, P=0.028). With more number of smokers at home, the thickness of the choroid was thinner at about 4-7μm in those regions. Finally, we also analyzed the effects of smoking during pregnancy on choroidal thickness in children, but since only 14 mothers smoked during pregnancy, the remaining 1386 mothers never smoked or quit smoking during pregnancy. So in this part of the study we did not observe any significant statistically significant association between smoking and choroidal thickness in children.In summary, this study confirmed the association between CT and parameters including age, gender, AL, and BMI which CT was negatively associated to AL but positively correlated to age. We also found effects of exposure to second hand smoking with choroidal thinning in children. There should be high awareness of the effects of smoking by the parents or family members on children’s eye health. To the best of our knowledge, this is the first study of the relationship between choroidal thickness in children and their exposure to second hand smoke, and gives important information and reference evidence to investigate the existence of choroidal thickness and exposure to second hand smoke. contact. It has certain reference significance for the early observation of other ophthalmic diseases related to choroidal thickness.吸烟是全身和眼部血管疾病的重要危险因素。已知在增加动脉壁动脉粥样硬化并影响微血管和大血管结构时引起动脉系统的解剖学改变。在眼睛中，吸烟会降低视网膜血流量和脉络膜厚度（CT）。脉络膜是高度血管化的组织，具有约90％的总眼动脉血流，用于将氧气和营养输送到视网膜，对眼内温度和压力有影响。脉络膜解剖和血流与眼部疾病相关，包括年龄相关性黄斑变性（AMD），青光眼和眼部炎症。大约15％至30％的女性在怀孕期间吸烟。已知母体吸烟对中枢神经系统中的胎儿发育产生不利影响，包括已经观察到的视神经和视网膜。鉴于这些已知的吸烟有害影响，本论文的工作旨在评估接触父母吸烟对儿童脉络膜厚度的影响。在这项研究中，我们从香港儿童眼科研究中招募儿童及家长，该研究是一项以人口为基础的研究，旨在研究6至9岁儿童的综合眼科检查及家庭教育，以及来自全港各地的家长。它于2015年3月开始，在香港眼科医院香港中文大学香港中文大学眼科中心举行。所有研究儿童都接受了完整而详细的眼科检查。检查他们的父母的视力，屈光度，眼压，角膜生物力学和轴长。对所有研究对象进行全身体检，包括身高，体重，腰围等。特别是，在儿童亚组中通过扫描光学相干（SS-OCT）测量双眼的脉络膜厚度。先前有眼外伤，先天性畸形和眼部疾病（近视和远视除外）的儿童未纳入研究。那些无法完成光学相干断层扫描或其他光学检查的人也被排除在外。因此，在香港儿童眼科研究的4,389名儿童中，有1,400名儿童被招募进入本研究。我们首先调查并确认了儿童的临床参数和脉络膜厚度之间的关联，年龄为7.64±0.99（平均值±SD）。有704名男生（50.3％）和696名女生（49.7％）。中心凹下脉络膜厚度（SFCT）的平均值±SD为271.50±56.31μm。 CT与轴长（AL）显着相关，23.13±0.93mm，（P <0.001; Beta = -18.771），但在这个区域内脉络膜厚度与年龄无关。我们首先调查并确认了儿童的临床参数和脉络膜厚度之间的关联，年龄为7.64±0.99（平均值±SD）。有704名男生（50.3％）和696名女生（49.7％）。中心凹下脉络膜厚度（SFCT）的平均值±SD为271.50±56.31μm。CT与轴长（AL）显着相关，23.13±0.93mm，（P