Effects of baffle and intraocular pressure on aerosols generated in the noncontact tonometer measurement during COVlD-19

INTRODUCTION

可惜，许元生的眼睛里只有一行行的代码。那天，如芸入手了一支很贵的口红，是纯正的大红，很衬她的肤色，她看着镜子里的自己，莫名地产生了一个小想法。中午她去餐厅，恰巧与许元生走了个对头，她笑了笑，冲他轻轻“嗨”了一声。

(6)环境重建指标。环境重建指标是绿色矿山建设中不可忽略的评价指标，环境重建指标中要求企业在矿山开采过程中制定合理的环境管理方案，以防企业再走先污染后治理的老路。根据相关规定，环境重建指标所占的费用应占到矿山企业年销售额的2%以上。

The noncontact tonometry (NCT) is the most commonly used examination equipment in ophthalmology. It uses pulse air to flatten the constant central surface of cornea (3.60 mm diameter) to measure intraocular pressure (IOP). Aerosol generation occurs when air accelerates across a fluid surface.In 1991, Brittused color fluorescence photography to film the moment when IOP was measured by an NCT.Most eyes revealed some degree of tear film dehiscence and microaerosol formation. Our previous research used an air quality detector to quantify aerosols, confirming that aerosols could be generated during the IOP measurement. Several literatures have reported that human tears and conjunctival secretions contain SARS-CoV-2. Therefore, if an asymptomatic COVID-19 patient with an eye condition undergoes an NCT examination, the aerosols containing SARS-CoV-2 may be formed, and thus may be transmitted to the ophthalmologists and the patients with compromised or no protective gear. According to this, several experts suggested that the baffles should be set up during the use of NCTs to resist aerosols splashing, but the clinical effect has not been reported yet. Additionally, the specific relationship between IOP and aerosol density during the IOP measurement has not been clarified. Based on our previous study, this study conducted an in-depth study on the effect of IOP on aerosols generated during the NCT measurement and the effect of baffle on aerosols distribution near the NCT, in order to provide recommendations for the prevention of COVID-19 in ophthalmology clinic.

SUBJECTS AND METHODS

This study followed the tenets of the Declaration of Helsinki and was approved by the Ethical Committee of The Eye Hospital, Wenzhou Medical University,China (No.2020-018-K-16). Prior to entering the study cohort, all subjects were notified of the methods along with the purpose of this study and signed a written consent form voluntarily. Throughout the course of clinical trial, all subjects wore same facial masks according to the prevention and control management measures of the hospital.

This cross-sectional clinical trial included 312 eyes of 252 subjects in The Eye Hospital, Wenzhou Medical University from March 7, 2020 to March 28, 2020. The inclusion criteria were as follows: no COVID-19 (the results of novel coronavirus nucleic acid test are negative); able to cooperate with eye examinations. The exclusion criteria were as follows: patients with epiphora or dry eye or corneal diseases; patients had just used artificial tears or other eyedrops before the IOP measurement; contact lens wears.

This study was divided into two parts: effect of baffle on aerosols accumulation, and effects of baffle and IOP on per capita aerosol density.

In normal eye groups, 60 subjects with normal IOP (120 eyes) were randomly divided into two groups. One group used an NCT without a baffle, another group used an NCT with a baffle.Subjects of both groups performed binocular IOP measurement in turn. Terminal values of aerosol density near the NCT were quantified by the air quality detectors after the IOP measurement in each subject. In model eye groups, one model eye group used an NCT without a baffle, another group used an NCT with a baffle. The two identical model eyes used in this study were the eyeball anatomical models without lubrication.During the trial, the model eyes were placed in front of the air jet port of the NCT and air jet frequency was the same as that of the normal eye groups (Figure 1). The values of aerosol density were recorded simultaneously. Compared with normal eyes, the surface of the model eye has no tear film. The purpose of using the model eye is to prove that the tear film of human body will rupture under the airflow impact of the NCT to form aerosols.

抗震设防烈度为8度，按罕遇地震设计基本地震加速度值为0.20g，设计地震属于第一组，场地类别为Ⅱ类，则Tg=0.4s。阻尼比取0.02，地震影响系数曲线的阻尼调整系数按1.0采用，竖直地震载荷对整个结构的动力响应影响较小，一般情况下，只考虑水平向地震作用[5]，故分别在结构的两个水平主轴方向计算地震作用。由图3求得加速度谱值如表2。

Totally 192 subjects (192 eyes) were divided into four groups according to whether the NCT was equipped with a baffle and whether the IOP values of the patients were normal: Group A(without a baffle+normal IOP,=59), Group A(without a baffle+high IOP,=58), Group B(with a baffle+normal IOP,=40) and Group B(with a baffle+high IOP,=35). Subjects of four groups performed monocular IOP measurement in turn. The baseline and terminal values of aerosol density were recorded before and after the IOP measurement in each eye.

二是部分河湖水脏不能用。近年全省河流湖泊水质下降趋势明显，部分水体污染严重。据统计，全省每年入河湖废污水排放量由20世纪末不足20亿t增加到现在的近40亿t。水污染已对全省经济社会发展带来一定影响，如乐安河流域德兴、乐平等地由于重金属污染，出现水质型缺水，乐平市不得不从原用于农业灌溉的共产主义水库取水以保证饮水安全。

Results from the Group Aand Group A, Group Band Group Bwere combined. The median of per capita PM2.5 and PM10 in the combined Group A+Awere 0.80 and 1.10 μg/mrespectively, which were higher than 0.20 and 0.60 μg/min the combined Group B+B(=2.722, 2.812, both＜0.01).

There were no statistically significant differences in gender,age, eye, diagnosis and other subject characteristics between the four groups (＞0.05). Comparison of IOP values between the four groups demonstrated that no statistically significant differences were observed in Group AGroup B(=0.985);Group AGroup B(=0.51), but the comparisons between other groups were statistically significant (＜0.05; Table 2).

Two identical air quality detectors (1000S+ Air Quality Detector, Temtop Co., USA)were used to quantify aerosol density, including particulate matter (PM) 2.5 and PM10, in real time. Both air quality detectors were turned on and calibrated by placing them in a ventilated space for 24h before the trial. During the trial, the detectors were fixed at the groove between the jet port and the chin rest. When the baffle was installed, the detectors were fixed in the same position in front of the baffle, leaning towards the side of patient (Figure 2). The difference between terminal value and baseline value was calculated as the actual aerosol density value generated during the IOP measurement in each subject, and the average value of the results of two air quality detectors was calculated.

Test Preparation

Binocular IOP measurements were performed in turn in both normal eye groups. In the normal eye group without a baffle, PM2.5 and PM10 increased in a wave-like shape near the NCT with the increase in the number of people measured for IOP,demonstrating a cumulative effect. However, there was not a cumulative effect in the normal eye group with a baffle.

Aerosol is a dispersion system of solid or liquid particles suspended in gas medium with a particle size of 0.01-10.00 μm. Pathogenic microorganisms (bacteria,fungus, virus,.) can attach to aerosols to form pathogenic microorganism aerosols. Some pathogens carried by aerosols are toxic and pathogenic causing infections for human body. A recent research shows that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can spread through aerosols, which can cause severe respiratory symptoms and even death. Mehmoodhave further strengthened the evidence linking coronavirus disease 2019 (COVID-19) cases with aerosol density.

A transparent plastic material was used to make a baffle with an area of 35×40 cm, which was installed and fixed at the jet port of the NCT, between the display screen and the head rest of the patient (Figure 3).

PM2.5 means that particles with an aerodynamic equivalent diameter are less than 2.5 μm, also known as fine particulate matter; the unit is μg/m. PM10 means that particles with an aerodynamic equivalent diameter are less than 10 μm, also known as inhalable particles; the unit is μg/m.

EpiData 3.1 was used to establish the database for parallel double entries and the verification file for computer logic verification. SPSS 25.0 statistical software was used for the statistical analysis. Quantitative data were expressed as mean±standard deviation (SD) or median,interquartile range; and independent sample-test or-test wasused for comparison between groups. Qualitative data were expressed as percentages; and Chi-square test was used for comparison between groups. The Shapiro-Wilk test showed that the evaluation indicators in this study were nonnormally distributed, and the differences in PM2.5 and PM10 in each group were compared using the rank-sum test.value less than 0.05 was considered statistically significant. A plot of the cumulative change curve of aerosol density generated during the use of an NCT with and without a baffle for 30 subjects was drawn.

The duration of four groups was same (about 30min).

RESULTS

Subjects Characteristics

Comparisons of subject characteristics such as gender, age,and IOP between the group with a baffle and the group without a baffle demonstrated no statistically significant differences(＞0.05; Table 1).

激光二维扫描传感器z方向测量线性度误差u5为0.5μm。回转误差对本系统测量影响较小，可以忽略。综上，测量小直径和大直径塞规直径时，系统的不确定度Δ1和Δ2为：

李志勇笑着说：“我们不生产食品，我们只是云南大山里的搬运工。我们把大自然赋予我们的美食转交给热爱天然食材的全球朋友，让健康和长寿赋予每个食客快乐和吉祥。”

此因素对工程质量的影响主要体现在两方面，即材料质量和设备质量。材料是建筑质量的基础保证，若其未达到相关标准就被使用在施工中，会大大缩短建筑寿命。很多施工单位为牟取巨大的利润，在材料购买上通常只要求价格低廉，并未将其质量和实际施工联系到一起，有的建筑完工后不久，就会出现坍塌现象，严重影响住户的人身安全。机械设备是现代建筑施工的必备品，针对施工需求，近年来我国对机械设备的优化力度很大，施工水平也在稳步提升当中[2]。但在机械的自动化研究方面还存在很多不足，若能进一步提升建筑机械的自动化水平，施工效率和质量会有很大提升。

The trial was conducted in a consulting room of more than 100 m. Prior to the trial, the floor, countertops and other surfaces were cleaned. Before the trial, the air circulation system was used to disinfect the circulated air for 30min, and it was closed during the trial.After each subject of IOP measurement, the ophthalmologist sterilized the rest chin, frontal rest and air jet port of the NCT with alcohol-soaked cotton balls. In addition, in order to maintain the stability of the air flow formed by the air jet of the NCT during the trial, other people were not allowed to enter the test site; In order to ensure the stability of the results of aerosol density over the different testing days, the ambient temperature should be maintained at 24℃±3℃ and the humidity at 68%±5%.

In this study, two model eye groups were set up, one with a baffle and another without a baffle. The PM2.5 and PM10 of both model eye groups fluctuated around the baseline. The two model eye groups were designed to eliminate the influence of pure air jet of the NCT on aerosol density, which indirectly proved that aerosols could be generated when the NCT was used to measure the IOP for subjects (Figure 4).

Monocular IOP measurements were performed in turn in four groups. PM2.5 and PM10 in Group Awere higher than Group A(=7.023, 6.034, both＜0.001). The PM2.5 and PM10 in Group Bwere higher than Group B(=3.131, 3.586,＜0.01,＜0.001 respectively). The PM10 of Group Bwas lower than Group A(=-2.622,＜0.01). PM2.5 in Group Bwere lower than Group A(=-2.664,＜0.01).

IOP was measured in all subjects with two identical NCTs (TX-20 Automatic NCT, Canon Co., Japan).Subjects will need to remain seated, wear face masks, and remain silent during the IOP measurement. They fixed their chin to the rest of the NCT and focused on the light source in the jet port. They opened their eyes naturally and exposed the cornea. The IOP of each eye was measured 3 times (3 times of air-puff for one eye), and the average IOP value of each eye was recorded. IOP values of the subjects in 10 mm Hg＜IOP≤21 mm Hg were normal IOP, IOP＞21 mm Hg were high IOP.The mean duration of the IOP measurement was about 1min for each subject. In the experiment to study the effect of baffle on aerosols accumulation, subjects were required to perform binocular IOP measurement in the order of right eye first and left eye later.

Results from the Group Aand Group B, Group Aand Group Bwere combined. The median of per capita PM2.5 and PM10 in the combined Group A+Bwere 0.10 and 0.20 μg/mrespectively, which were lower than 1.30 and 1.70 μg/min the combined Group A+B(=-7.309, -6.858, both＜0.001;Figures 5 and 6).

DISCUSSION

The NCT is a more commonly used equipment for the IOP measurement. In the past, it was believed that the NCT did not contact the cornea directly, which could avoid cross-infection of diseases. However, through this study, we found that, with the increase in the number of people measured for IOP, PM2.5 and PM10 increased in a wave-like shape near the NCT and had a cumulative effect, which was similar to the findings of Li.

Although it is not known for certain whether aerosols of different density generated during the IOP measurement are capable of transmitting COVID-19, existing virology literatures proved that human tears could contain one or several pathogenic substances, such as hepatitis B virus,hepatitis C virus, herpes simplex virus, Epstein-Barr virus,measles virus, mumps virus, human immunodeficiency virus, severe acute respiratory syndrome virus, middle east respiratory syndrome virus, SARS-CoV-2, and bacteria and fungi. These pathogenic microorganisms could adhere to the aerosols generated by tear film rupture. A recent study suggested that more than ten strains of microbes, all of which were non-pathogenic, were detected and identified during the IOP measurement. Hence, the NCT maybe a potential source of aerosols containing microorganisms that could lead to transmission of pathogens. Therefore, we suggest that each patient should accept the novel coronavirus nucleic acid test before the IOP measurement during the great pandemics of COVID-19 worldwide. If the testing result is negative, he/she can be measured for IOP by the NCT; if the testing result is positive, the NCT examination should be avoided. For patients with COVID-19, the rebound tonometer is recommended, and the probe should be replaced as soon as it is used.

In this study, a baffle was added to the NCT, and the results showed that with the increase in the number of people measured for IOP, the aerosols decreased in a wave-like shape near the NCT and had no cumulative effect. The normal eye group without a baffle, however, still demonstrated a cumulative effect. Besides, we found that the per capita aerosols generated in the group with a baffle were reduced by almost half compared with the group without a baffle.Therefore, the setting of a baffle was effective during the IOP measurement. We speculated that the possible reasons were as follows: The baffle adsorbed some aerosols; The baffle changed the trajectory of aerosols. Shettymade the similar proposals by quantifying aerosols and droplets generated during the IOP measurement and assessing the spread distance of the same. Chenand Lokeshalso have confirmed that a simple barrier drape significantly reduced particulate dispersion in mastoidectomy and temporal bone surgery. Therefore, we strongly recommend that during the great pandemics of COVID-19 worldwide, all ophthalmic clinics should install a transparent baffle between the NCT display screen and the head rest of the patient,such as homemade X-ray film, especially for the high IOP measurement, to reduce the spread of infectious diseases caused by aerosols. Additionally, the local public health policy for ventilation and disinfection should be followed, to dilute and inactivate pathogenic microorganism aerosols.

After grouping and comparing according to the IOP of the subjects, it was found that those with high IOP (IOP＞21 mm Hg)generated more aerosols. Brittalso confirmed that the subjects with high IOP (IOP＞30 mm Hg) generated more aerosols. It was speculated that the possible reason was that the cornea of the subjects with high IOP bore more jet force when they were measured for IOP, which made the tear film break and release more aerosols. Therefore, we recommend that during the IOP measurement, patients should be carried out in batches and the time interval between patients should be extended appropriately, especially for glaucoma patients or other patients with high IOP.

In addition, this study found that the results of PM2.5 and PM10 were synchronous, and there was no significant difference. From the definition of both, we could easily find PM10 includes PM2.5, but the range is much larger than PM2.5. PM10 can enter the upper respiratory tract, but some can be discharged from the human body through sputum,.Others will be blocked by the villi inside the nasal cavity.PM2.5 has a small particle size, larger than surface area,strong activity, prone to toxic and harmful substances (such as heavy metals, microorganisms,.), and a long stay in the atmosphere and a long transport distance, which has a greater impact on human health and atmospheric environmental quality.

In summary, this study quantified the aerosol density. Aerosols could be generated during the IOP measurement, and more aerosols could be generated by patients with high IOP, which could be one of the potential transmission routes of pathogenic microorganisms in ophthalmology clinic. The installation of the baffle was efficient in changing the distribution of aerosols near the NCT and reducing aerosol aggregation. Therefore,it is suggested that NCTs should be equipped with baffles,especially for patients with high IOP. The NCT should not be used if a patient has COVID-19 or any other infectious disease.This is fundamental in the control and prevention of viral transmission and protection of both the ophthalmologists and the patients during and after the prevalence of COVID-19.

Conceptualization: Chen YY;Data curation, formal analysis: Tang Y, Li CC, Chen ZY;Methodology: Chen YY, Tang Y, Li CC, Qu J, Huang XQ;Experiment: Tang Y, Li CC, Chen ZY; Funding acquisition,supervision, validation: Chen YY, Chen AA; Resources: Chen YY, Qu J; Writing-original draft: Tang Y; Writing-translation:Chen C, Wen SQ; Writing-review & editing: Chen YY, Qu J,Huang XQ, Chen YM, Chen AA.

我的做法是,坚持每天走一万步以上,同时保持不吃晚饭。几年以前,我就用这个办法成功瘦身,如今也自信能够照方抓药,再一次取得成功。这当然是一种苦刑,是用一种极端的方式来对待自己的身体。但是想一想那些跑马拉松的,每天要坚持跑上十几公里,我受这个苦也就算不了什么。

None;None;None;None;None;None;None;None;, None;None.