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

INTRODUCTION

可惜，許元生的眼睛里只有一行行的代碼。那天，如蕓入手了一支很貴的口紅，是純正的大紅，很襯她的膚色，她看著鏡子里的自己，莫名地產(chǎn)生了一個小想法。中午她去餐廳，恰巧與許元生走了個對頭，她笑了笑，沖他輕輕“嗨”了一聲。

(6)環(huán)境重建指標(biāo)。環(huán)境重建指標(biāo)是綠色礦山建設(shè)中不可忽略的評價(jià)指標(biāo)，環(huán)境重建指標(biāo)中要求企業(yè)在礦山開采過程中制定合理的環(huán)境管理方案，以防企業(yè)再走先污染后治理的老路。根據(jù)相關(guān)規(guī)定，環(huán)境重建指標(biāo)所占的費(fèi)用應(yīng)占到礦山企業(yè)年銷售額的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.

抗震設(shè)防烈度為8度，按罕遇地震設(shè)計(jì)基本地震加速度值為0.20g，設(shè)計(jì)地震屬于第一組，場地類別為Ⅱ類，則Tg=0.4s。阻尼比取0.02，地震影響系數(shù)曲線的阻尼調(diào)整系數(shù)按1.0采用，豎直地震載荷對整個結(jié)構(gòu)的動力響應(yīng)影響較小，一般情況下，只考慮水平向地震作用[5]，故分別在結(jié)構(gòu)的兩個水平主軸方向計(jì)算地震作用。由圖3求得加速度譜值如表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.

二是部分河湖水臟不能用。近年全省河流湖泊水質(zhì)下降趨勢明顯，部分水體污染嚴(yán)重。據(jù)統(tǒng)計(jì)，全省每年入河湖廢污水排放量由20世紀(jì)末不足20億t增加到現(xiàn)在的近40億t。水污染已對全省經(jīng)濟(jì)社會發(fā)展帶來一定影響，如樂安河流域德興、樂平等地由于重金屬污染，出現(xiàn)水質(zhì)型缺水，樂平市不得不從原用于農(nóng)業(yè)灌溉的共產(chǎn)主義水庫取水以保證飲水安全。

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).

激光二維掃描傳感器z方向測量線性度誤差u5為0.5μm?；剞D(zhuǎn)誤差對本系統(tǒng)測量影響較小，可以忽略。綜上，測量小直徑和大直徑塞規(guī)直徑時(shí)，系統(tǒng)的不確定度Δ1和Δ2為：

李志勇笑著說：“我們不生產(chǎn)食品，我們只是云南大山里的搬運(yùn)工。我們把大自然賦予我們的美食轉(zhuǎn)交給熱愛天然食材的全球朋友，讓健康和長壽賦予每個食客快樂和吉祥?！?/p>

此因素對工程質(zhì)量的影響主要體現(xiàn)在兩方面，即材料質(zhì)量和設(shè)備質(zhì)量。材料是建筑質(zhì)量的基礎(chǔ)保證，若其未達(dá)到相關(guān)標(biāo)準(zhǔn)就被使用在施工中，會大大縮短建筑壽命。很多施工單位為牟取巨大的利潤，在材料購買上通常只要求價(jià)格低廉，并未將其質(zhì)量和實(shí)際施工聯(lián)系到一起，有的建筑完工后不久，就會出現(xiàn)坍塌現(xiàn)象，嚴(yán)重影響住戶的人身安全。機(jī)械設(shè)備是現(xiàn)代建筑施工的必備品，針對施工需求，近年來我國對機(jī)械設(shè)備的優(yōu)化力度很大，施工水平也在穩(wěn)步提升當(dāng)中[2]。但在機(jī)械的自動化研究方面還存在很多不足，若能進(jìn)一步提升建筑機(jī)械的自動化水平，施工效率和質(zhì)量會有很大提升。

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,堅(jiān)持每天走一萬步以上,同時(shí)保持不吃晚飯。幾年以前,我就用這個辦法成功瘦身,如今也自信能夠照方抓藥,再一次取得成功。這當(dāng)然是一種苦刑,是用一種極端的方式來對待自己的身體。但是想一想那些跑馬拉松的,每天要堅(jiān)持跑上十幾公里,我受這個苦也就算不了什么。

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