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)環境重建指標。環境重建指標是綠色礦山建設中不可忽略的評價指標，環境重建指標中要求企業在礦山開采過程中制定合理的環境管理方案，以防企業再走先污染后治理的老路。根據相關規定，環境重建指標所占的費用應占到礦山企業年銷售額的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.

抗震設防烈度為8度，按罕遇地震設計基本地震加速度值為0.20g，設計地震屬于第一組，場地類別為Ⅱ類，則Tg=0.4s。阻尼比取0.02，地震影響系數曲線的阻尼調整系數按1.0采用，豎直地震載荷對整個結構的動力響應影響較小，一般情況下，只考慮水平向地震作用[5]，故分別在結構的兩個水平主軸方向計算地震作用。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下降趨勢明顯，部分水體污染嚴重。據統計，全省每年入河湖廢污水排放量由20世紀末不足20億t增加到現在的近40億t。水污染已對全省經濟社會發展帶來一定影響，如樂安河流域德興、樂平等地由于重金屬污染，出現水質型缺水，樂平市不得不從原用于農業灌溉的共產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).

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