Phenotypic appearance of central retinal vein occlusion post AstraZeneca vaccine

The COVID-19 pandemic has brought about the development of novel vaccines at a rapid pace. The AstraZeneca (AZ)COVID-19 adenovirus vector vaccine has been associated with thrombotic complications, the most serious of which includes cerebral venous sinus thrombosis. However, there are no reports in the literature to date regarding ocular manifestations secondary to the AZ COVID-19 vaccine. We present the cases of two otherwise healthy patients with no significant pre-existing co-morbidities presenting with a central retinal vein occlusion (CRVO) within 1wk following AZ COVID-19 vaccination and describe the typical phenotypic appearances.

The study was conducted in accordance with the principles of the Declaration of Helsinki. The informed consent was obtained from the subjects.

A 44-year-old lady presented to eye casualty complaining of two episodes of transient painless blurring of vision in her right eye 5d following her first AZ COVID vaccine. She had no significant past medical or ocular history,was not on any regular medication and was a non-smoker.

On examination Snellen visual acuities were 6/6 right eye and 6/6 left eye. Anterior segments and intraocular pressures were normal bilaterally. Dilated fundal examination of the right eye showed a few scattered flame and blot haemorrhages in all four quadrants (Figure 1). There was no evidence of cystoid macular edema (CME) on optical coherence tomography(OCT) imaging (Figure 2). The left fundus appeared normal.Blood pressure and routine bloods were all essentially normal.A diagnosis of non-ischaemic CRVO in the right eye was made and a 3-month follow up was arranged in the Ophthalmology Clinic. At her 3-month review, the vein occlusion in the right eye had completely resolved and she was discharged.

There appears to be increasing evidence in the literature suggesting a possible association between the AZ COVID-19 vaccine and thrombotic events. Potteg?rdreported a standardised morbidity ratio of 1.97 (1.50 to 2.54) and 11 (5.6 to 17.0)excess venous thromboembolic events per 100 000 vaccinations,with an excess of 2.5 (0.9 to 5.2) cerebral venous thrombotic events per 100 000 observed. This possible association has been recognized by European Medicines Agencyand United Kingdom Medicines and Healthcare Products Regulator.

The proposed mechanism of action of AZ COVID-19 related blood clots is an immune response that resembles a rare reaction to the drug heparin, called heparin-induced thrombocytopenia and is referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT). This disorder clinically resembles heparin-induced thrombocytopenia, which is a prothrombotic state caused by platelet-activating antibodies that recognise and bind to complexes of cationic platelet factor 4 (PF4) and anionic heparin. It has been recognised that other triggers apart from heparin can cause this reaction and it is believed that the AZ COVID-19 vaccine does so in this case.It is thought that interactions between the vaccine and platelets or between the vaccine and PF4 may play a role, but the exact pathogenesis still remains unclear.

全國的失能、半失能老年人高達3300萬，其中完全失能、需要照顧的老人1100萬，占老年總數(shù)的6.3%[3]。以現(xiàn)有的居家養(yǎng)老和社區(qū)養(yǎng)老條件，還難以實現(xiàn)對這些老人的人性化的關(guān)懷和照顧。

The occurrence of CRVO shortly after the mRNA COVID-19 vaccine has been reported previously, however our two cases represent the first documented reports of CRVO in association with the AZ COVID-19 vaccine. We hypothesize that the AZ COVID-19 vaccine predisposes to the development of CRVO with the VITT mechanism of action described in the two New England Journal of Medicine papers. From our two cases,CRVO occurring secondary to AZ COVID-19 vaccination appears to be non-ischaemic and relatively benign in nature,resolving rapidly without complications or requirement for any intervention. Further work in identifying cases may lead to improved understanding of the pathophysiology underlying this phenomenon of thrombosis secondary to AZ COVID-19 vaccination and verification of the VITT mechanism of action which has been proposed.

A 49-year-old lady presented to the eye clinic complaining of blurring of vision in her right eye 4d following inoculation with the AZ COVID-19 vaccine. She had no significant past medical or ocular history, was not on any regular medication and was a non-smoker.

On examination Snellen visual acuities were 6/12 right eye and 6/6 left eye. Anterior segments and intraocular pressures were normal bilaterally. Dilated fundal examination of the right eye showed a few scattered blot haemorrhages in all four quadrants with several cotton wool spots (Figure 3). There was no evidence of CME on OCT imaging (Figure 4). The left fundus appeared normal. Blood pressure and routine bloods were unremarkable. A diagnosis of non-ischaemic CRVO in the right eye was made and a 3-month follow up arranged in the Ophthalmology Clinic. At her 3-month review, Snellen visual acuities were 6/6 bilaterally, the vein occlusion in the right eye had completely resolved and she was discharged.

毫米波雷達測距可分為發(fā)射、接收、處理三部分。連續(xù)調(diào)頻毫米波信號通過發(fā)射天線發(fā)出，電磁波遇到障礙物以后會反射回來，之后被雷達接收天線接收，雷達接收機把接收到的回波信號和參考信號混頻，從而得到一個差頻信號，把差頻信號進行放大、濾波等處理后，通過采樣變?yōu)閿?shù)字基帶信號，把數(shù)字信號進行FFT頻譜分析后，就可以提取出目標的距離信息，如圖1所示。

Both of our patients were middle aged females, had no significant ocular or systemic risk factors and presented with a mild non-ischaemic CRVO characterised by a mild amount of haemorrhaging with or without cotton wool spots, and without evidence of CME within 1wk of AZ COVID-19 vaccination.Traditional methods of vaccination include attenuated vaccines which utilise microorganisms that have had their virulent properties disabled, or inactivated vaccines which contain microorganisms that have been destroyed and are no longer virulent. The AZ COVID-19 vaccine is a genetic vaccine and is in the sub-group viral vector vaccine. These vaccines use a safe virus to insert pathogen genes in the body to produce specific antigens. The AZ COVID-19 vaccine uses a modified version of a chimpanzee adenovirus, known as ChAdOx1, and contains the gene for the coronavirus spike protein. After inoculation with the AZ COVID-19 vaccine, the patient's immune system subsequently becomes primed to the coronavirus spike protein,enhancing the immune response if the patient encounters the COVID-19 virus in the future.

Honoraria from Bayer,

研究資料和研究結(jié)果等數(shù)據(jù)均采用SPSS23.0軟件進行統(tǒng)計分析,計量資料和計數(shù)資料分別以±s和%表示,組間比較分別采用t檢驗和χ2檢驗,其統(tǒng)計學意義以顯著差異P<0.05表示。

應用專用計算軟件對發(fā)電電動機進行靜止變頻器(SFC)起動仿真計算，發(fā)電電動機勵磁電流為1.0(p.u.)，勵磁控制方式為恒勵磁電流調(diào)節(jié)方式。起動過程為壓水起動，計算中考慮了各種損耗對電機產(chǎn)生的阻力矩，包括水輪機的水導軸承損耗、推力軸承損耗、主軸密封損耗、轉(zhuǎn)輪在空氣中旋轉(zhuǎn)的損耗、發(fā)電機的上導軸承損耗、下導軸承損耗、推力軸承損耗、通風損耗、鐵心損耗、定轉(zhuǎn)子繞組銅耗及雜散損耗等等[6]。另外，靜止變頻器的容量為18 MW。計算結(jié)果，電機的加速時間為210 s左右，即機組從靜止狀態(tài)加速到額定轉(zhuǎn)速的時間(不包括同步并網(wǎng)的時間)見圖4。

Allergan, Novartis, Roche and Travel Grants from Bayer,Allergan and Novartis;None;None;Travel Grant from Bayer.