Analysis of retinal vasculature changes in indirect traumatic optic neuropathy using optic coherence tomography angiography

INTRODUCTION

I ndirect traumatic optic neuropathy (ITON) refers to acute visual impairment due to optic nerve injury following remote forces applied to the head or face

. Common causes include vehicle and bicycle accidents, falling, or hits

, and ITON occurs in 2% to 5% of facial and 0.5% to 2% of head traumas

. Diagnostic characteristics of ITON include acutely decreased visual acuity (VA), change in color recognition,visual field defects, impaired visual evoked potentials (VEP)and relative afferent pupil defect (RAPD)

.

External concussive forces transmits shockwave to the optic nerve and causes indirect injuries

. A highly recognizable report by Gross

reported that the traumatic impact force may result in deformation of the ipsilateral orbital roof near the optic foramen, and such deformation could cause damage to the supporting vasculature and shear stress to the nerve

. The subsequent vascular ischemia-induced optic nerve swelling and compression due to optic canal are causes of insufficient blood supply to retinal ganglion cell (RGC)leading to irreversible degeneration of RGC axons at the time of injury or progress within ensuing weeks, and present with optic disc pallor

. This two-stage hypothesis is the basis for treatment of ITON with optic canal decompression

,among others such as steroid treatments and close observation with no interventions

. It is important to evaluate the degree of injury for trauma-induced indirect damages to the retina and optic nerve, therefore, it is necessary to adopt an appropriate examination method.

3.3.3學生對專業學習興趣的提升由課后的問卷調查結果發現，PBL教學改革提高了學生對專業課的學習興趣．在水文學教學改革開始前，S1班學生對地理學專業有了深入的認識，很多學生不再認為學習這種理論沒有用，而是覺得地理學能夠解決現實的問題，開始轉變對專業的排斥心理，超過70%的學生決定報考地理專業研究生．

Axon degeneration has been demonstrated in rodent models as reported by several studies

. Thinning of RNFL at the ONH region has shown to be strongly correlated with impaired visual function and visual field loss in patients with compressive lesions, and suggest that damaging to the anterior pathways may occur before visual field loss

. A report showed that a significant thinning of macular GCC (the combination of RGC and IPL) was observed in the outer nasal, superior and inferior field in early traumatic optic neuropathy, which implied that RGC loss may participate in the development of traumatic optic neuropathy

. Hence, visual dysfunction might delay in up to 10% of patients, which is attributed to a deferred clinical diagnosis

. Concordantly, we found significant thinning of macular GCC in all assessed sectors, and all patients presented with decreased VA and impaired visual functions assessed by VEP, suggesting that changes in retinal thickness had already occurred before their first visit to clinic. Yet, an interesting finding from our OCTA result demonstrated a slight increase in RNFL thickness within 7d after injury and followed by significant decrease from 7 to 30d, with observation in fundoscopy examination, together suggested that acute edema at the ONH may have occurred immediately after injury and subsiding of RNFL swelling took place in the next few weeks.The OCTA also provides measurement of vessel density,which is evidential to the alteration of blood supply following traumatic impact to the optic nerve. To date, the discussion on vascular changes in optic neuropathies with OCTA has been scarce. Chan

showed that significant decrease in blood suppl and oxygenation to the retina was associated with choroidal thinning in chronic ITON patients. Although a different OCTA platform was used, our OCTA findings showed apparent attenuation in microvasculature densities at the RPC region of the ONH cube scan, as well as the perifovea sectors at the macular, suggesting possible impaired perfusion to the retina.

SUBJECTS AND METHODS

This is a retrospective observational study. Ethical approval and patient consent were obtained before surgery and the procedures adhered to the tenets of the 1964 Declaration of Helsinki. For patients of age below 18,consent was obtained from their parents or legal guardians.Protocols were approved by the Institutional Ethics Committee(2019KYPJ155, Medical Ethics Committee, Zhongshan Ophthalmic Center, Guangzhou, Guangdong Province, China).

1941年4月4日，熊式輝向蔣介石進言:“領袖只宜以思想領導干部，功名利祿，只能奔走一般中下之士，凡為革命奮斗冒險犯難而不辭者，皆思想上信仰力之驅使，故把握正確的思想路線是第一要務?！?實則亦是針對蔣以功名利祿籠絡干部的做法提出的改進意見。

All statistical calculation and analysis were performed with IBM SPSS Statistics 24 software (IBM Corp., Armonk, NY, USA) and GraphPad Prism 8 (GraphPad Software, San Diego CA, USA). Alteration in retinal thickness and vasculature density were calculated as percentage of measurements in ITON eyes as compared to the contralateral unaffected eye. For continuous variables, data were presented as mean±standard deviation (SD) unless otherwise stated;parametric (

-tests or ANOVA) or non-parametric tests (Mann-Whitney

or Kruskal Wallis) for comparisons between groups(pairwise where appropriate); Pearson’s correlation analysis was performed to reveal time-dependent changes in parameters where appropriate. Statistical significance was calculated for two-tail significance and was defined with

-value of less than 0.05.

2006年首屆香山論壇舉辦時，僅有來自14個國家的24名外國代表與會。而在第八屆論壇上，來自74個國家和國際組織的400余名代表不遠萬里齊聚北京，共商打造新型安全伙伴關系之道。北京香山論壇之所以能在短短十幾年內異軍突起，是因為秉持平等、開放、包容、互鑒精神，求同存異、聚同化異，倡“和”而不倡“斗”，推動構建人類命運共同體。

All patients had comprehensive systemic and ophthalmic examination. ITON was diagnosed according to patients’traumatic history and ophthalmic examination, including symptoms: 1) a close head injury with no direct force trauma made to the optic nerve; 2) decrease of VA; 3) positive of RAPD; 4) abnormal VEP with normal fundus examination.

All subjects were examined under one OCTA system (AngioVue; Optovue Inc., Fremont, CA, USA), which scanned at speed of 70 000 A-scans per second, and wavelength of 840 nm. For each eye of all patients, 4.5×4.5 mm

cube angio scan was centered at the optic nerve head (ONH), and 3.0×3.0 mm

cube angio scan was centered at the fovea for macular region.

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Vessel density was defined as the proportion (in percentage)of perfused vascular area in the whole selected region in en face views. OCTA output data from the 4.5×4.5 mm

ONH scan included readings for vessel densities of whole ONH image (onh-wiVD), inside-disc and peripapillary sectors.The 3.0×3.0 mm

macular scan included readings for vessel densities of whole macular image (m-wiVD), fovea, parafovea and peri-fovea sectors. OCTA also provided automated measurements of retinal thickness parameters, which included retinal nerve fiber layer (RNFL) at the ONH and a complexed layer (GCC) at the macular B-scans. The latter is the combination of RNFL, RGC, and inner plexiform layers (IPL).Representative images of OCTA performed on both eyes of the same patient was shown in Figure 1. At very early stage of the disease (day 4 from injury), retina thickness and vessel density did not change greatly in the ITON eye as compared to the unaffected fellow eye. After approximately 3mo from injury,retina thickness and vessel density decreased significantly in the ITON eye, suggesting progression of RGC over time.

A total of 73 patients who were diagnosed of monocular ITON in Zhongshan Ophthalmic Center (ZOC)from August 2016 to May 2020 were recruited in this study.The inclusion criteria were as follows: 1) diagnosed of ITON;2) no history of other ophthalmic conditions or ocular surgeries apart from optic canal decompression. Patient details on age, gender,cause of injuries and time of visit after injury were recorded.

RESULTS

1.1.3 試驗用蝦 2018年4月從距武漢農業氣象試驗基地30 min車程的蝦苗養殖基地購入平均質量3～5 g的蝦苗，每個網箱蝦苗投放數量均為20尾。……