The retinal vasculature pathophysiological changes in vision recovery after treatment for indirect traumatic optic neuropathy patients

Remote Ischemic Post-Conditioning (RIC) Mediates Anti-Inflammatory Signaling via Myeloid AMPKα1 in Murine Traumatic Optic Neuropathy (TON)

Traumatic optic neuropathy (TON) has been regarded a vision-threatening condition caused by either ocular or blunt/penetrating head trauma, which is characterized by direct or indirect TON. Injury happens during sports, vehicle accidents and mainly in military war and combat exposure. Earlier, we have demonstrated that remote ischemic post-conditioning (RIC) therapy is protective in TON, and here we report that AMPKα1 activation is crucial. AMPKα1 is the catalytic subunit of the heterotrimeric enzyme AMPK, the master regulator of cellular energetics and metabolism. The α1 isoform predominates in immune cells including macrophages (Mφs). Myeloid-specific AMPKα1 KO mice were generated by crossing AMPKα1Flox/Flox and LysMcre to carry out the study. We induced TON in mice by using a controlled impact system. Mice (mixed sex) were randomized in six experimental groups for Sham (mock); Sham (RIC); AMPKα1F/F (TON); AMPKα1F/F (TON+RIC); AMPKα1F/F LysMCre (TON); AMPKα1F/F LysMCre (TON+RIC). RIC therapy was given every day (5–7 days following TON). Data were generated by using Western blotting (pAMPKα1, ICAM1, Brn3 and GAP43), immunofluorescence (pAMPKα1, cd11b, TMEM119 and ICAM1), flow cytometry (CD11b, F4/80, CD68, CD206, IL-10 and LY6G), ELISA (TNF-α and IL-10) and transmission electron microscopy (TEM, for demyelination and axonal degeneration), and retinal oxygenation was measured by a Unisense sensor system. First, we observed retinal morphology with funduscopic images and found TON has vascular inflammation. H&E staining data suggested that TON increased retinal inflammation and RIC attenuates retinal ganglion cell death. Immunofluorescence and Western blot data showed increased microglial activation and decreased retinal ganglion cell (RGCs) marker Brn3 and axonal regeneration marker GAP43 expression in the TON [AMPKα1F/F] vs. Sham group, but TON+RIC [AMPKα1F/F] attenuated the expression level of these markers. Interestingly, higher microglia activation was observed in the myeloid AMPKα1F/F KO group following TON, and RIC therapy did not attenuate microglial expression. Flow cytometry, ELISA and retinal tissue oxygen data revealed that RIC therapy significantly reduced the pro-inflammatory signaling markers, increased anti-inflammatory macrophage polarization and improved oxygen level in the TON+RIC [AMPKα1F/F] group; however, RIC therapy did not reduce inflammatory signaling activation in the myeloid AMPKα1 KO mice. The transmission electron microscopy (TEM) data of the optic nerve showed increased demyelination and axonal degeneration in the TON [AMPKα1F/F] group, and RIC improved the myelination process in TON [AMPKα1F/F], but RIC had no significant effect in the AMPKα1 KO mice. The myeloid AMPKα1c deletion attenuated RIC induced anti-inflammatory macrophage polarization, and that suggests a molecular link between RIC and immune activation. Overall, these data suggest that RIC therapy provided protection against inflammation and neurodegeneration via myeloid AMPKα1 activation, but the deletion of myeloid AMPKα1 is not protective in TON. Further investigation of RIC and AMPKα1 signaling is warranted in TON.

Intraretinal microvascular alterations in indirect traumatic optic neuropathy using optical coherence tomography angiography

PURPOSE

To quantitatively evaluate macular and peripapillary microvascular alterations in patients with indirect traumatic optic neuropathy (TON) compared to normal controls using optical coherence tomography angiography (OCT-A) and determine their associations with other ocular parameters.

METHODS

We enrolled 33 eyes of 33 patients with TON and 34 eyes of 34 healthy controls. OCT-A was used to generate microvascular structure images of the superficial retinal capillary plexus (SRCP), deep retinal capillary plexus (DRCP), and radial peripapillary capillary (RPC) segment in the macula and peripapillary area. Functional and structural parameters such as best-corrected visual acuity, visual field, peripapillary retinal nerve fibre layer (pRNFL) thickness, macular ganglion cell-inner plexiform layer (mGCIPL) thickness, OCT-A variables were compared between TON patients and controls. Age, gender, and spherical equivalent refractive errors were statistically adjusted for the analysis.

RESULTS

OCT-A revealed a significant reduction of the average vessel density in the RPC segment in TON patients compared to controls (48.5% ± 6.28 vs. 57.88% ± 3.06%, P < 0.0001, corrected P < 0.0001). When comparing sectors, the vessel density of the RPC segment in TON patients was also significantly lower in all four quadrants compared to healthy controls. The inferior sector vessel density of the RPC segment was significantly associated with visual field defects (P = 0.0253) and visual acuity (P = 0.0369). The temporal sector vessel density of DRCP was also associated with visual field defects (P = 0.0377). The RPC segment in the superior and inferior sector vessel density displayed a significant association with the corresponding regional pRNFL thickness (P = 0.0248 and <0.0001, respectively).

CONCLUSIONS

Patients with indirect TON exhibit significant microvascular alterations compared to controls. This study confirms that TON can induce intraretinal microvascular changes and suggests that OCT-A may serve as a useful biomarker for assessing visual functional and structural changes.

Factors predictive of poor visual outcome in indirect traumatic optic neuropathy: A retrospective cohort study

INTRODUCTION

The gold standard treatment for indirect traumatic optic neuropathy (ITON) has not yet been conclusively established, and it is essential to gain an understanding of visual prognosis and to counsel patients regarding the predictive risk factors of poor visual outcomes. Currently, there is limited information regarding ITON in Thai populations; therefore, this study aimed to determine the risk factors of poor visual outcome in patients with this condition.

METHODS

A retrospective review was conducted of all ITON cases diagnosed at Rajavithi Hospital and Sawanpracharak Hospital between January 2016 and December 2022 in order to determine clinical characteristics and evaluate associated risk factors of poor visual prognosis using binary logistic regression analysis.

RESULTS

The mean age of this cohort of 101 patients was 36.17 years, with a male predominance of 73.3 %. Motor vehicle accidents were the most common cause of ITON, with a statistically significant 79.2 % of cases. The patients were categorized into an "improved group" of 29 patients and an "unimproved group" of 72. The unimproved group had a significantly older mean age and poorer initial visual acuity of 20/200 (p-values 0.001 and p < 0.001 respectively). There was no significant difference between Computed Tomography (CT) findings in the two groups. The improved group had significantly better visual acuity (VA) at 1-month and final follow-up visit than the unimproved group (both p < 0.001). Differences between gender, Glasgow coma score, associated underlying diseases, and duration from trauma to intravenous glucocorticoids therapy in the two groups were not statistically significant. Multivariable logistic regression analysis identified patient age of 40 years or more (Odds ratio (OR) 3.447, 95 % CI, 1.085-10.955, p = 0.036) and poor baseline VA (OR 6.628, 95 % Confidence Interval (CI), 2.308-19.036, p < 0.001) as significant risk factors for poor visual outcome in ITON patients.

CONCLUSIONS

No clear benefit was found of intravenous glucocorticoids in treatment of ITON. Patients aged 40 years or more and/or with poor baseline visual status should be advised that they are at increased risk of poor final visual outcomes.

Retinal peripapillary microvasculature in indirect traumatic optic neuropathy predicted prognosis of endoscopic trans-ethmosphenoid optic canal decompression

PURPOSES

The purpose of this study is to quantify the alteration of retinal peripapillary microvasculature and structure in unilateral indirect traumatic optic neuropathy (ITON) and figure out predicted factors of visual improvement for ITON patients with endoscopic trans-ethmosphenoid optic canal decompression (ETOCD) after one month.

METHODS

Twenty healthy controls and 72 unilateral ITON patients were included. Optical coherence tomography angiography was used to analyse radial peripapillary capillary (RPC) density, peripapillary retinal nerve fibre layer (pRNFL) thickness, superficial retinal capillary plexus (SRCP) and deep retinal capillary plexus (DRCP) density. Associations between preoperative parameters and postoperative best-corrected visual acuity (BCVA) were determined. The receiver operating characteristic (ROC) curves were used to figure out predicted factors of visual improvement for ITON after ETOCD one month.

RESULTS

In ITON eyes, the preoperative global RPC density, pRNFL thickness and SRCP density were reduced compared with unaffected eyes (p ≤ 0.001). Multivariate linear regression showed that preoperative global RPC density (Standardized β = -0.273), SRCP density (Standardized β = -0.183), DRCP density (Standardized β = -0.098) and preoperative BCVA (Standardized β = 0.795) were associated with the postoperative BCVA (All p < 0.001). The area under the curve (AUC) of preoperative global RPC density to predict visual improvement after ETOCD was 0.816, while the AUCs of preoperative BCVA, global pRNFL thickness, SRCP and DRCP density were 0.575, 0.756, 0.516 and 0.615, respectively.

CONCLUSIONS

The alteration of peripapillary area, especially the reduced RPC density, occurred in ITON eyes. The preoperative RPC density was associated with postoperative BCVA and was shown to be highly predictive for visual improvement after ETOCD one month.

Analyses of Foveal Avascular Zone in Patients with General Blunt Ocular Trauma Using Optical Coherence Tomography Angiography

PURPOSE

To investigate the effect of blunt ocular trauma (BOT) on foveal circulation, and in particular the foveal avascular zone (FAZ), using optical coherence tomography angiography (OCTA).

METHODS

This retrospective study consisted of 96 eyes (48 traumatized eyes and 48 nontraumatized eyes) from 48 subjects with BOT. We analyzed the FAZ area of deep capillary plexus (DCP) and superficial capillary plexus (SCP) immediately after BOT and at 2 weeks after BOT. We also evaluated the FAZ area of DCP and SCP in patients with and without blowout fracture (BOF).

RESULTS

There were no significant differences in FAZ area between traumatized and nontraumatized eyes at DCP and SCP in the initial test. In traumatized eyes, the FAZ area at SCP was significantly reduced on follow-up when compared to initial test (p = 0.01). In case of eyes with BOF, there was no significant differences in FAZ area between traumatized and nontraumatized eyes at DCP and SCP on initial test. No significant difference of FAZ area was found on follow-up relative to the initial test, whether in the DCP or SCP. In case of eyes without BOF, there was no significant differences of FAZ area between traumatized and nontraumatized eyes at DCP and SCP in initial test. Also, no significant difference of FAZ area at DCP was found on follow-up test compared to initial test. However, the FAZ area at SCP was significantly reduced in follow-up test compared with that in the initial test (p = 0.04).

CONCLUSIONS

Temporary microvascular ischemia occurs in the SCP of patients after BOT. Patients should be warned of transient ischemic changes that may occur after trauma. OCTA can provide useful information regarding the subacute changes in the FAZ at SCP after BOT, even without evident findings of structural damage on fundus examination.