The blood supply of the optic nerve head and the evaluation of it - myth and reality

Clinical efficacy of dexamethasone parabulbar injection in patients with Nonarteritic anterior ischemic optic neuropathy

Background

Nonarteritic anterior ischemic optic neuropathy (NAAION) is a common optic neuropathy that often leads to significant visual acuity loss in patients. The present study evaluated the effects of parabulbar dexamethasone injection on visual outcomes in patients with NAAION.

Methods

This retrospective case-control study included patients diagnosed with NAAION between January 2019 and December 2022. Thirty-four patients with NAAION (34 eyes) received dexamethasone parabulbar injections, while 39 patients with NAAION (39 eyes) received oral corticosteroid treatment (control group). Best-corrected visual acuity (BCVA), visual field (VF) defect, and retinal nerve fiber layer (RNFL) thickness of the affected eye were compared between groups at baseline and 2, 6, and 12 weeks post-treatment.

Results

Mean BCVA significantly improved after 6 and 12 weeks in the injection groups compared with the control group (all P < 0.01). The visual field indices, mean deviation and pattern standard deviation significantly improved in the injection group compared with the control group after 2, 6, and 12 weeks (all P < 0.01). The RNFL showed a remarkable decrease in edema after 6 weeks (superior and nasal P values 0.005 and 0.013, respectively) in the injection group compared with the control group. Significant RNFL thinning was also observed in superior, inferior, temporal, and nasal quadrants in the control group after 12 weeks (all P values < 0.01). Also, fewer side effects were observed in the injection group compared to the control group.

Conclusions

The results of this study suggested that dexamethasone parabulbar injection might be a safe and effective intervention for relieving visual acuity and VF in patients with NAAION.

The Role of Optical Coherence Tomography Angiography in Glaucoma

Glaucoma is the leading cause of irreversible vision loss and comprises a group of chronic optic neuropathies characterized by progressive retinal ganglion cell (RGC) loss. Various etiologies, including impaired blood supply to the optic nerve, have been implicated for glaucoma pathogenesis. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality for visualizing the ophthalmic microvasculature. Using blood flow as an intrinsic contrast agent, it distinguishes blood vessels from the surrounding tissue. Vessel density (VD) is mainly used as a metric for quantifying the ophthalmic microvasculature. The key anatomic regions for OCTA in glaucoma are the optic nerve head area including the peripapillary region, and the macular region. Specifically, VD of the superficial peripapillary and superficial macular microvasculature is reduced in glaucoma patients compared to unaffected subjects, and VD correlates with functional deficits measured by visual field (VF). This renders OCTA similar in diagnostic capabilities compared to structural retinal nerve fiber layer (RNFL) thickness measurements, especially in early glaucoma. Furthermore, in cases where RNFL thickness measurements are limited due to artifact or floor effect, OCTA technology can be used to evaluate and monitor glaucoma, such as in eyes with high myopia and eyes with advanced glaucoma. However, the clinical utility of OCTA in glaucoma management is limited due to the prevalence of imaging artifacts. Overall, OCTA can play a complementary role in structural OCT imaging and VF testing to aid in the diagnosis and monitoring of glaucoma.

Prevalence and Distribution of Macular Fluid with Central Retinal Artery Occlusion and Anterior Ischemic Optic Neuropathy

Purpose

To examine the prevalence and distribution of fluid within a cohort of eyes with acute central retinal artery occlusion (CRAO) and non-arteritic anterior ischemic optic neuropathy (AION) using optical coherence tomography (OCT).

Methods

A retrospective analysis of patient records and OCT imaging. Patients presenting with acute CRAO or AION who had available macular OCT imaging and no co-morbidities known to cause macular fluid were included in the analysis. Baseline characteristics, visual acuity (VA), and fluid presence and distribution among the retinal layers were recorded.

Results

In the 16 eyes with acute CRAO, fluid was noted in 5 eyes (31%), which was mainly subretinal (3 eyes) or intraretinal located within the outer retinal layers (3 eyes). Only one eye had inner retinal cysts. Of the 11 eyes with acute AION, fluid was present in 8 eyes (73%). Subretinal fluid was noted in 4 eyes and extended to the foveal area in 3 of them, and outer retinal versus inner retinal cysts were noted in 6 versus 3 eyes, respectively. None of the eyes showed hard exudate deposition. In the small subset of eyes with CRAO and macular fluid that were followed-up, VA improved, while in eyes with AION, VA remained stable.

Conclusion

Macular fluid on OCT is not an uncommon feature of acute CRAO and AION and is mainly distributed within the outer retinal layers or subretinal space. Fluid is an understudied feature of retinal and optic nerve head infarction and may have a role in predicting neuronal damage extent and visual outcome.

The Relationship Between Artificial Intelligence-Assisted OCT Angiography-Derived Foveal Avascular Zone Parameters and Visual-Field Defect Progression in Eyes with Open-Angle Glaucoma

Purpose

To investigate clinical factors associated with foveal avascular zone (FAZ) parameters obtained using OCT angiography (OCTA) with assistance from a previously developed artificial intelligence (AI) platform in eyes with open-angle glaucoma (OAG).

Design

Retrospective longitudinal.

Participants

This study followed up 885 eyes of 558 patients with OAG for ≥ 2 years; all eyes underwent ≥ 5 Humphrey visual-field (VF) tests and had 3.0 × 3.0 mm macular OCTA scans available.

Methods

Average total deviation (TD) in the superior, superocentral, inferocentral, and inferior sectors of the Humphrey 24-2 program was calculated. We collected 3.0 × 3.0 mm macular OCTA images from each patient and used a previously developed AI platform with these images to obtain FAZ parameters, including FAZ area, FAZ circularity index (CI), and FAZ perimeter. Multivariable linear mixed-effects models were used to analyze the relationship between FAZ parameters, TD or TD slope in each quadrant, and systemic factors, adjusting for potential confounding factors, including axial length.

Main Outcome Measures

Ophthalmic and systemic variables, FAZ parameters, and TD or TD slope in each quadrant.

Results

The multivariable model showed that FAZ parameters were correlated with both TD and TD slope in the inferocentral quadrant (β = -0.244 - 0.168, P < 0.001). Both upper-half and lower-half FAZ parameters were better associated with TD-inferocentral and TD-inferocentral slope than TD-superocentral or TD-superocentral slope in terms of β size and statistical significance, indicating that there was no evident vertical anatomical correspondence between TD in the central quadrant and FAZ parameters. Foveal avascular zone area enlargement was associated with female gender (β = 0.242, P = 0.003). Loss of FAZ circularity was associated with both aging and comorbid sleep apnea syndrome (SAS) (yes: 1, no: 0) (β = -0.188, P < 0.001; β = -0.261, P = 0.031, respectively). Foveal avascular zone perimeter elongation was associated with aging and female gender (β = 0.084, P = 0.040; β = 0.168, P = 0.042, respectively).

Conclusions

Artificial intelligence-assisted OCTA-measured FAZ enlargement and irregular shape might be good markers of ocular hypoperfusion and associated inferocentral VF defect progression in eyes with OAG. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Influence of choroidal microvasculature dropout on progressive retinal nerve fibre layer thinning in primary open-angle glaucoma: comparison of parapapillary β-zones and γ-zones

BACKGROUND/AIMS

To compare the influence of choroidal microvasculature dropout (cMvD) on progressive retinal nerve fibre layer (RNFL) thinning in glaucomatous eyes with parapapillary β-zones and γ-zones.

METHODS

294 eyes with primary open-angle glaucoma (POAG) and parapapillary atrophy (PPA) underwent optical coherence tomography (OCT) to determine the type of PPA and OCT angiography scanning of the optic nerve head to determine the presence of cMvD. Eyes were classified based on the type of PPA (β-zones and γ-zones), and their clinical characteristics were compared. Factors associated with the rate of rapid progressive RNFL thinning were determined in each group, including the presence of cMvD as an independent variable.

RESULTS

Of the 294 eyes, 186 and 108 were classified as having β-zones and γ-zones, respectively. The rate of RNFL thinning was slower (p<0.001), axial length was longer (p<0.001) and presence of cMvD was less frequent (57.4% vs 73.1%, p=0.006) in eyes with γ-zone than those with β-zone. Multivariate analyses showed that greater lamina cribrosa curvature (p=0.047) and the presence of cMvD (p=0.010) were associated with a faster rate of RNFL thinning in eyes with β-zone, whereas larger intraocular pressure fluctuation (p<0.001), shorter axial length (p=0.042) and greater baseline RNFL thickness (p<0.001) were associated with a faster rate of RNFL thinning in eyes with γ-zone.

CONCLUSIONS

The presence of cMvD was significantly associated with a faster rate of RNFL thinning in POAG eyes with β-zone, but not γ-zone. The pathogenic consequences of cMvD in POAG eyes may depend on accompanying peripapillary structures.

Parapapillary choroidal microvasculature in retrobulbar optic neuritis: An optical coherence tomography angiography study

PURPOSE

To compare superficial and deep vascular characteristics of the optic disc in retrobulbar optic neuritis using optical coherence tomography angiography (OCT-A).

METHODS

Nineteen patients with unilateral non-infectious retrobulbar neuritis were included in the study. The contralateral eyes of each patient were served as controls. OCT-A scans of the optic discs were performed in a 4.5 × 4.5 mm rectangular area, while macular OCT-A scans were performed in a 6 × 6 mm rectangular area. Various parameters, including radial peripapillary capillary (RPC) density, peripapillary retinal nerve fibre layer (pRNFL) thickness, cup volume, rim area, disc area, cup-to-disc (c/d) area ratio, and vertical and horizontal c/d ratios were automatically obtained using the instrument software. The density for superficial capillary plexus (SCP) and deep capillary plexus (DCP) were assessed using macular OCT-A. Parapapillary choroidal microvascular (PPCMv) density was calculated using MATLAB software.

RESULTS

Parafoveal inferior, perifoveal total and inferior SCP densities were significantly decreased in eyes with optic neuritis when compared with contralateral control eyes in OCT-A measurements (respectively, p = 0.027, p = 0.041, p = 0.045). The axial lengths, (p = 0.72), vertical and horizontal cup-disc ratios, and disc area, cup-disc areas, cup volumes, and pRNFL thicknesses between the groups were similar (for each, p>0.05).

CONCLUSIONS

This study demonstrated for the first time that patients with retrobulbar optic neuritis had decreased SCP densities, though it did not cause any changes in PPCMv density.

Glaucoma Surgery and Ocular Blood Flow in Colour Doppler Imaging: Is There a Link?

Glaucoma is a common cause of blindness worldwide. This disease is characterised by increased intraocular pressure (IOP) and the concomitant disruption of ocular haemodynamic. Several studies have demonstrated that trabeculectomy is associated with changes in extraocular blood flow. In this study, we reviewed the available evidence on the use of colour Doppler imaging to evaluate and manage patients with open-angle glaucoma. We present the detailed anatomy of ocular blood flow to provide a background for the research findings. We also discuss the physiological foundations of ocular blood flow and detailed flow characteristics of specific extraocular vessels. Finally, we reviewed published studies that analysed the effects of glaucoma surgery on the blood flow parameters of the eye.

Changes in Optic Nerve Head Blood Flow During Horizontal Ocular Duction

Purpose

In this study, we aimed to compare blood flow changes in the optic nerve head (ONH) during horizontal ocular duction among normal, primary open-angle glaucoma (POAG), and normal-tension glaucoma (NTG) eyes.

Methods

In this cross-sectional study, we included 90 eyes from 90 participants (30 control eyes, 30 POAG eyes, and 30 NTG eyes). ONH blood flow was measured with laser speckle flowgraphy using an external fixation light to induce central gaze, abduction, and adduction at 30 degrees for each eye. The mean blur rate (MBR) of the entire ONH area (MA), vascular region (MV), and tissue region (MT), and the change ratio were analyzed. The change ratio was defined as abduction or adduction value/central gaze value.

Results

In the control group, MA significantly decreased during adduction (22.9 ± 3.7) compared with that during central gaze (23.6 ± 3.9, P < 0.05). In the POAG group, MA (adduction = 17.4 ± 3.8 and abduction = 17.3 ± 3.6) and MV (adduction = 37.9 ± 5.6 and abduction = 38.0 ± 5.6) significantly decreased during adduction and abduction compared with those during central gaze (18.0 ± 4.1 and 39.5 ± 6.3, respectively, P < 0.05). In the NTG group, MA significantly decreased during adduction (17.4 ± 4.2) compared with that during central gaze (18.1 ± 4.6) and abduction (18.1 ± 4.8, P < 0.05). The change ratio did not differ between the glaucoma and control groups.

Conclusions

ONH blood flow decreased during horizontal ocular duction regardless of normal or glaucoma states; however, the change ratio was comparable between the normal and glaucoma groups.

Diffusion-weighted imaging of the orbit

Orbital lesions compose a heterogeneous group of pathologies that often present with non-specific imaging findings on conventional magnetic resonance imaging (MRI) sequences (T1-and T2-weighted). Accordingly, the application of diffusion MRI offers an opportunity to further distinguish between lesions along this spectrum. Diffusion-weighted imaging (DWI) represents the simplest and most frequent clinically utilised diffusion imaging technique. Recent advances in DWI techniques have extended its application to the evaluation of a wider spectrum of neurological pathology, including orbital lesions. This review details the manifestations of select orbital pathology on DWI and underscores specific situations where diffusion imaging allows for increased diagnostic sensitivity compared to more conventional MRI techniques. These examples also describe preferred management for orbital lesions identified by DWI.

Diagnostic value of contrast-enhanced 3D FLAIR sequence in acute optic neuritis

PURPOSE

Contrast-enhanced fluid-attenuated inversion recovery (FLAIR) sequence of the brain has the potential for detecting optic nerve abnormality. This study aimed to compare the diagnostic value of whole-brain contrast-enhanced three-dimensional FLAIR with fat suppression (CE 3D FLAIR FS) sequence in detecting acute optic neuritis to dedicated orbit MRI and clinical diagnosis.

MATERIALS AND METHODS

Twenty-two patients with acute optic neuritis who underwent whole-brain CE-3D-FLAIR FS and dedicated orbit MRI were retrospectively included. The hypersignal FLAIR of the optic nerve on whole-brain CE-3D-FLAIR FS, enhancement, and hypersignal T2W on orbit images were assessed. The optic nerve to frontal white matter signal intensity ratio on CE-FLAIR FS was calculated as maximum signal intensity ratio (SIR) and mean SIR.

RESULTS

Twenty-six hypersignals of optic nerves were found on CE-FLAIR FS from 30 pathologic nerves. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of CE FLAIR FS brain and dedicated orbital images for diagnosing acute optic neuritis were 77%, 93%, 96%, 65%, and 82% and 83%, 93%, 96%, 72%, and 86%, respectively. Optic nerve to frontal white matter SIR of the affected optic nerves was higher than that of normal optic nerves. Using a cutoff maximum SIR of 1.24 and cutoff mean SIR of 1.16, the sensitivity, specificity, PPV, NPV, and accuracy were 93%, 86%, 93%, 80%, and 89% and 93%, 86%, 93%, 86%, and 91%, respectively.

CONCLUSION

The hypersignal of the optic nerve on whole-brain CE 3D FLAIR FS sequence has qualitative and quantitative diagnostic potential in patients with acute optic neuritis.

Alterations in retrobulbar haemodynamics in thyroid eye disease

PURPOSE

To study the orbital perfusion parameters of ophthalmic artery (OA) and central retinal artery (CRA) in inactive TED and the changes following surgical decompression.

METHODS

Non-randomised clinical trial. 24 inactive moderate-to-severe TED orbits of 24 euthyroid cases underwent surgical decompression and examined again at 3 months. The peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistivity index (RI) of OA and CRA were evaluated using colour doppler imaging and normative database was established using 18 healthy controls.

RESULTS

The mean age was 39.38 ± 12.56 years and male: female ratio was 1: 1.18. Intraocular pressure was higher, and CRA-PSV, CRA-RI, OA-PSV, and OA-EDV were lower in TED in comparison to heathy orbits. The CRA-PSV, CRA-EDV, OA-PSV, and OA-EDV negatively correlated with proptosis and duration of thyroid disease. The area under curve of OA-PSV (95% CI:0.964-1.000, p < 0.001) and OA-EDV (95% CI:0.699-0.905, p < 0.001) helped in differentiating TED orbits from HC, and in predicting the severity of disease. Post decompression, CRA-PSV, CRA-EDV, OA-PSV, and OA-EDV improved, with decrease in CRA-RI and OA-RI in both lipogenic and MO.

CONCLUSIONS

The orbital perfusion is reduced in inactive TED. The changes in OA flow velocities can help in differentiating inactive TED from healthy orbits and progression of TED. Sequential orbital CDI of OA and CRA can serve as an objective tool for case selection and monitoring response to surgical decompression.

Automated evaluation of parapapillary choroidal microvasculature in thyroid eye disease

PURPOSE

The purpose of the study was to investigate the parapapillary choroidal microvasculature in thyroid eye disease (TED) using optical coherence tomography angiography (OCTA).

METHODS

Only one eye of each subject was included in the study. Patients with TED and controls were included in the study. Participants were divided into three groups: control, inactive TED (ITED) and active TED (ATED). OCTA scans of the optic discs were obtained in a 4.5 × 4.5-mm rectangular area. Radial peripapillary capillary (RPC) density and peripapillary retinal nerve fibre layer (pRNFL) thickness were automatically calculated by the device software. Parapapillary choroidal microvasculature (PPCMv) density was automatically calculated using MATLAB software.

RESULTS

Forty-one patients with TED and 40 controls were included in the study. RPC density was significantly decreased in the ATED and dysthyroid optic neuropathy (DON) group compared to the controls and ITED group. There was significant increase in pRNFL in the ATED group. PPCMv density increased in the ATED group compared to the controls in whole ring area. The RPC density was significantly correlated with the TSHr Ab level (r < - 0.396, p < 0.001). Clinical activity score correlated positively with PPCMv density (r = 0.349, p = 0.001) but negatively with RPC density (r = - 0.321, p = 0.004).

CONCLUSION

Changes in peripapillary microvascular perfusion may play a role in the development of DON. As the severity of TED increases with clinical activity, so do the changes observed in peripapillary parameters. The decrease in RPC density may be due to compression caused by optic disc oedema, which may result in reduced blood flow. The increase in PPCMv density may be related to factors such as orbital congestion.

Rate of Retinal Nerve Fiber Layer Thinning in Glaucomatous Eyes With Optic Disc and Parapapillary Deep-Layer Microvasculature Loss

PRCIS

Microvasculature dropout in the parapapillary choroidal layer was a more important biomarker of glaucomatous nerve fiber layer thinning when it presented with deep-layer microvasculature of the optic disc rather than when it presents by itself.

PURPOSE

To characterize open angle glaucoma eyes with optic nerve head deep-layer microvasculature dropout (MvD-D) and parapapillary choroidal layer microvasculature dropout (MvD-P) and compare their retinal nerve fiber layer (RNFL) thinning rate.

MATERIAL AND METHODS

This study included 122 open angle glaucoma eyes that underwent ≥5 serial spectral-domain optical coherence tomography scans during a mean follow-up of 5.4 years. Swept-source optical coherence tomography angiography was used to evaluate MvD-P and MvD-D. Subjects were classified into 3 groups according to the presence of MvD-P and MvD-D: (1) no dropout (n=37); (2) solely MvD-P (n=40), and (3) both MvD-P and MvD-D (n=45). The RNFL thinning rate was compared among the 3 groups, and the associated factors were assessed by Cox proportional hazard analysis.

RESULTS

RNFL thinning rates were highest in the group with both MvD-P and MvD-D, followed by the group with solely MvD-P and finally by the no dropout group (-0.24 vs. -0.65 vs. -1.20 μm/y, P <0.001). Thinner central corneal thickness [hazard ratio (HR)0.990, P =0.003], presence of disc hemorrhage (HR=1.802, P =0.035), and coexistence of MvD-P and MvD-D (HR=2.941, P <0.001) were the factors associated with RNFL thinning.

CONCLUSIONS

The coexistence of MvD-P and MvD-D was associated with faster RNFL thinning than MvD-P alone or no dropout, which suggested that observing the optic disc deep microvasculature along with parapapillary choroidal layer using Swept-source optical coherence tomography angiography may be clinically relevant in monitoring glaucoma progression.

Choroidal thickness and effect of sex and age in Africans

Purpose

The purpose of the study is to evaluate choroidal thickness (CT) and the effect of age and gender in healthy Africans using enhanced depth imaging spectral-domain optical coherence tomography.

Materials and Methods

In 172 eyes of 88 volunteers, the CT in the central subfoveal (CSF) area and at 2.5 mm superior, inferior, nasal, and temporal quadrants was measured. Four eyes were excluded due to poor image quality and image decentration. Simple linear regression was used to measure the effect of age on CT, and statistical analysis was done using IBM SPSS Statistics version 22.

Results

The were 88 male and 84 female eyes, aged 30-80 years. The mean CT was CSF 265.44 ± 6.2 μm; inferior 256.19 ± 70.6 μm; superior 249.92 ± 76.2 μm; temporal 235.51 ± 70.3 μm; and nasal 199.53 ± 69.8 μm. The choroid was thickest in the CSF > Inferior > Superior > Temporal, and the nasal quadrant was thinnest in all age groups. There was a considerable decrease in the CSF with increasing age (P < 0.001). CT in males and females was similar since the difference in mean CSF CT between the genders was 2.085 μm (P = 0.858). Menopausal females had thinner CSF CT compared to premenopausal females (P < 0.001), but this was due to the aging effect.

Conclusion

CT decreases significantly with increasing age but shows no gender difference in Africans. A comparison of CT studies from other ethnic nationalities shows some similarity with CT in Africans, suggesting that CT findings from other ethnic groups can be extrapolated to Africans.

Impaired cerebrovascular reactivity correlates with reduced retinal vessel density in patients with carotid artery stenosis: Cross-sectional, single center study

BACKGROUND

The cerebral and retinal circulation systems are developmentally, anatomically, and physiologically interconnected. Thus, we hypothesized that hypoperfusion due to atherosclerotic stenosis of the internal carotid artery (ICA) can result in disturbances of both cerebral and retinal microcirculations. We aimed to characterize parameters indicating cerebrovascular reactivity (CVR) and retinal microvascular density in patients with ICA stenosis, and assess if there is correlation between them.

METHODS

In this cross-sectional study the middle cerebral artery (MCA) blood flow velocity was measured by transcranial Doppler (TCD) and, simultaneously, continuous non-invasive arterial blood pressure measurement was performed on the radial artery by applanation tonometry. CVR was assessed based on the response to the common carotid artery compression (CCC) test. The transient hyperemic response ratio (THRR) and cerebral arterial resistance transient hyperemic response ratio (CAR-THRR) were calculated. Optical coherence tomography angiography (OCTA) was used to determine vessel density (VD) on the papilla whole image for all (VDP-WIall) and for small vessels (VDP-WIsmall). The same was done in the peripapillary region: all (VDPPall), and small (VDPPsmall) vessels. The VD of superficial (VDMspf) and deep (VDMdeep) macula was also determined. Significance was accepted when p<0.05.

RESULTS

Twenty-four ICA stenotic patients were evaluated. Both CVR and retinal VD were characterized. There was a significant, negative correlation between CAR-THRR (median = -0.40) and VDPPsmall vessels (median = 52%), as well as between VDPPall vessels (median = 58%), and similar correlation between CAR-THRR and VDP-WIsmall (median = 49.5%) and between VDP-WIall (median = 55%).

CONCLUSION

The significant correlation between impaired cerebrovascular reactivity and retinal vessel density in patients with ICA stenosis suggests a common mechanism of action. We propose that the combined use of these diagnostic tools (TCD and OCTA) helps to better identify patients with increased ischemic or other cerebrovascular risks.

Uveal vascular bed in health and disease: uveal vascular bed anatomy. Paper 1 of 2

The uveal vascular bed is the largest vascular system in the eye and has a role in supplying almost every tissue in the eyeball. This makes it the most important ocular vascular system. This is an up-to-date review of the literature of the entire uveal vascular bed in health based on detailed anatomy of the posterior ciliary arteries (PCAs), anterior ciliary arteries, cilioretinal arteries, and vortex veins. Although postmortem injection cast preparations gave us useful information on the morphology of the choroidal vascular bed; in vivo studies showed that they misled us for centuries about the in vivo situation. According to the postmortem cast studies, the uveal vascular bed has no segmental distribution, the uveal vessels anastomose freely with one another, there are inter-arterial and arteriovenous anastomoses in the choroid, and the choriocapillaris form a freely communicating and an uninterrupted vascular bed in the entire choroid.

Uveal vascular bed in health and disease: lesions produced by occlusion of the uveal vascular bed and acute uveal ischaemic lesions seen clinically. Paper 2 of 2

From studies on postmortem anatomical descriptions of the uveal vascular bed, it was generally concluded that occlusion of PCA or its branches should not produce an ischemic lesion. However, in vivo studies have recorded that the PCAs and their branches, right down to the terminal choroidal arterioles, and the choriocapillaris, have a segmental distribution in the choroid, and that PCAs and choroidal arteries function as end-arteries. This explains the basis of the occurrence of isolated inflammatory, ischemic, metastatic, and degenerative choroidal lesions, which are usually localized. Thus, in vivo studies have completely revolutionized our concept of the uveal vascular bed in disease.

Estimating pulsatile ocular blood volume from intraocular pressure, ocular pulse amplitude, and axial length

The purpose of this study was to develop a method of estimating pulsatile ocular blood volume (POBV) from measurements taken during an ophthalmic exam, including axial length and using a tonometer capable of measuring intraocular pressure (IOP) and ocular pulse amplitude (OPA). Unpublished OPA data from a previous invasive study was used in the derivation, along with central corneal thickness (CCT) and axial length (AL), as well as IOP from the PASCAL dynamic contour tonometer (DCT) and intracameral (ICM) measurements of IOP for 60 cataract patients. Intracameral mean pressure was set to 15, 20, and 35 mmHg (randomized sequence) in the supine position, using a fluid-filled manometer. IOP and OPA measurements were acquired at each manometric setpoint (DCT and ICM simultaneously). In the current study, ocular rigidity (OR) was estimated using a published significant relationship of OR to the natural log of AL in which OR was invasively measured through fluid injection. Friedenwald’s original pressure volume relationship was then used to derive the estimated POBV, delivered to the choroid with each heartbeat as a function of OR, systolic IOP (IOP_sys), diastolic IOP (IOP_dia), and OPA, according to the derived equation POBV = log (IOP_sys/IOP_dia) / OR. Linear regression analyses were performed comparing OPA to OR and calculated POBV at each of the three manometric setpoints. POBV was also compared to OPA/IOP_dia with all data points combined. Significance threshold was p < 0.05. OR estimated from AL showed a significant positive relationship to OPA for both DCT (p < 0.011) and ICM (p < 0.006) at all three manometric pressure setpoints, with a greater slope for lower IOP. Calculated POBV also showed a significant positive relationship to OPA (p < 0.001) at all three setpoints with greater slope at lower IOP, and a significant negative relationship with IOP_dia. In the combined analysis, POBV showed a significant positive relationship to OPA/ IOP_dia (p < 0.001) in both ICM and DCT measurements with R² = 0.9685, and R² = 0.9589, respectively. POBV provides a straight-forward, clinically applicable method to estimate ocular blood supply noninvasively. Higher IOP in combination with lower OPA results in the lowest values of POBV. The simplified ratio, OPA/ IOP_dia, may also provide a useful clinical tool for evaluating changes in ocular blood supply in diseases with a vascular component, such as diabetic retinopathy and normal tension glaucoma. Future studies are warranted.

Optic nerve head vessel density using OCTA in patients with primary angle closure disease: A systematic review and network meta-analysis

PURPOSE

Elevated intraocular presure secondary to angle closure in angle closure glaucoma is considered the primary mechanism in the development of optic nerve damage. There is evidence that vascular mechanisms may play a role in the pathogenesis of primary angle closure disease (PACD). We aimed to evaluate optic nerve head vessel density in PACD.

METHODS

PubMed, Scopus, and Web of Science were searched. Observational investigations were included. A frequentist network meta-analysis was performed. The primary outcome was circumpapillary vessel density (cpVD), and the secondary outcome was peripapillary retinal nerve fiber layer (pRNFL) thickness.

RESULTS

One thousand twenty four eyes from eleven studies were included in the study. There was no difference in cpVD between the primary angle closure glaucoma (PACG) and acute primary angle closure (APAC) group however, there was a significant decreasing in pRNFL thickness in the PACG group compared to APAC group. In the PACG and APAC group, cpVD and pRNFL thickness were decreased compared to primary angle closure (PAC), primary angle closure suspect (PACS), and control group. There was no difference in cpVD and pRNFL thickness between PAC, PACS and control group.

CONCLUSION

This study has shown that the elevated intraocular pressure is an important factor affecting optical nerve perfusion in PACD. The decreasing in cpVD and RNFL thickness was more severe in the PACG and APAC group.

Choroidal Microvasculature Dropout in the Absence of Parapapillary Atrophy in POAG

Purpose

To describe the parapapillary choroidal microvasculature dropout (CMvD) in glaucomatous eyes without β-zone parapapillary atrophy (β-PPA) and compare its characteristics with that of CMvD with β-PPA.

Methods

Peripapillary choroidal microvasculature was evaluated on en face images obtained using optical coherence tomography angiography. CMvD was defined as a focal sectoral capillary dropout with no visible microvascular network identified in the choroidal layer. Peripapillary and optic nerve head structures, including the presence of β-PPA, peripapillary choroidal thickness and lamina cribrosa curvature index were evaluated using the images obtained by enhanced depth-imaging optical coherence tomography.

Results

The study included 100 glaucomatous eyes with CMvD (25 without and 75 with β-PPA) and 97 eyes without CMvD (57 without and 40 with β-PPA). Regardless of the presence of β-PPA, eyes with CMvD tended to have a worse visual field at a given RNFL thickness than eyes without CMvD, with patients having eyes with CMvD having lower diastolic blood pressure and more frequent cold extremities than patients with eyes lacking CMvD. Peripapillary choroidal thickness was significantly smaller in eyes with than without CMvD, but was not affected by the presence of β-PPA. β-PPA without CMvD was not associated with vascular variables.

Conclusions

CMvD were found in the absence of β-PPA in glaucomatous eyes. CMvDs had similar characteristics in the presence and absence of β-PPA. Clinical and optic nerve head structural characteristics potentially relevant to compromised optic nerve head perfusion were dependent on the presence of CMvD, rather than the presence of β-PPA.

Orbital and ocular perfusion in thyroid eye disease

Thyroid eye disease (TED) is characterized by enlargement of extraocular muscles, an increase in retrobulbar fat, orbital fibrosis, and fluctuations in plasma thyroid hormone levels in most patients, often associated with raised autoantibody titers. The occurrence of orbital space conflict compromises the orbital perfusion, unchecked progression of which results in irreversible loss of visual acuity and visual fields. The quantitative assessment of orbital perfusion can be done by measurement of blood flow velocities in the superior ophthalmic vein (SOV), ophthalmic artery (OA), central retinal artery (CRA), and posterior ciliary artery by color Doppler imaging. The retinal and choroidal microvasculature is studied by optical coherence tomography and optical coherence tomography angiography. The orbital and ocular perfusion fluctuates during the course of TED. Orbital congestion is reflected by the reduction or reversal of SOV flow and an increase in subfoveal choroidal thickness. The active phase is characterized by high blood flow velocities of the OA and CRA. The onset of dysthyroid optic neuropathy is associated with reduced arterial perfusion and reduction in parafoveal and peripapillary vascular density. Orbital decompression improves the SOV flow and decreases the resistivity index of CRA. Sequential evaluation of orbital hemodynamic changes can thus supplement the clinical scoring systems for monitoring and planning intervention in TED.

Association between glaucoma and risk of stroke: A systematic review and meta-analysis

Background/objectives

Recently, several studies explored the association between glaucoma and the risk of stroke, but these results were inconsistent. Therefore, we conducted a meta-analysis to examine this possible association.

Methods

We conducted a systematic literature search of PubMed, Embase, and Web of Science from inception until February 28, 2022. Random-effects meta-analysis was conducted by generic inverse variance method. Sensitivity and subgroup analyses were performed. The review protocol has been registered with PROSPERO (CRD42022312797).

Results

Seven studies (involving 362,267 participants) have been published from 2004 to 2017 and included in the meta-analysis. These studies included four retrospective cohort studies, two cross-sectional studies, and one case-control study. Meta-analysis of these data has shown that glaucoma was associated with an increased risk of stroke (OR = 1.94, 95% CI = 1.45-2.59). Most of the subgroup analyses demonstrated similar results. These findings were stable in sensitivity analyses.

Conclusions

We found that glaucoma was associated with an increased risk of stroke. The result suggests that patients with glaucoma need to be assessed the risk of stroke to reduce the incidence of stroke. To better explore the nature of any association, prospective studies that consider the stroke subtypes, sample size, district, and other confounding factors are needed.

Optical coherence tomography angiography (OCT angiography) in anterior ischemic optic neuropathy (AION): A systematic review and meta-analysis

PURPOSE

To summarize the evidence available on optical coherence tomography angiography (OCTA) in patients with anterior ischemic optic neuropathy (AION).

METHODS

Systematic searches were conducted on PubMed, Embase, Web of Science, Scopus, Cochrane, and Google Scholar Databases. The quality assessment of the included studies was performed using Newcastle -Ottawa Scale. The data were extracted to an Excel sheet. Vessel density (VD) data were pooled by random effects model, presented as pooled percentage change (PPC), and weighted mean differences (WMD). Additional subgroup analysis was also conducted.

RESULTS

In initial searches in online databases, we found 3535 citations, and after screening and checking the titles and abstracts, 26 articles were ultimately eligible for our meta-analysis. The overall PPC of Intra-optic-disc (IOD) VD (-10.73%; p = 0.017, I² = 0.0%; p = 0.898) was lower than that of radial peripapillary (RP) VD (-17.57%; p < 0.001, I² = 44.3%; p = 0.002). The overall PPC of peripapillary choroid VD (-6.99%; p < 0.001, I² = 0.0%; p = 0.766) was significant, but noticeably lower than the pooled percentage change of RPVD and IOD VD. The WMD of RPVD was significant when non-affected fellow eyes were compared to the healthy subjects' eyes (-36.26; p < 0.001, I² = 0.0%; p = 0.706).

CONCLUSIONS

The central retinal artery and its branches might be the main vessels which are affected in AION. The superficial retina was more affected than choroid layer in AION. Also, radial peripapillary retinal nerve fibre layer was more affected than the IOD area. OCTA might be a suitable tool for prediction of AION in susceptible eyes.

A comprehensive update on the use of optical coherence tomography angiography in glaucoma

PURPOSE

The primary purpose of this review is to provide a comprehensive summary on the technical principles of OCTA and to enumerate vascular parameters being explicated for glaucoma diagnosis and progression with emphasis on recent studies. In addition, the authors also summarize the future clinical potentials of OCTA in glaucoma and enumerate the limitations of this imaging modality in the present-day scenario.

METHODS

The index study is a narrative review on OCTA in glaucoma. The authors searched the PubMed database using the key phrases ''optical coherence tomography angiography" AND "glaucoma,'' AND/OR "vascular parameters" AND/OR "ocular perfusion." Being a relatively recent development in ocular imaging, studies in which OCTA imaging had been used for glaucoma evaluation since 2012 were included until March 2022. The literature search included original studies and previous review articles, while case reports were excluded. Preliminary search was based on relevant articles with search keywords in the title and abstract. The second screening was performed by reading the full text of the literature.

RESULTS

Recent studies indicate reduction in microcirculation in glaucomatous eyes compared to the normal subjects. The area of interest for glaucoma evaluation using OCTA varies among the different studies. Based on the literature reviewed here, (1) OCTA parameters measured in the peripapillary; ONH and macular area have been shown to differentiate between glaucoma and normal eyes with a discriminatory power comparable to OCT parameters used routinely in clinics, (2) monitoring of peripapillary and macular vessel density may provide important information to the evaluation of glaucoma progression and prediction of rates of disease worsening, (3) studies suggest strong correlation between the OCTA parameters, the OCT parameters and visual function, measured by visual field testing, in glaucomatous eyes, (4) future prospects of OCTA in glaucoma evaluations using AI predicting structural and functional features and prognosis based on early vascular findings would open up scope for early detection of high-risk suspects and fast progressors in glaucoma.

CONCLUSION

OCTA can be useful in quantifying vascular parameters in the optic disc, peripapillary and the macular regions for glaucoma evaluation. OCTA shows potential to become a part of everyday glaucoma management.

Peripapillary Microvascular and Structural Parameters in Atrophic Nonarteritic Anterior Ischemic Optic Neuropathy and Their Unaffected Fellow Eyes

BACKGROUND

This cross-sectional study aimed to evaluate the peripapillary vessel density (VD), peripapillary retinal nerve fiber layer (RNFL) thickness values of eyes with atrophic nonarteritic anterior ischemic optic neuropathy (NAION), and unaffected fellow eyes.

METHODS

Peripapillary VDs and RNFL thicknesses in the peripapillary region and 4 sectors (superior, inferior, nasal, and temporal) were evaluated using optical coherence tomography angiography among 19 atrophic NAION eyes, 19 unaffected fellow eyes, and 22 age-matched and sex-matched healthy controls.

RESULTS

The NAION eyes had lower peripapillary VD and RNFL thickness values in all areas compared with both the fellow and the healthy control eyes ( P < 0.001 for all). The fellow eyes also demonstrated lower peripapillary VD values ( P = 0.02) despite similar RNFL thickness values ( P = 0.99) in the peripapillary region compared with the age-matched and sex-matched healthy controls. The peripapillary RNFL thickness values significantly correlated with peripapillary VD values in both NAION and fellow eyes.

CONCLUSIONS

Diminished RNFL thickness and peripapillary VD values were observed in atrophic NAION eyes. In addition, a tendency for a lower peripapillary VD despite similar RNFL thickness values in the fellow eyes may indicate the potential vascular risk factors for NAION.

Post-cataract surgery optic neuropathy: a chronological narrative review of the literature and speculation on pathogenesis

PURPOSE OF REVIEW

To appraise the literature on the incidence of an acute anterior optic neuropathy resembling spontaneous nonarteritic anterior ischemic optic neuropathy (NAION) following uncomplicated cataract surgery and to explore the proposed pathogenesis of both immediate and delayed onset post-cataract surgery optic neuropathy (PCSON).

RECENT FINDINGS

A number of case reports, case series, and retrospective case-controlled, big data, and population-based studies have identified an apparent association between cataract surgery and the occurrence of an acute anterior optic neuropathy that can either be immediate or delayed in onset. However, a recent study found no link between modern day cataract surgery and an increased risk of an acute anterior optic neuropathy.

SUMMARY

Immediate PCSON appears to be related to negative perfusion pressure at the level of the optic disc due to increased intraocular pressure. The pathogenesis of delayed PCSON is unknown but probably multifactorial. Patients who have experienced spontaneous NAION or PCSON in one eye may be at risk of PCSON in the fellow eye.

Predictive Modeling of Long-Term Glaucoma Progression Based on Initial Ophthalmic Data and Optic Nerve Head Characteristics

Purpose

The purpose of this study was to develop a model, based on initial optic nerve head (ONH) characteristics, predictive of long-term rapid retinal nerve fiber layer (RNFL) thinning in patients with open-angle glaucoma (OAG).

Methods

This study evaluated 712 eyes with OAG that had been followed up for >5 years with annual evaluation of RNFL thickness. Baseline ophthalmic features were incorporated into the machine learning models for prediction of faster RNFL thinning. The model was trained and tested using a random forest (RF) method, and was interpreted using Shapley additive explanations. Factors associated with faster rate of RNFL thinning were statistically evaluated using a decision tree.

Results

The RF model showed that greater lamina cribrosa (LC) curvature, higher intraocular pressure (IOP), visual field mean deviation converging towards −5 dB, and thinner peripapillary choroid at baseline were the four most significant features predicting faster RNFL thinning. Partial interaction between the features showed that larger LC curvature was a strong factor for faster RNFL thinning when it exceeded approximately 12.0. When the LC curvature was ≤12, higher initial IOP and thinner peripapillary choroid played a role in the rapid RNFL thinning. Based on the decision tree, higher IOP (>26.5 mm Hg), greater laminar curvature (>13.95), and thinner peripapillary choroid (≤117.5 µm) were the 3 most important determinants affecting the rate of RNFL thinning.

Conclusions

Baseline ophthalmic data and ONH characteristics of patients with OAG were predictive of eyes at risk of faster progression. Combinations of important characteristics, such as IOP, LC curvature, and choroidal thickness, could stratify eyes into groups with different rates of RNFL thinning.

Translational Relevance

This work lays the foundations for developing prediction models to estimate glaucoma prognosis based on initial ONH characteristics.

The Topographic Relationship Between Choroidal Microvascular Dropout and Glaucomatous Damage in Primary Angle-Closure Glaucoma

Purpose

To study the topographic relationship between parapapillary choroidal microvasculature dropout (MvD) and parapapillary retinal nerve fiber layer (RNFL) defect in primary angle-closure glaucoma (PACG) eyes.

Methods

This cross-sectional study was carried out in a glaucoma clinic. Patients with PACG and healthy controls were consecutively enrolled. Each subject underwent optical coherence tomography angiography (OCTA) and OCT testing; additionally, visual field (VF) tests were also conducted in the patients with PACG. MvD was determined when choroidal layer images in OCTA showed a complete loss of the microvasculature. The study included 55 patients with PACG and 30 healthy controls.

Results

Fifty-five eyes in 55 patients with PACG and 30 eyes in 30 healthy controls were recruited. MvD was found in 26 PACG eyes (47.3%), but no MvD was found in the healthy eyes. Compared with PACG eyes without MvD, eyes with MvD had thinner average RNFL (P < 0.001), worse VF mean deviation (P = 0.006), and lower peripapillary vessel density (P < 0.001). Between MvD and RNFL defects, there was good topographic consistency in angular circumference (Bland–Altman 95% confidence interval [CI], −24.9° to 21.0°) and position (Bland-Altman 95% CI, −18.6° to 20.6°). There was a significant correlation between the MvD angular circumference and the average peripapillary vessel density (r = −0.505; P = 0.014), average RNFL thickness (r = −0.742; P < 0.001), and VF mean deviation (r = −0.572; P = 0.004).

Conclusions

In patients with PACG, the MvD angular circumference and position were highly topographic consistent with those of the peripapillary RNFL defect area. This study suggests that there is a significant correlation between MvD and glaucoma optic nerve injury.

Translational Relevance

Given the vascular etiology for glaucoma, the current research suggests that the MvD angular circumference may serve as a potential supplementary clue of glaucoma disease severity.

The relationship between choroidal blood flow and glaucoma progression in a Japanese study population

PURPOSE

To determine whether choroidal blood flow (BF) is related to visual field (VF) defect severity and progression in eyes with open-angle glaucoma (OAG).

STUDY DESIGN

Retrospective and longitudinal.

METHODS

This study comprised 443 eyes of 285 OAG patients who underwent laser speckle flowgraphy (LSFG), optical coherence tomography, and visual-field (VF) testing at baseline. The patients were then observed for at least 2 years and at least 5 reliable VF tests were performed. In the LSFG images, we set regions of interest at the optic nerve head (ONH) and the parapapillary choroid to obtain ONH-tissue mean blur rate (MBR) and choroidal MBR, respectively. We used univariable and multivariable linear mixed-effects models to determine clinical factors associated with choroidal MBR at baseline. We also used a linear mixed-effects model to determine the contribution of ONH-tissue MBR and choroidal MBR to baseline mean deviation (MD) and to MD slope during follow-up, adjusting for potential confounding factors, including circumpapillary retinal nerve fiber layer thickness.

RESULTS

Choroidal MBR was associated with age, MD slope, and ONH-tissue MBR (β = -0.181, P = 0.001; β = 0.134, P = 0.002; β = 0.096, P = 0.049, respectively). ONH-tissue MBR was associated with both MD and MD slope (β = 0.146, P = 0.004; β = 0.152, P = 0.009, respectively), whereas choroidal MBR was associated only with MD slope (β = 0.147, P = 0.005).

CONCLUSION

LSFG-derived choroidal MBR might be a useful biomarker to predict VF defect progression in a Japanese population.

Retinal microcirculation characteristics in obstructive sleep apnea/hypopnea syndrome evaluated by OCT-angiography: a literature review

PURPOSE

The retina may provide a window to estimate systemic vascular status; therefore, there has been interest in identifying microcirculation characteristics that possibly reflect hypoxic alterations in obstructive sleep apnea/hypopnea syndrome (OSAS). Emerging evidence has suggested that retinal microvasculature investigation holds the potential to characterize the pathophysiology involved in ocular manifestations of OSAS. The advent of optical coherence tomography angiography (OCT-A) has attracted significant attention as this technique offers detailed analysis of the retinal capillary plexus.

METHODS

A detailed literature search was performed in PubMed database until December 2021. We identified and reviewed all papers referring to the alterations of the retinal capillary plexus in OSAS using OCT-A.

RESULTS

A comprehensive update indicates that microcirculation alterations of the retinal capillary plexus utilizing OCT-A may differ with severity of OSAS and imply the potential underlying pathophysiology of ocular manifestations. The reviewed series have revealed variability concerning microvasculature characteristics at the macular and the peripapillary area. Further studies are warranted to establish the OCT-A parameters as biomarkers regarding the evaluation of OSAS in clinical practice.

CONCLUSION

Retinal capillary plexus characteristics as seen on OCT-A reflect microvasculature alterations, potentially leading to concomitant ocular comorbidity in the context of OSAS. The reviewed literature may confirm the diagnostic and prognostic value of OCT-A in the assessment of the pathophysiology of ocular manifestations in OSAS and highlight unmet needs to be addressed by future research.

Choroidal Thickness in Eyes with Band Atrophy of the Optic Nerve from Chiasmal Compression

Background

The choroid is a vascular tissue that helps maintain retinal and prelaminar optic nerve head function. Choroidal thickness has been previously studied in diseases accompanied by retinal neural loss, but the relationship between the two sets of measurements is not clear. In eyes with temporal hemianopia as a result of chiasmal compression lesions (CCL), retinal neural loss tends to be greater in the nasal than the temporal hemiretina, a fact that may be useful in evaluating the effect of inner retinal layer loss on choroidal thickness.

Purpose

To evaluate macular and peripapillary choroidal thickness on swept-source optical coherence tomography (SS-OCT) in eyes with temporal hemianopia as a result of chiasmal compression and in healthy controls.

Methods

33 eyes of 26 patients with band atrophy of the optic nerve and temporal visual field defects as a result of previously treated suprasellar tumors (CCL group) and 40 eyes of 21 healthy controls underwent SS-OCT scanning. The thickness of the peripapillary retinal nerve fiber layer (pRNFL), the peripapillary choroid (pChoroid), the macular RNFL (mRNFL), the macular ganglion cell layer (mGCL), and the macular choroid (mChoroid) was expressed globally and by sector (peripapillary quadrants and macular hemifield and quadrants). Ratios between macular nasal and temporal hemifield and quadrantic measurements were calculated using generalized estimated equation models, and the two groups were compared.

Results

The pRNFL, mRNFL, and mGCC thicknesses were significantly smaller in the CCL group than in the control group (64.67 ± 10.53 μm, 29.68 ± 5.80 μm, and 80.60 ± 10.17 μm vs. 103.78 ± 12.23 μm, 39.89 ± 3.82 μm, and 105.51 ± 7.76 μm, respectively; p < 0.001). For the choroid, the only difference between the groups was increased macular nasal hemifield and superonasal quadrant thickness in CCL (222.47 ± 61.05 μm and 230.45 ± 58.59 μm in the CCL group, respectively vs. 190.68 ± 52.54 μm and 197.65 ± 54.80 μm in the control group, respectively; p < 0.05). The temporal/nasal ratios were significantly higher for the mRNFL and mGCC parameters and significantly lower for the mChoroid parameters in the CCL group, except for the superotemporal/superonasal quadrant ratio.

Conclusions

The choroid does not thin after the inner retinal layer becomes damaged due to CCL and may even be thicker in some areas with corresponding severe retinal neural loss. While further studies are needed to interpret these findings, choroidal thinning is most likely not secondary to optic nerve disease-related inner retinal neural loss.

Normal-tension glaucoma: Current concepts and approaches-A review

Normal tension glaucoma (NTG) has remained a challenging disease. We review, from an epidemiological perspective, why we should redefine normality, act earlier at lower pre-treatment intraocular pressure (IOP) level, and the role of ocular perfusion pressures, noting that perfusion is affected by defective vascular bed autoregulation and endothelial dysfunction. The correlation of silent cerebral infarcts (SCI) and NTG may indicate that NTG belongs to a wider spectrum of small vessel diseases (SVD), with its main pathology being also on vascular endothelium. Epidemiological studies also suggested that vascular geometry, such as fractal dimension, may affect perfusion efficiency, occurrence of SCI, SVD and glaucoma. Artificial intelligence with deep learning, may help predicting NTG progression from vascular geometry. Finally, we review latest evidence on the role of minimally-invasive glaucoma surgery, lasers, and newer drugs. We conclude that IOP is not the only modifiable risk factors as, many vascular risk factors are readily modifiable.

Lamina cribrosa vessel and collagen beam networks are distinct

Our goal was to analyze the spatial interrelation between vascular and collagen networks in the lamina cribrosa (LC). Specifically, we quantified the percentages of collagen beams with/without vessels and of vessels inside/outside of collagen beams. To do this, the vasculature of six normal monkey eyes was labeled by perfusion post-mortem. After enucleation, coronal cryosections through the LC were imaged using fluorescence and polarized light microscopy to visualize the blood vessels and collagen beams, respectively. The images were registered to form 3D volumes. Beams and vessels were segmented, and their spatial interrelationship was quantified in 3D. We found that 22% of the beams contained a vessel (range 14%-32%), and 21% of vessels were outside beams (13%-36%). Stated differently, 78% of beams did not contain a vessel (68%-86%), and 79% of vessels were inside a beam (64%-87%). Individual monkeys differed significantly in the fraction of vessels outside beams (p < 0.01 by linear mixed effect analysis), but not in the fraction of beams with vessels (p > 0.05). There were no significant differences between contralateral eyes in the percent of beams with vessels and of vessels outside beams (p > 0.05). Our results show that the vascular and collagenous networks of the LC in monkey are clearly distinct, and the historical notions that each LC beam contains a vessel and all vessels are within beams are inaccurate. We postulate that vessels outside beams may be relatively more vulnerable to mechanical compression by elevated IOP than are vessels shielded inside of beams.

Papilledema: A review of etiology, pathophysiology, diagnosis, and management

Papilledema is optic nerve head edema secondary to raised intracranial pressure (ICP). It is distinct from other causes of optic disk edema in that visual function is usually normal in the acute phase. Papilledema is caused by transmission of elevated ICP to the subarachnoid space surrounding the optic nerve that hinders axoplasmic transport within ganglion cell axons. There is ongoing controversy as to whether axoplasmic flow stasis is produced by physical compression of axons or microvascular ischemia. The most common cause of papilledema, especially in patients under the age of 50, is idiopathic intracranial hypertension (IIH); however, conditions that decrease cerebrospinal fluid (CSF) outflow by either causing CSF derangements or mechanically blocking CSF outflow channels, and rarely conditions that increase CSF production, can be the culprit. When papilledema is suspected clinically, blood pressure should be measured, and pseudopapilledema should be ruled out. Magnetic resonance imaging of the brain and orbits with venography sequences is the preferred neuroimaging modality that should be performed next to look for indirect imaging signs of increased ICP and to rule out nonidiopathic causes. Lumbar puncture with measurement of opening pressure and evaluation of CSF composition should then be performed. In patients not in a typical demographic group for IIH, further investigations should be conducted to assess for underlying causes of increased ICP. Magnetic resonance imaging of the neck and spine, magnetic resonance angiography of the brain, computed tomography of the chest, complete blood count, and creatinine testing should be able to identify most secondary causes of intracranial hypertension. Treatment for patients with papilledema should be targeted toward the underlying etiology. Most patients with IIH respond to weight loss and oral acetazolamide. For patients with decreased central acuity and constricted visual fields at presentation, as well as patients who do not respond to treatment with acetazolamide, surgical treatments should be considered, with ventriculoperitoneal shunting being the typical procedure of choice.

Clinical characteristics of choroidal microvasculature dropout in normal-tension glaucoma versus nonarteritic anterior ischemic optic neuropathy: an optical coherence tomography angiography study

The present study investigated the characteristics of choroidal microvasculature dropout (CMvD) in eyes with nonarteritic anterior ischemic optic neuropathy (NAION) versus those in eyes with normal-tension glaucoma (NTG). This study included 27 NAION, 27 NTG, and 27 healthy control subjects. CMvD was observed in 15 eyes (55.6%) of the NAION group and 20 (74.1%) of the NTG group. The area and angular width of CMvD were significantly greater in eyes with NAION (0.278 ± 0.172 mm² and 86.5 ± 42.3°) than in those with NTG (0.138 ± 0.068 mm² and 35.1 ± 16.2°, p = 0.002 and p < 0.001, respectively). CMvD in eyes with NAION were distributed in 120–250° and most frequently located at the temporal region, while CMvD in eyes with NTG showed double peaks at 220–280° and 110–140° and most frequently located at the inferotemporal region. The factors associated with the discrimination of NAION from NTG were greater area of CMvD (OR, 1.181; 95% CI, 1.021–1.366; p = 0.025) and location closer to the temporal region of the CMvD (OR, 0.904; 95% CI, 0.838–0.975; p = 0.009). The clinical characteristics of CMvD differed between eyes with NAION and those with NTG. Optical coherence tomography angiography may provide an additional approach to differentiating glaucoma from NAION.

CILIORETINAL ARTERIES INFLUENCE OPTIC NERVE HEAD, PERIPAPILLARY, AND MACULAR VESSEL DENSITIES IN HEALTHY EYES: An Optical Coherence Tomography Angiography Study

BACKGROUND/PURPOSE

To analyze the influence of a cilioretinal artery (CRA) on macular and peripapillary vessel density in healthy eyes as measured using optical coherence tomography angiography.

METHODS

A total of 83 eyes of 83 patients were included in this study. Optical coherence tomography angiography was performed using the RTVue XR Avanti with AngioVue (Optovue Inc). The macula was imaged with a 3 × 3-mm scan, whereas for the optic nerve head a 4.5 × 4.5-mm scan was taken. Optical coherence tomography angiography images of the optic nerve head were screened for the presence of a CRA.

RESULTS

In 31 eyes, a CRA was detected (37.3%). The vessel density in eyes with a CRA was significantly lower within the optic nerve head (P = 0.005) but higher in the peripapillary capillary network (P < 0.001) and (whole en face) macular superficial capillary plexus (P = 0.025), when compared with eyes with no CRA.

CONCLUSION

Our findings reveal that in eyes with a CRA, the vessel density in the peripapillary and macular superficial capillary plexus is increased, whereas the optic nerve head perfusion (as indicated by vessel density in the inside disk region) is decreased. This has to be considered when analyzing quantitative optical coherence tomography angiography parameters in scientific and clinical applications.

Comparative Topographical Analysis of Choroidal Microvascular Dropout Between Glaucoma and Nonarteritic Anterior Ischemic Optic Neuropathy

Purpose

To identify the presence of choroidal microvascular dropout (MvD) in nonarteritic anterior ischemic optic neuropathy (NAION) eyes and to characterize the topographical distribution for the mechanistic interpretation of MvD development.

Methods

We performed optical coherence tomography angiography on 47 open-angle glaucoma (OAG) and 19 NAION eyes with β-zone peripapillary atrophy (βPPA). We recorded the presence of MvD and compared between the peripapillary topographical measures of MvD, retinal nerve fiber layer (RNFL) defect, and βPPA in angular width and location.

Results

MvD was present in both diseases, marginally more frequently in NAION eyes (19/19, 100.0%) than in OAG eyes (38/47, 80.6%, P = 0.050), without a discernable difference in appearance. NAION eyes also showed wider MvD and RNFL defects compared to OAG eyes (both P < 0.001). In topographical measurements, the distribution of MvD showed a strong correspondence to superimposition areas of βPPA and RNFL defects, more distinctly than to RNFL defects (all P < 0.001). The outline of superimposition area also remarkably resembled the MvD area.

Conclusions

MvD was present in both the OAG and NAION groups. The βPPA-RNFL defect superimposition area topographically and morphologically matched MvD. Further investigations are needed to elucidate the role of RNFL defects in the pathogenesis of MvD and the clinical significance.

Comparison of Choroidal Vascularity Index in Patients with Pseudoexfoliation Glaucoma, Pseudoexfoliation Syndrome, and Healthy Controls

PURPOSE

To compare peripapillary choroidal vascularity index (CVI) parameters in pseudoexfoliation glaucoma (PEG), pseudoexfoliation (PEX) syndrome, and healthy controls.

METHODS

A total of 240 eyes of 240 patients were included in this cross-sectional prospective study, and the three groups consisted of (i) 80 eyes of 80 patients with PEG, (ii) 80 eyes of 80 patients with PEX syndrome, and (iii) 80 healthy control eyes. Peripapillary enhanced depth imaging optical coherence tomography images were binarized via standard protocols with the ImageJ software. CVI was analyzed in all sectors of the peripapillary region.

RESULTS

Peripapillary CVI was found to be significantly lower in the PEG group (61.6 ± 2.32) compared with the PEX group (64.7 ± 3.15) and the control group (67.5 ± 2.44) (p < .001), and patients with PEX also had significantly lower values compared to controls (p < .001). Peripapillary CVI values were significantly lower in the temporal, nasal, superotemporal, superonasal, inferotemporal and inferonasal sectors of the PEG group compared to both the PEX group and controls (p < .001). Peripapillary CVI was also found to be lower in all sectors in the PEX group compared to controls (p < .001). Global peripapillary choroidal thickness was significantly thinner in the PEG group than the PEX and control groups (133.37 ± 39.16, 154.36 ± 33.28 and 157.82 ± 36.77 μm, respectively, p < .001).

CONCLUSIONS

In the current study, it was shown that the presence of PEX caused a decrease in CVI value and this decrease was highest in patients with PEG. CVI may be a useful parameter to show vascular dysfunction in PEG and PEX syndrome.

Posterior ischemic optic neuropathy following a major burn injury and review of the literature

Posterior ischemic optic neuropathy following burns is a rare but devastating condition that can result in total bilateral visual loss. Numerous treatment modalities have been trialed, yet there is no effective therapy to delay or reverse the disease. Hence, it is imperative for burns surgeons to be aware of the potential risk factors and have a high index of suspicion right from the outset to prevent this outcome. Here, we discuss the case of a patient that developed posterior ischemic optic neuropathy subsequent to a major burn injury. We also present a literature review on optic neuropathies following burns to describe the etiology, clinical signs, and potential management.

Relationship between peripapillary choroidal thickness and retinal nerve fiber layer in young people with myopia

Aim

To study the characteristics and relationship between peripapillary retinal nerve fiber layer (RNFL) and choroidal thickness in young people with myopia.

Methods

We retrospectively analyzed 92 cases (52 myopia, 40 emmetropia) regarding age, sex, refractive power, axial length (AL), and intraocular pressure. Peripapillary RNFL and choroidal thicknesses were measured by optical coherence tomography (OCT) in six sectors. Differences in thicknesses between the two groups were compared by single-factor analysis.

Results

RNFL was thickest in the inferotemporal sector (157.3 ± 19.66 µm) and thinnest in the nasal sector (58.78 ± 18.41 µm). Peripapillary choroid was thickest in the superonasal sector (176.37 ± 33.92 µm) and thinnest in the inferotemporal sector (131.79 ± 25.22 µm). The RNFL was thinner in the myopia group (99.04 ± 8.23 µm) vs the emmetropia group (103.25 ± 8.32 µm); significantly different in the superotemporal and inferonasal sectors. Peripapillary choroid thickness in the myopia group (148.65 ± 26.64 µm) was lower vs the emmetropia group (160.88 ± 29.06 µm); significantly different in the nasal, inferonasal, and inferotemporal sectors. RNFL thickness was negatively correlated with choroidal thickness in the nasal sector (r = −0.288).

Conclusion

Peripapillary RNFL and choroidal thicknesses showed regional distributions. RNFL was negatively correlated with PCT in the nasal sector, possibly related to eye axis growth and choroidal compensation.

Investigation of the Peripapillary Choriocapillaris in Normal Tension Glaucoma, Primary Open-angle Glaucoma, and Control Eyes

PRECIS

The peripapillary choriocapillaris (CC) was observed to be significantly impaired in normal tension glaucoma (NTG) subjects compared with normal controls using optical coherence tomography angiography (OCTA).

PURPOSE

The aim was to quantitatively evaluate the peripapillary CC in NTG, primary open-angle glaucoma (POAG), and control eyes using OCTA.

MATERIALS AND METHODS

Ninety eyes (30 controls, 30 NTG, and 30 POAG) from 73 patients were imaged using the Zeiss Plex Elite 9000. Five repeat 3×3 mm OCTA scans were acquired both nasally and temporally to the optic disc and subsequently averaged. Four CC flow deficit (FD) measures were calculated using the fuzzy C-means approach: FD density (FDD), mean FD size (MFDS), FD number (FDN), and FD area (FDA).

RESULTS

Temporal NTG CC parameters were associated with visual field index and mean deviation (P<0.05). The control group showed a significantly lower nasal FDD (nasal: 3.79±1.26%, temporal: 4.48±1.73%, P=0.03), FDN (nasal: 156.43±38.44, temporal: 178.40±45.68, P=0.02), and FDA (nasal: 0.22±0.08, temporal: 0.26±0.10, P=0.03) when compared with temporal optic disc. The NTG group showed a significantly higher FDD (NTG: 5.04±2.38%, control: 3.79±1.26%, P=0.03), FDN (NTG: 185.90±56.66, control: 156.43±38.44, P=0.04), and FDA (NTG: 0.30±0.14 mm2, control: 0.22±0.08 mm2, P=0.03) nasal to the optic disc compared with controls.

CONCLUSIONS

Association between CC parameters and glaucoma severity in NTG, but not POAG subjects, suggests vascular abnormalities may be a potential factor in the multifactorial process of glaucoma damage in NTG patients.

Choriocapillaris: Fundamentals and advancements

The choriocapillaris is the innermost structure of the choroid that directly nourishes the retinal pigment epithelium and photoreceptors. This article provides an overview of its hemovasculogenesis development to achieve its final architecture as a lobular vasculature, and also summarizes the current histological and molecular knowledge about choriocapillaris and its dysfunction. After describing the existing state-of-the-art tools to image the choriocapillaris, we report the findings in the choriocapillaris encountered in the most frequent retinochoroidal diseases including vascular diseases, inflammatory diseases, myopia, pachychoroid disease spectrum disorders, and glaucoma. The final section focuses on the development of imaging technology to optimize visualization of the choriocapillaris as well as current treatments of retinochoroidal disorders that specifically target the choriocapillaris. We conclude the article with pertinent unanswered questions and future directions in research for the choriocapillaris.

Effect of changes in optic nerve elasticity on central retinal artery blood flow in patients with idiopathic intracranial hypertension

PURPOSE

To assess changes in central retinal artery (CRA) blood flow by orbital color-coded Doppler ultrasonography in patients with idiopathic intracranial hypertension (IIH) and their relation with optic nerve (ON) elasticity assessed by shear wave elastography (SWE).

METHODS

This study was carried out on 68 eyes of patients diagnosed with IIH and 32 eyes of healthy controls. The severity of papilledema in IIH patients was sub-classified into mild and moderate/severe groups. Color-coded Doppler was used to measure peak systolic velocity (PSV), end diastolic velocity (EDV), mean velocity (V_mean) and pulsatility index (PI) of the CRA.

RESULTS

PSV, V_mean, and SWE were significantly higher in patients with IIH than in controls (p = 0.001). The optimal cut-off values of PSV and V_mean for differentiating IIH patients from controls were 11.25 and 6.75 cm/s with AUC 0.81 and 0.785 respectively. AUC was 0.92 and accuracy 91% for combined PSV, V_mean and SWE differentiation between IIH patients and controls. PSV, V_mean and SWE were significantly different between mild versus moderate/severe papilledema (p = 0.001). PSV and V_mean were correlated with papilledema (r = 0.790 and 0.722 respectively) and SWE (r = 0.818 and 0.761 respectively).

CONCLUSION

IIH is associated with decreased ON elasticity and reduced CRA blood flow. Individual and combined color-coded Doppler of the CRA and SWE help in diagnosis of IIH. CRA hemodynamic changes are correlated with papilledema severity and with the extent of biomechanical changes in the ON represented by SWE.

Effect of Hemodialysis on Peripapillary Choroidal Thickness Measured by Swept-Source Optical Coherence Tomography

PURPOSE

The aim was to investigate the effects of hemodialysis (HD) on peripapillary choroidal thickness (PCT) by swept-source optical coherence tomography and on other ophthalmologic parameters in patients with end-stage kidney disease.

MATERIALS AND METHODS

This was a prospective observational study. The authors evaluated 29 patients who underwent HD for end-stage kidney disease. Detailed ophthalmologic examinations and swept-source optical coherence tomography were performed immediately before and after HD. PCT was measured using the modification tool in the built-in OCT image viewer program. Changes in PCT before and after HD were statistically analyzed.

RESULTS

The average PCT significantly decreased from 127.3±49.2 μm before HD to 117.1±50.9 μm after HD (P<0.001). A significant correlation was found between changes in PCT and macular choroidal thickness (ρ=0.547, P=0.002). Changes in mean ocular perfusion pressure did not significantly correlate with changes in PCT (ρ=-0.049, P=0.803).

CONCLUSIONS

PCT significantly decreased after HD. HD could influence the optic nerve head and its surrounding structures.

Vascular Aspects in Glaucoma: From Pathogenesis to Therapeutic Approaches

Glaucomatous optic neuropathies have been regarded as diseases caused by high intraocular pressure for a long time, despite the concept of vascular glaucoma dating back to von Graefe in 1854. Since then, a tremendous amount of knowledge about the ocular vasculature has been gained; cohort studies have established new vascular risk factors for glaucoma as well as identifying protective measures acting on blood vessels. The knowledge about the physiology and pathophysiology of the choroidal, retinal, as well as ciliary and episcleral circulation has also advanced. Only recently have novel drugs based on that knowledge been approved for clinical use, with more to follow. This review provides an overview of the current vascular concepts in glaucoma, ranging from novel pathogenesis insights to promising therapeutic approaches, covering the supply of the optic nerve head as well as the aqueous humor production and drainage system.

Decreased retinal nerve fiber and choroidal thickness in chronic rhinosinusitis

PURPOSE

The assessment of the retina and choroid of patients with chronic rhinosinusitis (CRS), via spectral domain-optical coherence tomography (SD-OCT), was aimed in this study. We proposed that chronic upper airway restriction caused by chronic sinusitis could deteriorate the retinal and choroid morphology.

METHODS

This prospective controlled study included a total of 90 eyes of 90 patients, 30 of whom were CRS with nasal polyposis (CRSwNP), 30 of whom were CRS without nasal polyposis (CRSsNP) and 30 of whom were healthy controls (HC). Only the right eye of the patients were evaluated. All patients underwent full otorhinolaryngologic and ophthalmologic examinations, including SD-OCT.

RESULTS

Average retinal nerve fiber layer (RNFL) and RNFL in superior and inferior quadrants were measured significantly lower in CRS patients compared to HC. Ganglion cell-inner plexiform layer (GCIPL) thickness in all sectors was thinner in patients with CRS than in HC with significantly lower values in all sectors except inferior. Mean average GCIPL thickness and GCIPL thickness in the inferior sector were significantly lower in CRSwNP than CRSsNP patients.

CONCLUSION

CRS may lead to thinning in the choroidal thickness, RNFL thickness, especially in the superior and inferior quadrants and GCIPL thickness, presumably related with hypoxia, endothelial dysfunction, inflammation and vascular dysregulation. Ocular manifestations of the CRS should be taken in the consideration during the management of this disease.

Blind Source Separation of Retinal Pulsatile Patterns in Optic Nerve Head Video-Recordings

Dynamic optical imaging of retinal hemodynamics is a rapidly evolving technique in vision and eye-disease research. Video-recording, which may be readily accessible and affordable, captures several distinct functional phenomena such as the spontaneous venous pulsations (SVP) of central vein or local arterial blood supply etc. These phenomena display specific dynamic patterns that have been detected using manual or semi-automated methods. We propose a pioneering concept in retina video-imaging using blind source separation (BSS) serving as an automated localizer of distinct areas with temporally synchronized hemodynamics. The feasibility of BSS techniques (such as spatial principal component analysis and spatial independent component analysis) and K-means based post-processing method were successfully tested on the monocular and binocular video-ophthalmoscopic (VO) recordings of optic nerve head (ONH) in healthy subjects. BSSs automatically detected three spatially distinct reproducible areas, i.e. SVP, optic cup pulsations (OCP) that included areas of larger vessels in the nasal part of ONH, and "other" pulsations (OP). The K-means post-processing reduced a spike noise from the patterns' dynamics while high linear dependence between the non-filtered and post-processed signals was preserved. Although the dynamics of all patterns were heart rate related, the morphology analysis demonstrated significant phase shifts between SVP and OCP, and between SVP and OP. In addition, we detected low frequency oscillations that may represent respiratory-induced effects in time-courses of the VO recordings.

Nasal displacement of retinal vessels on the optic disc in glaucoma associated with a nasally angled passage through lamina cribrosa

To investigate nasal displacement of central retinal vessel (CRV) on the optic nerve head (ONH) in glaucoma in association with its passage through lamina cribrosa (LC). This cross-sectional study included 113 eyes with glaucoma and 60 normal eyes. Horizontal spectral-domain optical coherence tomography (SD-OCT) scans of the ONH were acquired, and point where CRV emerged on the ONH surface was defined as the position of the CRV. Next, radial scans of the ONH were acquired, and angle of the CRV passing through the LC was measured. These parameters were compared between glaucomatous and normal eyes by t-test, and their relationship with possible confounders was assessed by multiple regression analyses. In glaucoma, CRV was significantly more nasally displaced than it was in normal eyes (66.0 ± 8.6 vs. 54.3 ± 9.5, P < 0.0001), and eyes with more vessel displacement exhibited significantly worse glaucomatous visual field defects (P = 0.0004). Greater nasal displacement of the CRV was significantly associated with a more nasally angled path through the LC (rs = 0.569, P < 0.0001). By using SD-OCT, we confirmed that nasal displacement of the CRV on the ONH was associated with glaucoma and was induced by its nasally angled path through the LC.