Retinal Vascular and Neural Remodeling Secondary to Optic Nerve Axonal Degeneration: A Study Using OCT Angiography

Benefit of Optical Coherence Tomography-Angiography in Patients Undergoing Transsphenoidal Pituitary Adenoma Surgery: A Prospective Controlled Study

BACKGROUND

Although visual field (VF) defects are common in compressive pituitary adenoma (CPA), their pathophysiology has not been fully elucidated. The mechanical theory (i.e., direct compression of the optic chiasm by the CPA) and the vascular theory (i.e., compression of the vessels supplying the visual path by the CPA) or their association could explain the visual impairment. The aim of this study was to determine whether the vascular density (VD) improved after surgical decompression of the optic chiasm in CPA patients and whether OCT-A could help to identify predictive factors for postoperative visual recovery.

METHODS

A prospective controlled study was conducted in patients who underwent transsphenoidal pituitary adenoma surgery. Patients were divided into two groups: with CPA and without CPA (NCPA). All patients underwent a neuro-ophthalmological examination, VF testing, macular and optic disc structural OCT [retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) thicknesses] and OCT-A before and then 1 and 6 months after surgery.

RESULTS

Twenty-four eyes and fourteen eyes were included, respectively, in the CPA and NCPA groups. None of the VD parameters assessed by OCT-A were significantly improved after surgery in the CPA group. In the CPA group, the mean macular superficial VD was significantly decreased at 6 months. The multivariate analysis failed to identify any preoperative parameters predictive of postoperative VF improvement.

CONCLUSIONS

Our preliminary findings suggest that the visual impairment observed in CPA patients could not be explained by the vascular theory. None of the preoperative OCT-A parameters allowed a postoperative VF recovery assessment. Trial registration number NCT04074642, ID-RCB 2019-A01186-51 date of registration 30 July 2019.

The neurovascular retinal involvement in a large population of patients recovered from COVID-19: an OCT and OCT angiography study

BACKGROUND

This study aimed to assess the neuronal and microvascular retinal and choroidal involvement in COVID-19 recovered patients using optical coherence tomography (OCT) and OCT angiography (OCTA).

METHODS

This observational cross-sectional study recruited patients recovered from COVID-19 and a group of healthy controls for comparisons. OCT (peripapillary scan and macular map) and OCTA (macular map) were performed to obtain: the central subfield thickness (CST), the macular volume (MV), the peripapillary retinal nerve fibre layer (pRNFL) thickness, the vessel area density (VAD), vessel length fraction (VLF), vessel diameter index (VDI) and fractal dimension (FD) of the superficial vascular plexus (SVP), intermediate capillary plexus (ICP) and deep capillary plexus (DCP), and the vessel density (VD), stromal density (SD) and vascular/stromal (V/S) ratio of the choriocapillaris (CC) and choroid (Ch). Data regarding disease severity, administered therapy and prior comorbidities were collected.

RESULTS

We recruited 676 eyes from 338 patients and 98 eyes from 49 healthy controls. VAD of all the three retinal plexuses, VLF and VDI of ICP and DCP and VD of CC were significantly reduced in patients versus controls. No differences were found in CST, MV and pRNFL. A multivariate analysis showed that oxygen therapy, previous cardio/cerebrovascular events and hypertension negatively influenced vascular parameters.

CONCLUSION

A microvascular retinal and choriocapillaris damage may be identified secondary to SARS-CoV-2 infection, even after recovery. OCTA may represent a reproducible and non-invasive tool to assess microangiopathy in these patients, with particular regard to those with previous cardio/cerebrovascular events, hypertension and those who received oxygen therapy.

The Role of Optical Coherence Tomography Angiography in the Evaluation of Chiasmal and Retrochiasmal Compression

The compression of the visual pathway is associated with structural retinal changes due to retrograde neurodegeneration. It was brought into question whether visual pathway compression is also associated with retinal vascular changes as assessed by optical coherence tomography angiography (OCT-A). The objective of this review is to discuss the role of OCT-A in the evaluation of patients with tumours of the sellar, parasellar, and retrochiasmal regions. The reported OCT-A parameters were the vessel densities of radial peripapillary capillary network, macular superficial vascular plexus and/or macular deep vascular complex. Optic nerve and macular OCT-A parameters were impaired in patients versus controls. These changes were associated with altered structural OCT parameters and visual field defects. OCT-A could be considered a marker of neurodegeneration in addition to structural OCT, and it has the potential to become a visual prognostic tool in patients with visual pathway compression.

The use of optical coherence tomography angiography in patients with chiasmal compression (literature review)

Optical coherence tomography (OCT) is currently the leading method for the observation and evaluation of microstructural changes in the retina in vivo. In recent years, OCT has been used in clinical practice to monitor the progression of compressive optic neuropathy in patients with chiasmal-sellar region neoplasms. The results obtained in the course of the studies opened up new opportunities for studying the pathogenesis of the development of compressive optic neuropathy in patients of this group. The advent of OCT-angiography (OCTA), developed on the basis of OCT, made it possible to study changes in the blood flow of the radial peripapillary capillary network, superficial and deep capillary plexuses, which opens up many opportunities for further research into the pathogenesis of visual impairment in this group of patients, prognosis of the development of the disease, and selection optimal terms of treatment. The literature review presents and analyzes the currently available results of the use of OCTA in patients with chiasmal compression.

Peripapillary Microvascularization Analysis Using Swept-Source Optical Coherence Tomography Angiography in Optic Chiasmal Compression

Purpose

To evaluate the vessel density (VD) of the radial peripapillary capillary (RPC) network using swept-source optical coherence tomography angiography (SS-OCTA) “en face” images of eyes with chiasmal compression caused by brain tumors before and after decompressive surgery compared with healthy controls.

Methods

A cross-sectional study was conducted in 12 patients with chiasmal compression confirmed by neuroimaging. Sixteen healthy participants were also included. All patients with chiasmal compression underwent a neuro-ophthalmological examination one week before and 6 months after brain surgery, including static automated perimetry as well as measurement of the thickness of the retinal nerve fiber layer (RNFL) and the ganglion cell complex (GCC) with spectral-domain optical coherence tomography (SD-OCT). Based on this neuro-ophthalmological examination, the presence of an optic neuropathy (ON) was evaluated. Peripapillary VD was obtained in four sectors on a 6 × 6 mm SS-OCTA image using the Cirrus Plex Elite 9000.

Results

Baseline average VD was significantly lower in patients with chiasmal compression and ON than in controls (median: 55.62; interquartile range (IQR): 2.96 vs. 58.53; IQR: 2.02; p=0.003). This decrease was also found in the temporal, superior, and nasal sectors. Average postoperative VD was decreased in patients with chiasmal compression compared with average preoperative VD (median: 56.16; IQR: 4.07 vs. 57.48; IQR: 3.83; p=0.004). Preoperative VD was significantly correlated with RNFL, GCC thickness, and visual field defects.

Conclusions

The VD of the RPC network was decreased in chiasmal compressive ON, and it was further decreased at 6 months after decompressive surgery.

Vascular density of optic nerve head in diabetic retinopathy using optical coherence tomography angiography

PURPOSE

To measure optic nerve head (ONH) blood perfusion using optical coherence tomography angiography (OCTA) at various stages of diabetic retinopathy (DR).

METHODS

One hundred seventy six eyes of 94 patients included in this retrospective single-centre cross-sectional study. The subjects were studied in normal, no diabetic retinopathy (NDR), non-proliferative diabetic retinopathy (NPDR) and proliferative retinopathy (PDR) groups. The eyes were subjected to AngioDisc ONH imaging using OCTA for papillary (Disc) and peripapillary (RPC) vascular density (VD) evaluation.

RESULTS

The mean age of the participants was 56.08 ± 8.87 years and 34 (36.2 percent) were male. With increased DR severity, a statistically significant decrease in peripapillary VD was found. The study showed that only VD of the whole RPC (W-RPC) could be a valid biomarker in the staging assessment. VD of RPC, in all subsections, was considerably different from normal cases in the PDR group. Visual acuity was correlated with whole image ONH VD. The duration of DM, FBS, hyperlipidemia and DME had no effect on the ONH perfusion.

CONCLUSIONS

The study showed that only the W-RPC VD could be a reasonable marker in the staging assessment. VDs assessed by OCTA can be useful for assessing and tracking early ONH changes in DR patients.

Chorioretinal Side Effects of Therapeutic Ocular Irradiation: A Multimodal Imaging Approach

Radiation chorioretinopathy, radiation maculopathy, and radiation optic neuropathy are the major complications of ophthalmic radiotherapy. Optical coherence tomography (OCT) and OCT angiography (OCTA) are revolutionary imaging methods, allowing the visualization of the retinal cellular architecture and the retinal vascular system, respectively. In recent years this multimodal imaging approach has been applied to several retinal disease, but its role in the clinical characterization of retinal complications secondary to ophthalmic radiotherapy has not yet been defined. The purpose of this review is to critically evaluate the role of OCT and OCTA in the clinical assessment of radiation-induced chorioretinopathy, maculopathy, and optic neuropathy.

Quantification of vascular and neuronal changes in the peripapillary retinal area secondary to diabetic retinopathy

PURPOSE

To investigate and quantify peripapillary vascular and neuronal changes secondary to diabetic retinopathy, using spectral-domain optical coherence tomography (OCT) and OCT angiography (OCTA).

DESIGN

This was a cross-sectional study.

METHODS

51 eyes of 51 patients affected by non-proliferative diabetic retinopathy (NPDR) and 19 age-matched healthy control eyes underwent full ophthalmic examination, including OCT and OCTA in the peripapillary area. Vessel area density (VAD), vessel length fraction (VLF) and vessel diameter index (VDI) were quantified in a ring-shaped region of interest of each OCTA image. Capillaries and larger vessels were separately analysed. The thickness of the peripapillary retinal nerve fibre layer (pRNFL) and macular ganglion cell complex (GCC) was also analysed.

RESULTS

VAD and VLF of peripapillary capillaries were significantly reduced in NPDR eyes, along with the progression of NPDR (p<0.05). VDI was significantly reduced in mild (p=0.0093) and moderate (p=0.0190) NPDR eyes, but not in severe NPDR (p=0.0841). Larger peripapillary vessels showed a significant increase of both VAD and VDI in NPDR eyes. pRNFL and GCC thickness decreased in NPDR eyes, reaching statistical significance only for GCC. No statistically significant correlation was found between perfusion parameters and pRNFL and GCC thickness.

CONCLUSIONS

Retinal capillary remodelling in NPDR involves the peripapillary vascularisation too, as confirmed by OCTA quantitative parameters. The peripapillary macrovasculature and microvasculature need to be separately evaluated. The lack of direct correlation between peripapillary capillaries changes and the loss of retinal nerve fibres suggests that neuronal damage cannot be simply considered secondary to the microvascular one.

Optical Coherence Tomography Angiography in Neurodegenerative Diseases: A Review

Background

Optical coherence tomography angiography (OCT-A) has emerged as a novel, fast, safe and non-invasive imaging technique of analyzing the retinal and choroidal microvasculature in vivo. OCT-A captures multiple sequential B-scans performed repeatedly over a specific retinal area at high speed, thus enabling the composition of a vascular map with areas of contrast change (high flow zones) and areas of steady contrast (slow or no flow zones). It therefore provides unique insight into the exact retinal or choroidal layer and location at which abnormal blood flow develops. OCTA has evolved into a useful tool for understanding a number of retinal pathologies such as diabetic retinopathy, age-related macular degeneration, central serous chorioretinopathy, vascular occlusions, macular telangiectasia and choroidal neovascular membranes of other causes. OCT-A technology is also increasingly being used in the evaluation of optic disc perfusion and has been suggested as a valuable tool in the early detection of glaucomatous damage and monitoring progression.

Objective

To review the existing literature on the applications of optical coherence tomography angiography in neurodegenerative diseases.

Summary

A meticulous literature was performed until the present day. Google Scholar, PubMed, Mendeley search engines were used for this purpose. We used 123 published manuscripts as our references. OCT-A has been utilized so far to describe abnormalities in multiple sclerosis (MS), Alzheimer’s disease, arteritic and non-arteritic optic neuropathy (AION and NAION), Leber’s hereditary optic neuropathy (LHON) papilloedema, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis (ALS), Wolfram syndrome, migraines, lesions of the visual pathway and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). It appears that OCT-A findings correlate quite well with the severity of the aforementioned diseases. However, OCT-A has its own limitations, namely its lack of wide-field view of the peripheral retina and the inaccurate interpretation due to motion artifacts in uncooperative groups of patients (e.g. children). Larger prospective longitudinal studies will need to be conducted in order to eliminate the aforementioned limitations.

Optic Pathway Glioma in Type 1 Neurofibromatosis: Review of Its Pathogenesis, Diagnostic Assessment, and Treatment Recommendations

Type 1 neurofibromatosis (NF1) is a dominantly inherited condition predisposing to tumor development. Optic pathway glioma (OPG) is the most frequent central nervous system tumor in children with NF1, affecting approximately 15-20% of patients. The lack of well-established prognostic markers and the wide clinical variability with respect to tumor progression and visual outcome make the clinical management of these tumors challenging, with significant differences among distinct centers. We reviewed published articles on OPG diagnostic protocol, follow-up and treatment in NF1. Cohorts of NF1 children with OPG reported in the literature and patients prospectively collected in our center were analyzed with regard to clinical data, tumor anatomical site, diagnostic workflow, treatment and outcome. In addition, we discussed the recent findings on the pathophysiology of OPG development in NF1. This review provides a comprehensive overview about the clinical management of NF1-associated OPG, focusing on the most recent advances from preclinical studies with genetically engineered models and the ongoing clinical trials.

Circumpapillary and macular vessel density assessment by optical coherence tomography angiography in eyes with temporal hemianopia from chiasmal compression. Correlation with retinal neural and visual field loss

AIMS

To compare the circumpapillary and macular vessel density (cpVD/mVD) of eyes with temporal visual field (VF) defect and band atrophy (BA) of the optic nerve and normal controls using OCTA and to verify the association of VD parameters with circumpapillary retinal nerve fibre layer (cpRNFL) thickness, macular ganglion cell complex (mGCC) thickness and VF loss.

METHODS

Thirty-three eyes of 26 patients with BA and 42 eyes of 22 age-matched normal controls underwent OCT + OCTA scanning. cpVD and cpRNFL were expressed as average and sector measurements. mVD and mGCC were calculated as averages and in quadrants and hemiretinas. VF loss was estimated using the 24-2 and the 10-2 protocols. Generalized estimated equation models were used for comparisons and area under the receiver operating characteristics (AROC) were calculated.

RESULTS

Compared with controls, BA eyes displayed smaller average cpVD and mVD values (p < 0.001 and AROC = 0.91 for both). Sectorial measurements were also reduced, especially the nasotemporal sector average cpVD (p < 0.001 and AROC = 0.96) and the nasal retina mVD measurements (p < 0.001 and AROC = 0.93). cpVD and mVD correlated strongly with corresponding cpRNFL and mGCC thickness measurements in affected regions (r range: 0.67-0.78 and 0.56-0.76, respectively). Similarly, cpVD and mVD parameters correlated significantly with corresponding VF loss (r range: 0.45-0.68).

CONCLUSIONS

cpVD and mVD are significantly reduced in BA eyes compared with controls and are strongly correlated with retinal neural and VF loss. cpVD and mVD reduction on OCTA could serve as a surrogate for retinal neural loss in compressive optic neuropathy and might be useful in its management.

IDENTIFICATION AND CLASSIFICATION OF MACULAR MORPHOLOGIC BIOMARKERS RELATED TO VISUAL ACUITY IN RADIATION MACULOPATHY: A Multimodal Imaging Study

PURPOSE

To identify and classify, by a multimodal imaging approach, the most relevant macular morphologic biomarkers related to visual acuity in patients affected by radiation maculopathy secondary to brachytherapy.

METHODS

Fifty-one consecutive patients previously treated with Iodine-125 brachytherapy because of uveal melanoma were enrolled. Each patient underwent full ophthalmologic examination including best-corrected visual acuity and multimodal macular imaging analysis. Macular morphological parameters were processed by a stepwise selection analysis.

RESULTS

Three macular parameters were identified as the most relevant macular morphologic biomarkers of poor visual acuity: the vertical thickness of the thickest macular cyst (P = 0.0001), the presence of foveal inner segment/outer segment (IS/OS) layer disruption (P = 0.0054), and the presence of foveal retinal pigment epithelium atrophy (0.0884). The intergrader agreement for these morphologic biomarkers was 0.98, 0.92, and 0.92, respectively (interclass correlation coefficient).

CONCLUSION

The vertical thickness of the thickest macular cyst, the presence of foveal retinal pigment epithelium atrophy, and IS/OS layer disruption can be used to clinically characterize radiation maculopathy. These parameters allow for separation of the edematous component of radiation maculopathy, which is potentially treatable in early disease stages, from late onset atrophic components, which are theoretically irreversible.

Correlation of peripapillary retinal nerve fibre layer thickness with visual acuity in paediatric patients affected by optic pathway glioma

PURPOSE

To evaluate peripapillary retinal nerve fibre layer (RNFL) thickness, measured by spectral-domain optical coherence tomography (SD-OCT), as a surrogate of visual function in a population of paediatric patients affected by optic pathway glioma (OPG) associated with neurofibromatosis type 1 (NF1).

METHODS

A total of 38 paediatric patients (66 eyes) affected by MRI-proven OPG were included. Each patient underwent complete ophthalmological examination, including age-appropriate visual acuity (VA) assessment and RNFL analysis by SD-OCT. Visual acuity was classified as normal or pathologic using age-based normative data. Visual acuity was correlated to mean RNFL thickness of the whole peripapillary area and of each single analyzed sector (nasal, superior, temporal, inferior).

RESULTS

Visual acuity was normal in 43 (65%) and pathologic in 23 (35%) eyes. Mean parapapillary RNFL thickness of each analyzed sector was significantly lower in eyes with abnormal VA (p < 0.05). The best balanced cut-off value of global RNFL thickness allowing to discriminate between eyes with normal and pathologic VA was 76.25 μm (91%, 76%, 67% and 94% of sensitivity, specificity, positive and negative predicting value, respectively). Considering best balanced cut-off values of other analyzed RNFL sectors, the superior (p = 0.0029) and the inferior (p = 0.0024) sectors reached the higher sensitivity (87% and 87%, respectively) and specificity (81% and 79%, respectively).

CONCLUSION

Retinal nerve fibre layer thickness is directly related to VA in children affected by NF1-related OPG, and should be considered as a potential surrogate marker of VA. Retinal nerve fibre layer thickness cut-off values can be used in paediatric patients to discriminate false-positive results obtained by VA measurement.

Principles of OCTA and Applications in Clinical Neurology

PURPOSE OF REVIEW

The article reviews the recent findings on the use of optical coherence tomography angiography (OCTA) in neurology.

RECENT FINDINGS

OCTA is a new addition to the powerful and complementary technology of the OCT. Due to its noninvasiveness, and reproducibility, it is possible to obtain high-resolution 3D images of the vessels of the human eye. As the vessels of the retina with the presence of endothelial cell's tight junctions resemble the brain vessels, it was hypothesized that the imaging of the retinal vessels might bring insight into brain vessels. OCTA has been effectively used to predict retinal vessel abnormalities in dementia, demyelization, optic disc neuropathies, and inherited degenerative diseases. Most common findings were decrease of vascular density and flow and an increase of avascular zones. Although OCTA is a relative new technology, recent studies show that it can be successfully applied in neurology.