Quantitative analysis of the RPC vessel density and the RNFL thickness in patients with type 2 diabetes mellitus by using OCT angiography

Characteristics of the radial peripapillary capillary network in patients with COVID-19 based on optical coherence tomography angiography: A literature review

PURPOSE

This review aimed to evaluate the significance of assessing radial peripheral capillary (RPC) network parameters by optical coherence tomography angiography (OCTA) in patients with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection confirmed by polymerase chain reaction.

METHODS

A literature search was conducted in the PubMed database to select high-quality reviews and original articles on the use of OCTA for visualizing the RPC network and calculating RPC parameters.

RESULTS

The study revealed that systemic hypoxia, hypercoagulable state, and inflammation affect the RPC network in patients with coronavirus disease 2019 (COVID-19). Reduced RPC parameters were observed early in the course of SARS-CoV-2 infection and after several months of follow-up. Additionally, there was a correlation between reduced RPC parameters and subsequent thinning of the retinal nerve fiber layer.

CONCLUSIONS

The OCTA examination of the retina and optic disc should be considered in patients with a history of COVID-19 to assess the impact of systemic hypoxia and inflammation on ocular function. Follow-up assessment of these patients is also necessary to understand the potential consequences of ischemia affecting the optic nerve, retina, and choroid.

Optic nerve head alterations after COVID-19: an optical coherence tomography angiography-based longitudinal study

OBJECTIVE

To evaluate longitudinal changes in peripapillary vessel density (VD) following coronavirus disease 2019 (COVID-19) using optical coherence tomography angiography.

METHODS

As part of a prospective longitudinal observational study, we studied healthy individuals with a history of mild COVID-19 confirmed via real-time polymerase chain reaction. After recovery, we used the Optovue RTVue XR Avanti machine to perform optic nerve head (ONH) imaging. We also assessed the VD of all vessels and of small vessels in the disc and the radial peripapillary capillary (RPC) network at 1 and 3 months post-recovery.

RESULTS

We included 17 patients (34 eyes; mean age: 36.9 ± 10.2 years, range: 24-62 years) who had recovered from COVID-19. No changes were observed in the ONH parameters. However, there was a noticeable trend of increased small vessel VD values in the RPC. These increases were significant for the peripapillary whole, superior hemifield, inferior-temporal, temporal-superior, and superior-temporal small vessels. Moreover, the evaluation of all vessel VD values in the RPC revealed a significant decrease in the inside disc and a significant increase in a grid-based inferior region.

CONCLUSION

COVID-19 may affect VD of the RPC in the ONH, and should be considered in ONH evaluations.

Optical coherence tomography angiography in diabetic retinopathy: A major review

Diabetic retinopathy (DR) is characterized by retinal vasculopathy and is a leading cause of visual impairment. Optical coherence tomography angiography (OCTA) is an innovative imaging technology that can detect various pathologies and quantifiable changes in retinal microvasculature. We briefly describe its functional principles and advantages over fluorescein angiography and perform a comprehensive review on its clinical applications in the screening or management of people with prediabetes, diabetes without clinical retinopathy (NDR), nonproliferative DR (NPDR), proliferative DR (PDR), and diabetic macular edema (DME). OCTA reveals early microvascular alterations in prediabetic and NDR eyes, which may coexist with sub-clinical neuroretinal dysfunction. Its applications in NPDR include measuring ischemia, detecting retinal neovascularization, and timing of early treatment through predicting the risk of retinopathy worsening or development of DME. In PDR, OCTA helps characterize the flow within neovascular complexes and evaluate their progression or regression in response to treatment. In eyes with DME, OCTA perfusion parameters may be of predictive value regarding the visual and anatomical gains associated with treatment. We further discussed the limitations of OCTA and the benefits of its incorporation into an updated DR severity scale.

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.

Evaluation of Posterior Ocular Blood Flow in Diabetic Retinopathy Patients Without Macular Edema Using Optical Coherence Tomography Angiography

AIM

The objective of this study is to investigate and compare the superficial and deep vascular structures of the retina, as well as the changes in the choriocapillaris (CC) and optic disc microvasculature, using optical coherence tomography angiography (OCTA) in patients diagnosed with diabetes mellitus (DM) without diabetic retinopathy (DR), patients with non-proliferative and proliferative DR, and healthy individuals.

MATERIALS AND METHODS

This prospective study conducted between July 2020 and July 2021 included patients diagnosed with type 2 DM without DR, as well as patients with mild nonproliferative, moderate nonproliferative, and proliferative DR without macular oedema. A control group of 25 age- and gender-matched healthy individuals was also included. OCTA parameters of the patients were examined.

RESULTS

In the DR groups, compared to the control group, there was a significant decrease in macular superficial, deep, and CC perfusion areas as the severity of DR increased (p<0.001). The vascular density (VD) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) exhibited a statistically significant decrease in all quadrants of the DR group compared to the control group (p = 0.033 for SCP in the fovea, p<0.001 for all other quadrants). The superficial and deep FAZs showed a significant expansion in the DR group compared to the control group (p = 0.003 for superficial FAZ, p<0.001 for deep FAZ). As the severity of DR increased, there was a statistically significant decrease in the perfusion areas of the optic nerve head (ONH), radial peripapillary capillary (RPC), and vitreous segments (p<0.001 for ONH, p = 0.031 for RPC, p<0.001 for vitreous). There was a statistically significant decrease in RPC VD in all quadrants as the severity of DR increased. Moreover, as the severity of DR increased, a statistically significant decrease in the VD of the ONH was observed in all quadrants except for the inferior nasal (p = 0.094), inferior temporal (p = 0.111), superior temporal (p = 0.18), and temporal (p = 0.284) quadrants.

CONCLUSION

Our study demonstrated the involvement of macular and optic nerve perfusion areas (PA) and VD in diabetic patients. OCTA proved to be a valuable and noninvasive imaging modality, providing an easy and repeatable assessment of posterior segment vascular changes in patients with DR.

Early diagnosis of retinal neurovascular injury in diabetic patients without retinopathy by quantitative analysis of OCT and OCTA

AIMS

To quantitatively analyze and compare the differences in retinal neurovascular units (NVUs) between healthy individuals and patients with type 2 diabetes mellitus (DM) by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) techniques and to determine the value of this technique for the early diagnosis of retinal neurovascular damage in patients with diabetes mellitus without retinopathy (NDR).

METHODS

This observational case‒control study was conducted from July 1, 2022, to November 30, 2022, at the outpatient ophthalmology clinic of the Affiliated Hospital of Shandong University of Traditional Chinese Medicine. All subjects underwent baseline data entry and mean thickness of the peripapillary retinal nerve fiber layer (pRNFL), the thickness of each retinal layer in the macula 3 × 3 mm, and vascular density (VD) examination.

RESULTS

The study included 35 healthy individuals and 48 patients with DM. The retinal VD as well as partial pRNFL, macular nerve fiber layer (NFL), and macular ganglion cell layer (GCL) thickness in DM patients exhibited significantly lower VD in the DM group than in the control group (p < 0.05). Age and disease duration of DM patients showed a negative trend with pRNFL thickness, macular NFL thickness, macular GCL thickness, and VD. However, a positive trend was observed between DM duration and partial inner nuclear layer (INL) thickness. Moreover, there was a positive correlation between macular NFL and GCL thickness and VD for the most part, while a negative correlation was shown between INL temporal thickness and DVC-VD. pRNFL-TI and GCL-superior thickness were screened as two variables in the analysis of the predictors of retinal damage in DM according to the presence or absence of DM. The AUCs were 0.765 and 0.673, respectively. By combining the two indicators for diagnosis, the model predicted prognosis with an AUC of 0.831. In the analysis of retinal damage indicators associated with the duration of DM, after regression logistic analysis according to the duration of DM within 5 years and more than 5 years, the model incorporated two indicators, DVC-VD and pRNFL-N thickness, and the AUCs were 0.764 and 0.852, respectively. Combining the two indicators for diagnosis, the AUC reached 0.925.

CONCLUSIONS

Retinal NVU may have been compromised in patients with DM without retinopathy. Basic clinical information and rapid noninvasive OCT and OCTA techniques are useful for the quantitative assessment of retinal NVU prognosis in patients with DM without retinopathy.

Increased peripapillary capillaries in patients with acute leukemia by using optical coherence tomography angiography

PURPOSE

To evaluate the radial peripapillary capillary vessel density (RPC-VD) and thickness of the retinal nerve fiber layer (RNFL) in acute leukemia (AL) and the associations of these characteristics with blood laboratory parameters.

METHODS

A cross-sectional study was performed at the Ophthalmology Department of the Sun Yat-sen Memorial Hospital from February 2019 to April 2022. Sixty eyes of 30 patients diagnosed with AL and sixty eyes of 30 matched healthy controls were included. Optical coherence tomography angiography (OCTA) in the 4.5-mm Angio Disc scan mode and the Ganglion cell complex scan mode were performed for all participants. Correlation analyses were used to examine the associations of RPC-VD and RNFL with blood laboratory parameters.

RESULTS

Patients in the AL group had significantly increased RPC-VD in the whole-image (51.42±0.35 vs. 49.52±0.36) and peripapillary fields (53.90±0.43 vs. 51.17±0.50) compared with people in the control group (all P<0.001), while no difference was found for RPC-VD in the inside optic disc fields in the two groups. The RNFL in the AL group was significantly thicker than that in the control group (131.10±3.89 μm vs. 115.03±2.22 μm, P<0.05). Complete blood count (CBC) parameters, including red blood cells, hemoglobin and hematocrit, had a significant negative correlation with RPC-VD and RNFL (all P <0.05).

CONCLUSION

An increased RPC-VD and a thicker RNFL are evidence of fundus changes in patients with early-stage AL, and these metrics may be related to decreases in red blood cells, hemoglobin and hematocrit.

Wide-field swept-source OCTA in the assessment of retinal microvasculature in early-stage diabetic retinopathy

BACKGROUND

To perform a quantitative analysis of retinal microvasculature in patients with early-stage diabetic retinopathy (DR) using wide-field swept-source optical coherence tomography angiography (SS-OCTA).  METHODS: One hundred nineteen eyes of 119 patents (67 eyes with no DR and 52 eyes with mild-moderate nonproliferative diabetic retinopathy (NPDR)) were enrolled in this observational and cross-sectional cohort study, and an age-matched group consisting of 39 eyes of 39 non-diabetic subjects were set as the control. Each participant underwent a full ophthalmic examination, including wide-field SS-OCTA imaging. On OCTA scans (12 mm * 12 mm), the mean perfusion area (PA) and vessel density (VD) were independently measured in all 16 Early Treatment Diabetic Retinopathy Study (ETDRS) sectors. Linear regression analyses were conducted to evaluate the influences of PA.

RESULTS

In the central ring, there were no significant differences in the average PA and VD among the groups. In the 3 mm radius, the PA and VD of the no DR and mild-moderate NPDR were significantly decreased compared with the control group in superior and inferior quadrants. In the wide-field scans (9 and 12 mm radius), there was no significant difference in average PA and VD between the groups in each sectors (p > 0.05). Regression analysis found that the effect of VD on PA was statistically different (b = 1.311, p < 0.001).

CONCLUSION

Wide-field OCTA imaging is useful for evaluating peripheral capillary perfusion in eyes with early-stage DR. Decrease in PA and VD was greater in the S3 and I3 sectors, and reductions in PA and VD were uneven in wide-filed sectors (9 and 12 mm radius).

Comparison of age-related vascular changes in the optic disc of patients with diabetes, with glaucomatous and non-glaucomatous features

Objective

To identify age-related vascular changes in the optic discs of patients with diabetes with and without signs of glaucoma.

Methods and analysis

A total of 2153 eyes of 1797 patients with diabetes without significant retinopathy were monitored with 10 Topcon-NW400 images obtained over 10.27±1.58 years. 571 non-diabetics eyes were selected as controls. Laguna ONhE uses convolutional neural networks to identify optic disc edges, vessels, cup and rim, and provides a glaucoma assessment index—Globin Distribution Function (GDF).

Results

In the first image, vessel pixels accounted for 33.88% of the disc area (SD=3.72) in non-glaucoma (DN) and 31.35% (SD=4.05; p<0.0001) in glaucoma cases (DG). This number of pixels was reduced by −0.55% each year (SD=0.77) in the DN and −0.76% (SD=0.86; p=0.0014) in the DG. In the first image, 76.55% of the disc pixels (SD=11.13) belonged to the rim in the DN and 62.05% (SD=11.00; p=0.0014) in the DG, decreasing annually by −0.33% (SD=0.99) in the DN and −0.68% (SD=1.08; p<0.00001) in the DG groups. All rim sectors were reduced over time in the DG group, particularly superotemporal (41°–80°) and inferotemporal (271°–310°). The reduction was smaller in DN, presenting as progressive thickening of the temporal sector (311°–40°). No changes in age were observed in healthy controls.

Conclusion

Patients with diabetes show progressive reduction of vessels and neuroretinal rim at the optic disc, which is more intense in association with glaucoma. In the absence of glaucoma, the temporal sector of the diabetic rim was not reduced but thickened, displacing the cup nasally.

Macular and Optic Disc Parameters in Children with Amblyopic and Nonamblyopic Eyes under Optical Coherence Tomography Fundus Images

The aim of this study was to investigate the characteristics of macular and optic disc parameters in children with amblyopic and nonamblyopic eyes, using fundus images under optical coherence tomography (OCT). 36 patients with anisometropic amblyopia were selected in the experimental group, and another 36 healthy volunteers were selected in the control group, OCT examinations were performed in all groups, and the mean diopter, mean corrected visual acuity (CVA), mean axial length, mean optic disc retinal nerve fiber layer (RNFL) thickness, and mean macular fovea thickness were recorded in the two groups. The results found that the average diopter of the patients in the control group and the experimental group was +2.30 ± 2.54 D and +5.51 ± 1.76 D, respectively. The average CVA was 0.86 ± 0.07 and 0.22 ± 0.16, respectively; the average eye axial length was 22.41 ± 1.20 mm and 21.11 ± 0.78 mm, respectively. As P < 0.05, the differences were statistically significant in the three indicators between the two groups. There was no significant difference between the two groups in the average thickness of the RNFL of the optic disc and the average thickness of the central fovea of macula (P > 0.05). There was some correlation among CVA, diopter, eye axial length, RNFL thickness, and average thickness of macular fovea, but the correlation was not significant. It was suggested that there were certain differences in the macular and optic disc parameters between amblyopic and nonamblyopic children, but the difference is little. Thereout, a certain objective basis was provided for the early detection and treatment of amblyopia.