The Quantitative Measurements of Vascular Density and Flow Area of Optic Nerve Head Using Optical Coherence Tomography Angiography

Are optic nerve head and choroidal circulation affected by eye movements?

AIM

Although it has been reported that the optic nerve can be mechanically affected by the eye's horizontal movements, studies examining horizontal movements with optical coherence tomography angiography (OCTA) have only recently begun to emerge. This study aimed to investigate whether there are changes in the OCTA data of healthy individuals in the primary gaze, abduction, and adduction.

METHOD

Thirty volunteers (15-73 years old) were included in this prospectively designed study. Radial peripapillary capillary density parameters (RPCD) taken with OCTA in cases of primary gaze, abduction, and adduction were examined. With the OCTA device Angio Disc QuickVue that was used in the study, 3 main vessel structures could be examined.

RESULT

In the patients' primary, abduction, and adduction positions, a difference was observed only in the superior hemifield area of the left eye (P = 0.032). The superior hemifield all vessels vessel densities (AV VD) were 60.1 ± 2.7 in the central gaze, 59.9 ± 2.6 in the adduction, and 60.8 ± 2.6 in the abduction positions, with a relative decrease observed in adduction. This was also related to age. No difference was detected in terms of the other RPCD parameters.

CONCLUSION

In healthy individuals, short-term horizontal eye movements may not result in significant changes except for superior hemifield in OCTA data.

OCTA on the density of optic nerve microvessels in myopic population with ocular hypertension

OBJECTIVE

To measure functional, structural, and blood flow parameters of the optic disk in myopic patients with ocular hypertension (OHT) and myopic patients using optical coherence tomography angiography (OCTA), this study aims to investigate the variability of each parameter between the two groups, and to analyze the correlation between the RNFL thickness and blood flow parameters, as well as the diagnostic value of these blood flow parameters for myopic patients with OHT.

METHODS

This was a cross-sectional study. Myopic adults who were attending the Eye Center of Jinan Second People's Hospital between December 2020 and January 2022, and who had a confirmed diagnosis of OHT, were enrolled. This cohort constituted the myopic group. In these subjects, retinal nerve fiber layer (RNFL) thickness and blood flow parameters within the superficial optic disk 6 × 6 mm area were measured using OCTA. The optic disk blood flow parameters included radial peripapillary capillaries (RPC) perfusion density (PD) in nasal, temporal, superior, and inferior sectors. Visual field assessments were conducted using a Humphrey visual field meter to obtain the visual field index (VFI) and pattern standard deviation (PSD). SPSS 22.0 statistical software was utilized to determine if statistical differences existed between the parameters of the two groups and to analyze the correlation between blood flow parameters and RNFL thickness. Additionally, the area under the subject's operating characteristic curve (AUROC) was used to assess the diagnostic value of blood flow parameters for myopic patients with OHT.

RESULTS

There was no statistical difference in PSD and VFI in the OHT group compared with the myopic group (P = 0.351, 0.242). The RNFL thickness was (103.64 ± 8.13) μm and (97.56 ± 12.94) μm in the myopic and OHT groups, respectively. There was no statistical difference in RNFL thickness between the OHT and myopic group (P = 0.052). The PD of radial peripapillary capillaries (RPC) in nasal, temporal, superior, and inferior sectors showed an overall decreasing trend between the myopic and OHT groups, but there was a statistical difference only in the temporal sector (P = 0.008). Correlation analysis of blood flow parameters and structural parameters showed that the PD in the temporal sector and RNFL thickness were not correlated (P = 0.263). By plotting the AUROC of blood flow parameter, it was found that OCTA had good value in diagnosing myopic patients with OHT, and the PD of the temporal sector had higher diagnostic value for differentiating the OHT group from myopic group (AUROC = 0.718, P = 0.008) CONCLUSIONS: Compared with the myopic group, blood flow parameters decreased in the OHT group, while structural and functional parameters did not change significantly, suggesting that blood flow damage may have occurred earlier in myopic patients with OHT, by the correlation analysis between structural and blood flow parameters. OCTA has good diagnostic value for myopic patients with OHT.

Optical coherence tomography angiography assessment of retinochoroidal microcirculation differences in preeclampsia

BACKGROUND

To investigate microvascular changes in pregnant women with preeclampsia using optical coherence tomography angiography (OCTA) and compare the results with healthy pregnant and non-pregnant subjects.

METHODS

Superficial capillary plexus (SCP), deep capillary plexus (DCP) choriocapillaris (CC) vessel density (VD) and foveal avascular zone area (FAZ), retina, retinal nerve fiber layer (RNFL), the ganglion cell layer (GCL) and the choroidal thickness were examined and compared in preeclamptic pregnant (group 1), healthy pregnant women (group 2) and non-pregnant, age-matched female controls (group 3). The correlations of the parameters with each other and with blood pressure were evaluated.

RESULTS

No significant difference was found between the groups when retinal, RNFL and GCL thickness values (p> 0.05). The choroidal thickness values were significantly lower in group 1 than in group 2 (p = 0.029). The central foveal VD of the SCP and DCP was significantly lower in group 1 compared to groups 2 and 3 (p = 0.03, p< 0.01 respectively). The mean VD of the SCP was significantly higher in groups 1 and 2 than in group 3 (p = 0.01). The FAZ area was statistically significantly lower in group 3 than in group 2 (p = 0.032). The CC VD was lower in group 3 compared to the other groups in all measurements (p < 0.01).The FAZ area was positively correlated with systolic blood pressure in group 1.

CONCLUSION

The use of OCTA, a non-invasive imaging technique, to assess the retinal microcirculation appears to have the potential to in the early diagnosis or follow up in preeclampsia before signs of hypertensive retinopathy.

Axial length, more than aging, decreases the thickness and superficial vessel density of retinal nerve fiber layer in non-glaucomatous eyes

PURPOSE

This study seeks to build a normative database for the vessel density of the superficial retina (SVD) and evaluate how changes and trends in the retinal microvasculature may be influenced by age and axial length (AL) in non-glaucomatous eyes, as measured with optical coherence tomography angiography (OCTA).

METHODS

We included 500 eyes of 290 healthy subjects visiting a county hospital. Each participant underwent comprehensive ophthalmological examinations and OCTA to measure the SVD and thickness of the macular and peripapillary areas. To analyze correlations between SVD and age or AL, multivariable linear regression models with generalized estimating equations were applied.

RESULTS

Age was negatively correlated with the SVD of the superior, central, and inferior macular areas and the superior peripapillary area, with a decrease rate of 1.06%, 1.36%, 0.84%, and 0.66% per decade, respectively. However, inferior peripapillary SVD showed no significant correlation with age. AL was negatively correlated with the SVD of the inferior macular area and the superior and inferior peripapillary areas, with coefficients of -0.522%/mm, -0.733%/mm, and -0.664%/mm, respectively. AL was also negatively correlated with the thickness of the retinal nerve fiber layer and inferior ganglion cell complex (p = 0.004).

CONCLUSION

Age and AL were the two main factors affecting changes in SVD. Furthermore, AL, a relative term to represent the degree of myopia, had a greater effect than age and showed a more significant effect on thickness than on SVD. This relationship has important implications because myopia is a significant issue in modern cities.

Papillary and peripapillary vascular densities and corresponding correlation with peripapillary retinal thicknesses using optical coherence tomography angiography in healthy children and adolescents

To evaluate the peripapillary retinal thickness (PPRT), vascular density (PPVD), and disc vascular density (PVD) and their correlations in normal healthy children using optical coherence tomography angiography (OCTA). This was a cross-sectional study of 70 eyes from 36 normal healthy children aged 6-18 years who performed optic nerve head scans using OCTA. The PPRT included the peripapillary nerve fiber layer (PP-RNFLT), inner retina (PP-IRT), middle retinal thickness, and outer retinal thicknesses. The PP-RNFLT and PP-IRT were not significantly different between males and females. Superior nasal peripapillary RNFLT and IRT were significantly affected by age (ANOVA, P > 0.05). The PP-IRT and PP-RNFLT were lower in the 7-11 years old group in comparison with the other 3 groups (Post hoc Tukey test, P value < 0.05). Age and sex-matched PVD were not correlated with PPVD (partial correlation, P > 0.05). PPRT was not correlated with PVD, PPVD, superficial and deep retinal vascular densities, and choroidal vascular density. This study demonstrated that PPRT appears to change during growth in childhood. Superior nasal PPRT was affected more in the groups, decreasing from less than 7 years old to 7-11 years old and then back to pre-reduction values after 11 years old.

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.

The Effect of Myopia on Vessel Density in Glaucomatous Patients by Optical Coherence Tomography Angiography

Background

Glaucoma is a degenerative optic neuropathy that causes anatomical and functional visual impairment.

Aim and Objectives

This investigation's primary goal was to perform a qualitative and quantitative assessment of macular and peripapillary vessels to detect the impairment of blood flow in glaucomatous patients with or without myopia which can affect the prognosis of glaucoma and visual field.

Subjects and Methods

This prospective, cross-sectional, observational research was performed for glaucomatous patients with and without myopia who attend the outpatient clinic at the ophthalmology department, at Benha University. The study was conducted on 50 subjects with glaucomatous eyes, divided into two groups: the first group consisted of (25 subjects) of glaucoma with myopia and the second group (25 subjects) of glaucoma with the same severity of mean deviation in the visual field of group 1 without myopia, using OCTA to measure retinal vessel density (superficial vessel density) and OCT thickness ILM-RPE, RNFL thickness, GCL and small vessel density (RADIAL PERI PAPILLARY PLEXUS).

Results

Regarding demographic data of myopia in the studied eyes, there were (9) 18% with low myopia with no significance, (32) 64% with moderate myopia, and (9) 18% with high myopia, with open-angle glaucoma patients showed a highly significant decline in total retinal nerve fiber layer thickness, superior-nasal RNFL thickness, Inferior-nasal RNFL thickness, superior-temporal RNFL and inferior-temporal RNFL thickness compared to open-angle glaucoma patients without myopia.

Conclusion

Our results show that microvascular attenuation occurs more significantly in OAG than in myopia. When both myopia and OAG are present, there is a higher reduction in microvascular attenuation than with either disease alone. The development and progression of glaucoma in individuals with high myopia are more aggressive than in low or non-myopia, so by using OCTA detection of early microvascular changes in high myopia, individuals help the early detection and management of glaucoma.

The Differences in the Pattern of OCT and OCTA Examinations between Early Normal- and High-Tension Pseudoexfoliative Glaucoma

Purpose. The aim of this study was to compare the results of optical coherence tomography angiography (OCTA) and optical coherence tomography (OCT) examinations in patients with normal-tension glaucoma (NTG) in comparison to high-tension pseudoexfoliative glaucoma (HTG) patients at the early stage of glaucoma. Material and methods. The studied groups consisted of patients in the early stage of NTG (70 eyes) and the early stage of HTG (71 eyes). In NTG and HTG groups, a detailed ophthalmic examination was performed. Optic disc OCT with peripapillary RNFL measurements and OCTA examination with the evaluation of the macula and optic disc were performed for all participants using Zeiss Cirrus 5000. Results. NTG and HTG groups were statistically similar as far as the MD was concerned, and both groups had early glaucoma. When evaluating the RNFL thickness, the only statistical difference between early NTG and HTG was observed in the thicknesses in the temporal sector of peripapillary RNFL, with thinner values in the NTG group (53.94 vs. 59.94, p = 0.0071). When the OCTA results of the macula and optic disc were evaluated, there were no statistical differences between early NTG and HTG. Conclusions. The vascular density and flow parameters assessed in OCTA were equal between early NTG and HTG, and therefore the involvement of vascular factors in NTG pathogenesis could not be confirmed. Our results confirm the preponderance of more frequent temporal RNFL involvement in early NTG.

The evaluation of the effect of Nd-YAG capsulotomy on posterior ocular vascular structures by Optical coherence tomography angiography

BACKGROUND

We aimed to examine the changes in retinal, choroidal and optic nerve head vascular structures after Nd-YAG laser application due to posterior capsule opacification after cataract surgery by Optical coherence tomography angiography (OCTA).

METHODS

Fifteen eyes of 15 patients who have posterior capsule opasification and underwent Nd-YAG laser capsulotomy were included in the study. OCTA imagings of patients were made before and one hour, one week and one month later after the laser procedure.

RESULTS

No significant change was determined before and after capsulotomy in macular thickness measurements, flow areas and vessel densities (all p > 0.05). Optic nerve head vessel densities and flow areas didn't differ preoperatively and postoperatively (p > 0.05).

CONCLUSIONS

Nd-YAG laser capsulotomy for posterior capsule opacification has no detectable effect on macular and optic nerve flows and vessel densities.

Precision (repeatability and reproducibility) of papillary and peripapillary vascular density measurements using optical coherence tomography angiography in children

Importance

Optical coherence tomography angiography (OCTA) has been widely applied into children, however, few studies have assessed the repeatability and reproducibility of papillary and peripapillary VD in healthy children.

Objective

To assess the precision of papillary and peripapillary vascular density (VD) measurements using optical coherence tomography angiography (OCTA) and analyze the effects of the signal strength index (SSI) and axial length (AL) on precision estimates.

Design setting and participants

This was a prospective observational study. Seventy-eight children aged 6-16 years underwent 4.5 × 4.5 mm OCTA (RTVue XR Avanti) disc scans: two scans by one examiner (repeatability) and two additional scans by another examiner (reproducibility). Within-subject standard deviation (Sw), test-retest reproducibility (TRT), within-subject coefficient of variation (CoV), intraclass correlation coefficient (ICC), and Bland-Altman analysis were performed.

Main outcomes and measures

In repeatability measurement, the fluctuation ranges (minimum to maximum) of VD between intraexaminer A/B in Sw, TRT, CoV, and ICC were (1.05-2.17)% / (1.16-2.32)%, (2.9-6)% / (3.21-6.44)%, (1.9-4.47)% / (2.08-5)%, and (0.588-0.783)% / (0.633-0.803)%, respectively. In reproducibility measurement, the fluctuation ranges of VD in Sw, TRT, CoV, and ICC were 1.11-2.13%, 3.07-5.91%, 1.99-4.41%, and 0.644-0.777%, respectively. VD was negatively correlated with SSI in most sectors of the peripapillary (e.g., inferior nasal, temporal inferior, temporal superior, superior temporal, and superior nasal). AL was positively correlated with inferior temporal VD and negatively correlated with superior nasal VD.

Conclusion and relevance

Optical coherence tomography angiography showed moderate-to-good repeatability and reproducibility for papillary and peripapillary perfusion measurements in healthy children. The SSI value affects most of the peripapillary VD, while AL affects only the temporal inferior and nasal superior peripapillary VD.

Assessment of relationship between retinal perfusion and retina thickness in healthy children and adolescents

Purpose

To determine the correlations between inner, mid, and outer retinal thickness (RT) and allied retinal and choroidal vascular densities (VD) at macula in normal healthy children and adolescents.

Methods

This cross-sectional study included a total of 108 eyes of 59 subjects. Optical coherence tomography angiography (OCTA-Optovue) was used to measure the thickness of the inner-retina (IRT), mid-retina (MRT), and outer-retina (ORT) at foveal (central 1mm), parafoveal (1–3 mm), and perifoveal (3–6 mm) areas, as well as the corresponding VD of the superficial capillary plexus (SVD), deep capillary plexus (DVD), and choricapillaris (CVD).

Results

The study enrolled 108 normal eyes from 54 participants with a mean age of 10.9 years. Partial correlations showed that the nasal and inferior parafoveal and perifoveal subsegments IRT, MRT and ORT are more affected by all SVD, DVD, and CVD. Nasal parafoveal and perifoveal MRT and all three capillary layers have a constant negative correlation. ORT was not affected by all three layers except for CVD at fovea. The regression analysis revealed that SVD and CVD were significantly associated with foveal and parafoveal and perifoveal IRT. DVD and gender could significantly affect perifoveal IRT. However, only CVD was significantly affected foveal MRT. Based on regression analysis, only CVD was significantly associated with foveal and parafoveal ORT, but not with perifoveal ORT.

Conclusion

The thickness of different retinal layers correlates with retinal and choroidal VD in different ways according to their zones.

Quantitative Measurements of Vessel Density and Blood Flow Areas Primary Angle Closure Diseases: A Study of Optical Coherence Tomography Angiography

(1) Purpose: To measure the change in vessel density (VD) and the flow area (FA) on the retina of eyes with primary angle-closure diseases (PACD), including primary angle-closure suspect (PACS), primary angle-closure (PAC), acute primary angle-closure (APAC) and primary angle-closure glaucoma (PACG). (2) Methods: Patients with PACD were prospectively enrolled in this study. All participants underwent thorough ophthalmic examinations. The mean defect (MD), retinal nerve fiber layer (RNFL), ganglion cell complex (GCC) thickness, VD measurement, and blood FA were measured. (3) Results: A total of 147 eyes from 121 subjects were included in this study. The VD of the nerve head layer was significantly lower in PACG and APAC (all p < 0.001). APAC and PACG had lower FA of all layers, except for the choroid layer (p < 0.05). The macular VD of the whole image and blood FA in the superficial layer was significantly lower in PACG (all p < 0.001). The MD, RNFL, and GCC thickness demonstrated a strong correlation with whole image VD in the superficial layer (p < 0.001), while the inside disc VD did not show a significant correlation with MD, RNFL, and GCC thickness (p > 0.05). (4) Conclusions: There was a significant decrease in the VD and FA on the optic disc as well as the VD and FA of the superficial layer in the macular area in APAC and PACG. The changes in VD and FA are correlated with the severity of the glaucomatous structural damage and functional impairment.

Normative Data and Determinants of Macular, Disc, and Peripapillary Vascular Density in Healthy Myopic Children Using Optical Coherence Tomography Angiography

Objective

To establish a normative database for the vascular density (VD) in macular, disc, and peripapillary regions in healthy myopic children and to evaluate associated ocular features with optical coherence tomography angiography (OCTA).

Methods

This was an observational, prospective and cross-sectional study. 776 Chinese healthy myopic children (375 boys and 401 girls) were enrolled, mean (±SD) age 9.84 ± 1.98 (range 6–16) years. En-face angiogram OCTA was performed on 6 mm × 6 mm retinal and 4.5 mm × 4.5 mm disc regions. VD measurements in the macular retina were segmented into the four regions: superficial capillary plexus (SCP), intermediate capillary plexus (ICP), deep capillary plexus (DCP), and choriocapillaris (CC). Correlations between macular, disc, and peripapillary VD and possible influencing factors [age, gender, axial length (AL), spherical equivalent refraction (SER), right/left eye, and signal strength index (SSI)] were assessed by Pearson’s correlation and multivariate regression analysis.

Results

For macular scans, the corrected VD in the ICP region was (48.25 ± 4.24)% for the whole macular retina. The macular ICP VD in most sections was lower than the SCP, DCP, and CC (all P < 0.001). The corrected VD in CC was (72.96 ± 4.42)% for the whole macular retina. The macular CC VD in every section was all higher than the SCP, ICP, and DCP (all P < 0.001). The size of foveal avascular zone (FAZ) and foveal VD 300 (FD-300) was 0.28 mm²± 0.10 mm² and (58.43 ± 4.17)% respectively. For disc scans, the corrected VD was (58.04 ± 2.73)% for the whole disc area. Both AL and SER were strongly correlated with ICP, DCP, and CC VD in all regions (all P < 0.01). Larger SSI was correlated with a lower VD in the SCP and ICP, and a higher VD in DCP and CC (all P < 0.01).

Conclusion

Vascular density values provide large scale normative data on macular, disc, and peripapillary vascular parameters in a large sample of healthy myopic children with OCTA measured in the four different retinal plexuses and regions. The VD in different regions had various influencing factors; mainly a close correlation with AL and SSI.

Evaluation of the Optic Disc and Macula in Healthy Children Using Optical Coherence Tomography Angiography

Objectives

To perform the measurements of the optic disc and macula in healthy children using optical coherence tomography angiography (OCTA) in order to determine the normative data values and compare these by age, gender, spherical equivalent (SE), and axial length (AL).

Materials and Methods

A total of 146 eyes belonging to 146 healthy children (74 girls, 72 boys) aged 6 to 16 years were included in this prospective study. Refraction and biometry measurements were performed. Retinal nerve fiber layer thickness (RNFLT), central macular volume, and central macular thickness (CMT) were measured by optical coherence tomography (OCT) after dilatation. Using the OCTA device, foveal avascular zone (FAZ) area, vascular density (VD) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) of the macula, and the VD of the radial peripapillary capillary plexus (RPCP) of the optic disc were recorded.

Results

The mean age of the study group was 11.27±3 years, the mean AL was 23.39±1.18 mm and the mean SE was -1.31±1.61 diopters. The mean FAZ area was 0.3±0.09 mm2, the mean SCP-VD was 43.88±3.4%, the mean DCP-VD was 39.6±3.55%, and the mean RPCP-VD was 52.47±3.42%. When the relationship between the OCTA measurements and the SE and AL values were analyzed, there was no statistical significance (p>0.05). When age and OCTA measurements were compared, only DCP-VD values were found to significantly decrease with increasing age (p=0.015). There was no significant difference in OCTA measurements based on gender (p>0.05). Similarly, no statistical age-based differences were observed in RNFLT, CMV and CMT values (p>0.05).

Conclusion

With its short procedure time and no dye requirement, OCTA can be safely used in the evaluation of the optic disc and macular perfusion in children. Determination of normative values in children will be useful in detecting pathologic changes in tissue in patients with retinal diseases.

Predictors of Peripapillary and Macular Optical Microangiography Measurements in Healthy Eyes

PRECIS

The vessel density (VD) and perfusion density (PD) generated by optical microangiography (OMAG) is significantly affected by the signal strength (SS). Sex, hypertension, diabetes, and axial length did not have any statistically significant effect on these measurements.

PURPOSE

The aim was to assess the effect of subject-related factors (age, sex, systemic hypertension, diabetes, and axial length) and machine-related factor (SS) on VD and PD generated by OMAG in peripapillary and macular regions.

METHODS

In an observational, cross-sectional study of 200 eyes of 100 healthy individuals (age: 18 to 80 y), mean and sectoral VD and PD were calculated on disc and macular scans. Effect of subject-related and machine-related factors on VD and PD parameters were evaluated using multivariate mixed effect models.

RESULTS

Mean±SD peripapillary and macular VD of the study population was 18.56±1.11 and 20.59±1.85 mm-1, respectively. Mean peripapillary and macular PD was 46.43±3.22% and 37.61±3.26%, respectively. Sex, hypertension, diabetes, and axial length did not have any statistically significant effect on the OMAG measurements (P>0.05 for all associations). However, the SS had significant effect on the OMAG measurements. Mean peripapillary and macular VD on scans with SS of 10 was 1.4 and 3.79 mm-1 greater, respectively, than that on scans with SS of 7. Mean peripapillary and macular PD on scans with SS of 10 was 4.43% and 7.85% greater, respectively, than that on scans with SS of 7.

CONCLUSION

Significant association exists between SS of the scan and the optical coherence tomography angiography measurements generated by OMAG even when the scans have acceptable SS as recommended by the manufacturer (≥7). This needs to be considered while interpreting optical coherence tomography angiography measurements.

Does exogenous androgen use affect the retinal blood flow: An OCTA study in transgender men

PURPOSE

This study aims to investigate the effect of using exogenous androgen on retinal microvascular structures in transgender men.

METHODS

Retinal microvascular structures of transgender men and healthy women in the control group were visualized with optical coherence tomography angiography (OCTA). Foveal avascular zone (FAZ), superficial capillary vascular density (sCVD), deep capillary vascular density (dCVD), and radial peripapillary capillary (RPC) vascular density were evaluated.

RESULTS

Thirty transgender men and 30 healthy women were included in the study. There were no significant differences between transgender men and the control group in terms of FAZ, central macular thickness, parafoveal, and perifoveal retinal thicknesses (p = 0.859, 0.288, 0.561, and 0.719; respectively). sCVD were found to be low in transgender men in the whole image, parafoveal, and perifoveal zones (p = 0.006, 0.025, and 0.005; respectively). Although there were low values of dCVD of the whole image, parafoveal, and perifoveal zones in transgender men, the difference was not statistically significant (p = 0.295, 0.085, and 0.270; respectively). RPC vessel densities in the whole image, peripapillary zone, and the inferior of the optic disc were found to be significantly low in transgender men (p = 0.003, 0.005, and 0.003; respectively).

CONCLUSION

In this study, a decrease in vessel density in the superficial retinal layers and around the optic disc was detected in transgender men. These findings suggest that routine ophthalmological examination may be important in individuals who use exogenous androgens.

Peripapillary and parafoveal microvascular changes in eyes with optic neuritis and their fellow eyes measured by optical coherence tomography angiography: an Exploratory Study

PURPOSE

This study aimed to evaluate parafoveal and peripapillary microvascular alterations in eyes with optic neuritis (ON) along with their fellow eyes compared to healthy control eyes using optical coherence tomography angiography (OCT-A).

METHODS

We included 31 ON-affected eyes and 31 fellow eyes of 31 patients who had experienced unilateral ON and 33 eyes of 33 healthy controls in this exploratory retrospective cross-sectional study. Optical coherence tomography angiography (OCT-A) was used to generate microvascular structural images and quantify the vessel density of the superficial retinal capillary plexus (SRCP), the deep retinal capillary plexus (DRCP) and radial peripapillary capillary (RPC) segments. We used the Kruskal-Wallis test for the comparison of OCT-A results between the three groups and generalized estimating equation models for the pairwise comparisons.

RESULTS

There were significant differences of SRCP (p = 0.0003) and RPC segment (p < 0.0001) vessel densities between the three groups. Specifically, there was a reduction in parafoveal and peripapillary vessel density in the ON-affected eyes compared to fellow eyes (SRCP, estimates, -1.97, 95% confidence interval [CI], -3.07, -0.87; RPC, -6.95, 95% CI, -8.70, -5.19) and controls (SRCP, -3.15, 95% CI, -4.61, -1.69; RPC, -8.66, 95% CI, -10.55, -6.76). The superior sector of the RPC segments vessel density in the fellow eyes was decreased compared to the controls (-4.93, 95% CI, -8.07, -1.80).

CONCLUSIONS

The results of this study suggest that microvascular changes occur in both the affected eye and unaffected fellow eye after a unilateral ON episode. Future studies are needed to clarify the clinical implications of these findings.

Quantitative assessment and determinants of the papillary microvasculature in healthy subjects

BACKGROUND

It is critical to monitor the optic disc's vessel density using Optical coherence tomography angiography (OCTA) and evaluate its determinants. In the current study, we investigate the superficial vessel density (VD) of the papillary microvasculature and its determinants in healthy subjects of Southern China.

METHODS

This was a prospective, cross-sectional study. Superficial VD in healthy individuals' optic disc region was measured by OCTA. The factors associated with ocular and systemic parameters were analyzed using a generalized estimation equation (GEE) model.

RESULTS

A total of 510 eyes of 260 healthy subjects were analyzed in the study. The total VD in the optic disc area was 17.21 ± 2.15 mm- 1 (95% CI, 17.02-17.40 mm- 1). The VD in the inner ring and the outer ring of the optic disc were significantly higher compared with the central ring, while the VD of the superior quadrant and inferior quadrant was significantly higher compared with the temporal and nasal quadrant. After adjusting for the ocular factors and systemic factors, AL (β = - 0.4917, P = 0.0003), disc area (β = - 0.3748, P = 0.0143), CMT (β = - 0.0183, P = 0.0003) and SSI (β = 1.0588, P < 0.001) were significantly associated with total VD of the optic disc.

CONCLUSION

The mean total VD in the optic disc area was 17.21 ± 2.15 mm- 1 in healthy subjects, and the superior and inferior VD was significantly higher than the temporal and nasal VD. AL, disc area, CMT, and SSI may affect the total VD in the optic disc area and should be considered in clinical practice.

Association between risk factors and retinal nerve fiber layer loss in early stages of diabetic retinopathy

AIM

To investigate the changes of retinal nerve fiber layer (RNFL) among normal individuals, diabetic patients without diabetic retinopathy (NDR) and non-proliferative diabetic retinopathy (NPDR), and explore the possible risk factors of early diabetic retinopathy (DR).

METHODS

In this cross-sectional study, 107 participants were divided in three groups. Totally 31 normal individuals (control group), 40 diabetic patients without DR (NDR group) and 36 patients with NPDR (NPDR group) were included. Optical coherence tomography (OCT) was used to detect RNFL thickness and other optic disc parameters among different groups. The potential association between RNFL loss and systemic risk factors were assessed for DR, including diabetes duration, body mass index (BMI), hemoglobin A1c (HbA1c), serum lipids, and blood pressure.

RESULTS

The average and each quadrant RNFL thickness were thinner in NPDR group compared to control group of the right (P=0.00, P=0.01, P=0.01, P=0.02, P=0.04) and left eyes (P=0.00, P=0.00, P=0.00, P=0.03, P=0.04). The average, superior and inferior RNFL thickness were thinner in NDR group compared to the NPDR group of the right (P=0.00, P=0.02, P=0.03) and left eyes (P=0.00, P=0.00, P=0.01). Diabetic duration was negatively correlated with the superior, inferior, and average RNFL thickness of the right (r=-0.385, P=0.001; r=-0.366, P=0.001; r=-0.503, P=0.000) and left eyes (r=-0.271, P=0.018; r=0.278, P=0.015; r=-0.260, P=0.023). HbA1c was negatively correlated with the superior, inferior, and average RNFL thickness of the right (r=-0.316 P=0.005; r=-0.414, P=0.000; r=-0.418, P=0.000) and left eyes (r=-0.367, P=0.001; r=-0.250, P=0.030; r=-0.393, P=0.000). Systolic pressure was negatively correlated with the inferior and average RNFL thickness of the right eye (r=-0.402, P=0.000; r=-0.371, P=0.001) and was negatively correlated with the superior and average RNFL thickness of the left eye (r=-0.264, P=0.021; r=-0.233, P=0.043).

CONCLUSION

RNFL loss, especially in the superior and inferior quadrants, may be the earliest structural change of the retina in diabetic patients, and is also associated with diabetic duration, HbA1c, and systolic pressure.

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.

Optical coherence tomography angiography (OCTA) applications in ocular oncology

Optical coherence tomography angiography (OCTA) is a revolutionary method in the visualization of the vascular system in different retinal and choroidal layers. During the last 4 years since the commercial availability of different OCTA devices, attempts have been made to utilize this technology in various aspects of ocular oncology from the differentiation of benign and malignant lesions to assisting in evaluation of post-treatment complications, such as radiation retinopathy. However, current OCTA technology is restricted by various artefacts and inherent limitations, some of which are more pronounced in the presence of elevated tumoural lesions. Imminent advancements in OCTA systems and image acquisition processes promise a great potential for application of OCTA in ocular oncology.

Normative Database of Peripapillary Vessel Density Measured by Optical Coherence Tomography Angiography and Correlation Study

Purpose: To provide a normative data set of swept-source optical coherence tomography angiography (SS-OCTA) peripapillary vessel density (VD) measurements and assess correlations with age, gender, disc area and axial length (AL). Material and Methods: This was an observational cross-sectional study conducted on 346 right eyes of healthy subjects. Peripapillary SS-OCTA VD measurements were obtained in the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) in all four quadrants using the Triton device (Topcon, Nagoya, Japan). AL measurements were made by optical biometry. Results: Mean participant age was 37.7 ± 19.8 years (range 5- 83), AL was 23.9 ± 1.3 mm (21-27), and 59% were women. Mean VDs for all quadrants were 57.2 ± 5.7% for SCP (52.4 ± 4.0% - 62.1 ± 4.2%), 46.3 ± 6.5% for DCP (41.9 ± 5.8% - 49.7 ± 4.8%) and 60.8 ± 7.4% for CC (53.4 ± 5.8% - 65.7 ± 5.5%). Negative correlation was detected between SCP VD and age (R = -0.264; P < .001), while correlation between DCP densities and age was positive (R = 0.202; P = .002). No associations were detected between peripapillary VD and gender (P ≥ 0.087) and negative correlation was found with AL and disc area only in the CC (P ≤ 0.004). In a subgroup analysis of 33 individuals, we noted no differences in VD between fellow eyes (P ≥ 0.139). Conclusion: Peripapillary VD showed wide individual variation when measured with the Triton SS-OCTA in the different retinal plexuses and CC. While correlations were observed with age, no relationships emerged with gender and only CC showed negative correlation with AL and disc area.

Ocular blood flow as a clinical observation: Value, limitations and data analysis

Alterations in ocular blood flow have been identified as important risk factors for the onset and progression of numerous diseases of the eye. In particular, several population-based and longitudinal-based studies have provided compelling evidence of hemodynamic biomarkers as independent risk factors for ocular disease throughout several different geographic regions. Despite this evidence, the relative contribution of blood flow to ocular physiology and pathology in synergy with other risk factors and comorbidities (e.g., age, gender, race, diabetes and hypertension) remains uncertain. There is currently no gold standard for assessing all relevant vascular beds in the eye, and the heterogeneous vascular biomarkers derived from multiple ocular imaging technologies are non-interchangeable and difficult to interpret as a whole. As a result of these disease complexities and imaging limitations, standard statistical methods often yield inconsistent results across studies and are unable to quantify or explain a patient's overall risk for ocular disease. Combining mathematical modeling with artificial intelligence holds great promise for advancing data analysis in ophthalmology and enabling individualized risk assessment from diverse, multi-input clinical and demographic biomarkers. Mechanism-driven mathematical modeling makes virtual laboratories available to investigate pathogenic mechanisms, advance diagnostic ability and improve disease management. Artificial intelligence provides a novel method for utilizing a vast amount of data from a wide range of patient types to diagnose and monitor ocular disease. This article reviews the state of the art and major unanswered questions related to ocular vascular anatomy and physiology, ocular imaging techniques, clinical findings in glaucoma and other eye diseases, and mechanistic modeling predictions, while laying a path for integrating clinical observations with mathematical models and artificial intelligence. Viable alternatives for integrated data analysis are proposed that aim to overcome the limitations of standard statistical approaches and enable individually tailored precision medicine in ophthalmology.

Optical coherence tomography angiography-derived flow density: a review of the influencing factors

Research interest in the possibility of quantifying macular and optic nerve head perfusion through optical coherence tomography angiography (OCTA) is rapidly advancing. Numerous scientific trials have furthered our understanding of the capabilities and the limitations of this novel technology, while applying OCTA to various ocular pathologies. In recent years, different parameters such as age, gender, intraocular pressure, spherical equivalent, physical activity, systemic diseases, and medication have been shown to have a significant impact on quantitative OCTA metrics. Since OCTA is likely to remain a "hot topic" in the near future, it is crucial to be aware of influencing factors in order to ensure correct interpretation of imaging results. This article reviews the factors currently known to influence flow density (FD) as measured by OCTA in healthy eyes.

Differences in macular capillary parameters between healthy black and white subjects with Optical Coherence Tomography Angiography (OCTA)

PURPOSE

To investigate if there are differences in macular capillaries between black and white subjects using optical coherence tomography angiography (OCTA) and identify potential factors underlying the epidemiologically-based higher vulnerability of black populations to diabetic retinopathy (DR).

METHODS

This prospective, observational cross-sectional study included 93 eyes of 47 healthy subjects with no medical history and ocular history who self-identified as black or white and were matched for age, sex, refractive error, and image quality. Subjects underwent OCTA imaging (RTVue-XR Avanti) of the superficial (SCP) and deep (DCP) capillary plexuses and choriocapillaris. AngioAnalytics was used to analyze vessel density (VD) and choriocapillaris % blood flow area (BFA) in the 1mm-diameter fovea, parafovea, and 3mm-diameter circular area including the fovea and parafovea (3x3mm image). Foveal avascular zone (FAZ) was also analyzed. Linear mixed models were used to evaluate for differences between the study groups.

RESULTS

Compared to the white subjects in this study, black subjects were found to have: lower foveal VD in the SCP (p<0.05); lower VD in the parafovea and in the 3x3mm image in the DCP (p<0.05); larger FAZ in SCP and DCP (p<0.05); and decreased choriocapillary BFA in the area underlying the fovea, parafovea, and 3x3mm image (p<0.05).

CONCLUSION

In our study, our black subjects had decreased macular capillary vasculature compared to matched white subjects, even in early adulthood and the absence of any systemic or ocular conditions. To our knowledge, this is the first report showing that retinal and choriocapillary vascular differences may contribute to racial disparities in vulnerability to DR.

Association of Myopia With Peripapillary Perfused Capillary Density in Patients With Glaucoma: An Optical Coherence Tomography Angiography Study

Importance

This study used optical coherence tomographic angiography to assess for impaired blood flow in myopic eyes with or without open-angle glaucoma.

Objective

To compare the peripapillary perfused capillary density (PCD) between eyes with and without glaucoma.

Design, Setting, and Participants

In this cross-sectional study at a tertiary glaucoma referral practice, we recruited patients with myopic eyes of spherical equivalent of more than -3.0 diopters with and without open-angle glaucoma, patients with nonmyopic eyes with glaucoma, and patients with no disease from February 2016 to October 2016. We obtained 4.5 × 4.5-mm optical coherence tomographic angiography images of the optic nerve head and calculated PCD as the ratio of pixels associated with capillaries to the number of pixels in the region of interest after large blood vessel removal. Both eyes of each patient were used in the analysis. Continuous variables were assessed by analysis of variance and Tukey tests. A marginal model of generalized estimating equations was performed to adjust for confounding factors and intraclass correlations.

Main Outcomes and Measures

Mean PCD.

Results

We matched 87 patients with myopic eyes with glaucoma (of whom 39 [45%] were women), 17 with myopic eyes without glaucoma (of whom 10 [59%] were women), and 93 with non-myopic eyes with glaucoma (of whom 55 [59%] were women) for visual field defects and included 51 control participants (or whom 38 [75%] were women). Mean (SD) ages were 67.5 (12.0) years for patients with myopia and glaucoma, 48.2 (19.0) years for those with myopia without glaucoma, 67.3 (11.0) years for those with glaucoma without myopia, and 64.7 (8.9) years in control participants. Global PCD demonstrated a progressive decrease from the control group (mean [SD], 41.0 [4.2]) to those with myopia without glaucoma (38.4 [5.8]) to those with glaucoma without myopia (31.9 [7.5]) to those with both (28.2 [6.0]; all P < .001). The mean difference in global PCD between the 3 groups and control group, adjusted for age and axial length, was greatest in those with myopia and glaucoma (-11.1; 95% CI, -14.0 to -8.1; P < .001), followed by those with glaucoma without myopia (-8.6; 95% CI, -10.9 to -6.3; P < .001) and those with myopia without glaucoma (-2.8; 95% CI, -6.9 to 1.2; P = .17). No interaction was found between glaucoma and myopia.

Conclusions and Relevance

These findings demonstrate peripapillary microvascular attenuation to a greater extent in open-angle glaucoma than myopia. The cross-sectional design means we cannot determine if this association is a cause and/or is associated with other confounding factors.

Peripapillary Region Perfusion and Retinal Nerve Fiber Layer Thickness Abnormalities in Diabetic Retinopathy Assessed by OCT Angiography

Purpose

To quantify peripapillary region perfusion and retinal nerve fiber layer (RNFL) thickness abnormalities in different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA).

Methods

Seventy-two eyes of 72 patients with diabetes were included as follows: 23 with no DR (No DR), 24 with mild-to-moderate nonproliferative DR (mild DR), 25 with severe nonproliferative to proliferative DR (severe DR), and 26 age-matched healthy controls. All eyes underwent a 4.5 × 4.5-mm rectangle scan centered on the optic nerve head. Vessel densities and RNFL thickness for the peripapillary area were calculated.

Results

A statistically significant decrease in vessel density was found in the peripapillary region with increased DR severity (all P < 0.001). There were significant correlations between DR severity and vessel density in the peripapillary region (P < 0.001), but not between DR severity and RNFL thickness (P > 0.05). There was a significantly positive correlation between vessel density and RNFL thickness of the peripapillary region in the mild DR group (r = 0.726, P < 0.001) but not in the no DR group (r = 0.008, P = 0.973) or the severe DR group (r = 0.281, P = 0.173).

Conclusions

Vessel density in the peripapillary region correlated significantly with DR severity, decreasing with DR aggravation. There was no obvious correlation observed between RNFL thickness and DR severity.

Translational Relevance

Vessel density in the peripapillary region, assessed by OCTA technology, can be potentially useful for analyzing and monitoring retinal nerve changes in DR patients.

Effects of panretinal photocoagulation on retinal vasculature and foveal avascular zone in diabetic retinopathy using optical coherence tomography angiography: A pilot study

Purpose

To evaluate the optical coherence tomography angiography (OCTA) parameters in patients with diabetic retinopathy following panretinal photocoagulation (PRP).

Methods

Eleven eyes of 6 patients with very severe nonproliferative diabetic retinopathy (NPDR) or early proliferative diabetic retinopathy (PDR) were recruited in this prospective interventional pilot study. All patients underwent OCTA imaging at baseline, and choroidal flow, foveal avascular zone (FAZ), retinal thickness, and vascular density were measured at baseline. Three months after treatment, OCTA was repeated, and the alteration in variables was analyzed.

Results

The FAZ area remained unchanged following treatment, (P = 0.75). Retinal thickness increased along (P = 0.02) with an increase in vascular density in the superficial and deep foveal area and the macular temporal sector (P = 0.007, 0.03 and 0.049, respectively). Choroidal flow surface area was unchanged (P = 0.10).

Conclusion

In this study, foveal vascular density increased and FAZ remained unchanged after PRP for diabetic retinopathy.

Optical Coherence Tomography Angiography in Familial Exudative Vitreoretinopathy: Clinical Features and Phenotype-Genotype Correlation

Purpose

To evaluate the microstructure of the fovea in patients with familial exudative vitreoretinopathy (FEVR) compared to healthy controls using optical coherence tomography angiography (OCTA).

Methods

In this consecutive, cross-sectional, observational case series, 41 eyes of 41 patients diagnosed as FEVR and 37 eyes in 37 control subjects were studied. OCTA was utilized to automatically measure the foveal avascular zone (FAZ) and the vessel density (VD). Inner retinal thicknesses (IRT) and central retinal thickness (CRT) were measured with the instrument caliper. Targeted next-generation sequencing was performed, and phenotype-genotype association was analyzed.

Results

Small FAZ was found in 31.70% (13/41) FEVR eyes but not in controls. Greater CRT and lower superficial foveal VD were noted in FEVR patients. FAZ is negatively correlated with IRT. Persistence of the inner retinal layer (IRL) in fovea was present in 48.78% (20/41) FEVR eyes but not found in controls. Zero percent (0/10) of patients with the low-density lipoprotein receptor-related protein 5 (LRP5) mutation, 50% (1/2) with the frizzled-4 (FZD4) mutation, and 66.67% (3/4) with the tetraspanin-12 (TSPAN12) mutation had preserved foveal IRL and small FAZ.

Conclusions

Our data indicate FEVR status is associated with a significantly smaller FAZ, decreased vascular density in both the superficial and deep layers of parafoveal area, a thicker fovea, and an abnormally preserved IRL in fovea. In addition, patients with the LRP5 mutation had a milder phenotype than those with the FDZ4 or TSPAN12 mutations. These novel findings could provide insight into the understanding of the pathogenesis of FEVR.

Age related changes of the central lamina cribrosa thickness, depth and prelaminar tissue in healthy Chinese subjects

AIM

To investigate the variation in the central lamina cribrosa thickness (cLCT), and the central anterior lamina cribrosa surface depth (cALCSD), as well as the central prelaminar tissue thickness (cPLTT) related to age in healthy Chinese subjects.

METHODS

A total of 96 eyes from 96 Chinese healthy subjects were recruited. According to age, the 96 cases were divided into three groups: the young group (YG, 18-39y), middle-age group (MG, 40-59y) and older-age group (OG, 60y and above). Lamina cribrosa images were obtained from all participants using radial linear protocol by enhanced depth imaging spectral-domain optical coherence tomography. The cLCT, cALCSD and cPLTT were calculated from the average value of the lamina cribrosa thickness, anterior lamina cribrosa surface depth and prelaminar tissue thickness in the optic nerve head (ONH) centre point and paracentral points (150 µm from the centre point in the horizontal and vertical directions).

RESULTS

For the total subjects, the mean cLCT, cALCSD and cPLTT were 235.18±41.27, 358.02±93.80 and 182.02±92.11 µm, respectively. No statistically significant differences in cLCT, cALCSD or cPLTT were found between gender and different eyes (P=0.27-0.92). The cLCT of the OG was the thickest among the three groups, while the cPLTT of the YG was the thickest among the three groups (P<0.05). Age was positively correlated with cLCT (r=0.42, P<0.001), and negatively correlated with cPLTT (r=-0.24, P=0.02). No significant correlation was found between the age and cALCSD (r=-0.06, P=0.55). And no correlation has been found between axial length and cLCT, cALCSD and cPLTT (P=0.11-0.81).

CONCLUSION

The impact of age on the cLCT and the cPLLTT should be taken into account when analysing glaucoma and other diseases related to lamina cribrosa.

Comparison of methods to quantify macular and peripapillary vessel density in optical coherence tomography angiography

Purpose

To compare macular and peripapillary vessel density values calculated on optical coherence tomography angiography (OCT-A) images with different algorithms, elaborate conversion formula, and compare the ability to discriminate healthy from affected eyes.

Methods

Cross-sectional study of healthy subjects, patients with diabetic retinopathy, and glaucoma patients (44 eyes in each group). Vessel density in the macular superficial capillary plexus (SCP), deep capillary plexus (DCP), and the peripapillary radial capillary plexus (RCP) were calculated with seven previously published algorithms. Systemic differences, diagnostic properties, reliability, and agreement of the methods were investigated.

Results

Healthy eyes exhibited higher vessel density values in all plexuses compared to diseased eyes regardless of the algorithm used (p<0.01). The estimated vessel densities were significantly different at all the plexuses (p<0.0001) as a function of method used. Inter-method reliability and agreement was mostly poor to moderate. A conversion formula was available for every method, except for the conversion between multilevel and fixed at the DCP. Substantial systemic, non-constant biases were evident between many algorithms. No algorithm outperformed the others for discrimination of patients from healthy subjects in all the retinal plexuses, but the best performing algorithm varied with the selected plexus.

Conclusions

Absolute vessel density values calculated with different algorithms are not directly interchangeable. Differences between healthy and affected eyes could be appreciated with all methods with different discriminatory abilities as a function of the plexus analyzed. Longitudinal monitoring of vessel density should be performed with the same algorithm. Studies adopting vessel density as an outcome measure should not rely on external normative databases.

Glaucoma: Biological Trabecular and Neuroretinal Pathology with Perspectives of Therapy Innovation and Preventive Diagnosis

Glaucoma is a common degenerative disease affecting retinal ganglion cells (RGC) and optic nerve axons, with progressive and chronic course. It is one of the most important reasons of social blindness in industrialized countries. Glaucoma can lead to the development of irreversible visual field loss, if not treated. Diagnosis may be difficult due to lack of symptoms in early stages of disease. In many cases, when patients arrive at clinical evaluation, a severe neuronal damage may have already occurred. In recent years, newer perspective in glaucoma treatment have emerged. The current research is focusing on finding newer drugs and associations or better delivery systems in order to improve the pharmacological treatment and patient compliance. Moreover, the application of various stem cell types with restorative and neuroprotective intent may be found appealing (intravitreal autologous cellular therapy). Advances are made also in terms of parasurgical treatment, characterized by various laser types and techniques. Moreover, recent research has led to the development of central and peripheral retinal rehabilitation (featuring residing cells reactivation and replacement of defective elements), as well as innovations in diagnosis through more specific and refined methods and inexpensive tests.