Radial Peripapillary Capillary Network in Patients with Retinitis Pigmentosa: An Optical Coherence Tomography Angiography Study

Multimodal Imaging of Optic Nerve Head in Retinitis Pigmentosa

BACKGROUND

A pallor optic nerve head (ONH) is one of the three features of retinitis pigmentosa (RP). This study aimed to assess the ONH prospectively by color tone, presence of hyper-reflective tissue, blood flow, retinal nerve fiber layer (RNFL) thickness, ganglion cell complex (GCC) and investigate the change in these parameters with and without ONH pallor.

METHODS

The presence of ONH pallor was assessed by three independent examiners through careful examination using fundus photographs. The presence of a hyper-reflective structure on the ONH was carefully evaluated using a volume scan optical coherence tomography (OCT). RNFL thickness and ellipsoid zone (EZ) width around the macula were also evaluated by OCT. Laser speckle flowgraphy was used to measure the mean blur rate of the entire ONH area, which was subsequently divided into the vessel area (MV) and tissue area (MT).

RESULTS

Twenty-eight eyes of 28 patients with RP (55.4 ± 16.23 years of age) were included. The pale ONH was observed in 10 (35%) eyes. Hyper-reflective structures were observed in seven (25%) eyes. No significant correlation was found between the pale ONH and the presence of a hyper-reflective structure (Pearson's chi-squared test, p = .364). The average of the ONH area, MV, and MT was 8.65 ± 3.08 AU, 17.81 ± 7.54 AU, and 6.4 ± 2.66 AU, respectively, which significantly decreased in patients with pallor ONH (all p < .05). The global RNFL thickness was 73.54 ± 18.82 μm. The nasal and superior quadrants and global RNFL thickness in patients with a pale ONH were significantly thinner than in patients without a pale ONH (all p < .05). The global and superior and inferior GCC thickness in patients with a pale ONH were significantly thinner than in patients without a pale ONH(all p < .05).There was no difference in the EZ width between patients with and without a pale ONH (p = .107).

CONCLUSION

We conducted multiple assessments of the ONH in RP patients and investigated its clinical significance. Our findings suggest that ONH pallor may indicate a comprehensive change that emerges alongside the progression of retinal degeneration in RP.

TRIAL REGISTRATION

This trial was retrospectively registered in the UMIN Clinical Trial Registry (UMIN ID: 000048168).

Optical coherence tomography (OCT) and OCT-angiography in syndromic versus non-syndromic USH2A-associated retinopathy

PURPOSE

To compare non-syndromic and syndromic forms of USH2A-related retinitis pigmentosa (RP) by means of structural optical coherence tomography (OCT) and OCT-angiography (OCTA).

METHODS

Observational, cross-sectional, multicenter study. All patients underwent best corrected visual acuity (BCVA) measurement, OCT (Spectralis HRA + OCT, Heidelberg Engineering) and OCTA (OCT DRI Topcon Triton, Topcon Corporation). We compared subfoveal choroidal thickness (SCT), choroidal vascularity index (CVI), presence of cystroid macular edema (CME), macular vessel density (VD) at the superficial and deep capillary plexa, as well as VD of the radial peripapillary capillary (RPC) network, between syndromic and non-syndromic patients with USH2A-associated retinopathy.

RESULTS

Thirty-four eyes from 18 patients (7 females) were included. Thirteen patients (72.2%) were affected by Usher syndrome type 2, whereas the remaining 5 subjects (27.8%) had non-syndromic retinitis pigmentosa (nsRP). Syndromic patients were younger than nsRP (p = 0.01) and had a worse visual acuity than those with the exclusively retinal phenotype. Patients with Usher syndrome type 2 had a higher prevalence of CME and a thicker choroid compared to nsRP, although these results were not statistically significant (p = 0.775 and p = 0.122, respectively). Similarly, none of the other quantitative OCT and OCTA parameters was statistically different between the two groups.

CONCLUSIONS

Despite their younger age, patients with Usher syndrome type 2 displayed similar choroidal and microvascular changes compared to those with nsRP.

New insights in the multimodal imaging of retinitis pigmentosa

Retinitis pigmentosa (RP) is a group of inherited rod-cone dystrophies, noted for a high genotypical and phenotypical heterogeneity.Traditionally, VA, visual field, and electroretinography have been used to assess RP progression. However, visual acuity and visual field tests are essentially subjective and, especially in the late stages of the disease, are unable to confidently reveal minor progression. Therefore, there is a need for novel examination modalities that rely on quantitative, structural measurements. In this regard, several non-invasive imaging techniques have been studied, including spectral-domain optical coherence tomography, optical coherence tomography angiography, and fundus autofluorescence. By correlating surrogate biomarkers with functional measurements of the disease, these techniques may be able to develop reliable outcome meters that can be used to gain a deeper understanding of the underlying causes of the disease and to assess the effectiveness of therapy even before an actual loss of vision occurs.In this review, we will summarize the recent imaging findings and biomarkers that have been identified in RP patients. Our goal is to provide information that can promptly aid in selecting patients for clinical trials and new gene therapies, monitoring the disease progression, and evaluating treatment outcomes.

Optical coherence tomography angiography in retinitis pigmentosa: A narrative review

Retinitis pigmentosa (RP) is a group of inherited retinal disorders characterized by progressive rod and cone photoreceptor degeneration. Changes in retinal vasculature have long been associated with RP. Optical coherence tomography angiography (OCTA) is a novel imaging technology that enables noninvasive visualization of the retinal and choroidal microvasculature. OCTA enables quantification of microvascular changes in the retinal capillary plexus and choriocapillaris, in addition to qualitative feature description. Therefore, OCTA has the potential to become an important tool for better understanding, early detection, progression, and treatment of RP. In this review, we focus on the applications of OCTA in clinical research on RP. We also discuss future improvements in the OCTA technology for RP management. We believe that the advancement of the OCTA technique will ultimately lead to a better understanding of RP and aid in the prevention of visual impairment.

Relationship between the vessel density around the optic nerve head and visual field deterioration in eyes with retinitis pigmentosa

PURPOSE

To analyze the vessel density around the optic nerve head (ONH) by optical coherence tomography angiography (OCTA) in patients with retinitis pigmentosa (RP), and to evaluate its correlation with visual functions.

METHODS

Thirty-eight eyes with RP with visual field constriction within the central 10° were enrolled. The mean (± SD) age of the patients was 43.7 ± 15.1 years. In addition to visual acuity (VA) measurements and visual field tests (Humphrey Field Analyzer 10-2 test), we also measured the vessel density at the macula by OCTA (superficial and deep vessel density: sVD(m) and dVD(m)) and in multiple layers around the ONH (vessel density in the radial peripapillary capillary [RPC] layer and in the nerve head [NH] layer: VDrpc and VDnh). The vessel density was calculated by binarizing the OCTA images. The associations between the logMAR VA and mean deviation (MD) values and the variables of central retinal thickness (CRT), sVD(m), dVD(m), VDrpc, VDnh, and also the size of the foveal avascular zone were investigated.

RESULTS

The mean logMAR VA was 0.16 ± 0.34 and the MD value was - 17.2 ± 10.3 dB; the MD value was significantly related to the logMAR VA (p = 0.0028). Multivariate analysis with AICc model selection suggested only dVD(m) was associated with logMAR VA. On the other hand, the optimal model for the MD value included the CRT, dVD(m), and VDnh.

CONCLUSION

The vessel density in the deep layer around the ONH was significantly associated with the visual field deterioration in patients with RP.

Choroidal Patterns in Retinitis Pigmentosa: Correlation with Visual Acuity and Disease Progression

Purpose

The main aim was to identify different choroidal patterns in retinitis pigmentosa (RP) and to assess their clinical and anatomical meanings after 1 year of follow-up.

Methods

Forty-five patients with RP (29 men; mean age 44.5 ± 11.7 years) and 45 healthy controls (29 men; mean age 44.2 ± 9.8 years) were recruited. Optical coherence tomography (OCT) and OCT angiography (OCTA) images were obtained. By means of structural OCT, the following three choroidal patterns were identified: normal-appearing choroid (pattern 1), reduced Haller and Sattler layers (pattern 2), and pattern 2 + choroidal caverns (pattern 3). Main outcome measures were best-corrected visual acuity (BCVA), central macular thickness (CMT), choroidal thickness (CT), vessel density, vessel tortuosity, vessel dispersion, vessel rarefaction, and choroidal stromal index (CSI).

Results

Mean BCVA was 0.27 ± 0.30 LogMAR for patients with RP and 0.0 ± 0.0 LogMAR for controls (P < 0.01). CMT, CT, CSI, and OCTA parameters were statistically different between patients with RP and controls (P < 0.01). Choroidal patterns 1, 2, and 3 were identified in 20 (44%), 15 (33%), and 10 (23%) patients with RP, respectively. Several statistically significant correlations were also found. Interestingly, after 1 year of follow-up, only the pattern 3 subgroup showed significant worsening of BCVA, CMT, and OCTA parameters (P < 0.01).

Conclusions

Choroidal patterns were associated with different RP clinical forms as well as with different progression after 1 year.

Translational Relevance

Choroidal patterns evaluation may provide useful clinical information for patients with RP.

Quantification of Macular Microvascular Changes in Retinitis Pigmentosa Using Optical Coherence Tomography Angiography

Purpose

To investigate macular structural and microvascular changes in retinitis pigmentosa (RP) eyes compared to age-matched controls using spectral domain optical coherence tomography (SD-OCT) and OCT angiography (OCTA).

Methods

This was a cross-sectional study. The foveal and parafoveal thickness and extent of ellipsoid zone (EZ) disruption were measured on OCT. The foveal avascular zone (FAZ) area and retinal vessel density (VD) were automatically calculated for superficial (SCP) and deep capillary plexuses (DCP) and choriocapillaris using OCTA-integrated software. VD was assessed for the whole 6 × 6 mm image, foveal and parafoveal regions. Quantitative measures were compared between healthy and diseased eyes.

Results

The study included 30 eyes of 30 RP patients and 24 eyes of 24 controls. Mean age was 26.9±6.4 years for RP patients and 27.4±4.9 years for controls (p=0.76). Mean LogMAR visual acuity (VA) was 0.9±0.5 for RP patients and 0.05±0.05 for controls (p <0.001). Foveal and parafoveal thicknesses were significantly lower in RP cases as compared to the control group. EZ disruption was observed in RP cases only (869±211 µm). Mean FAZ area was significantly larger in RP eyes in both SCP and DCP. VD was significantly reduced in RP eyes at the level of SCP, DCP and choriocapillaris. VA, deep parafoveal VD, foveal, parafoveal and whole image choriocapillaris VD were negatively correlated with the extent of EZ disruption.

Conclusion

We report OCTA findings in a relatively young cohort of RP patients. We demonstrated a reduction of retinal microvascular density in all studied layers on OCTA. We believe studying retinal vasculature in these patients is important, as a healthy blood supply is a prerequisite for the success of new cell-based therapies under trial for RP.

Vascular Density and Retinal Function in Patients with Retinitis Pigmentosa Evaluated by Swept-Source OCT Angiography and Microperimetry

PURPOSE

To determine the retinal and choroidal vessel density in the macular area with swept-source optical coherence tomography (OCT) angiography (SS-OCTA) in patients affected by retinitis pigmentosa (RP), to compare their data with those on healthy subjects, and to study a possible morphofunctional correlation by microperimetry (MP-1).

METHODS

A total of 40 eyes of 40 patients affected by RP and 24 eyes of 24 healthy subjects were included in the study. Manually moving down the segmentation line of the SS-OCTA, we have evaluated the vessel density for the superficial retinal plexus, deep retinal plexus, choriocapillaris, and three levels of the choroid.

RESULTS

Linear regression analyses were performed of the retinal structure and function. No significant correlation was detected in any case (R2 = 0, p > 0.05). A comparison between RP and healthy controls revealed a significant reduction in SS-OCTA mean capillary density in the RP group (p = 0.0011). This relationship was consistent across vascular layers (p = 0.2413). A significant association between the capillary density of the various vascular complexes was detected within individual eyes (p < 0.0001).

CONCLUSIONS

This study represents the first comparing MP-1 and SS-OCTA data in the largest cohort of patients. RP patients showed a reduction in both the retinal and the choroidal vascular network in the macular area compared to healthy subjects.

Optical Coherence Tomography Angiography Assessed Retinal and Choroidal Microvasculature Features in Patients with Retinitis Pigmentosa: A Meta-Analysis

Background

The aim of this study was to assess the retinal and choroidal microvasculature features using optical coherence tomography angiography (OCTA) in patients with retinitis pigmentosa (RP).

Methods

This study was a meta-analysis of relevant published studies that were included after a comprehensive search of PubMed, Embase, Cochrane Library, and Web of Science databases. Mean difference (MD) with a 95% confidence interval was used to assess continuous variable outcomes. Heterogeneity was evaluated using the chi-squared test based on the values of P and I².

Results

Seven studies were included in this meta-analysis. The vessel density values measured in the superficial and deep foveal zones of RP patients using OCTA were significantly lower than the recorded values in the control groups (MD = −3.58, P=0.04; MD = −4.93, P=0.02, respectively). The superficial and deep parafoveal vessel density values measured with OCTA were also significantly lower in RP patients than in control groups (MD = −9.09, P < 0.00001; MD = −10.74, P < 0.00001, respectively); for choriocapillaris vessel density, there was no statistically significant difference between RP patients and controls (MD = −1.33, P=0.09). The deep foveal avascular zone (FAZ) was significantly larger in RP patients than in controls (MD = 0.15, P=0.01), whereas there was no significant difference in the superficial foveal avascular zones in the two groups (MD = 0.08, P=0.11).

Conclusions

We showed that retinal and choroidal vessels were attenuated in RP patients. Additionally, we revealed that the FAZ was larger in RP patients, especially the deep FAZ. OCTA may become a useful modality in the diagnosis and monitoring of patients with RP.

Vascular Patterns in Retinitis Pigmentosa on Swept-Source Optical Coherence Tomography Angiography

Background: Retinitis Pigmentosa (RP) represents a retinal dystrophy with an extremely complex pathogenesis further worsened by the impairment of the retinal vascular supply. The main goal of this study was to identify different vascular patterns in RP, by means of optical coherence tomography angiography (OCTA). Methods: A total of 32 RP patients (16 males, 50%; mean age 45.93 ± 11.4) and 32 healthy age-matched controls (16 males, 50%; age 42.8 ± 11.2). High resolution OCT and OCTA images were obtained from all participants. Several quantitative parameters were extracted both from structural OCT and OCTA images. A post-hoc analysis assessed the relationship between the quantitative OCTA parameters adopted and the following measures: best corrected visual acuity (BCVA), central macular thickness (CMT) and retinal nerve fiber layer (RNFL). Results: Mean LogMAR BCVA was 0.24 ± 0.32 for RP patients and 0.0 ± 0.0 for controls (p < 0.01). CMT, choroidal thickness and RNFL were statistically different between RP and controls (p < 0.01). OCTA parameters showed strong alterations of the retinal vascular network in RP (all p < 0.01). Several statistically significant correlations were also found. Furthermore, a vessel tortuosity cut-off of 4.80 and a vessel rarefaction cut-off of 0.62 enabled the RP cohort to be divided into two significantly different sub-groups in terms of BCVA, RNFL and CMT. Conclusions: Quantitative OCTA parameters help identify vascular abnormalities in RP, separating two different vascular patterns.

Macular vascular density at the superficial capillary plexus using the optical coherence tomography angiography

Purpose

The aim of this study was to assess the effects of age, gender, axial length and retinal thickness on the vascular density in a normal population using the Optovue optical coherence tomography angiography (OCT-A).

Methods

A total of 209 eyes of 209 healthy subjects were scanned using the OCT-A on an outpatient basis. Patients were 20–75 years of age. The built-in software covered a 3×3 mm circle centered at the macula. The circle was divided into five sectors: a 1 mm central foveal circle and an upper, lower, nasal and temporal sector each spanning 1–3 mm away from the central circle. The vascular density (VD) at the superficial capillary plexus was measured, which spanned from the inner limiting membrane to the inner plexiform layer.

Results

The fovea was the least dense area (32.5%±5.9%), and the temporal area was the densest (52.4%± 4.4%). Similarly, the fovea was the thinnest part of the retina (237.8±20.7 µm); however, the nasal sector was the thickest (308.5±15.1 µm). We found a correlation of the retinal thickness (r=0.541, P<0.001) with VD only at the fovea. Similarly, males had a greater density at the fovea (P=0.002). All regions significantly and negatively correlated with age even after adjusting for axial length. The age sees a decline in the density after the fifth decade where the variability also seems to increase.

Conclusion

This study provides normative data for the Pakistani population. Additionally, it demonstrates that VD is affected by the retinal thickness at the fovea and the density begins to decline after the fifth decade.

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.

Quantitative progression of retinitis pigmentosa by optical coherence tomography angiography

Optical coherence tomography angiography (OCT-A) is a non-invasive alternative to fluorescein angiography that allows for the study of the retinal and choroidal vasculatures. In this retrospective cohort study of 28 patients with retinitis pigmentosa (RP), we used OCT-A to quantify changes in perfusion density, foveal avascular zone (FAZ) area, and choriocapillaris blood flow over time and correlated these variables with ellipsoid zone (EZ) line width and best-corrected visual acuity (BCVA). Perfusion density decreased by 2.42 ± 0.62% per year at the superior capillary plexus (SCP) (P = 0.001) and 2.41 ± 0.76% per year at the deep capillary plexus (DCP) (P = 0.004). FAZ area increased by 0.078 ± 0.021 mm² per year (P = 0.001) at the SCP and 0.152 ± 0.039 mm² per year (P = 0.001) at the DCP. No changes were observed in the choriocapillaris blood flow. EZ line width had the strongest correlation to perfusion density at the SCP (r = 0.660 and 0.635, first and second visit, respectively, P = 0.001), while BCVA most strongly correlated with FAZ area at the SCP (r = 0.679 and 0.548, P = 0.001 and 0.003). Our results suggest that OCT-A is a useful tool for monitoring RP disease progression and may be used to measure retinal vascular parameters as outcomes in clinical trials.