CHOROIDAL STRUCTURAL CHANGES AND VASCULARITY INDEX IN STARGARDT DISEASE ON SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY

Techniques for imaging the choroid and choroidal blood flow in vivo

The choroid, which is a highly vascularized layer between the retina and sclera, is essential for supplying oxygen and nutrients to the outer retina. Choroidal vascular dysfunction has been implicated in numerous ocular diseases, including age-related macular degeneration, central serous chorioretinopathy, polypoidal choroidal vasculopathy, and myopia. Traditionally, the in vivo assessment of choroidal blood flow relies on techniques such as laser Doppler flowmetry, laser speckle flowgraphy, pneumotonometry, laser interferometry, and ultrasonic color Doppler imaging. While the aforementioned methods have provided valuable insights into choroidal blood flow regulation, their clinical applications have been limited. Recent advancements in optical coherence tomography and optical coherence tomography angiography have expanded our understanding of the choroid, allowing detailed visualization of the larger choroidal vessels and choriocapillaris, respectively. This review provides an overview of the available techniques that can investigate the choroid and its blood flow in vivo. Future research should combine these techniques to comprehensively image the entire choroidal microcirculation and develop robust methods to quantify choroidal blood flow. The potential findings will provide a better picture of choroidal hemodynamics and its effect on ocular health and disease.

Choroidal Perfusion Changes After Vitrectomy for Myopic Traction Maculopathy

BACKGROUND

The choroidal vasculature supplies the outer retina and is altered in many retinal diseases, including myopic traction maculopathy (MTM). Choroid health is typically assessed by measuring the choroidal thickness; however, this method has substantial limitations. The choroidal vascularity index (CVI) was recently introduced to provide quantitative information on the vascular flow in the choroid. This index has been evaluated in a wide range of diseases but has not been extensively used to characterize MTM.

AIM

This study aimed to investigate the CVI across different stages of MTM and the influence of macular surgery on choroidal perfusion markers in different surgically resolved MTM stages.

METHODS

Eighteen healthy myopic eyes in the control group and forty-six MTM eyes in the surgical group were evaluated using enhanced optical coherence tomography (OCT) imaging. Binarized OCT images were processed to obtain the luminal choroidal area (LCA) and stromal choroidal area (SCA), which were used to calculate CVI in the form of a percentage ratio. CVI data were collected at baseline, one and four months postoperatively, and at the final clinical visit. MTM eyes were divided into four stages based on disease severity. The choriocapillaris flow area (CFA) and central subfield thickness (CSFT) were measured along side the CVI.

RESULTS

No significant differences were observed between the two groups at baseline, except for visual acuity (p  < 0.0001). Surgery significantly improved vision at all postoperative time points (p  < 0.0001). At baseline, there were no significant differences in CVI, CFA, or CSFT scores between the control and surgical groups. However, all three measurements were lower at the final visit in the surgical group (p ≤0.0001). No significant differences were found in any of the parameters among the four stages of MTM (p  > 0.05). Ultimately, correlation and multivariate linear regression analyses did not reveal any significant association between CVI and visual acuity.

CONCLUSIONS

This study did not find significant preoperative differences in CVI between healthy myopic eyes and eyes with MTM. However, the postoperative CVI and CFA values were significantly lower than those of the control eyes. Thus, CVI may not be a good biomarker for surgical outcomes, as the correlation between CVI and visual acuity was not statistically significant.The CVI and CFA decreased after surgery, providing evidence of choroidal changes after surgical management.

Optical Coherence Tomography and Optical Coherence Tomography Angiography in Pediatric Retinal Diseases

Indirect ophthalmoscopy and handheld retinal imaging are the most common and traditional modalities for the evaluation and documentation of the pediatric fundus, especially for pre-verbal children. Optical coherence tomography (OCT) allows for in vivo visualization that resembles histology, and optical coherence tomography angiography (OCTA) allows for non-invasive depth-resolved imaging of the retinal vasculature. Both OCT and OCTA were extensively used and studied in adults, but not in children. The advent of prototype handheld OCT and OCTA have allowed for detailed imaging in younger infants and even neonates in the neonatal care intensive unit with retinopathy of prematurity (ROP). In this review, we discuss the use of OCTA and OCTA in various pediatric retinal diseases, including ROP, familial exudative vitreoretinopathy (FEVR), Coats disease and other less common diseases. For example, handheld portable OCT was shown to detect subclinical macular edema and incomplete foveal development in ROP, as well as subretinal exudation and fibrosis in Coats disease. Some challenges in the pediatric age group include the lack of a normative database and the difficulty in image registration for longitudinal comparison. We believe that technological improvements in the use of OCT and OCTA will improve our understanding and care of pediatric retina patients in the future.

Postoperative choroidal vascularity index after the management of macula-off rhegmatogenous retinal detachment

BACKGROUND

Rhegmatogenous retinal detachment (RRD) is a vision-threatening condition that can be treated with various surgical approaches. The role of scleral buckling remains controversial because of its potential long-term deleterious effects on choroidal vascular perfusion and the limited knowledge of this entity.

METHODS

A total of 135 eyes were retrospectively selected, including 115 with surgically resolved RRD and 20 healthy control eyes. Of the surgically treated eyes, 64 underwent vitrectomy alone, while 51 underwent scleral buckling combined with vitrectomy. Best-corrected visual acuity (BCVA) was evaluated along with the choroidal vascularity index (CVI) as a metric for the state of the choroidal vasculature. BCVA was compared before and after surgery, and the postoperative BCVA was analyzed with the CVI using correlation and multivariate regression analyses.

RESULTS

The preoperative BCVA of the RRD eyes was significantly worse than that of the control eyes, and significantly improved after surgery. However, the long-term postsurgical BCVA was still inferior to that of the control eyes. No significant differences in visual function were found between the two surgical groups. The average CVI was 57.35% in the control eyes, 63.76% in the eyes that underwent vitrectomy, and 53.37% in buckled eyes. The differences in CVI were significant among the three groups. Among the surgical patients, negative Pearson's correlations were found between CVI and postoperative BCVA (expressed in logMAR). A multivariate linear regression model containing four parameters revealed that CVI was the only variable with a significant influence on postoperative BCVA, while the length of time with a detached macula did not have an effect.

CONCLUSIONS

RRD surgery drastically restored vision, but the effect of RRD lingered, as postsurgical visual acuity remained inferior to that of the control eyes. The CVI varied between the treatment groups, likely due to both disease pathology and the impact of the surgery. The correlation between CVI and BCVA indicates the important role that the choroidal vasculature plays in visual function.

Choroidal structure investigated by choroidal vascularity index in patients with inherited retinal diseases

PURPOSE

To evaluate the choroidal structure in patients with inherited retinal diseases (IRDs) by investigating the choroidal vascularity index (CVI).

METHODS

The present study was conducted on 113 IRD patients and 113 sex- and age-matched healthy individuals. Patients' data was extracted from the Iranian National Registry for IRDs (IRDReg®). Total choroidal area (TCA) was determined between retinal pigment epithelium and choroid-scleral junction,1500 microns on either side of the fovea. Luminal area (LA) was considered as the black area corresponding to the choroidal vascular spaces, following Niblack binarization. CVI was calculated as the ratio of the LA to the TCA. CVI and other parameters were compared among different types of IRD and the control group.

RESULTS

The IRD diagnosis included retinitis pigmentosa (n = 69), cone-rod dystrophy (n = 15), Usher syndrome (n = 15), Leber congenital amaurosis (n = 9), and Stargardt disease (n = 5). Sixty-one (54.0%) individuals of each of the study and control groups were male. The average CVI was 0.65 ± 0.06 in the IRD patients and 0.70 ± 0.06 in the control group (P < 0.001). Accordingly, the average of TCA and LA were 2.32 ± 0.63 and 1.52 ± 0.44 mm [1] in patients with IRDs, respectively. The measurements for the TCA and the LA were significantly lower in all subtypes of IRD (P-values < 0.05).

CONCLUSION

CVI is significantly lower in patients with IRD than in healthy age-matched individuals. Choroidal changes in IRDs may be related to the changes in the lumen of the choroidal vessels rather than the stromal changes.

Vessel density and choroidal vascularity index in patients with Bietti crystalline dystrophy and retinitis pigmentosa

OBJECTIVE

To evaluate and compare the vessel density (VD) using swept-source optical coherence tomography angiography (OCT-A) and the choroidal vascularity index (CVI) using spectral-domain optical coherence tomography (SD-OCT) in patients with Bietti crystalline dystrophy (BCD) and retinitis pigmentosa (RP).

MATERIALS AND METHODS

A cross-sectional retrospective study was conducted on 26 eyes of 13 BCD patients, 26 eyes of 13 RP patients, and 26 eyes of 13 age- and gender-matched healthy individuals. BCD patients were further staged as having early, intermediate, and advanced disease. VD was assessed in five quadrants of the macula (superior, temporal, inferior, nasal, and center) using a modified ETDRS technique with OCT-A. SD-OCT scans were binarized using Niblack's autolocal threshold, and CVI was determined as the ratio of the luminal area to the total choroidal area.

RESULTS

A significant difference was found in VD in all quadrants of the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) slabs among the three groups (p < 0.001). A statistically significant difference was noted in the mean VD of temporal and inferior quadrants of the SCP and between the BCD and RP groups (p = 0.005, p = 0.015, respectively). A statistically significant difference was observed in the mean VD of the temporal, inferior, and nasal quadrants between the BCD and RP groups on DCP slabs (p = 0.002, p = 0.003, p = 0.003, respectively). The mean central choroidal thickness was 214.65±87.10 μm in the BCD group, 351.69±67.94 μm in the RP group, and 320.92±59.26 μm in the control group (p < 0.001). We found that CVI was significantly higher in the control group than BCD group (p < 0.001), and it was significantly lower in the BCD group when compared to the RP group (p < 0.001).There was no difference in CVI between RP and control groups (p = 0.948). Furthermore, the CVI was significantly lower in the intermediate and advanced disease stages than the early disease stage in the subgroup analysis of BCD patients (p < 0.001, p < 0.001, respectively).

CONCLUSION

CVI is a novel investigative tool to monitor disease progression. The CVI value was lower in BCD and RP patients than in the healthy subjects, and lower CVI values seem to be related to the disease severity in BCD patients. VD was also significantly lower in BCD patients when compared to RP patients, and VD analysis may help clinicians better understand the disease pathophysiology.

Compartmental analysis of three-dimensional choroidal vascularity and thickness of myopic eyes in young adults using SS-OCTA

Purpose: We aimed to investigate the change of three-dimensional (3D) choroidal thickness (ChT), choroidal vessel volume (CVV), and choroidal vessel index (CVI) in young myopic adults using swept-source optical coherence tomography angiography (SS-OCTA) and compare the difference of these indicators in different quadrants of the macula and optic disc.

Methods: A total of 248 eye samples from 135 participants were used in this cross-sectional study. Each participant underwent detailed history taking and ocular examinations. Based on axial length (AL), patients were divided into the emmetropia (EM) group, mild-myopia (MIM) group, moderate-myopia (MOM) group, and high-myopia (HM) group. 6 mm × 6 mm (1,024 × 1024 B-scans) SS-OCTA scans were performed centered on the fovea and optic disc. 3D ChT, CVV, and CVI were measured based on a built-in deep learning algorithm. Differences in ChT, CVV, and CVI were analyzed in different regions and different myopic groups.

Results: Significant reduction in the global CVV were found in the HM group (1.930 ± 0.865) in comparison with the EM (3.486 ± 0.992), MIM (3.238 ± 1.033), and MOM (2.589 ± 1.083) groups (p < 0.001). The global CVI was also lower in the HM group (0.258 ± 0.061) than in the EM (0.320 ± 0.055), MIM (0.320 ± 0.051), and MOM (0.286 ± 0.066) groups (p < 0.001). The ChT was thinner in eyes with HM (242.753 ± 65.641) than in eyes with EM (377.532 ± 80.593), MIM (348.367 ± 78.191), or MOM (300.197 ± 87.175) (p < 0.001). Compartmental analysis revealed that ChT, CVV, and CVI in the nasal quadrant of the macula and temporal and inferior quadrants of the optic disc were much lower than those in other quadrants (p < 0.05). Correlation analyses found that ChT, CVV, and CVI were negatively correlated with AL and spherical equivalence.

Conclusion: 3D ChT, CVV, and CVI gradually decreased as the degree of myopia increased. The changes were more dramatic on the nasal side of the macula and the temporal and inferior sides of the optic disc. These findings demonstrated the 3D choroidal change and highlighted the papillo-macular bundle as a sensitive region in myopic development.

The Role of the Choroid in Stargardt Disease

Stargardt disease is the commonest juvenile macular dystrophy. It is caused by genetic mutations in the ABCA4 gene. Diagnosis is not always straightforward, and various phenocopies exist. Late-onset disease can be misdiagnosed with age-related macular disease. A correct diagnosis is particularly critical because of emergent gene therapies. Stargardt disease is known to affect retinal pigment epithelium and photoreceptors. Many studies have also highlighted the importance of the choroid in the diagnosis, pathophysiology, and progression of the disease. The choroid is in an integral relationship with the retinal pigment epithelium and photoreceptors, and its possible involvement during the disease should be considered. The purpose of this review is to analyze the current diagnostic tools for choroidal evaluation and the extrapolation of useful data for ophthalmologists and researchers studying the disease.

CVIS: Automated OCT-scan-based software application for the measurements of choroidal vascularity index and choroidal thickness

PURPOSE

To develop an automated image recognition software for the objective quantification of choroidal vascularity index (CVI) and choroidal thickness (CT) at different choroidal locations on images obtained from enhanced depth imaging optical coherence tomography (EDI-OCT), and to validate its reliability and investigate the difference and correlation between measurements made by manual and software.

METHODS

A total of 390 EDI-OCT scans, captured from 130 eligible emmetropic or myopic subjects, were categorized into four grades in terms of their accessibility to identify the choroidal-scleral interface (CSI) and were further assessed for CT and CVI at five locations (subfoveal, nasal, temporal, superior and inferior) by the newly developed Choroidal Vascularity Index Software (CVIS) and three ophthalmologists. Choroidal parameters acquired from CVIS were evaluated for its reliability and correlation with ocular factors, in comparison to manual measurements. Distribution of difference and correlation coefficient between CVIS and manual measurements were also analysed.

RESULTS

Choroidal Vascularity Index Software (CVIS) demonstrated excellent intra-session reliability for CT (ICC: 0.992) and CVI (ICC: 0.978) measurements, compared to the relatively lower intra- and inter-observer reliability of manual measurements. Choroidal Vascularity Index Software (CVIS) and manual assessments had the highest correlation at nasal choroid (CT: r = 0.829, p < 0.001; CVI: r = 0.665, p < 0.001). Choroidal parameters identified with CVIS showed stronger correlations with axial length than manual measurements.

CONCLUSION

This automated software, CVIS, exhibited excellent reliability compared to manual measurements, which are subject to image quality and clinical experience. With its validated clinical relevance, CVIS holds promise to serve as a flexible and robust tool in future vitreoretinal and chorioretinal studies.

Three-Dimensional Choroidal Vascularity Index in High Myopia Using Swept-Source Optical Coherence Tomography

PURPOSE

To characterize the choroidal vasculature in high myopic eyes by three-dimensional choroidal vascularity index (CVI) using swept-source optical coherence tomography (SS-OCT).

SUBJECTS AND METHODS

A cross-sectional observational study of 98 right eyes from 98 consecutive nonpathological myopic patients, including 46 high myopes (HM) and 52 low to moderate myopes (LMM). OCT and OCT angiography covering an area of 6 × 6 mm² centered on the fovea was conducted with a commercially available SS-OCT device. Three-dimensional CVI was defined as the ratio of choroidal vessel volume (CVV) to total choroidal volume. With the built-in automated quantification software, we assessed choroidal vascular and stromal features: three-dimensional CVI; CVV; choriocapillaris flow density and choroidal stroma volume (CSV) apart from choroidal thickness (CT).

RESULTS

Compared to LMM, there was a significant reduction in three-dimensional CVI, CVV and CSV along with choroidal thinning in HM at both subfoveal and macular regions (all P < .01). The nasal quadrant had both the lowest CVI and the thinnest choroid. The greatest CVI was at the subfovea, while the choroid at the subfovea was thinner than that at the superior, temporal, and inferior quadrants. Multiple linear regression indicated that choroidal characteristics (CVI, CVV, CSV, CT) were mainly negatively correlated with axial length (all P < .01) instead of myopic spherical equivalent (all P > .05).

CONCLUSIONS

Besides two-dimensional choroidal thinning, we also found the axial length-related reduction of three-dimensional choroidal vessel and stroma components in high myopic eyes without myopic maculopathy. The quadrantal distribution characteristics of three-dimensional CVI indicate the subfovea and the nasal quadrant to be the essential quadrants for monitoring the choroidal vasculature alteration in the progression of myopia. The novel quantitative analyses of the choroidal vasculature by three-dimensional CVI may help to characterize the underlying pathophysiology of nonpathological high myopia.

Choroidal vascularity index changes during the Valsalva manoeuvre in healthy volunteers

PURPOSE

To evaluate the effects of the Valsalva manoeuvre (VM) on the choroidal vascularity index (CVI) in healthy volunteers.

METHODS

This prospective, cross-sectional study included 60 eyes of 30 healthy volunteers. Enhanced depth imaging-optical coherence tomography scans of both eyes involving the fovea were taken, and a 1500 μm subfoveal choroidal area was selected for image binarization with open-access Fiji software. The binarized image was segmented into the stromal area (SA) and luminal area (LA), and CVI was calculated as the ratio (%) of LA to the total choroidal area (TCA). CVI, subfoveal choroidal thickness (SFCT), IOP, systolic and diastolic blood pressure were evaluated at rest and during the VM.

RESULTS

During the VM, a mean ± standard deviation increase in LA (0.02 ± 0.05 mm² , p < 0.001) and CVI (1.72 ± 2.83%, p < 0.001) was observed, whereas SA (-0.02 ± 0.05 mm² , p < 0.001) decreased. There was no significant change in TCA (0.00 ± 0.03 mm² , p = 0.55) or SFCT (1.05 ± 10.92 μm, p = 0.46). There was a moderate positive correlation between the spherical equivalent refractive error (SE) and SFCT both at rest and during VM (r₅₈  = 0.49, p < 0.0005 and r₅₈  = 0.49, p < 0.0005, respectively). However, there was no significant correlation between SE and CVI either at rest or during VM (p = 0.11 and 0.06, respectively). In a multiple linear regression analysis, CVI was only associated with SFCT; however, SFCT was also associated with SE, both at rest and during VM (p < 0.001).

CONCLUSION

Valsalva manoeuvre increases CVI by choroidal vascular dilation as demonstrated by an increase in LA and a decrease in SA. Researchers should be careful about unintentional VM during examinations.

Localized Structural and Functional Deficits in a Nonhuman Primate Model of Outer Retinal Atrophy

Purpose

Cell-based therapy development for geographic atrophy (GA) in age-related macular degeneration (AMD) is hampered by the paucity of models of localized photoreceptor and retinal pigment epithelium (RPE) degeneration. We aimed to characterize the structural and functional deficits in a laser-induced nonhuman primate model, including an analysis of the choroid.

Methods

Macular laser photocoagulation was applied in four macaques. Fundus photography, optical coherence tomography (OCT), dye angiography, and OCT-angiography were conducted over 4.5 months, with histological correlation. Longitudinal changes in spatially resolved macular dysfunction were measured using multifocal electroretinography (MFERG).

Results

Lesion features, depending on laser settings, included photoreceptor layer degeneration, inner retinal sparing, skip lesions, RPE elevation, and neovascularization. The intralesional choroid was degenerated. The normalized mean MFERG amplitude within lesions was consistently lower than control regions (0.94 ± 0.35 vs. 1.10 ± 0.27, P = 0.032 at month 1, 0.67 ± 0.22 vs. 0.83 ± 0.15, P = 0.0002 at month 2, and 0.97 ± 0.31 vs. 1.20 ± 0.21, P < 0.0001 at month 3.5). The intertest variation of mean MFERG amplitudes in rings 1 to 5 ranged from 13.0% to 26.0% in normal eyes.

Conclusions

Laser application in this model caused localized outer retinal, RPE, and choriocapillaris loss. Localized dysfunction was apparent by MFERG in the first month after lesion induction. Correlative structure-function testing may be useful for research on the functional effects of stem cell-based therapy for GA. MFERG amplitude data should be interpreted in the context of relatively high intertest variability of the rings that correspond to the central macula. Sustained choroidal insufficiency may limit long-term subretinal graft viability in this model.

Stargardt disease: Multimodal imaging: A review

Stargardt disease (STGD1) is an autosomal recessive retinal dystrophy, characterised by bilateral progressive central vision loss and subretinal deposition of lipofuscin-like substances. Recent advances in molecular diagnosis and therapeutic options are complemented by the increasing recognition of new multimodal imaging biomarkers that may predict genotype and disease progression. Unique non-invasive imaging features of STDG1 are useful for gene variant interpretation and may even provide insight into the underlying molecular pathophysiology. In addition, pathognomonic imaging features of STGD1 have been used to train neural networks to improve time efficiency in lesion segmentation and disease progression measurements. This review will discuss the role of key imaging modalities, correlate imaging signs across varied STGD1 presentations and illustrate the use of multimodal imaging as an outcome measure in determining the efficacy of emerging STGD1 specific therapies.

Imaging the pediatric retina: An overview

Recent decade has seen a shift in the causes of childhood blinding diseases from anterior segment to retinal disease in both developed and developing countries. The common retinal disorders are retinopathy of prematurity and vitreoretinal infections in neonates, congenital anomalies in infants, and vascular retinopathies including type 1 diabetes, tumors, and inherited retinal diseases in children (up to 12 years). Retinal imaging helps in diagnosis, management, follow up and prognostication in all these disorders. These imaging modalities include fundus photography, fluorescein angiography, ultrasonography, retinal vascular and structural studies, and electrodiagnosis. Over the decades there has been tremendous advances both in design (compact, multifunctional, tele-consult capable) and technology (wide- and ultra-wide field and noninvasive retinal angiography). These new advances have application in most of the pediatric retinal diseases though at most times the designs of new devices have remained confined to use in adults. Poor patient cooperation and insufficient attention span in children demand careful crafting of the devices. The newer attempts of hand-held retinal diagnostic devices are welcome additions in this direction. While much has been done, there is still much to do in the coming years. One of the compelling and immediate needs is the pediatric version of optical coherence tomography angiography. These needs and demands would increase many folds in future. A sound policy could be the simultaneous development of adult and pediatric version of all ophthalmic diagnostic devices, coupled with capacity building of trained medical personnel.

Choroidal vessel density in unilateral hyperopic amblyopia using en-face optical coherence tomography

Background

Structural changes of the choroid, such as choroidal thickening, have been indicated in amblyopic eyes with hyperopic anisometropia as compared to fellow or healthy eyes. The purpose of the present study was to investigate choroidal vascular density (CVD) in children with unilateral hyperopic amblyopia.

Methods

This study included 88 eyes of 44 patients with unilateral amblyopia due to hyperopic anisometropia with or without strabismus and 29 eyes of 29 age-matched normal controls. The CVD of Haller’s layer was quantified from en-face images constructed by 3-dimensional swept-source optical coherence tomography images flattened relative to Bruch’s membrane. The analysis area was a 3 × 3-mm square of macula after magnification correction. Relationships between CVD and other parameters [best-corrected visual acuity (BCVA), refractive error and subfoveal choroidal thickness (SFCT)] were investigated, and CVDs were compared between amblyopic, fellow, and normal control eyes.

Results

Mean CVD was 59.11 ± 0.66% in amblyopic eyes, 59.23 ± 0.81% in fellow eyes, and 59.29 ± 0.74% in normal control eyes. CVD showed a significant positive relationship with SFCT (p = 0.004), but no relationships with other parameters. No significant differences in CVD were evident among amblyopic, fellow, and normal control eyes after adjusting for SFCT (p = 0.502).

Conclusions

CVD was unrelated to BCVA, and CVD did not differ significantly among amblyopic, fellow and normal control eyes. These results suggest that the local CVD of Haller’s layer is unaffected in unilateral hyperopic amblyopic eyes.

Choroidal hyper-reflective foci and vascularity in retinal dystrophy

Purpose:

To investigate choroidal hyper-reflective foci (HRF) in subjects with retinal dystrophy [Stargardt's disease (SGD) and retinitis pigmentosa (RP)] and their association with demographics, visual acuity, choroidal thickness (CT), and choroidal vascularity index (CVI).

Methods:

Single center retrospective study of subjects with previously diagnosed SGD or RP. Swept-source optical coherence tomography images were analyzed for the presence of choroidal HRFs and CVI using previously validated automated algorithm. A Spearman's rank correlation coefficient was used to evaluate the correlation between the number of HRF and various baseline parameters including age, visual acuity, intraocular pressure, and other optical coherence tomography (OCT) parameters (CT, choroidal area, and CVI) were evaluated in these subjects.

Results:

This study included 46 eyes (23 subjects) and 55 eyes (28 subjects) with previously diagnosed RP and SGD, respectively. In the RP group, the mean number of HRFs was 247.9 ± 57.1 and mean CVI was 0.56 ± 0.04. In SGD group, mean HRF was 192.5 ± 44.3 and mean CVI was 0.41 ± 0.04. Mean HRF was significantly greater in the RP group (0.02), however, the mean CVI was not statistically different. In RP, mean HRF were correlated only with CVI (r = 0.49; P = 0.001), however, in SGD, it correlated with only choroidal area (r = 0.27; P = 0.04).

Conclusion:

Choroidal HRF were present in both RP and SGD subjects with more HRFs in those with RP. These HRFs were associated with alteration in choroidal vascularity, which further adds into the pathogenesis of these diseases.

Choroidal vascular changes in retinitis pigmentosa patients detected by optical coherence tomography angiography

BACKGROUND

To evaluate choroidal vascular changes, including choriocapillaris (CC) and middle/large choroidal vessels, in retinitis pigmentosa (RP) patients using wide-angle optical coherence tomography angiography (OCTA) and to determine whether changes in the choroidal vascularity have a relationship with visual function and retinal structural changes.

METHODS

34 patients with a confirmed diagnosis of RP and 48 controls were recruited. All patients underwent detailed ophthalmologic and imaging examinations, including two types of OCTA (Optovue, 3 × 3 mm, 6 × 6 mm; VG-200, 12 × 12 mm). CC defects were defined according to the choroidal vascular structure in five degrees. To evaluate middle and large choroidal vascular changes, the choroidal vascularity index (CVI), which was the luminance volume to the total choroidal volume, was used.

RESULTS

Defects of choroidal vascularity of RP eyes were detected in comparison to control eyes. The defects were observed in the CC layer with a concentric or lobular pattern at different degrees. CVI, which was used to reflect middle/large choroidal vascularity, decreased in the perifoveal, pararetinal and periretinal regions in the RP eyes. CC defects degree were correlated with the BCVA (p = 0.001, r = - 0.556), the Humphrey indexes (mean deviation, MD, p < 0.001, r = - 0.673; PVF, p = 0.003, r = - 0.639; 10° mean sensitivity, 10° MS, p = 0.002, r = - 0.651) and microperimetry index (mean sensitivity, MS, p < 0.001, r = - 0.807). The preserved CC area (mean value: 28.65 ± 12.50 mm²) was negatively correlated with MS measured by microperimetry (p = 0.005, r = - 0.449). Ordinary regression analysis revealed that the CC defect degree was associated with the CVI of perifovea (p = 0.002, 95% CI: - 102.14 to - 24.01), the EZ length (p = 0.006, 95% CI: - 0.006 to - 0.001) and the VAD (vascular area density) of the DCP (deep capillary plexus) in the fovea (p = 0.022, 95% CI: 0.038-0.478). No correlations were detected between BCVA and CVI in any retinal regions. No correlations were found between the CVI and the VAD in any retinal regions.

CONCLUSION

The choroidal vascularity was widely defected in RP. Choriocapillaris and middle/large choroidal vascularity defects were correlated with each other. Visual function and retinal structural changes were found to be associated with choriocapillaris defects but not with middle/large choroidal vascular defects.

Choroidal Anatomic Alterations After Photodynamic Therapy for Chronic Central Serous Chorioretinopathy: A Multicenter Study

PURPOSE

To study the early anatomic choroidal alterations in eyes with chronic central serous chorioretinopathy (CSCR) undergoing photodynamic therapy (PDT).

DESIGN

Multicenter retrospective cohort study.

METHODS

A total of 77 patients and 81 eyes with chronic CSCR treated with PDT and 64 untreated fellow eyes were evaluated. Central macular thickness (CMT) and choroidal features including subfoveal choroidal thickness (SFCT), total choroidal area (TCA), luminal choroidal area (LCA), and stromal choroidal area (SCA) were analyzed. Choroidal vascularity index (CVI) was calculated in all study eyes at baseline and at 1- and 3-months post-PDT.

RESULTS

In eyes receiving PDT, Snellen visual acuity (VA) significantly improved at months 1 and 3 (P < .001). CMT and SFCT showed a significant reduction from baseline at months 1 and 3 (P < .001), whereas TCA and LCA showed a significant decrease only at the 1-month follow-up visit. Baseline mean TCA and LCA were 2.30 ± 1.41 mm² and 1.23 ± 0.73 mm², respectively, and decreased to 2.07 ± 1.21 mm² and 1.08 ± 0.63 mm² at the 1-month follow-up visit, respectively (P = .01). No significant changes were recorded for SCA and CVI. In the fellow eye group, VA, CMT, and all choroidal parameters showed no differences between baseline and any follow-up visits (all P > .05).

CONCLUSIONS

After PDT for chronic CSCR we observed sustained reductions in CMT and SFCT, while reductions in TCA and LCA were only noted at the 1-month follow-up interval. These choroidal parameters may provide additional quantitative biomarkers to evaluate the anatomic response to therapy but await further prospective validation.

Choroidal structural changes in preterm children with and without retinopathy of prematurity

PURPOSE

Evaluate choroidal structural changes in preterm children with and without retinopathy of prematurity (ROP) using image binarization technique on swept-source optical coherence tomography (SS-OCT) scans.

METHODS

Prospective case-control study. Forty-one (79 eyes) children aged 5-15 years with a history of preterm birth and 33 (63 eyes) age-matched full-term children were recruited. Demographics including gestational age at birth, birth weight and history of ROP were documented. All subjects had undergone complete eye examinations, including best-corrected visual acuity and SS-OCT imaging. Subfoveal choroidal thickness (SFCT) was calculated, and images were binarized to obtain stromal and luminal areas (LA). The choroidal vascularity index (CVI) was derived from the proportion of LA to the total subfoveal choroidal area.

RESULTS

There were no significant differences in SFCT between the preterm children with (286.63 ± 83.98 μm) or without (306.59 ± 77.29 μm) ROP and the full-term children (311.82 ± 42.87; p = 0.20 and 0.67, respectively). The CVI was significantly reduced in the preterm children with ROP (68.66 ± 3.24%; p = 0.005) compared with the CVI in the full-term control group (71.37 ± 3.63%); however, the CVI in the preterm children without ROP (71.68 ± 3.09%; p = 0.93) was not significantly affected.

CONCLUSION

The reduced CVI in preterm children with ROP may indicate compromised choroidal vascularity. The CVI was found to be a more sensitive OCT biomarker than the SFCT and may be helpful in evaluating associated choroidal structural changes in preterm children, especially those with a history of ROP.

Effects of different mydriatics on the choroidal vascularity in healthy subjects

PURPOSE

To evaluate choroidal vasculature changes after the instillation of mydriatic parasympatholytic and sympathomimetic agents in healthy subjects.

METHODS

A total of 95 healthy subjects were enrolled in this prospective, randomized comparative study. Study participants were divided into three different groups depending on the drug to be administered: tropicamide (1%) group (n = 31), tropicamide (0.5%) + phenylephrine (10%) group (n = 30) and control group receiving artificial tears (n = 34). All participants underwent a complete ophthalmological examination including best corrected visual acuity, refractive status and axial length. Subfoveal choroidal thickness (CT), total choroidal area (TCA), luminal and stromal choroidal area (LCA and SCA) and choroidal vascularity index (CVI) were measured before and after eye drops instillation.

RESULTS

All the baseline characteristics were matched between the three groups (all P > 0.05). Before the mydriatic instillation, there were no significant differences of CT, TCA, LA, SCA, and CVI among the three groups (all P > 0.05). After drug administration, CT, TCA, LCA, SCA, and CVI did not show any significant change as well (respectively, P = 0.265; P = 0.483; 0.573; P = 0.405 and P = 0.708).

CONCLUSIONS

Instillation of mydriatic eye drops did not induce significant changes of the choroidal vasculature, suggesting that their use do not alter CT and CVI evaluation.

Choroidal Vascularity Index: An In-Depth Analysis of This Novel Optical Coherence Tomography Parameter

Remarkable improvements in optical coherence tomography (OCT) technology have resulted in highly sophisticated, noninvasive machines allowing detailed and advanced morphological evaluation of all retinal and choroidal layers. Postproduction semiautomated imaging analysis with dedicated public-domain software allows precise quantitative analysis of binarized OCT images. In this regard, the choroidal vascularity index (CVI) is emerging as a new imaging tool for the measurement and analysis of the choroidal vascular system by quantifying both luminal and stromal choroidal components. Numerous reports have been published so far regarding CVI and its potential applications in healthy eyes as well as in the evaluation and management of several chorioretinal diseases. Current literature suggests that CVI has a lesser variability and is influenced by fewer physiologic factors as compared to choroidal thickness. It can be considered a relatively stable parameter for evaluating the changes in the choroidal vasculature. In this review, the principles and the applications of this advanced imaging modality for studying and understanding the contributing role of choroid in retinal and optic nerve diseases are discussed. Potential advances that may allow the widespread adoption of this tool in the routine clinical practice are also presented.

Exploring choroidal angioarchitecture in health and disease using choroidal vascularity index

The choroid is one of the most vascularized structures of the human body and plays an irreplaceable role in nourishing photoreceptors. As such, choroidal dysfunction is implicated in a multitude of ocular diseases. Studying the choroid can lead to a better understanding of disease pathogenesis, progression and discovery of novel management strategies. However, current research has produced inconsistent findings, partly due to the physical inaccessibility of the choroid and the lack of reliable biomarkers. With the advancements in optical coherence tomography technology, our group has developed a novel quantitative imaging biomarker known as the choroidal vascularity index (CVI), defined as the ratio of vascular area to the total choroidal area. CVI is a potential tool in establishing early diagnoses, monitoring disease progression and prognosticating patients. CVI has been reported in existing literature as a robust marker in numerous retinal and choroidal diseases. In this review, we will discuss the current role of CVI with reference to existing literature, and make postulations about its potential and future applications.

En-face choroidal vascularity map of the macula in healthy eyes

PURPOSE

To report the en-face choroidal vascularity index in healthy eyes.

METHODS

Thirty eyes of 30 healthy individuals were studied. Multiple high-density cross-sectional swept source optical coherence tomography scans were obtained to create a volume scan. The choroid was segmented for the whole volume scan and choroidal inner boundaries were flattened. Subsequently, multiple en-face scans separated by 25 µm were obtained and binarized. Choroidal vascularity index was calculated at level of choriocapillaris, medium, and large choroidal vessels.

RESULTS

The mean age of the study cohort was 35.6 ± 8.8 years. The overall mean en-face choroidal vascularity index was 54.25 ± 0.55%. There was a statistically significant difference of choroidal vascularity index in choriocapillaris (53.16 ± 0.43%), medium choroidal vessel (51.38 ± 0.27%), and large choroidal vessel (55.69 ± 0.87%) (p < 0.01). Choroidal vascularity index analysis in three subgroups based on subfoveal choroidal thickness (low: <300 µm, medium: 300-400 µm, high: >400 µm) showed a statistically significant difference (p = 0.001). Choroidal vascularity index showed a significant correlation with subfoveal choroidal thickness (r = 0.441; p = 0.015), whereas there was no significant correlation of age (p = 0.21), refraction (p = 0.20), and gender (p = 0.67) with en-face choroidal vascularity index.

CONCLUSION

En-face choroidal vascularity index shows a significant variation at the level of choriocapillaris, medium choroidal vessel, and large choroidal vessel in normal eyes. Choroidal vascularity index reaches a nadir at the level of medium choroidal vessel and reaches the maximum value at large choroidal vessel near choroidoscleral interface. En-face choroidal vascularity index shows a significant physiological variation and appears to increase with increase in subfoveal choroidal thickness.

Age-Related Changes in Choroidal Thickness and the Volume of Vessels and Stroma Using Swept-Source OCT and Fully Automated Algorithms

PURPOSE

To determine age-related changes in choroidal thickness and the volume of choroidal vessels and stroma using automated algorithms based on structural swept-source OCT (SS-OCT) scans.

DESIGN

Prospective and observational study.

PARTICIPANTS

The study included 144 normal participants with ages ranging from 20 to 88 years.

METHODS

A previously reported strategy was used to automatically segment the choroid using SS-OCT structural images. Attenuation correction was applied on B-scans to enhance the choroidal contrast and facilitate more accurate automatic segmentation of the 3-dimensional choroidal vessel and stroma. The parameters that we investigated included mean choroidal thickness (MCT), choroidal vessel volume (CVV), choroidal stroma volume (CSV), choroid vascularity index (CVI), and the choroidal stroma-to-vessel volume ratio (CSVR). Correlations between MCT and choroidal vessel metrics of CVV, CSV, CVI, and CSVR were studied. Regional distributions of MCT and CVI were analyzed using a grid centered on the fovea. Age-related changes in MCT, CVV, CSV, and CVI were studied in the entire scanning region, as well as in the subregions of the grids.

MAIN OUTCOME MEASURES

Age-related changes in MCT, CVV, CSV, and CVI using 6×6-mm and 12×12-mm SS-OCT scans.

RESULTS

The automated choroid segmentations were validated against manual segmentations, and MCT measurements were shown to be in good agreement (P < 0.0001). Choroidal vessel volume and CSV showed significant correlations with MCT (all P < 0.0001). Interestingly, CVI and CSVR were constant, with little variation among all participants regardless of age and MCT (61.1±1.8% and 0.64±0.05, respectively). Measurements on 12×12-mm and 6×6-mm scans showed excellent agreement in all scan regions (all P < 0.0001). While choroidal thickness and choroidal volume, which includes both choroidal vessels and stroma, decrease with age (all P < 0.0001), the CVI and CSVR vary little among all ages in all regions.

CONCLUSIONS

Whereas MCT, CVV, and CSV decrease with age, the CVI and CSVR remain constant in all regions with age. Ongoing studies are using these automated algorithms on SS-OCT structural datasets to investigate the diagnostic usefulness of these choroidal parameters in a myriad of ocular and systemic diseases.

Choroidal Patterns in Stargardt Disease: Correlations with Visual Acuity and Disease Progression

Background: To identify different choroidal patterns in Stargardt disease (STGD) and to assess their clinical correlates. Methods: 100 STGD eyes (29 males; mean age 42.6 ± 16.5 years) and 100 control eyes (29 males; mean age 43.2 ± 8.5 years) were included. Optical coherence tomography (OCT) and OCT angiography (OCTA) images were obtained. Four different choroidal patterns, quantitative OCT and OCTA parameters were assessed and statistically analyzed. The main outcome was the correlation between each choroidal pattern and anatomical and functional retinal status. Furthermore, we assessed structural and best corrected visual acuity (BCVA) changes of each STGD subgroup after one-year. Results: Mean BCVA was 0.63 ± 0.44 LogMAR for STGD patients and 0.0 ± 0.0 LogMAR for controls (p < 0.01). All quantitative parameters appeared deteriorated in STGD compared to controls (p < 0.01). Choroidal patterns were distributed as follows: Pattern 1 (normal appearing choroid) (15%), Pattern 2 (reduced Sattler or Haller layer) (29%), Pattern 3 (reduced Sattler and Haller layers) (26%), Pattern 4 (Pattern 3 + choroidal caverns) (30%). More advanced patterns significantly correlated with a more severe loss of retinal structural integrity. Furthermore, only Pattern 3 and Pattern 4 showed remarkable signs of progression after one year. Conclusions: Choroidal patterns were related with retinal structural status and BCVA loss, and with different disease progression.

Correlation of Outer Retinal Degeneration and Choriocapillaris Loss in Stargardt Disease Using En Face Optical Coherence Tomography and Optical Coherence Tomography Angiography

PURPOSE

This study measured and correlated degeneration of the junction between the inner and outer segments (IS/OS), the retinal pigment epithelium (RPE), and the choriocapillaris (CC) in Stargardt disease (STGD).

DESIGN

Prospective cross-sectional study.

METHODS

This study was conducted at the Casey Eye Institute. A total of 23 patients with STGD were enrolled and underwent optical coherence tomography angiography (OCTA). Scans were centered on the fovea. OCT slab projections and en face boundary maps were used to create masks to measure total IS/OS loss or RPE atrophy as well as regions of isolated IS/OS loss, isolated RPE atrophy, and matched IS/OS and RPE degeneration or intact IS/OS junction and RPE. CC vascular density (CCVD) was quantified from the CC angiogram. Outcomes included the area of loss, and the CCVD of degeneration in different areas was quantified and correlated.

RESULTS

The total area of IS/OS loss was strongly correlated with the total area of RPE atrophy (r = 0.96; P < 0.0001) by a 1.6:1 ratio (r² = 0.90). CCVD within regions of matched degeneration (85.6% ± 2.7%; P < 0.0001), isolated IS/OS junction loss (93.6% ± 1.0%; P = 0.0011), and isolated RPE atrophy (94.1% ± 1.1%; P = 0.0065) were all significantly lower than normal (99.0% ± 0.17%). There was a trend for CCVD within intact areas (97.6% ± 0.38%) to decline as the area diminished (r = 0.68).

CONCLUSIONS

Photoreceptor and RPE degeneration exhibited a strong relationship wherein the IS/OS loss was 1.6-fold greater than that of RPE atrophy, supporting the theory that photoreceptor degeneration precedes RPE in STGD. Both the photoreceptors and the RPE degeneration contributed synergistically to CCVD attenuation, but extralesional CCVD also tended to be abnormal. The findings and techniques in this study may be of utility in developing endpoints for clinical trials.

Choroidal binarization analysis: clinical application

INTRODUCTION

Image processing of optical coherence tomography scans through binarization techniques represent a non-invasive way to separately asses and measure choroidal components, in vivo. In this review, we systematically search the scientific literature regarding binarization studies published so far.

METHODS

A systematic research was conducted at PubMed database, including English literature articles for all of the following terms in various combinations: binarization, choroid/al, enhanced depth spectral domain/swept source optic coherence tomography, and latest publications up to November 2018 were reviewed.

RESULTS

Thirty-seven articles were included and analyzed regarding studied disease, binarization method, studied variables, and outcomes. Most of the studies have focused on the more common retinal pathologies, such as age-related macular degeneration, central serous chorioretinopathy and diabetic retinopathy but binarization techniques have also been applied to the study of choroidal characteristics in ocular inflammatory diseases, corneal dystrophies and in postsurgical follow-up. Advantages and disadvantages of binarization techniques are also discussed.

CONCLUSION

Binarization of choroidal images seems to represent a promising approach to study choroid subcomponents in an increasingly detailed manner.

Qualitative comparison of choroidal vascularity measurement algorithms

Purpose:

To compare the accuracy of manual and automated binarization technique for the analysis of choroidal vasculature.

Methods:

This retrospective study was performed on a total of 98 eyes of 60 healthy subjects. Fovea-centered swept source optical coherence tomography (SS-OCT) scans were obtained and choroidal area was binarized using manual and automated image binarization technique separately. Choroidal vessel visualization in the binarized scans were subjectively graded (grades 0–100) by comparing them with the original OCT scan images by two masked graders. The subjective variability and repeatability was compared between two binarization method groups. Intergrader and intragrader variability was estimated using paired t-test. The degree of agreement between the grades for each observer and between the observers was evaluated using Bland–Altman plot.

Results:

The mean accuracy grades of the automatically binarized images were significantly (P < 0.001) higher (93.38% ± 1.70%) than that of manually binarized images (78.06% ± 2.92%). There was a statistically significant variability and poor agreement between the mean interobserver grades in the manual binarization arm.

Conclusion:

Automated image binarization technique is faster and appears to be more accurate in comparison to the manual method.

Visual rehabilitation using video game stimulation for Stargardt disease

BACKGROUND

Stargardt disease, a common form of heredomacular degeneration, leads to severe vision loss. Video game play can act as a positive biofeedback to reinforce visual rehabilitation and fixation training. It can potentially lead to visual improvement. This study was done to explore the possibility of visual improvement using video game stimulation for visual rehabilitation in Stargardt disease.

METHODS

We evaluated eight patients with Stargardt disease who had nonatrophic retina surrounding the area of degeneration at the macula. They underwent extensive baseline testing to determine their Snellen visual acuity, pattern visual evoked potentials, retinal sensitivity, and fixation analysis with microperimetry, electroretinography, fundus photography, optical coherence tomography, and autofluorescence. They were given 40 h of training with video game play and re-evaluated on all the tests.

RESULTS

They showed both subjective and objective evidence of improvement in visual functions and vision-related tasks. Visual acuity (from 0.77 ± 0.29 to 0.71 ± 0.32 logMAR, p = 0.027), contrast sensitivity (from 1.28 ± 0.25 to 1.46 ± 0.17, p = 0.002), and fixation stability (log of bivariate contour ellipse area from 6.67 ± 0.52 to 5.85 ± 0.84, p = 0.022) improved significantly. The retinal sensitivity improved by 0.47 ± 3.39 dB (p = 0.67). Stereopsis and pattern visual evoked potentials showed improvement. A low vision questionnaire documented subjective improvement.

CONCLUSION

Visual stimulation by video game play can result in improvement in visual acuity, fixation pattern, and retinal sensitivity with improvement in vision-related tasks. It can serve as a simple rehabilitatory technique for patients with central vision loss due to Stargardt disease.

Monitoring and Management of the Patient with Stargardt Disease

Stargardt disease (STGD1) represents one of the major common causes of inherited irreversible visual loss. Due to its high phenotypic and genotypic heterogeneity, STGD1 is a complex disease to understand. Non-invasive imaging, biochemical, and genetic advances have led to substantial improvements in unveiling the disease processes and novel promising therapeutic landscapes have been proposed. This review recapitulates the modalities for monitoring patients with STGD1 and the therapeutic options currently under investigation for the different stages of the disease.

Choroidal imaging biomarkers

The choroid is the vascular coat of the eye, and its role has been studied in multiple chorioretinal disorders. Recent advancements in choroidal imaging techniques, including enhanced depth imaging optical coherence tomography, swept source optical coherence tomography, en face optical coherence tomography, and optical coherence tomography angiography have facilitated an in-depth analysis of the choroid. The gradual shift from manual to automated segmentation and binarization methods have led to precise and reproducible measurements of choroidal parameters. These qualitative and quantitative parameters, called choroidal imaging biomarkers, have evolved over the past decade from a simple linear subfoveal choroidal thickness to more complex 3D choroidal reconstruction, thus widening the spectrum encompassing multiple parameters. These biomarkers have provided a better understanding of the pathogenesis, are helpful in diagnostic dilemmas, and, in the future may also help to devise treatment options. The lack of normative data, absence of standardized parameters, and limitations of the imaging techniques, however, have led to ambiguity and difficulty in the interpretation of these variables. We attempt to address these lacunae in the literature and provide a basic understanding of the choroid in both health and disease using these choroidal biomarkers.