Assessment of intraretinal hyperreflective foci using multimodal imaging in eyes with age-related macular degeneration.

PURPOSE: This study aimed to investigate the correspondence between intraretinal hyperreflective foci (IHRF) identified on optical coherence tomography (OCT) B-scans with hyperpigmentation on colour fundus photography (CFP) or hyperreflectivity on infrared reflectance (IR) images in eyes with age-related macular degeneration (AMD). METHODS: Flash CFP, IR images and OCT B-scans obtained at the same visit were evaluated. Individual IHRF identified on OCT B-scans were assessed for the qualitative presence or absence of a hypotransmission tail into the choroid. The corresponding IR image obtained at the time of OCT acquisition was analysed for the presence or absence of hyperreflectivity in this region. The IR images were manually registered to the CFP image, and CFP images were inspected for the presence or absence of hyperpigmentation at the location of IHRF. RESULTS: From 122 eyes, a total of 494 IHRF were evaluated. For the primary analysis of qualitative presence or absence of hyperpigmentation on CFP and hyperreflectivity on IR at the locations corresponding to IHRF on OCT, 301 (61.0%) of the IHRFs demonstrated evidence of hyperpigmentation on CFP, while only 115 (23.3%) showed evidence of hyperreflectivity on IR. The qualitative determination of the presence or absence of an abnormality on CFP or IR were significantly different (p < 0.0001). 327 (66.2%) of the IHRF showed hypotransmission, and 80.4% of these IHRF showed hyperpigmentation on CFP, though only 23.9% (p < 0.0001) demonstrated hyperreflectivity on IR. CONCLUSIONS: Less than two-thirds of IHRF evident on OCT manifest as hyperpigmentation on colour photos, though IHRF with posterior shadowing are more likely to be evident as pigment. IR imaging appears to be even more poorly sensitive for visualizing IHRF.

Comparison of diabetic retinopathy severity grading on ETDRS 7-field versus ultrawide-field assessment.

OBJECTIVES: To compare the diabetic retinopathy (DR) severity level determined when considering only the ETDRS 7-field region versus the entire ultrawidefield (UWF) image. METHODS: In this retrospective, cross-sectional study, UWF pseudocolor images were graded on the Eyenuk image viewing, grading, and annotation platform for the severity of DR considering only the regions within the ETDRS 7-fields as well as the entire UWF image using two different protocols: 1) the simple International Classification of Diabetic Retinopathy (ICDR) scale and 2) the more complex DRCR.net Protocol AA grading scale. RESULTS: A total of 250 eyes from 157 patients were included in this analysis. Six eyes (2.4%) demonstrated a discrepancy in severity level between the ETDRS 7-field region and the entire UWF image when using the ICDR classification system. The discrepancies were due to the presence of lesions [intraretinal haemorrhage (n = 2), neovascular disease (n = 4)] in the peripheral fields which were not identified in the ETDRS 7-fields. Fourteen eyes (5.6%) had a discrepancy in severity level between the ETDRS 7-field region and the entire UWF image when using the ETDRS DRSS Protocol AA grading scale. The discrepancies were due to the presence of a higher level of disease [intraretinal haemorrhage (n = 4), neovascularization (n = 4), preretinal haemorrhage (n = 2), scatter laser scars (n = 4)] in the peripheral fields. CONCLUSION: Although considering regions outside of the ETDRS 7-fields altered the DR severity level assessment in <5% of cases in this cohort, significant and potentially vision-threatening lesions including neovascularization and preretinal haemorrhage were identified in these peripheral regions. This highlights the importance of evaluating the entire UWF region when assessing patients with diabetic retinopathy.

Agreement, repeatability, and reproducibility of quantitative retinal layer assessment using swept-source and spectral-domain optical coherence tomography in eyes with retinal diseases.

Purpose: To evaluate the agreement and precision of retinal thickness measurements obtained using swept-source optical coherence tomography (SS-OCT) and spectral-domain OCT (SD-OCT) in healthy eyes and eyes with retinopathy. Methods: This cross-sectional prospective study involved three DRI-OCT Triton (SS-OCT) and three 3D-OCT-1 Maestro (SD-OCT) devices. One of each device (Maestro and Triton) was paired with a single operator. Healthy subjects and patients with retinal diseases were recruited, with study eye and testing order randomized. At least 3 scans per eye were captured for wide scan (12 mm × 9 mm-Triton and Maestro) and macular cube scan (7 mm × 7 mm-Triton, 6 mm × 6 mm-Maestro). Thickness of the full retina, ganglion cell layer + inner plexiform layer (GCL+), and ganglion cell complex (GCL++) were obtained from wide scan and cube scans. Agreement of the measurements between the Triton and Maestro was evaluated by Bland-Altman analysis and Deming regression for each group. Repeatability and reproducibility were assessed using a two-way random effect analysis of variance (ANOVA) model for each parameter by group. Results: Twenty-five healthy subjects (25 eyes) and 26 patients with retinal diseases (26 eyes), including, but not limited to, age-related macular degeneration, macular hole, and diabetic retinopathy were recruited. Overall, the measurement differences between Triton and Maestro were <6 µm (mean differences of full retina, GCL++, and GCL+ thickness were ≤5.5 µm, 1.3 µm, and 2.8 µm, respectively) and not statistically significant across the parameters. The repeatability and reproducibility estimates indicate high precision in both devices and groups. Across all the parameters, the repeatability limit was ≤7.6 µm for Triton and ≤12.7 µm for Maestro; reproducibility limit was ≤9.2 µm for Triton and ≤14.4 µm for Maestro. In eyes with retinal pathology, the repeatability coefficient of variation (CV)% was ≤2.6% for Triton and ≤3.4% for Maestro; reproducibility CV% was ≤3.3% for Triton and ≤3.5% for Maestro. Conclusion: Both Triton SS-OCT and Maestro SD-OCT provide reliable measurements of retinal thickness in healthy eyes and eyes with retinal diseases. Excellent agreement between the two devices indicates interoperability when testing healthy eyes or eyes with retinal pathology. These findings support the use of thickness measurements from Triton SS-OCT and Maestro SD-OCT in clinical practice.

Age-related assessment of foveal avascular zone and surrounding capillary networks with swept source optical coherence tomography angiography in healthy eyes.

AIM: To assess the macular capillary networks and foveal avascular zone (FAZ) with swept-source optical coherence tomography angiography in healthy eyes. METHODS: This cross-sectional, prospective, observational study enrolled 222 eyes of 116 healthy participants with no ocular or systemic disease. SS-OCTA images were captured using the PLEX Elite 9000 (Carl Zeiss Meditec Inc., Dublin, CA, USA) with a 6 × 6 mm pattern centered on the foveal center. Vessel length density (VLD), perfusion density (PD), and FAZ parameters were analyzed using the manufacturer's automated software. RESULTS: A significant negative correlation was observed between age and average VLD in the superficial plexus, and average PD in both the superficial plexus and the whole retina. A significant positive correlation between age and foveal avascular zone perimeter and area was also noted. Age-wise comparisons showed a trend for an increase in VLD and PD until 40 years of age, with a subsequent decrease in the older age in the macular region. The central subfield showed a decrease in the vessel density measurements in the 21-40 age group. FAZ area and perimeter were the mirror inverse of the central subfield vessel density measurements with a numerically greater area and perimeter in the 21-40 age group compared to the 0-20 and 41-60 age groups. FAZ circularity was significantly reduced after 40 years of age. CONCLUSION: Age-related changes in the vessel density and FAZ parameters in the healthy macula are complex and vary with the macular location. These results carry significance when interpreting the data from diseased eyes.

Longitudinal Assessment of Ellipsoid Zone Recovery Using En Face Optical Coherence Tomography After Retinal Detachment Repair.

PURPOSE: Suboptimal functional outcomes after rhegmatogenous retinal detachment (RRD) repair may be related to photoreceptor abnormalities, including alterations of the ellipsoid zone (EZ) that may not be apparent on cross-sectional optical coherence tomography (OCT). This study assessed EZ recovery using en face OCT after RRD repair and its association with visual acuity. DESIGN: Post hoc analysis of a randomized controlled trial. METHODS: Patients with macula-off RRD were monitored at 3, 6, 12, and 24 months postoperatively and annually thereafter. En face OCT of the EZ slab were analyzed. Hyporeflective areas were colocalized with EZ abnormalities on cross-sectional OCT B-scans and measured by 2 masked graders. Primary outcome was change in area of EZ hyporeflectivity from 3 to 24 months, and its association with Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity recovery was also assessed. RESULTS: In total, 271 images of 61 patients were assessed. Mean area of hyporeflectivity significantly decreased from 3 to 24 months (-2.98 mm2; 95% CI, 1.82-4.13 mm2; P < .0001), with further reductions up to 4 years. Linear regression revealed an association between change in hyporeflective area and change in the ETDRS letter score from 3 to 24 months (ß = -0.31, P = .009, R2 = 14.8%) and between duration of macula-off and change in hyporeflective area from 3 to 24 months (ß = -0.37, P = .018, R2 = 13.7%). CONCLUSIONS: En face OCT provides a novel biomarker for visualizing and quantifying EZ recovery after RRD repair that is associated with ETDRS visual acuity recovery. A steady decline in the area of EZ hyporeflectivity was observed over many years with delayed recovery in patients with longer duration of macula-off.

Ocular Imaging for Enhancing the Understanding, Assessment, and Management of Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is a progressive neuro-retinal disease and the leading cause of central vision loss among elderly individuals in the developed countries. Modern ocular imaging technologies constitute an essential component of the evaluation of these patients and have contributed extensively to our understanding of the disease. A challenge with any review of ocular imaging technologies is the rapid pace of progress and evolution of these instruments. Nonetheless, for proper and optimal use of these technologies, it is essential for the user to understand the technical principles underlying the imaging modality and their role in assessing the disease in various settings. Indeed, AMD, like many other retinal diseases, benefits from a multimodal imaging approach to optimally characterize the disease. In this chapter, we will review the various imaging technologies currently used in the assessment and management of AMD.

Quantitative assessment of choriocapillaris flow deficits in eyes with macular neovascularization.

PURPOSE: To investigate choriocapillaris flow deficits (CC FD) in a group of eyes with Type 3 macular neovascularization (MNV) versus a group of eyes with Type 1 and/or 2 MNV versus healthy eyes. METHODS: In this cross-sectional, retrospective, multicenter, observational study, consecutive patients with Type 3 MNV, Type 1 and/or 2 MNV, and age-matched controls were included. PLEX Elite optical coherence tomography angiography was performed with a 6 × 6 mm scan pattern centered on the fovea. The CC FD was computed in 4 peripheral 1 × 1 mm squares to allow comparison between equidistant regions unaffected by MNV. RESULTS: Twenty Type 3, 20 Type 1 and/or 2 MNV [13 (65%) Type 1 MNV, 1 (5%) Type 2 MNV, and 6 (30%) mixed Type 1 and 2 MNV], and 20 age-matched controls were included. The mean impairment in the CC in the 4 peripheral squares was 16.07 ± 7.27% in Type 3 MNV eyes, 11.48 ± 5.59% in Type 1/2 MNV eyes, and 9.64 ± 3.59% in controls. Type 3 MNV displayed a statistically significantly higher CC FD compared with both Type 1/2 MNV (P = 0.031) and controls (P < 0.0001). No significant differences were observed between Type 1/2 MNV and controls (P = 0.223). CONCLUSIONS: CC FD was significantly greater in the peripheral macular regions of eyes with Type 3 MNV compared to eyes with Type 1/2 MNV and normal control eyes. Pathogenic choroidal mechanisms may differ in eyes with different MNV subtypes. Whereas focal CC impairment may drive the development of Type 1/2 MNV, diffuse CC disruption may be more important in eyes with Type 3 MNV.

TOPOGRAPHIC ASSESSMENT OF CHORIOCAPILLARIS FLOW DEFICITS IN THE INTERMEDIATE AGE-RELATED MACULAR DEGENERATION EYES WITH HYPOREFLECTIVE CORES INSIDE DRUSEN.

PURPOSE: To evaluate the choriocapillaris (CC) flow deficit (FD) in eyes with hyporeflective cores (HCs) inside drusen in eyes with intermediate age-related macular degeneration. METHODS: Intermediate age-related macular degeneration subjects underwent optical coherence tomography and optical coherence tomography angiography using a Cirrus HD-optical coherence tomography (Carl Zeiss Meditec, Dublin, CA). All B-scans were inspected for the presence of drusen with an HC that was defined as dark, condense materials inside drusen. Drusen regions delineated in the manufactures advanced retinal pigment epithelium elevation map were superimposed to the compensated CC optical coherence tomography angiography images. Quantitative analysis of CC FD% was performed under drusen with and without HCs, 150-µm-wide ring region around drusen with and without HCs, drusen-free region, and whole macula. RESULTS: Fifty eyes were included in this cross-sectional study. Twenty eyes had drusen with HCs. Thirty eyes without HCs were matched for age and sex. The CC FD% of whole macula was significantly greater in eyes with an HC than those without it (46.3% vs. 42.9%; P = 0.001). In eyes with HCs, regional CC FD% was the greater under drusen (59.8%) and in a 150-µm-wide ring surrounding drusen with HCs (53.0%) than corresponding regions for drusen without HCs (52.5% and 47.3%, respectively) (P < 0.005 in all, Bonferroni correction). The CC FD% in macular regions remote from drusen was 43.2%. CONCLUSION: Intermediate age-related macular degeneration eyes with HCs demonstrated more impaired CC flow, compared with those without this featured. The CC was also more severely impaired directly below these drusen with HCs. These findings highlight that the appearance of HCs may be an indicator of a more advanced disease phenotype.

Reproducibility of qualitative assessment of drusen volume in eyes with age related macular degeneration.

BACKGROUND: Although an optical coherence tomography (OCT)-derived central drusen volume ≥0.03 mm3 has been found to be a risk factor for progression to late age-related macular degeneration (AMD), this parameter is not currently available on most OCT devices or acquisition protocols. The purpose of this study was to evaluate the ability of human graders to qualitatively assess drusen volume by inspection of OCT B-scans. METHODS: 100 subjects (200 eyes) from the Amish Eye Study diagnosed with early or intermediate AMD underwent OCT imaging with both Cirrus OCT and Spectralis OCT. Drusen volume was automatically computed from the Cirrus OCT volumes using the Cirrus Advanced RPE Analysis software. Spectralis volume scans were reviewed by two independent, masked graders who were asked to determine whether the central drusen volume was ≥0.03 mm3. Cohen's kappa coefficients were computed to assess the agreement. RESULTS: After excluding 11 eyes with poor image quality and 5 eyes used for training of the graders, the remaining 184 eyes were included in this analysis. The agreement between the graders and the automated evaluation of drusen volume by the Cirrus OCT was excellent with K = 0.88 for grader 1 and K = 0.82 for grader 2. The agreement between graders was also excellent with a K = 0.88. CONCLUSIONS: The presence of a high central drusen volume can be assessed reliably by qualitative inspection of OCT B-scans. This approach may be useful in the assessment of risk for progression to late AMD.

QUANTITATIVE ASSESSMENT OF CHORIOCAPILLARIS FLOW DEFICITS SURROUNDING CHOROIDAL NEOVASCULAR MEMBRANES.

PURPOSE: To quantify the regional variation in choriocapillaris (CC) flow deficits percentage (FD%) surrounding treatment-naïve Type 1 choroidal neovascularization (CNV) associated with age-related macular degeneration. METHODS: Patients were imaged with swept-source optical coherence tomography angiography system (Carl Zeiss PLEX Elite 9000; Carl Zeiss Meditec AG, Jena, Germany). Two 6 × 6-mm volume scans were acquired. Boundary-specific segmentation was used to isolate the Type 1 CNV. For CC assessment, both structural and optical coherence tomography angiography CC slabs (10-µm thick, starting 21 µm below the retinal pigment epithelium fit reference) were exported for signal compensation and averaging using ImageJ. The resultant CC image was binarized to calculate the FD%, for para-CNV and peri-CNV rings (each 500-µm wide). In a subgroup of 20 eyes, the FD% was compared with similar regions of age-matched controls. The FD% was also analyzed in small 500 × 500-µm squares equidistant from the fovea to compensate for regional variation of CC FD% as a potential confounding factor. RESULTS: Thirty-two eyes from 27 subjects were enrolled in this study. The CC FD% in the para-CNV ring was 26.58 ± 7.36, which was significantly higher than the peri-CNV ring (21.94 ± 6.31); P < 0.001. The FD% in para-CNV and peri-CNV rings was significantly greater than that of healthy controls (15.82 ± 1.29% and 15.53 ± 1.32%, respectively); P < 0.001. The FD% computed in the 500-µm squares equidistant from the fovea was also greater in the para-CNV ring (26.14 ± 7.11) than that in the peri-CNV ring (22.31 ± 6.21); P < 0.001. CONCLUSION: Choriocapillaris FD% is the highest in the region immediately surrounding the CNV.

Quantitative Assessment of the Severity of Diabetic Retinopathy.

PURPOSE: To determine whether a quantitative approach to assessment of the severity of diabetic retinopathy (DR) lesions on ultrawide field (UWF) images can provide new parameters to predict progression to proliferative diabetic retinopathy (PDR). METHODS: One hundred forty six eyes from 73 participants with DR and 4 years of follow-up data were included in this post hoc analysis, which was based on a cohort of 100 diabetic patients enrolled in a previously published prospective, comparative study of UWF imaging at the Joslin Diabetes Center. Diabetic Retinopathy Severity Score level was determined at baseline and 4-year follow-up visits using mydriatic 7-standard field Early Treatment Diabetic Retinopathy Study (ETDRS) photographs. All individual DR lesions (hemorrhage [H], microaneurysm [ma], cotton wool spot [CWS], intraretinal microvascular abnormality [IRMA]) were manually segmented on stereographic projected UWF. For each lesion type, the frequency/number, surface area, and distances from the optic nerve head (ONH) were computed. These quantitative parameters were compared between eyes that progressed to PDR in 4 years and eyes that did not progress. Univariable and multivariable logistic regression analyses were performed to identify parameters that were associated with an increased risk for progression to PDR. RESULTS: A total of 146 eyes of 73 subjects were included in the final analysis. The mean age of the study cohort was 53.1 years, and 42 (56.8%) subjects were female. The number and surface area of H/ma's and CWSs were significantly (P ≤ .05) higher in eyes that progressed to PDR compared with eyes that did not progress by 4 years. Similarly, H/ma's and CWSs were located further away from the ONH (ie, more peripheral) in eyes that progressed (P < .05). DR lesion parameters that conferred a statistically significant increased risk for proliferative diabetic retinopathy in the multivariate model included hemorrhage area (odds ratio [OR], 2.63; 95% confidence interval [CI], 1.25-5.53), and greater distance of hemorrhages from the ONH (OR, 1.24; 95% CI, 0.97-1.59). CONCLUSIONS: Quantitative analysis of DR lesions on UWF images identifies new risk parameters for progression to PDR including the surface area of hemorrhages and the distance of hemorrhages from the ONH. Although these risk factors will need to be confirmed in larger, prospective studies, they highlight the potential for quantitative lesion analysis to inform the design of a more precise and complete staging system for diabetic retinopathy severity in the future. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Quantitative assessment of the retinal microvasculature and choriocapillaris in myopic patients using swept-source optical coherence tomography angiography.

PURPOSE: To study the retinal capillary microvasculature and the choriocapillaris (CC) in myopic eyes using swept-source optical coherence tomography angiography (SS-OCTA). METHODS: Patients with high myopia (≥ - 6D; axial length ≥ 26.5 mm), moderate myopia (≥ - 3D, < - 6D), and age-matched healthy subjects presenting to the Shanghai General Hospital and Doheny-UCLA Eye Centers were enrolled in this prospective, multicenter study. Any subjects with evidence of macular abnormalities suggestive of pathologic myopia were excluded. SS-OCTA at both sites was performed using a Zeiss PLEX Elite instrument with a 6 × 6 mm scan pattern centered on the fovea. Two repeated volume scans were acquired for image averaging. The instrument pre-defined en face slab of the superficial and deep retinal capillary microvasculature was used to isolate and display the superficial and deep retinal capillaries. A slab spanning from 21 to 31 µm deep to the RPE fit line was used to isolate and display the CC. The OCTA images were exported for averaging using Image J. Littmann's method and the Bennett formula were applied to adjust for the impact of magnification in the high and moderate myopia groups. The resultant images were then binarized. Though projection artifact removal software was used, regions below the large superficial retinal vessels were excluded for quantitative analyses of the deep retinal capillary plexus and the CC. Vessel density (VD) and vessel length density (VLD) of the superficial and deep retinal capillary plexus (SCP, DCP) and CC flow deficit (FD) were analyzed, quantified, and compared between different groups. RESULTS: Twenty-five eyes of 25 patients with high myopia, 25 eyes of 25 patients with moderate myopia, and 25 eyes of 25 normal age-matched controls were included in this study. The VD of the SCP was lower in the high myopia group compared with the emmetropic control groups (p < 0.05), but the VD of the DCP demonstrated no significant difference among the three groups (p > 0.05). The VLDs of the SCP were lower in the high and moderate myopia groups compared with the control group (p < 0.05), while the VLD of the DCP was lower in the high myopia group compared with the moderate myopia and emmetropic control group (p < 0.05). The CC FD% in the high myopia group was significantly greater than both the control and moderate myopia subjects (p < 0.05). Of note, the severity of the CC flow deficit was not correlated with choroidal thickness (p > 0.05). CONCLUSION: The retinal microvasculature may demonstrate alterations in highly myopia eyes. The CC in macular regions shows greater impairment in eyes with high myopia compared with eyes with lesser degrees of myopia, and these deficits are already present in the absence of features of pathologic or degenerative myopia. The threshold of CC FD leading to myopic maculopathy remains to be defined.

Quantitative Assessment of Choriocapillaris Flow Deficits in Eyes with Advanced Age-Related Macular Degeneration Versus Healthy Eyes.

PURPOSE: To compare choriocapillaris (CC) flow deficits in eyes with geographic atrophy (GA) or choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD) and age-matched healthy control subjects. DESIGN: Cross-sectional study. METHODS: Patients with GA due to AMD, CNV due to AMD, and age-matched healthy subjects presenting to the Doheny-UCLA Eye Centers were enrolled in this cross-sectional institutional review board-approved study. Swept-source optical coherence tomography angiography was performed using a Zeiss PLEX Elite instrument with a 6 × 6-mm scan pattern centered on the fovea. Two repeated volume scans were acquired to allow for image averaging. The instrument predefined en face slab of the CC was used to isolate and display the CC. Both the structural and optical coherence tomography angiography slabs from this location were exported for averaging and signal compensation using Image J. The resultant image was then binarized. The CC flow deficit percentage (FD%) was computed in 4 peripheral 1 × 1-mm squares located at the corners of the images to allow comparison between equidistant regions unaffected by atrophy or CNV. RESULTS: Twenty eyes of 20 subjects were enrolled in each of the 3 groups (CNV, GA, normal) for this study. The average CC FD% of the 4 peripheral squares was 17.24% ± 2.86% in GA eyes, 15.55% ± 1.03% in CNV eyes, and 15.31% ± 0.93% in healthy controls of a similar age. The FD% in GA eyes was significantly greater than in both normal eyes and eyes with CNV (p= 0.012 and 0.038 respectively). The difference in FD% was not significantly different between CNV eyes and normal eyes for the tested peripheral macular regions (P = .678). CONCLUSIONS: The CC in peripheral macular regions in eyes with GA shows greater impairment than in eyes with CNV.

Impact of segmentation density on spectral domain optical coherence tomography assessment in Stargardt disease.

PURPOSE: Automated spectral domain optical coherence tomography (SD-OCT) segmentation algorithms currently do not perform well in segmenting individual intraretinal layers in eyes with Stargardt disease (STGD). We compared selective B-scan segmentation strategies for generating mean retinal layer thickness and preserved area data from SD-OCT scans in patients with STGD1. METHODS: Forty-five eyes from 40 Stargardt patients were randomly selected from the ongoing Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study. All eyes underwent SD-OCT using a standard macular volume consisting of 1024 × 49 equally spaced B-scans within a 20 × 20 degree field centered on the fovea. All 49 B-scans were segmented manually to quantify total retina, outer nuclear layer (ONL), photoreceptor inner segments, photoreceptor outer segments (OS), and retinal pigment epithelial layer (RPE). Mean thickness and total area were generated using all 49 B-scans (spaced 122 µm apart), 25 B-scans (every other B-scan, spaced 240 µm apart), 17 B-scans (every third scan, 353 µm apart), and 13 B-scans (every fourth scan, 462 µm apart), as well as by using an "adaptive" method where a subset (minimum 25 B-scans) of B-scans that the grader deemed as significantly different from adjacent B-scans were utilized. Mean absolute and percentage errors were calculated for macular thickness and area of different retinal layers for the different B-scan subset selection strategies relative to using all 49 B-scans, which was considered the reference or ground truth. RESULTS: Mean thickness and area measurements were significantly different for any regularly spaced reduction in B-scan density relative to the ground truth. When an adaptive approach was applied using a minimum of half the scans, the differences relative to ground truth were no longer significantly different. The mean percent differences for the area and thicknesses of the various layers ranged from 0.02 to 33.66 (p < 0.05 for all comparisons) and 0.44 to 7.24 (p > 0.05) respectively. CONCLUSION: Manual segmentation of a subset of B-scans using an adaptive strategy can yield thickness and area measurements of retinal sublayers comparable to the reference ground truth derived from using all B-scans in the volume. These results may have implications for increasing the efficiency of SD-OCT grading strategies in clinical trials for STGD and other related macular degenerative disorders.

Assessment of Corneal Changes Associated with Topical Antiglaucoma Therapy Using in vivo Confocal Microscopy.

PURPOSE: Ocular surface disease (OSD) is highly prevalent in eyes treated with chronic, topical antiglaucoma (A/G) therapy. The purpose of this study was to utilize in vivo confocal microscopy (IVCM) to evaluate the corneal morphology, including characteristics of corneal epithelial cells, presence of epithelial dendritic cells (DCs), and characteristics of subbasal nerve plexus, of eyes under topical A/G therapy versus normal eyes. METHODS: Central corneal images were prospectively captured from 30 eyes of 16 patients under topical A/G therapy (>6 months) and 20 normal control eyes, using IVCM (HRT 3 RCM, Heidelberg, Germany). Demographic data were collected, as well as information on the types and duration of A/G therapy. In addition, OSD index (OSDI) score, tear film breakup time, Schirmer 1 test results, density of epithelial wing cells (WCs) and basal cells (BCs), subbasal nerve features (density, tortuosity, and reflectivity), and presence of DCs were all assessed and recorded by trained Doheny Image Reading Center graders. RESULTS: IVCM findings of 30 glaucomatous eyes and 20 normal control eyes were analyzed. The mean OSDI score was 8.72 in controls and 32.06 in patients under A/G therapy (p = 0.002). Nerve fiber density, nerve fiber reflectivity, and BC density were all decreased in the A/G group (1,789.07 ± 785.70 µm/frame, 2.79 ± 0.83, 6,457.67 ± 692.55 cells/mm2, respectively) as compared to controls (2,815.981 ± 563.77 µm/frame, 3.52 ± 0.50, 7,854.13 ± 1,073.69 cells/mm2, respectively) (p < 0.05), whereas the decrease in WC density was statistically nonsignificant (p = 0.5). Nerve tortuosity and DC density were both significantly greater in the A/G eyes (3.00 ± 0.57, 71.24 ± 61.74 cells/mm2, respectively) compared to controls (2.10 ± 0.42, 34.08 ± 11.70 cells/mm2, respectively) (p < 0.05). Tear film breakup time and Schirmer 1 test results were significantly lower in the A/G group as compared to controls (p < 0.001). CONCLUSIONS: Using IVCM, our study identified significant microstructural alterations in the corneas of eyes treated with topical A/G therapy. In addition, our study also revealed that glaucoma patients treated with topical A/G therapy report significantly higher OSDI scores compared to controls. Thus, IVCM may be a useful tool in providing structural parameters to correlate with the functional OSDI assessments in the evaluation of ocular surface toxicity associated with topical A/G therapy.

Parafoveal Retinal Vessel Density Assessment by Optical Coherence Tomography Angiography in Healthy Eyes.

BACKGROUND AND OBJECTIVE: To assess variability in vessel density (VD) measurements across three optical coherence tomography angiography (OCTA) devices to identify a methodology that offers the least amount of variation in VD, and to assess the effect of averaging of multiple scans on VD variability. PATIENTS AND METHODS: Fifteen eyes of eight healthy individuals were imaged consecutively on three OCTA devices. Segmentations at the superficial, deep, and full retinal layers were generated. Repeat scans for each retinal layer were registered and averaged to generate one OCTA image. Two different automated thresholding techniques were used to calculate vessel area density (VAD) from binarized images and vessel skeleton density (VSD) from skeletonized images. Vessel length, a linear measure of the combined lengths of vessels, was calculated. Foveal avascular zone (FAZ) area was measured. RESULTS: All three OCTA devices were significantly different (P < .0001). This finding remained after averaging images (P < .0001). VSD was more repeatable within a device but less reproducible across devices. Conversely, VAD demonstrated less repeatability but greater reproducibility. Differences in VSD between devices were systematic and attributable to differences in resolution. Vessel length, unaffected by resolution, demonstrated no significant differences between the devices (P > .107). There was no significant difference in FAZ area across devices (P = .51). After averaging images, VD was significantly different from the single images for each device and plexus (P < .05) but remained within 1% of the value of a single scan. CONCLUSIONS: OCTA devices show variability in VD for healthy individuals. With greater repeatability, VSD appeared useful for following a patient on one device. VAD and vessel length seemed ideal for comparing vessel parameters between OCTA devices. After averaging multiple scans, VSD remained within 1% of a single scan, for which clinical significance remains to be determined. Caution is advised when comparing quantitative analyses across OCTA devices. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:S5-S17.].

Comparison of Subjective Assessment and Precise Quantitative Assessment of Lesion Distribution in Diabetic Retinopathy.

Importance: Predominantly peripheral disease in eyes with nonproliferative diabetic retinopathy (DR) is suggested as a potential strong risk factor for progression to proliferative disease. However, the reliability and optimal method for the assessment of lesion distribution are still uncertain. Objective: To compare agreement between subjective assessment and precise quantification of lesion burden in ultrawidefield (UWF) images of eyes with DR. Design, Setting, and Participants: This multisite cross-sectional study examines UWF pseudocolor images acquired from DR screening clinic patients from December 20, 2014, through August 1, 2014. Of 104 cases, 161 eyes with DR were included. Data analysis was conducted from June 1, 2016, through December 1, 2016 at the Doheny Image Reading Center. Main Outcomes and Measures: Distribution of DR lesions in eyes was assessed subjectively and quantitatively, and eyes were classified as having predominantly central lesions (PCLs) or predominantly peripheral lesions (PPLs). The frequency and surface area (SA) of each lesion type were quantified. Intergrader and subjective vs quantitative classification were compared for level of agreement. Several methods of determining PPL distribution were also compared. Results: On subjective frequency-based evaluation by graders, 133 eyes were classified as having PCL, and 28 eyes as having PPL. On exact quantification of lesion SA, 121 eyes were classified as PCL, and 40 eyes as having PPL. On SA-based quantification, 134 eyes were classified as having PCL, and 27 eyes as having PPL. There was a significant difference between qualitative and quantitative classification of DR lesion distribution for both frequency-based (mean difference [SD]: PCL, 6 [2]; PPL, 13 [6]; P < .001) and SA-based (mean difference [SD]: PCL, 6 [1]; PPL, 20 [7]; P < .001) methods. Both intergrader reproducibility and subjective vs quantitative agreement were higher with frequency-based classification. Conclusions and Relevance: Subjective assessment of PPL DR lesions on UWF images differed in some cases from precise quantitative assessments, particularly when considering the area of lesions. These findings highlight the benefit of objective quantitative approaches to DR assessment, which may facilitate the development of a more precise DR scoring system.

Impact of Multiple En Face Image Averaging on Quantitative Assessment from Optical Coherence Tomography Angiography Images.

PURPOSE: To investigate the impact of multiple en face image averaging on quantitative measurements of the retinal microvasculature using optical coherence tomography angiography (OCTA). DESIGN: Prospective, observational, cross-sectional case series. PARTICIPANTS: Twenty-one healthy individuals with normal eyes. METHODS: Macular OCTA images were acquired from all participants using the Zeiss Cirrus 5000 with Angioplex OCTA software (Carl Zeiss Meditec, Dublin, CA). Nine OCTA cube scans per eye were obtained and 9 superficial retinal layer (SRL) and deep retinal layer (DRL) en face OCTA image slabs were averaged individually after registration. Quantitative parameters from the retinal microvasculature were measured on binarized and skeletonized OCTA images and compared with single OCTA images without averaging. MAIN OUTCOME MEASURES: Vessel density (VD), vessel length density (VLD), vessel diameter index (VDI), and fractal dimension (FD). RESULTS: Participants with artifact or poor image quality were excluded, leaving 18 eyes for the analysis. After averaging, qualitatively there was apparent reduction in background noise, and fragmented vessels in the images before averaging became continuous with smoother walls and showed sharper contrast in both the SRL and DRL. Binarized and skeletonized derivates of these averaged images also showed fewer line fragments and dots in nonvascular areas and more continuous vessel images than those of images without averaging. In both SRL and DRL, VD (P = 0.0010 and P = 0.0003, respectively), VLD (P < 0.0001 for both), and FD (P < 0.0001 for both) significantly decreased and VDI significantly increased after averaging (P < 0.0001 for both). CONCLUSIONS: Averaging of multiple en face OCTA images improves image quality and also significantly impacts quantitative measurements. Reducing noise that could be misinterpreted as flow and annealing discontinuous vessel segments seem to be major mechanisms by which averaging may be of benefit.

ASSESSMENT OF RETINAL BLOOD FLOW IN DIABETIC RETINOPATHY USING DOPPLER FOURIER-DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

PURPOSE: To evaluate retinal blood flow measurements in normal eyes and eyes with varying levels of diabetic retinopathy (DR) using Doppler Fourier-domain optical coherence tomography (FD-OCT). METHODS: Twenty-two eyes of 19 subjects, 10 with severe nonproliferative DR (NPDR) and 12 with proliferative DR (PDR), were compared with 44 eyes of 40 healthy control subjects. All eyes were scanned by RTvue FD-OCT. Color disk photographs and cube/volume scans of the optic nerve head were obtained. Doppler OCT scans and accessory imaging data were imported into Doppler OCT of Retinal Circulation grading software to calculate TRBF and vascular parameters (e.g., venous and arterial cross-sectional area). Measurements were compared between cases and controls using independent t-tests. RESULTS: Mean TRBF was 44.98 ± 9.80 (range: 30.18-64.58) µL/minute for normal eyes, 35.80 ± 10.48 (range: 20.69-49.56) µL/minute for eyes with severe NPDR, and 34.79 ± 10.61 (range: 16.77-48.9) µL/minute for eyes with PDR. Mean TRBF was significantly lower in eyes with severe NPDR (P = 0.01) and PDR (P = 0.003) than in normal eyes. CONCLUSION: Total retinal blood flow was significantly lower in eyes with severe NPDR and PDR compared with normal eyes. Retinal blood flow determined by Doppler OCT may be a useful parameter for evaluating patients with DR.