LONGITUDINAL CHANGES IN QUANTITATIVE AUTOFLUORESCENCE DURING PROGRESSION FROM INTERMEDIATE TO LATE AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To prospectively investigate the development of quantitative autofluorescence (qAF) during progression from intermediate to late age-related macular degeneration (AMD). METHODS: Quantitative autofluorescence images from patients with intermediate AMD were acquired every three months with a Spectralis HRA + OCT (Heidelberg Engineering, Heidelberg, Germany) using a built-in autofluorescence reference. The association between changes in longitudinal qAF and progression toward late AMD was assessed using Cox regression models with time-dependent covariates. RESULTS: One hundred and twenty-one eyes of 71 patients were included, and 653 qAF images were acquired. Twenty-one eyes of 17 patients converted to late AMD (median follow-up: 21 months; 12 eyes: atrophic AMD; nine eyes: neovascular AMD). The converting patients' mean age was 74.6 ± 4.4 years. Eleven eyes in the converting group (52.4%) were pseudophakic. The presence of an intraocular lens did not affect the qAF regression slopes (P > 0.05). The median change for atrophic AMD was -2.34 qAF units/3 months and 0.78 qAF units/3 months for neovascular AMD. A stronger decline in qAF was significantly associated with an increased risk of developing atrophic AMD (hazard ratio = 1.022, P < 0.001). This association, however, was not present in the group progressing toward neovascular AMD (hazard ratio = 1.001, P = 0.875). CONCLUSION: The qAF signal declines with progression to atrophy, contrary to developing neovascularization. Quantitative autofluorescence may allow identification of patients at risk of progressing to late AMD and benefits individualized patient care in intermediate AMD.

SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY, FLUORESCEIN ANGIOGRAPHY, AND INDOCYANINE GREEN ANGIOGRAPHY COMPARISONS REVISITED: Using a Novel Deep-Learning-Assisted Approach for Image Registration.

PURPOSE: To compare area measurements between swept source optical coherence tomography angiography (SSOCTA), fluorescein angiography (FA), and indocyanine green angiography (ICGA) after applying a novel deep-learning-assisted algorithm for accurate image registration. METHODS: We applied an algorithm for the segmentation of blood vessels in FA, ICGA, and SSOCTA images of 24 eyes with treatment-naive neovascular age-related macular degeneration. We trained a model based on U-Net and Mask R-CNN for each imaging modality using vessel annotations and junctions to estimate scaling, translation, and rotation. For fine-tuning of the registration, vessels and the elastix framework were used. Area, perimeter, and circularity measurements were performed manually using ImageJ. RESULTS: Choroidal neovascularization lesion size, perimeter, and circularity delineations showed no significant difference between SSOCTA and ICGA (all P > 0.05). Choroidal neovascularization area showed excellent correlation between SSOCTA and ICGA (r = 0.992) and a Bland-Altman bias of -0.10 ± 0.24 mm. There was no significant difference in foveal avascular zone size between SSOCTA and FA (P = 0.96) and an extremely small bias of 0.0004 ± 0.04 mm and excellent correlation (r = 0.933). Foveal avascular zone perimeter was not significantly different, but foveal avascular zone circularity was significantly different (P = 0.047), indicating that some small cavities or gaps may be missed leading to higher circularity values representing a more round-shaped foveal avascular zone in FA. CONCLUSION: We found no statistically significant differences between SSOCTA and FA and ICGA area measurements in patients with treatment-naive neovascular age-related macular degeneration after applying a deep-learning-assisted approach for image registration. These findings encourage a paradigm shift to using SSOCTA as a first-line diagnostic tool in neovascular age-related macular degeneration.

SPECTRAL DOMAIN-OPTICAL COHERENCE TOMOGRAPHY IMAGE CONTRAST AND BACKGROUND COLOR SETTINGS INFLUENCE IDENTIFICATION OF RETINAL STRUCTURES.

PURPOSE: To evaluate image contrast and color setting on assessment of retinal structures and morphology in spectral-domain optical coherence tomography. METHODS: Two hundred and forty-eight Spectralis spectral-domain optical coherence tomography B-scans of 62 patients were analyzed by 4 readers. B-scans were extracted in 4 settings: W + N = white background with black image at normal contrast 9; W + H = white background with black image at maximum contrast 16; B + N = black background with white image at normal contrast 12; B + H = black background with white image at maximum contrast 16. Readers analyzed the images to identify morphologic features. Interreader correlation was calculated. Differences between Fleiss-kappa correlation coefficients were examined using bootstrap method. Any setting with significantly higher correlation coefficient was deemed superior for evaluating specific features. RESULTS: Correlation coefficients differed among settings. No single setting was superior for all respective spectral-domain optical coherence tomography parameters (P = 0.3773). Some variables showed no differences among settings. Hard exudates and subretinal fluid were best seen with B + H (κ = 0.46, P = 0.0237 and κ = 0.78, P = 0.002). Microaneurysms were best seen with W + N (κ = 0.56, P = 0.025). Vitreomacular interface, enhanced transmission signal, and epiretinal membrane were best identified using all color/contrast settings together (κ = 0.44, P = 0.042, κ = 0.57, P = 0.01, and κ = 0.62, P ≤ 0.0001). CONCLUSION: Contrast and background affect the evaluation of retinal structures on spectral-domain optical coherence tomography images. No single setting was superior for all features, though certain changes were best seen with specific settings.

Point-to-point associations of drusen and hyperreflective foci volumes with retinal sensitivity in non-exudative age-related macular degeneration.

OBJECTIVES: To evaluate the quantitative impact of drusen and hyperreflective foci (HRF) volumes on mesopic retinal sensitivity in non-exudative age-related macular degeneration (AMD). METHODS: In a standardized follow-up scheme of every three months, retinal sensitivity of patients with early or intermediate AMD was assessed by microperimetry using a custom pattern of 45 stimuli (Nidek MP-3, Gamagori, Japan). Eyes were consecutively scanned using Spectralis SD-OCT (20° × 20°, 1024 × 97 × 496). Fundus photographs obtained by the MP-3 allowed to map the stimuli locations onto the corresponding OCT scans. The volume and mean thickness of drusen and HRF within a circle of 240 µm centred at each stimulus point was determined using automated AI-based image segmentation algorithms. RESULTS: 8055 individual stimuli from 179 visits from 51 eyes of 35 consecutive patients were matched with the respective OCT images in a point-to-point manner. The patients mean age was 76.85 ± 6.6 years. Mean retinal sensitivity at baseline was 25.7 dB. 73.47% of all MP-spots covered drusen area and 2.02% of MP-spots covered HRF. A negative association between retinal sensitivity and the volume of underlying drusen (p < 0.001, Estimate -0.991 db/µm3) and HRF volume (p = 0.002, Estimate -5.230 db/µm3) was found. During observation time, no eye showed conversion to advanced AMD. CONCLUSION: A direct correlation between drusen and lower sensitivity of the overlying photoreceptors can be observed. For HRF, a small but significant correlation was shown, which is compromised by their small size. Biomarker quantification using AI-methods allows to determine the impact of sub-clinical features in the progression of AMD.

Profiling neovascular age-related macular degeneration choroidal neovascularization lesion response to anti-vascular endothelial growth factor therapy using SSOCTA.

PURPOSE: To identify the changes in distinct vascular parameters of choroidal neovascularization (CNV) in eyes with treatment-naïve neovascular age-related macular degeneration (nAMD) during the primary response to anti-VEGF therapy using aflibercept. METHODS: Patients were prospectively followed during the first 3 months according to a standardized protocol with mandatory visits at days 7 and 14 after each anti-VEGF treatment up to day 90. Fourteen eyes were seen in addition at days 1 and 3 post-initial injection. Aflibercept was administered at baseline (BL), day 30 and 60. 6 × 6mm SSOCTA (PlexElite, Zeiss) images were acquired. Using the semi-automated AngioTool, CNV area, vessel area, vessel density (VD), the number of junctions, junctions density, total vessel length, average vessel length, total number of endpoints and lacunarity were assessed. RESULTS: Thirty-two consecutive patients presenting with treatment-naïve, SSOCTA-positive CNV lesions were included. Close follow-up showed a characteristic neovascular response curve with a dynamic decrease in lesion size within days and a reactive increase following 2 weeks after initial treatment. An undulating pattern was seen for all neovascular parameters except for vascular density, with variable statistical significance. Due to a flattening of the therapeutic response as early as after the second treatment, CNV lesion size and most of the related parameters had an increase in activity above baseline values at the end of the loading phase. Lesion size was the leading feature of reactivation by a mean increase of 19.3% after three monthly aflibercept injections. Subgroup analysis based on lesion size revealed a significant correlation between best-corrected visual acuity and quantitative change in lesion size over time, but not baseline size. CONCLUSIONS: Using SSOCTA, a morphologic neovascular response pattern can be identified in anti-VEGF treatment of CNV. A synchronized early decrease and consecutive reactivation in a large spectrum of neovascular biomarkers including size and internal structure are visualized in a qualitative and quantitative manner. SSOCTA analyses allow new insights in CNV morphology changes and therapeutic response.

Topographic Distribution and Progression of Soft Drusen Volume in Age-Related Macular Degeneration Implicate Neurobiology of Fovea.

Purpose: To refine estimates of macular soft drusen abundance in eyes with age-related macular degeneration (AMD) and evaluate hypotheses about drusen biogenesis, we investigated topographic distribution and growth rates of drusen by optical coherence tomography (OCT). We compared results to retinal features with similar topographies (cone density and macular pigment) in healthy eyes. Methods: In a prospective study, distribution and growth rates of soft drusen in eyes with AMD were identified by human observers in OCT volumes and analyzed with computer-assistance. Published histologic data for macular cone densities (n = 12 eyes) and in vivo macular pigment optical density (MPOD) measurements in older adults with unremarkable maculae (n = 31; 62 paired eyes, averaged) were revisited. All values were normalized to Early Treatment Diabetic Retinopathy Study (ETDRS) subfield areas. Results: Sixty-two eyes of 44 patients were imaged for periods up to 78 months. Soft drusen volume per unit volume at baseline is 24.6-fold and 2.3-fold higher in the central ETDRS subfield than in outer and inner rings, respectively, and grows most prominently there. Corresponding ratios (central versus inner and central versus outer) for cone density in donor eyes is 13.3-fold and 5.1-fold and for MPOD, 24.6 and 23.9-fold, and 3.6 and 3.6-fold. Conclusions: Normalized soft drusen volume in AMD eyes as assessed by OCT is ≥ 20-fold higher in central ETDRS subfields than in outer rings, paralleling MPOD distribution in healthy eyes. Data on drusen volume support this metric for AMD risk assessment and clinical trial outcome measure. Alignment of different data modalities support the ETDRS grid for standardizing retinal topography in mechanistic studies of drusen biogenesis.

Impact of drusen and drusenoid retinal pigment epithelium elevation size and structure on the integrity of the retinal pigment epithelium layer.

PURPOSE: To evaluate the impact of drusen size and structure on retinal pigment epithelium (RPE) and photoreceptor layers in eyes with early to intermediate age-related macular degeneration (AMD) using polarisation-sensitive optical coherence tomography (OCT). DESIGN: Retrospective investigation of an observational cross-sectional study. PARTICIPANTS: Patients with early to intermediate AMD. METHODS: Twenty-five eyes of 25 patients with drusen were imaged with polarisation-sensitive OCT using macular volume scans. Each scan was manually graded for six distinct drusen characteristics and the integrity of both the overlying RPE and photoreceptor layer. The central scan of each single druse, as well as its diameter and location, were selected for statistical calculations. RESULTS: A total number of 5933 individual drusen including their adjacent RPE and photoreceptor layer were evaluated. 41.3% of all drusen demonstrated an intact overlying RPE; in 28.1% the RPE layer was irregular, but continuous. In 30.6%, the RPE layer signal was discontinuous above the area of drusen. The level of RPE alteration was significantly related to shape (p<0.001), internal reflectivity (p<0.001) and homogeneity (p<0.001) of the drusen and their diameter, with a higher probability for larger drusen to have a discontinuous RPE (OR 3.2, p<0.001). The number of drusen showing overlying foci or an altered photoreceptor layer was too small to be conclusive, but showed a trend towards an altered RPE if present. CONCLUSIONS: Polarisation-sensitive OCT reveals a correlation between specific drusen characteristics and the integrity of the overlying RPE layer. Drusen diameter and configuration were significantly associated with RPE loss.

Impact of Drusen Volume on Quantitative Fundus Autofluorescence in Early and Intermediate Age-Related Macular Degeneration.

Purpose: Drusen volume (DV) and quantitative autofluorescence (qAF) are potential indicators of progression in age-related macular degeneration (AMD). This prospective and observational study examined the association between DV and qAF of the retinal pigment epithelium. Methods: Eighty-eight eyes of 52 patients with early and intermediate AMD were included. The mean follow-up was 9.2 ± 5.6 months, resulting in 312 examinations. DV was extracted from 6 × 6-mm spectral-domain optical coherence tomography scans. qAF was measured using a rotated Delori pattern. The associations between qAF and DV, age, sex, and lens status were investigated using linear mixed models. Results: Patients' mean age was 75.6 ± 5.0 years (range, 61.0-83.4 years). Sixty-eight eyes (77.3%) were from females. No significant association between DV and qAF was found, neither within the total outer Early Treatment Diabetic Retinopathy Study (ETDRS) grid nor for ETDRS segments six to nine (all P > 0.05). Sex and lens status were not associated with qAF (P = 0.429 and P = 0.213, respectively). A significant association between age and qAF (P = 0.025) was found, indicating a decrease of qAF with age. Conclusions: Quantification of DV and fundus autofluorescence did not reveal any correlation in early and intermediate AMD. qAF decreased with age, whereas DV increased in about half of the patients. This finding is a quantitative corroboration that fundus autofluorescence and the buildup of drusen are not correlated processes in AMD.

Repeatability and reliability of quantitative fundus autofluorescence imaging in patients with early and intermediate age-related macular degeneration.

PURPOSE: Quantification of fundus autofluorescence has only recently become available. We report our findings on the evaluation of the repeatability and reliability of quantitative fundus autofluorescence (qAF) measurements in patients with early and intermediate age-related macular degeneration (AMD), using the first approved and commercially available instrument. METHODS: A total of 43 eyes of 22 patients (aged between 52 and 84 years) diagnosed with early and intermediate AMD were included. All eyes were imaged at day 1, 3 months and 6 months using a modified scanning laser ophthalmoscope, equipped with an internal fluorescent reference. Mean qAF values were calculated for the fovea and for each concentric ring of the Delori pattern. Repeatability and reliability were calculated using Bland-Altman analysis and intraclass correlation (ICC). RESULTS: The mean patient age was 73.5 ± 7.9 years. Sixteen patients (73%) were female. qAF repeatability of the eight segments in the middle ring of the Delori pattern (qAFM 8 ) for between sessions was ±8.2%. Agreement at 3- and 6-month follow-up in eyes without retinal changes was ±8.3% and ±9.8%, respectively. Reliability of qAFM 8 was high for all images acquired [ICC = 0.98 (CI: 0.96-0.99), 0.97 (0.93-0.99) and 0.98 (0.92-0.99)]. Agreement at 3- and 6-month follow-up in eyes with retinal changes was ±18.1% and ±20.2%, respectively. Intraclass correlation (ICC) was slightly lower in eyes with retinal changes at 0.93 (0.84-0.97) and 0.96 (0.91-0.98), respectively. CONCLUSIONS: Quantitative autofluorescence shows excellent repeatability and reliability as well as follow-up agreement in patients with early and intermediate AMD without retinal changes. This is relevant when conducting longitudinal studies using qAF.

Longitudinal Association Between Drusen Volume and Retinal Capillary Perfusion in Intermediate Age-Related Macular Degeneration.

Purpose: To evaluate vascular changes in the superficial and deep retinal capillary plexus (SCP, DCP) and their association with drusen volume changes in intermediate age-related macular degeneration (iAMD). Methods: Patients with iAMD were examined at baseline and 12 months thereafter. Drusen volume was extracted from 20° × 20° OCT scans using a 3-mm ETDRS grid using a customized algorithm with manual correction. Vessel density (VD) and flow area (FA) were extracted from 3 × 3 mm SD-OCT-A scans after manual correction of the segmentation. Associations were investigated using multiple regression models. Results: We used 31 eyes of 31 patients for evaluation. The mean age at baseline was 74.9 ± 5.4 years; 26 patients were female. Baseline visual acuity (VA) was 0.05 ± 0.08 logMAR (Snellen equivalent approximately 20/22). The initial mean 3-mm central drusen volume was 0.144 ± 0.136 mm3. A significant association with the signal strength index was consistently found, therefore all capillary measurements were corrected. VD in the same area was 49.88% ± 7.38% and 55.43% ± 9.31% for the SCP and DCP, respectively. The baseline FA resulted in 3.292 ± 0.218 mm2 and 3.433 ± 0.224 mm2 for the SCP and DCP, respectively. No association was found between changes in drusen volume and FA or VD after 12 months (all P > 0.05). VA worsened (P = 0.013) and the foveal FA of the SCP increased significantly (P = 0.014). Conclusions: No significant association was found between the increase in drusen volume in iAMD and capillary retinal perfusion over a 12-month follow-up. Although VA decreased statistically over this time period, the foveal FA of the SCP increased.

Comparison of SD-Optical Coherence Tomography Angiography and Indocyanine Green Angiography in Type 1 and 2 Neovascular Age-related Macular Degeneration.

Purpose: The purpose of this study is to compare the ability of spectral domain optical coherence tomography angiography (SD-OCTA) and indocyanine green angiography (ICGA) to detect and measure lesion area in patients with type 1 and 2 choroidal neovascularization (CNV). Methods: Types 1 and 2 neovascular AMD (nAMD) were included in this prospective and observational case series. ETDRS best-corrected visual acuity (BCVA), ophthalmic examination with funduscopy, OCTA (AngioVue), fluorescein angiography (FA), ICGA, and OCT (Spectralis) were performed. CNV measurements were done manually by two experienced graders using the systems' innate region selection tools. Results: Forty eyes of 39 consecutive patients with nAMD were included. Mean age was 77 ± 6.4 years, ETDRS BCVA was 67 ± 13 letters, and 11 eyes were treatment naïve. Nineteen CNV lesions were classified as type 1 and 21 as type 2. ICGA was able to identify CNV in all eyes. By contrast, OCTA detected CNV in 95% of type 1 and 86% of type 2 nAMD eyes. Mean overall CNV area (CNV-A) was 2.8 ± 2.7 mm2 in ICGA and 2.1 ± 2.7 mm2 in OCTA. Both lesion types CNV-A appeared significantly smaller in OCTA compared with ICGA (P < 0.01). Bland-Altman plot revealed a mean difference (bias) between OCTA and ICGA CNV-A of 0.76 ± 1.74 mm2. Intraclass correlation coefficient (ICC) for CNV-A was 0.91 and 0.93 for ICGA and OCTA, respectively. ICGA CNV-A in the four OCTA-negative eyes (median 4.7 mm2) was not significantly different from the 36 OCTA-positive eyes (median 1.7 mm2). Conclusions: Type 1 and 2 CNV-A were significantly smaller in OCTA than in ICGA. OCTA was generally less successful in detecting CNV than ICGA in patients who were included into this study based on FA and OCT. However, OCTA detected all type 1 lesions except for one, indicating that the SD-OCTA signal is limited by detection limits of blood flow velocity rather than lesion type. Further efforts are needed pushing the limits of lowest detectable and fastest distinguishable flow until OCTA can deliver realistic qualitative and quantitative imaging of type 1 and 2 CNV for diagnosis and monitoring.

Machine Learning of the Progression of Intermediate Age-Related Macular Degeneration Based on OCT Imaging.

Purpose: To develop a data-driven interpretable predictive model of incoming drusen regression as a sign of disease activity and identify optical coherence tomography (OCT) biomarkers associated with its risk in intermediate age-related macular degeneration (AMD). Methods: Patients with AMD were observed every 3 months, using Spectralis OCT imaging, for a minimum duration of 12 months and up to a period of 60 months. Segmentation of drusen and the overlying layers was obtained using a graph-theoretic method, and the hyperreflective foci were segmented using a voxel classification method. Automated image analysis steps were then applied to identify and characterize individual drusen at baseline, and their development was monitored at every follow-up visit. Finally, a machine learning method based on a sparse Cox proportional hazard regression was developed to estimate a risk score and predict the incoming regression of individual drusen. Results: The predictive model was trained and evaluated on a longitudinal dataset of 61 eyes from 38 patients using cross-validation. The mean follow-up time was 37.8 ± 13.8 months. A total of 944 drusen were identified at baseline, out of which 249 (26%) regressed during follow-up. The prediction performance was evaluated as area under the curve (AUC) for different time periods. Prediction within the first 2 years achieved an AUC of 0.75. Conclusions: The predictive model proposed in this study represents a promising step toward image-guided prediction of AMD progression. Machine learning is expected to accelerate and contribute to the development of new therapeutics that delay the progression of AMD.

Retinal pigment epithelial features indicative of neovascular progression in age-related macular degeneration.

BACKGROUND/AIMS: To identify characteristic retinal pigment epithelium (RPE) changes in fellow eyes of patients with neovascular age-related macular degeneration (nAMD) using polarisation-sensitive optical coherence tomography (PS-OCT). METHODS: Thirty-one fellow eyes of 31 patients with unilateral nAMD were evaluated in this cohort study of a prospective interventional trial. PS-OCT as well as conventional imaging including spectral-domain (SD)-OCT and fluorescein angiography (FA) were performed using a standardised protocol. Monitoring visits were performed continuously at 1-month intervals. Morphological RPE features associated with the development of choroidal neovascularisation (CNV) were systematically analysed. RESULTS: Mean follow-up was 29 months (±17, SD). Thirteen (42%) of 31 eyes developed de novo CNV: 9 eyes type I CNV, 2 eyes type II CNV, 2 eyes a retinal angiomatous proliferation lesion. RPE thickening and reticular pseudodrusen (RPD) were observed significantly more often in eyes that developed CNV than in eyes without CNV development (p<0.01). Monthly increase in drusen volume was higher in the CNV group with a median increase of +2.2% in area and +2.9% in volume compared with +0.8% and +0.6% in the non-progressing group. RPE migration within the neurosensory retina and at the level of the RPE resulting in RPE thickening was seen topographically and chronologically associated with CNV development. CONCLUSIONS: Conversion to CNV is associated with RPE-related changes such as RPE migration, RPE thickening, drusen volume or the presence of RPD. Early detection of these features may allow more efficient screening in risk eyes and timely vision-preserving treatment in eyes developing neovascular disease.

Drusen volume development over time and its relevance to the course of age-related macular degeneration.

AIMS: To quantify the change in drusen volume over time and identify its prognostic value for individual risk assessment. METHODS: A prospective observational study over a minimum of 3 years and maximum of 5 years and follow-up examination every 3 months was conducted at the ophthalmology department of the Medical University of Vienna. 109 patients presenting early and intermediate age-related macular degeneration (AMD) were included, of which 30 patients concluded a regular follow-up for at least 3 years. 50 eyes of 30 patients were imaged every 3 months using spectral-domain and polarisation-sensitive optical coherence tomography (OCT). Drusen volume was measured using an automated algorithm. Data of a 6-month follow-up were segmented manually by expert graders. RESULTS: Gradings from 24 000 individual B-scans showed solid correlation between manual and automated segmentation with an initial mean drusen volume of 0.17 mm3. The increase in drusen volume was shown to be comparable among all eyes, and a model for long-term drusen volume development could be fitted as a cubic polynomial function and an R2=0.955. Spontaneous drusen regression was observed in 22 of 50 eyes. In this group, four eyes developed choroidal neovascularisation and three geographic atrophy. CONCLUSIONS: Drusen volume increase over time can be described by a cubic function. Spontaneous regression appears to precede conversion to advanced AMD. OCT might be a promising tool for predicting the individual risk of progression of AMD.

Identification of Drusen Characteristics in Age-Related Macular Degeneration by Polarization-Sensitive Optical Coherence Tomography.

PURPOSE: To describe qualitative characteristics of drusen in eyes with nonadvanced age-related macular degeneration (AMD) using polarization-sensitive optical coherence tomography (OCT). DESIGN: Cross-sectional study. METHODS: Twenty-five eyes of 25 patients with early to intermediate (nonadvanced) AMD were imaged with polarization-sensitive OCT using macular volume scans. All individual drusen in each B-scan were manually delineated by experts certified by a reading center and graded for 6 different morphologic characteristics based on a defined classification scheme, including the presence of internal depolarizing structures and associated depolarizing foci. With the use of a custom-made software, the central B-scan of each individual druse was selected and used to analyze its location, diameter, and characteristics and assess the prevalence of the different features and relations between them. RESULTS: Using the macular volume scans, 6224 individual drusen could be identified, including their position within the retina, their characteristics, and their association with any pigmentary alterations. The most common drusen type was a convex-shaped druse with homogeneous medium internal reflectivity and no depolarizing contents (55.3% of drusen). A total of 30.5% of the drusen exhibited internal depolarizing material; 0.3% presented overlying hyperreflective foci, and in 54.5% the foci were also depolarizing. Significant correlations were found between the diameter of the drusen and their distribution throughout the retina, shape, homogeneity of internal reflectivity, presence of internal depolarizing characteristics, and presence of overlying foci (P < .001 each). Significant relations were found between reflectivity, homogeneity, and polarization-sensitive internal characteristics (P < .001). CONCLUSIONS: Polarization-sensitive OCT reveals characteristic morphologic features of different druse types highlighting the pathophysiological spectrum of early to intermediate AMD.

Detection and analysis of hard exudates by polarization-sensitive optical coherence tomography in patients with diabetic maculopathy.

PURPOSE: To image and analyze hard exudates (HEs) and their precursors in patients with diabetic macular edema (DME) by using polarization-sensitive optical coherence tomography (PS-OCT). METHODS: Twenty-two eyes of 16 patients with DME were imaged by using color fundus photography (CF) and PS-OCT. In PS-OCT, HEs were automatically detected by their distinct polarization-scrambling qualities. Color fundus images were manually graded for the presence of HEs by two masked graders and correlated with the corresponding PS-OCT HE maps: corresponding images were overlaid and an identical grid of 128 × 128 fields was used for correlation of detected HEs. RESULTS: In all eyes, HEs were present owing to DME. Agreement of a pixel-to-pixel analysis of HEs in CF images was 0.72 (Cohen's κ) between graders and 0.44 between graders and automated detection by PS-OCT. Mean ± SD detection of HEs was significantly higher in PS-OCT than in manual grading (1180.5 ± 1009.8 fields versus 828.8 ± 695.0 fields; P = 0.02). The higher detection rate of PS-OCT was confirmed by a linear regression analysis with a slope of ß = 1.18 (r = 0.81). CONCLUSIONS: PS-OCT enables not only two-dimensional imaging of the extent of HEs, as in CF, but also allows tissue-specific, three-dimensional imaging of HEs throughout retinal layers, based on their distinct polarization-scrambling characteristics. The higher detection rate in PS-OCT images indicates an increased sensitivity of PS-OCT imaging over conventional CF.

Polarization sensitive optical coherence tomography of melanin provides intrinsic contrast based on depolarization.

Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT. In addition to imaging based on tissue reflectivity, PS-OCT also enables depth-resolved mapping of sample polarization properties such as phase-retardation, birefringent axis orientation, Stokes vectors, and degree of polarization uniformity (DOPU). In this study, PS-OCT was used to investigate the polarization properties of melanin. In-vitro measurements in samples with varying melanin concentrations revealed polarization scrambling, i.e. depolarization of backscattered light. Polarization scrambling in the PS-OCT images was more pronounced for higher melanin concentrations and correlated with the concentration of the melanin granules in the phantoms. Moreover, in-vivo PS-OCT was performed in the retinas of normal subjects and individuals with albinism. Unlike in the normal eye, polarization scrambling in the retinal pigment epithelium (RPE) was less pronounced or even not observable in PS-OCT images of albinos. These results indicate that the depolarizing appearance of pigmented structures like, for instance, the RPE is likely to be caused by the melanin granules contained in these cells.

Quantification of the therapeutic response of intraretinal, subretinal, and subpigment epithelial compartments in exudative AMD during anti-VEGF therapy.

PURPOSE: To analyze the functional and morphologic effects of different ranibizumab treatment regimens on retinal and subretinal as well as sub-RPE compartments in neovascular age-related macular degeneration (nAMD) using spectral-domain optical coherence tomography (SD-OCT) and manual segmentation software. METHODS: Twenty-seven eyes of 27 patients with nAMD were examined over a 12-month period. Two treatment arms received either monthly or quarterly administered intravitreal ranibizumab. Intraretinal, subretinal, and sub-RPE volume equivalents were delineated using manual segmentation software over a defined series of B-scans obtained by SD-OCT. The mean area in pixels was calculated for each compartment at each time interval. RESULTS: SD-OCT and manual segmentation allowed for exact identification of intraretinal, subretinal and sub-RPE compartments and their responses to different treatment regimens. The loading dose demonstrated a corresponding treatment effect on all anatomic parameters. In contrast to the sub-RPE compartment, intraretinal fluid accumulation and subretinal fluid accumulation (SRFA) demonstrated an immediate response to ranibizumab therapy. The overall plasticity of the morphologic response declined over time. In general, SRFA demonstrated greater sensitivity for therapeutic effects and was more frequently associated with recurrent disease. CONCLUSIONS: An exact quantification of fluid in different anatomic compartments based on SD-OCT imaging, using appropriate segmentation software systems, may be useful to determine optimal treatment and retreatment parameters and explains the lack of correlation of best-corrected visual acuity and conventional OCT values.

Performance of automated drusen detection by polarization-sensitive optical coherence tomography.

PURPOSE: To estimate the potential of polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of drusen in patients with early age-related macular degeneration (AMD). METHODS: Fifteen eyes from 13 patients presenting drusen consistent with Age-Related Eye Disease Study classifications (grades 2 and 3) were examined ophthalmoscopically, followed by fundus photography, autofluorescence imaging, and three-dimensional scanning using a PS-OCT. For the automated evaluation of drusen location, area, and volume, a novel segmentation algorithm was developed based on the polarization scrambling characteristics of the retinal pigment epithelium (RPE) and applied to each complete data set. Subsequently, the drusen in each individual B-scan were identified by two independent expert graders. Concordance between manual and automated segmentation results was analyzed. Errors in the automated segmentation performance were classified as nonsignificant, moderate, or severe. RESULTS. In all, 2355 individual drusen, with a mean of 157 drusen per eye, were analyzed. Of drusen seen in the individual B-scans, 91.4% were detected manually by both expert graders. The automated segmentation algorithm identified 96.5% of all drusen without significant error. The mean difference in manual and automated drusen area (mean, 4.65 mm(2)) was 0.150. The number of detected drusen was significantly higher with automated than that with manual segmentation. PS-OCT segmentation was generally superior to fundus photography (P < 0.001). Particularly in nondetected drusen, a large variability in drusen morphology was noted. CONCLUSIONS: Automated drusen detection based on PS-OCT technology allows a fast and accurate determination of drusen location, number, and total area.

Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography.

We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the performance of the described methods. PS-OCT appears as a promising imaging modality for three-dimensional retinal imaging and ranging with additional contrast based on the structures' tissue-inherent polarization properties.