Optical Coherence Tomography Predictors of Risk for Progression to Non-Neovascular Atrophic Age-Related Macular Degeneration

Localized Optical Coherence Tomography Precursors of Macular Atrophy and Fibrotic Scar in the Comparison of Age-Related Macular Degeneration Treatments Trials

PURPOSE

To identify precursors of macular atrophy (MA) and of fibrotic scar (FS) in eyes treated with anti-vascular endothelial growth factor through pixel-mapping analysis of baseline optical coherence tomography (OCT).

METHODS

Design: Cross-sectional analysis.

SETTING

Multicenter clinical trial.

PATIENT POPULATION

68 eyes from the Comparison of Age-Related Macular Degeneration Treatments Trials.

INTERVENTION

Treatment with anti-vascular endothelial growth factor agents.

MAIN OUTCOME MEASURE

The percentage of MA or FS pixels with each OCT feature at baseline, and the odds ratio for baseline pixels with an OCT feature to develop MA or FS.

RESULTS

Retinal pigment epithelium atrophy and photoreceptor loss on OCT were highly predictive of MA at that location at years 2 and 5 (P < .0001), but accounted for only 22.5% of the ensuing atrophy at year 2 and less at year 5. Among pixels of MA at year 2, 78% were preceded by thick drusen, 54% by subretinal macular neovascularization (MNV), and 22.5% by no detectable OCT features. MNV, subretinal hyperreflective material, pigment epithelial detachment, intraretinal fluid, and sub-retinal pigment epithelium fluid were predictive of FS at that location (P values <.05). More than 75% of the pixels of FS at years 2 and 5 were preceded by pixels of baseline MNV.

CONCLUSIONS

Most pixels of FS were preceded by components of neovascularization. Although one-quarter of MA was accounted for by pre-existing evidence of atrophy on OCT alone, the development of MA in areas of thick drusen, areas with and without subretinal MNV lesion, and areas without detectable OCT precursors argues that the development of MA is multifactorial and may follow, in part, a non-neovascular pathway.

Interspecies Correlations between Human and Mouse NR2E3-Associated Recessive Disease

NR2E3-associated recessive disease in humans is historically defined by congenital night blinding retinopathy, characterized by an initial increase in short-wavelength (S)-cone sensitivity and progressive loss of rod and cone function. The retinal degeneration 7 (rd7) murine model, harboring a recessive mutation in the mouse ortholog of NR2E3, has been a well-studied disease model and recently evaluated as a therapeutic model for NR2E3-associated retinal degenerations. This study aims to draw parallels between human and mouse NR2E3-related disease through examination of spectral domain optical coherence tomography (SD-OCT) imaging between different stage of human disease and its murine counterpart. We propose that SD-OCT is a useful non-invasive diagnostic tool to compare human clinical dystrophy presentation with that of the rd7 mouse and make inference that may be of therapeutically relevance. Additionally, a longitudinal assessment of rd7 disease progression, utilizing available clinical data from our patients as well as extensive retrospective analysis of visual acuity data from published cases of human NR2E3-related disease, was curated to identify further valuable correlates between human and mouse Nr2e3 disease. Results of this study validate the slow progression of NR2E3-associated disease in humans and the rd7 mice and identify SD-OCT characteristics in patients at or near the vascular arcades that correlate well with the whorls and rosettes that are seen also in the rd7 mouse and point to imaging features that appear to be associated with better preserved S-cone mediated retinal function. The correlation of histological findings between rd7 mice and human imaging provides a solid foundation for diagnostic use of pathophysiological and prognostic information to further define characteristics and a relevant timeline for therapeutic intervention in the field of NR2E3-associated retinopathies.

Quantitative Fundus Autofluorescence in Rhesus Macaques in Aging and Age-Related Drusen

Purpose

To employ quantitative fundus autofluorescence (qAF) imaging in rhesus macaques to noninvasively assess retinal pigment epithelial (RPE) lipofuscin in nonhuman primates (NHPs) as a model of aging and age-related macular degeneration (AMD).

Methods

The qAF imaging was performed on eyes of 26 rhesus macaques (mean age 18.8 ± 8.2 years, range 4–27 years) with normal-appearing fundus or with age-related soft drusen using a confocal scanning laser ophthalmoscope with 488 nm excitation and an internal fluorescence reference. Eyes with soft drusen also underwent spectral-domain optical coherence tomography imaging to measure drusen volume and height of individual drusen lesions. The qAF levels were measured from the perifoveal annular ring (quantitative autofluorescence 8 [qAF8]) using the Delori grid, as well as focally over individual drusen lesions in this region. The association between qAF levels and age, sex, and drusen presence and volume were determined using multivariable regression analysis.

Results

Mean qAF levels increased with age (P < 0.001) and were higher in females (P = 0.047). Eyes with soft drusen exhibited reduced mean qAF compared with age-matched normal eyes (P = 0.003), with greater drusen volume showing a trend toward decreased qAF levels. However, qAF levels are focally increased over most individual drusen (P < 0.001), with larger drusen appearing more hyperautofluorescent (R² = 0.391, P < 0.001).

Conclusions

In rhesus macaques, qAF levels are increased with age and female sex, but decreased in eyes with soft drusen, similar to human AMD. However, drusen lesions appear hyperautofluorescent unlike those in humans, suggesting similarities and differences in RPE lipofuscin between humans and NHPs that may provide insight into drusen biogenesis and AMD pathogenesis.

Innate Immunity in Age-Related Macular Degeneration

Multiple lines of investigation have demonstrated that inflammation plays significant roles in etiology of age-related macular degeneration (AMD). Although interventional trials in AMD therapy targeting inflammatory pathways have been conducted, they have not yet been successful and a detailed understanding as to why some have failed is still elusive. One limitation is the relative dearth of information on how immune cells interact with retinal cells to generate AMD phenotypes at each disease stage. Here, we summarize current research evidence and hypotheses regarding potential pathogenic roles of innate immune cells in the eye, which include resident retinal microglia, macrophages derived from infiltrating systemic monocytes, and macrophages resident in the choroid. We relate recent findings regarding the physiology, function, and cellular interactions involving innate immune cells in the retina and choroid to AMD-related processes, including: (1) drusen formation and regression, (2) the onset and spread of degeneration in late atrophic AMD, and (3) the initiation, growth, and exudation of neovascular vessels in late "wet" AMD. Understanding how innate immune cells contribute to specific AMD phenotypes can assist in generating a comprehensive view on the inflammatory etiology of AMD and aid in identifying anti-inflammatory therapeutic strategies and selecting appropriate clinical outcomes for the planned interventions.

Current Management of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) remains a leading cause of blindness worldwide. The assessment and management of patients with this condition has evolved in the last decades. In this chapter, current standards for diagnosis, follow-up, and treatment of patients with AMD are reviewed and summarized. Namely, we highlight how current assessment has moved from conventional ophthalmoscopy and fluorescein angiography testing to a multimodal approach, and its important advantages. Alternatives to visual acuity for functional assessment of patients with AMD are also presented. Regarding strategies for follow-up and treatment, we provide specific information for the different stages (i.e., early, intermediate, and late) and forms (for example, choroidal neovascularization and geographic atrophy) of AMD. Specifically, we discuss the relevance and options for self-monitoring and non-pharmacological interventions. Additionally, a summary of the important trials (both on exudative and non-exudative AMD) that have helped inform clinical practice is provided, including data on antiangiogenic agents currently available, and outcomes of the different regimens that have been studied. The influence of advances in imaging on treatment strategies is also discussed.In summary, this chapter is a resource for all clinicians engaged in providing state of the art care for patients with AMD, and can help improve diagnosis, management, and outcomes of individuals with this blinding condition.

Local Anatomic Precursors to New-Onset Geographic Atrophy in Age-Related Macular Degeneration as Defined on OCT

PURPOSE

In macula-wide analyses, spectral-domain (SD) optical coherence tomography (OCT) features including drusen volume, hyperreflective foci, and OCT-reflective drusen substructures independently predict geographic atrophy (GA) onset secondary to age-related macular degeneration (AMD). We sought to identify SD OCT features in the location of new GA before its onset.

DESIGN

Retrospective study.

PARTICIPANTS

Age-Related Eye Disease Study 2 Ancillary SD OCT Study participants.

METHODS

We analyzed longitudinally captured SD OCT images and color photographs from 488 eyes of 488 participants with intermediate AMD at baseline. Sixty-two eyes with sufficient image quality demonstrated new-onset GA on color photographs during study years 2 through 7. The area of new-onset GA and one size-matched control region in the same eye were segmented separately, and corresponding spatial volumes on registered SD OCT images at the GA incident year and at 2, 3, and 4 years previously were defined. Differences in SD OCT features between paired precursor regions were evaluated through matched-pairs analyses.

MAIN OUTCOME MEASURES

Localized SD OCT features 2 years before GA onset.

RESULTS

Compared with paired control regions, GA precursor regions at 2, 3, and 4 years before (n = 54, 33, and 25, respectively) showed greater drusen volume (P = 0.01, P = 0.003, and P = 0.003, respectively). At 2 and 3 years before GA onset, they were associated with the presence of hypertransmission (P < 0.001 and P = 0.03, respectively), hyperreflective foci (P < 0.001 and P = 0.045, respectively), OCT-reflective drusen substructures (P = 0.004 and P = 0.03, respectively), and loss or disruption of the photoreceptor zone, ellipsoid zone, and retinal pigment epithelium (RPE, P < 0.001 and P = 0.005-0.045, respectively). At 4 years before GA onset, precursor regions were associated with photoreceptor zone thinning (P = 0.007) and interdigitation zone loss (P = 0.045).

CONCLUSIONS

Evolution to GA is heralded by early local photoreceptor changes and drusen accumulation, detectable 4 years before GA onset. These precede other anatomic heralds such as RPE changes and drusen substructure emergence detectable 1 to 2 years before GA. This study thus identified earlier end points for GA as potential therapeutic targets in clinical trials.

Geographic Atrophy Growth Is Strongly Related to Lesion Perimeter: Unifying Effects of Lesion Area, Number, and Circularity on Growth

PURPOSE

To investigate the underlying reason for the previously observed impact of baseline lesion size, number, and circularity on geographic atrophy (GA) growth rate.

DESIGN

Retrospective analysis of a multicenter, prospective, randomized controlled trial.

PARTICIPANTS

Age-Related Eye Disease Study participants with GA secondary to nonexudative age-related macular degeneration.

METHODS

We manually delineated atrophic lesions on color fundus photographs of 318 eyes with GA followed up over at least 2 visits (mean follow-up duration, 5.1 ± 3.0 years). We calculated GA area growth rate for each eye based on the first and last visit. GA perimeter-adjusted growth rate was defined as the ratio between GA area growth rate and mean GA perimeter between the first and last visit for each eye.

MAIN OUTCOME MEASURES

GA area growth rate, growth rate of the square root of GA area, and GA perimeter-adjusted growth rate.

RESULTS

GA area growth rate was correlated strongly with mean GA perimeter (r² = 0.66). GA area growth rate was associated with baseline GA area (r² = 0.39; P < 0.001), lesion number (r² = 0.10; P < 0.001), and circularity index (r² = 0.28; P < 0.001). The use of the square root of GA area reduced the influence of baseline GA area (but not lesion number or circularity) on GA growth rate. In comparison, GA perimeter-adjusted growth rate (0.098 ± 0.062 mm/year) was not correlated with baseline GA area (r² = 0.005; P = 0.20), lesion number (r² = 0.00009; P = 0.86), or circularity index (r² = 0.007; P = 0.14). GA perimeter-adjusted growth rate was 50.0% higher in eyes whose fellow eyes showed GA at any visit (0.102 ± 0.062 mm/year) than in eyes whose fellow eyes never demonstrated GA during follow-up (0.068 ± 0.049 mm/year).

CONCLUSIONS

The growth rate of GA area is associated strongly with lesion perimeter. This relationship explains the previously observed influences of baseline GA size, lesion number, and circularity on GA growth rate. GA perimeter-adjusted growth rate is uncorrelated with the 3 morphologic factors and may serve as a surrogate outcome measure to monitor GA progression in future studies.

Use of Composite End Points in Early and Intermediate Age-Related Macular Degeneration Clinical Trials: State-of-the-Art and Future Directions

The slow progression of early age-related macular degeneration (AMD) stages to advanced AMD requires the use of surrogate end points in clinical trials. The use of combined end points may allow for shorter and smaller trials due to increased precision. We performed a literature search for the use of composite end points as primary outcome measures in clinical studies of early AMD stages. PubMed was searched for composite end points used in early/intermediate AMD studies published during the last 10 years. A total of 673 articles of interest were identified. After reviewing abstracts and applicable full-text articles, 33 articles were eligible and thus included in the qualitative synthesis. The main composite end point categories were: combined structural and functional end points, combined structural end points, combined functional end points and combined multicategorical end points. The majority of the studies included binary composite end points. There was a lack of sensitivity analyses of different end points against accepted outcomes (i.e., progression) in the literature. Various composite outcome measures have been used but there is a lack of standardization. To date no agreement on the optimal approach to implement combined end points in clinical studies of early stages of AMD exists, and no surrogate end points have been accepted for AMD progression.

Can the Onset of Neovascular Age-Related Macular Degeneration Be an Acceptable Endpoint for Prophylactic Clinical Trials?

Many studies over the past 20 years have pursued the goal of preventing or deferring progression from early and intermediate age-related macular degeneration (AMD) to advanced AMD. The onset of neovascular AMD has been used as a primary endpoint in some prophylactic clinical trials because it is easy to assess and relatively well-defined. Nevertheless, the use of this endpoint for assessing progression of AMD lacks validation. The aims of this paper are to review the current practice of clinical trials investigating the prevention of progression of early or intermediate AMD to neovascular AMD, so-called prophylactic trials, as well as identify ongoing efforts to standardize endpoints and select the ideal population for such studies.

Validation of an Automated Quantification of Relative Ellipsoid Zone Reflectivity on Spectral Domain-Optical Coherence Tomography Images

Purpose

Relative ellipsoid zone reflectivity (rEZR) represents a potential biomarker of photoreceptor health on spectral-domain optical coherence tomography (SD-OCT). Because manual quantification of rEZR is laborious and lacks of spatial resolution, automated quantification of the rEZR would be beneficial. The purpose of this study was to evaluate the reliability and reproducibility of an automated rEZR quantification method.

Methods

The rEZR was acquired using a manual and an automated approach in eyes with age-related macular degeneration (AMD) and healthy controls. The rEZR obtained from both methods was compared and the agreement between the methods and their reproducibility assessed.

Results

Forty eyes of 40 participants with a mean (± standard deviation) age of 65.2 ± 7.8 years were included. Both the manual and automated method showed that control eyes exhibit a greater rEZR than AMD eyes (P < 0.001). Overall, the limits of agreement between the manual and automated method were -7.5 to 7.3 arbitrary units (AU) and 95% of the data points had a difference in the rEZR between the methods of ±8.2%. An expected perfect reproducibility was observed for the automated method, whereas the manual method had a coefficient of repeatability of 6.3 arbitrary units.

Conclusions

The automated quantification of rEZR method is reliable and reproducible. Further studies of the rEZR as a novel biomarker for AMD severity and progression are warranted.

Translational Relevance

Automated quantification of SD-OCT-based rEZR allows for its comprehensive and longitudinal characterization evaluating its relevance as an in vivo biomarker of photoreceptor function and its prognostic value for AMD progression.

Drusenoid pigment epithelial detachment volume is associated with a decrease in best-corrected visual acuity and central retinal thickness: the Norwegian Pigment Epithelial Detachment Study (NORPED) report no. 1

PURPOSE

To investigate the association of drusenoid pigment epithelial detachment (DPED) volume and change in best-corrected visual acuity (BCVA) and central retinal thickness (CRT) during the growth phase of large DPEDs.

METHODS

Patients from an ongoing prospective observational study, the Norwegian Pigment Epithelial Detachment Study (NORPED), with 1 year of follow-up and DPEDs ≥1000 µm in diameter, examined with the Heidelberg Spectralis HRA-OCT were included. Patients with DPEDs in the regression phase were excluded. Multicolour, near-infrared reflectance, optical coherence tomography (OCT) and OCT angiography images were obtained every 6 months. Fluorescein angiography and indocyanine green angiography were performed at baseline and yearly to exclude choroidal neovascularization (CNV).

RESULTS

Forty-four patients and 66 eyes were included. In the statistical model for BCVA, every 1.0 mm³ increase in DPED volume led to a decrease in BCVA of 4.0 ETDRS letters (95% CI, -7.0 to -1.0, p = 0.008). A decrease in BCVA was significantly associated with older patient age, the presence of acquired vitelliform lesions and subfoveal location of the DPEDs. In the model for CRT, every 1.0 mm³ increase in DPED volume led to a decrease in CRT of 26.7 µm (95% CI, -44.4 to -9.0, p = 0.003). Two eyes had progression of geographic atrophy and none developed CNV.

CONCLUSION

The increasing volume of DPEDs during the growth phase is associated with a decrease in BCVA and CRT. The subfoveal location of DPEDs and the presence of acquired vitelliform lesions appear to be associated with a further reduction in BCVA.

Fundus-controlled perimetry (microperimetry): Application as outcome measure in clinical trials

Fundus-controlled perimetry (FCP, also called 'microperimetry') allows for spatially-resolved mapping of visual sensitivity and measurement of fixation stability, both in clinical practice as well as research. The accurate spatial characterization of visual function enabled by FCP can provide insightful information about disease severity and progression not reflected by best-corrected visual acuity in a large range of disorders. This is especially important for monitoring of retinal diseases that initially spare the central retina in earlier disease stages. Improved intra- and inter-session retest-variability through fundus-tracking and precise point-wise follow-up examinations even in patients with unstable fixation represent key advantages of these technique. The design of disease-specific test patterns and protocols reduces the burden of extensive and time-consuming FCP testing, permitting a more meaningful and focused application. Recent developments also allow for photoreceptor-specific testing through implementation of dark-adapted chromatic and photopic testing. A detailed understanding of the variety of available devices and test settings is a key prerequisite for the design and optimization of FCP protocols in future natural history studies and clinical trials. Accordingly, this review describes the theoretical and technical background of FCP, its prior application in clinical and research settings, data that qualify the application of FCP as an outcome measure in clinical trials as well as ongoing and future developments.

Structural Features Associated With the Development and Progression of RORA Secondary to Maternally Inherited Diabetes and Deafness

PURPOSE

To investigate the development and progression of retinal pigment epithelial and outer retinal atrophy (RORA) secondary to maternally inherited diabetes and deafness (MIDD).

DESIGN

Retrospective observational case series.

METHODS

Thirty-six eyes of 18 patients (age range, 22.4-71.6 years) with genetically proven MIDD and serial optical coherence tomography (OCT) images were included. As proposed reference standard to diagnose and stage atrophy, OCT images were longitudinally evaluated and analyzed for presence and precursors of RORA. RORA was defined as an area of (1) hypertransmission, (2) disruption of the retinal pigment epithelium, (3) photoreceptor degeneration, and (4) absence of other signs of a retinal pigment epithelial tear.

RESULTS

The majority of patients revealed areas of RORA in a circular area around the fovea of between 5° and 15° eccentricity. Over the observation time (range, 0.5-8.5 years), evidence for a consistent sequence of OCT features from earlier disease stages to the end stage of RORA could be found, starting with loss of ellipsoid zone and subretinal deposits, followed by loss of external limiting membrane and loss of retinal pigment epithelium with hypertransmission of OCT signal into the choroid, and leading to loss of the outer nuclear layer bordered by hyporeflective wedges. Outer retinal tabulations seemed to develop in regions of coalescent areas of RORA.

CONCLUSIONS

The development and progression of RORA could be tracked in MIDD patients using OCT images, allowing potential definition of novel surrogate markers. Similarities to OCT features in age-related macular degeneration, where mitochondrial dysfunction has been implicated in the pathogenesis, support wide-ranging benefits from proof-of-concept studies in MIDD.

Can the Onset of Atrophic Age-Related Macular Degeneration Be an Acceptable Endpoint for Preventative Trials?

The slowly progressive nature of age-related macular degeneration (AMD) means that establishing the efficacy of novel preventative treatments aiming to slow progression of disease, remains challenging, and where earlier endpoints are needed to improve their feasibility. This review examines whether the onset of atrophic AMD, as seen as anatomical signs on optical coherence tomography termed nascent geographic atrophy, could act as a useful surrogate endpoint for early intervention trials.

Role of Deep Learning-Quantified Hyperreflective Foci for the Prediction of Geographic Atrophy Progression

PURPOSE

To quantitatively measure hyperreflective foci (HRF) during the progression of geographic atrophy (GA) secondary to age-related macular degeneration (AMD) using deep learning (DL) and investigate the association with local and global growth of GA.

METHODS

Eyes with GA were prospectively included. Spectral-domain optical coherence tomography (SDOCT) and fundus autofluorescence images were acquired every 6 months. A 500-μm-wide junctional zone adjacent to the GA border was delineated and HRF were quantified using a validated DL algorithm. HRF concentrations in progressing and nonprogressing areas, as well as correlations between HRF quantifications and global and local GA progression, were assessed.

RESULTS

A total of 491 SDOCT volumes from 87 eyes of 54 patients were assessed with a median follow-up of 28 months. Two-thirds of HRF were localized within a millimeter adjacent to the GA border. HRF concentration was positively correlated with GA progression in unifocal and multifocal GA (all P < .001) and de novo GA development (P = .037). Local progression speed correlated positively with local increase of HRF (P value range <.001-.004). Global progression speed, however, did not correlate with HRF concentrations (P > .05). Changes in HRF over time did not have an impact on the growth in GA (P > .05).

CONCLUSION

Advanced artificial intelligence (AI) methods in high-resolution retinal imaging allows to identify, localize, and quantify biomarkers such as HRF. Increased HRF concentrations in the junctional zone and future macular atrophy may represent progressive migration and loss of retinal pigment epithelium. AI-based biomarker monitoring may pave the way into the era of individualized risk assessment and objective decision-making processes. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Characterization of Drusen and Hyperreflective Foci as Biomarkers for Disease Progression in Age-Related Macular Degeneration Using Artificial Intelligence in Optical Coherence Tomography

Importance

The morphologic changes and their pathognomonic distribution in progressing age-related macular degeneration (AMD) are not well understood.

Objectives

To characterize the pathognomonic distribution and time course of morphologic patterns in AMD and to quantify changes distinctive for progression to macular neovascularization (MNV) and macular atrophy (MA).

Design, Setting, and Participants

This cohort study included optical coherence tomography (OCT) volumes from study participants with early or intermediate AMD in the fellow eye in the HARBOR (A Study of Ranibizumab Administered Monthly or on an As-needed Basis in Patients With Subfoveal Neovascular Age-Related Macular Degeneration) trial. Patients underwent imaging monthly for 2 years (July 1, 2009, to August 31, 2012) following a standardized protocol. Data analysis was performed from June 1, 2018, to January 21, 2020.

Main Outcomes and Measures

To obtain topographic correspondence between patients and over time, all scans were mapped into a joint reference frame. The time of progression to MNV and MA was established, and drusen volumes and hyperreflective foci (HRF) volumes were automatically segmented in 3 dimensions using validated artificial intelligence algorithms. Topographically resolved population means of these markers were constructed by averaging quantified drusen and HRF maps in the patient subgroups.

Results

Of 1097 patients enrolled in HARBOR, 518 (mean [SD] age, 78.1 [8.2] years; 309 [59.7%] female) had early or intermediate AMD in the fellow eye at baseline. During the 24-month follow-up period, 135 (26%) eyes developed MNV, 50 eyes (10%) developed MA, and 333 (64%) eyes did not progress to advanced AMD. Drusen and HRF had distinct topographic patterns. Mean drusen thickness at the fovea was 29.6 μm (95% CI, 20.2-39.0 μm) for eyes progressing to MNV, 17.2 μm (95% CI, 9.8-24.6 μm) for eyes progressing to MA, and 17.1 μm (95% CI, 12.5-21.7 μm) for eyes without disease progression. At 0.5-mm eccentricity, mean drusen thickness was 25.8 μm (95% CI, 19.1-32.5 μm) for eyes progressing to MNV, 21.7 μm (95% CI, 14.6-28.8 μm) for eyes progressing to MA, and 14.4 μm (95% CI, 11.2-17.6 μm) for eyes without disease progression. The mean HRF thickness at the foveal center was 0.072 μm (95% CI, 0-0.152 μm) for eyes progressing to MNV, 0.059 μm (95% CI, 0-0.126 μm) for eyes progressing to MA, and 0.044 μm (95% CI, 0.007-0.081) for eyes without disease progression. At 0.5-mm eccentricity, the largest mean HRF thickness was seen in eyes progressing to MA (0.227 μm; 95% CI, 0.104-0.349 μm) followed by eyes progressing to MNV (0.161 μm; 95% CI, 0.101-0.221 μm) and eyes without disease progression (0.085 μm; 95% CI, 0.058-0.112 μm).

Conclusions and Relevance

In this study, drusen and HRF represented imaging biomarkers of disease progression in AMD, demonstrating distinct topographic patterns over time that differed between eyes progressing to MNV, eyes progressing to MA, or eyes without disease progression. Automated localization and precise quantification of these factors may help to develop reliable methods of predicting future disease progression.

Hyperreflective Foci and Specks Are Associated with Delayed Rod-Mediated Dark Adaptation in Nonneovascular Age-Related Macular Degeneration

PURPOSE

Hyperreflective foci (HRF) are OCT biomarkers for the progression of nonneovascular age-related macular degeneration (AMD) attributed to anteriorly migrated retinal pigment epithelial cells. We examined associations between rod- and cone-mediated vision and HRF plus smaller hyperreflective specks (HRS); we identified a histologic candidate for HRS.

DESIGN

Cross-sectional study and histologic survey.

PARTICIPANTS

Patients with healthy maculae (n = 34), early AMD (n = 26), and intermediate AMD (n = 41).

METHODS

AMD severity was determined by color fundus photography. In OCT scans, HRF and HRS were counted manually. Vision tests probed cones (best-corrected visual acuity [VA], contrast sensitivity), mixed cones and rods (low-luminance VA, low-luminance deficit, mesopic light sensitivity), or rods (scotopic light sensitivity, rod-mediated dark adaptation [RMDA]). An online AMD histopathologic resource was reviewed.

MAIN OUTCOME MEASURES

Vision in eyes assessed for HRF and HRS; histologic candidate for HRS.

RESULTS

In 101 eyes of 101 patients, HRF and HRS were identified in 25 and 95 eyes, respectively, with good reliability. Hyperreflective foci were present but sparse in healthy eyes, infrequent in early AMD eyes, and frequent but highly variable among intermediate AMD eyes (mean±standard deviation [SD] number per eye, 0.1 ± 0.2, 0.2 ± 0.5, and 1.9 ± 3.4 for healthy, early AMD, and intermediate AMD eyes, respectively). Hyperreflective specks outnumbered HRF in all groups (mean±SD, 4.5 ± 3.2, 6.3 ± 5.8, and 19.4 ± 22.4, respectively). Delayed RMDA was associated strongly with more HRF and HRS (P < 0.0001). Hyperreflective foci also were associated with worse low-luminance VA (P = 0.0117). Hyperreflective specks were associated with worse contrast sensitivity (P = 0.0278), low-luminance VA (P = 0.0010), low-luminance deficit (P = 0.0031), and mesopic (P = 0.0018) and scotopic (P < 0.0001) sensitivity. By histologic analysis, cone lipofuscin was found in outer retinal layers of 25% of healthy aged eyes.

CONCLUSIONS

Hyperreflective foci and HRS are markers of cellular activity associated with visual dysfunction, especially delayed RMDA, an AMD risk indicator assessing efficiency of retinoid resupply. Hyperreflective specks may represent lipofuscin translocating inwardly within cones. HRF and HRS may serve as structural end points in clinical trials targeting AMD stages earlier than atrophy expansion. These results should be confirmed in a larger sample.

Disease Progression in Patients with Autosomal Dominant Retinitis Pigmentosa due to a Mutation in Inosine Monophosphate Dehydrogenase 1 (IMPDH1)

Purpose

Mutations in the inosine monophosphate dehydrogenase 1 (IMPDH1) gene are a common cause of inherited retinal degeneration (IRD). Due to species- and tissue-dependent expression of IMPDH1, there are no appropriate models of human IMPDH1 disease. Therefore, a limited understanding remains of disease expression and rates of progression for IMPDH1-related IRD.

Methods

We evaluated semiautomated kinetic and chromatic static perimetry, spectral-domain optical coherence tomography (SD-OCT), and ultra-wide field fundus images with autofluorescence in a cohort of 12 patients (ages 11–58 at first visit). Ten patients had longitudinal data for which rates of progression were estimated.

Results

Visual acuities were relatively stable over time and the photoreceptors within the central retina remained intact. Perifoveal photoreceptor loss measured over a period of years coincided with visual fields, which were constricted and progressed over time in all patients. Rod sensitivity showed a similar pattern of defect to that of the kinetic perimetry and the autofluorescence ultra-wide field imaging. Full-field electroretinograms were severely reduced and the dark-adapted rod and mixed responses were extinguished at earlier visits than the light-adapted cone responses.

Conclusions

There was variability in disease severity at the first visit, but results show that the peripheral retina is more susceptible to the deleterious consequences of an IMPDH1 mutation. Given the pattern of degeneration and the alternatively spliced isoforms of IMPDH1, potential interventions may consider targeting the periphery early in disease, modulating transcript expression, and/or preserving central vision at late stages of the disease.

Translational Relevance

These results inform clinical prognosis and offer evidence strategies toward therapeutic intervention.

Association Between Perifoveal Drusen Burden Determined by OCT and Genetic Risk in Early and Intermediate Age-Related Macular Degeneration

Purpose

The purpose of this study was to determine associations between macular drusen parameters derived from an automatic optical coherence tomography (OCT) algorithm, nonadvanced age-related macular degeneration (AMD) stage, and genetic variants.

Methods

Eyes classified as early or intermediate AMD with OCT imaging and genetic data were selected (n = 239 eyes). Drusen area and volume measurements were estimated using the Zeiss Cirrus advanced retinal pigment epithelium analysis algorithm in a perifoveal zone centered on the fovea. Associations between drusen measurements and common genetic variants in the complement and high-density lipoprotein (HDL) lipid pathways and the ARMS2/HTRA1 variant were calculated using generalized estimating equations and linear mixed models adjusting for age, sex, smoking, body mass index, and education.

Results

Drusen area ≥ the median was independently associated with a higher number of risk alleles for CFH risk score and risk variants in C3 and ARMS2/HTRA1 compared with eyes with no measurable drusen. Similar results were obtained for drusen volume. When all genes were analyzed in the same model, only CFH score and ARMS2/HTRA1 were associated with drusen measurements. HDL pathway genes were not significantly related to drusen parameters. Nonadvanced AMD stages were associated with OCT-derived drusen area and volume.

Conclusions

Variants in CFH and ARMS2/HTRA1, commonly associated with advanced AMD, were independently associated with an increase in drusen burden determined by OCT in an allele dose dependent manner, in eyes with early and intermediate AMD. Biomarkers such as a quantitative classification of nonadvanced AMD and other OCT-derived subphenotypes could provide earlier anatomic endpoints for clinical trials and facilitate the development of new therapies for AMD.

Validation of Optical Coherence Tomography Retinal Segmentation in Neurodegenerative Disease

Purpose

This study assessed agreement between an automated spectral-domain optical coherence tomography (SD-OCT) retinal segmentation software and manually corrected segmentation to validate its use in a prospective clinical study of neurodegenerative diseases (NDD).

Methods

The sample comprised 30 subjects with NDD, including vascular cognitive impairment, frontotemporal dementia, Parkinson's disease, and Alzheimer's disease. Macular SD-OCT scans were acquired and segmented using Heidelberg Spectralis. For the central foveal B scan of each eye, eight segmentation lines were examined to determine the proportion of each line that the software erroneously delineated. Errors in four lines were manually corrected in all B scans spanning a 6-mm circle centered on the foveola. Mean volume and thickness measurements for four retinal layers (total retina, retinal nerve fiber layer [RNFL], inner retinal layers, and outer retinal layers) were obtained before and after correction.

Results

The outer plexiform layer line had one of the lowest mean error ratios (2%), while RNFL had the highest (23%). Agreement between automated software and trained observer was excellent (ICC > 0.98) for retinal thickness and volume of all layers. Mean volume differences between software and observers for the four layers ranged from −0.003 to 0.006 mm³. Mean thickness differences ranged from −1.855 to 1.859 μm.

Conclusions

Despite occasional small errors in software-generated retinal sublayer segmentation, agreement was excellent between software-derived and observer-corrected mean volume and thickness sublayer measurements.

Translational Relevance

Automated SD-OCT segmentation software generates valid measurements of retinal layer volume and thickness in NDD subjects, thereby avoiding the need to manually correct nonobvious delineation errors.

Increased serum proteins in non-exudative AMD retinas

The blood retinal barrier (BRB) closely regulates the retinal microenvironment. Its compromise leads to the accumulation of retinal fluid containing potentially harmful plasma components. While eyes with non-exudative age-related macular degeneration (AMD) were previously felt to have an intact BRB, we propose that the BRB in non-exudative AMD eyes may be subclinically compromised, allowing entry of retina-toxic plasma proteins. We test this hypothesis by measuring retinal levels of abundant plasma proteins that should not cross the intact BRB. Two cohorts of frozen, post mortem neurosensory retinas were studied by Western analysis. One cohort from Alabama had 4 normal controls and 4 eyes with various forms of AMD. Another cohort from Minnesota had 5 intermediate AMD eyes and 5 normals. Both cohorts were age/post mortem interval (PMI) matched. The non-exudative AMD retinas in the Alabama cohort had significantly higher levels of albumin and complement component 9 (C9) than normal controls. The positive control exudative AMD donor retina had higher levels of all but one serum protein. In both macular and peripheral neurosensory retina samples, intermediate AMD retinas in the Minnesota cohort had significantly higher levels of albumin, fibrinogen, IgG, and C9 than controls. Our results suggest that there may be moderate subclinical BRB leakage in non-exudative AMD. Potentially harmful plasma components including complement or iron could enter the neurosensory retina in AMD patients prior to advanced disease. Thus, therapies aiming to stabilize the BRB might have a role in the management of non-exudative AMD.

Prognostic Value of Retinal Layers in Comparison with Other Risk Factors for Conversion of Intermediate Age-related Macular Degeneration

PURPOSE

To analyze longitudinal thickness changes of retinal layers in comparison with established risk factors in eyes with age-related macular degeneration (AMD) with regard to their prognostic value for conversion into advanced AMD stages.

DESIGN

Prospective, longitudinal natural history study.

PARTICIPANTS

Ninety-one eyes of 91 patients with AMD (73.3±7.3 years; 62 female patients [50.4%]) of the Molecular Diagnostic of Age-related Macular Degeneration (MODIAMD) study without exudative or nonexudative late-stage AMD in the study eye at baseline.

METHODS

At each annual follow-up visit, all subjects underwent ophthalmic examination with assessment of best-corrected visual acuity (BCVA) and retinal imaging, including spectral-domain OCT (SD-OCT), over a study period of 6 years.

PURPOSE

To analyze longitudinal thickness changes of retinal layers in comparison with established risk factors in eyes with age-related macular degeneration (AMD) with regard to their prognostic value for conversion into advanced AMD stages.

MAIN OUTCOME MEASURES

Qualitative structural AMD features and SD-OCT-based quantitative thickness changes of different retinal layers, such as the retinal pigment epithelium-drusen complex (RPEDC), were assessed by multimodal imaging. Their prognostic relevance regarding disease conversion was determined using Cox regression (cloglog link function).

RESULTS

In the multivariable analysis, the presence of focal hyperpigmentation, almost reaching statistical significance, showed the strongest effect regarding the development of nonexudative late-stage AMD (hazard ratio [HR], 5.88; 95% confidence interval [CI], 0.69-50.2; P = 0.052) followed by the presence of refractile drusen (HR, 4.82; 95% CI, 1.33-17.44; P = 0.0164). A thickening of the RPEDC was the only assessed retinal layer that exhibited a significant effect on the development of nonexudative advanced AMD (HR, 1.03; 95% CI, 1.0-1.07; P = 0.0393), whereas no association was observable for the other retinal layers. Neither qualitative nor quantitative markers were significant predictors for the development of exudative late-stage AMD (P > 0.05).

CONCLUSIONS

The results indicate that the development of both exudative and nonexudative AMD is associated with distinct prognostic features. However, compared with the assessment of qualitative AMD features, the quantification of retinal layers on average across the central retina had less prognostic impact. Further studies are needed to identify and validate robust biomarkers in early AMD stages.

Automated Quantification of Hyperreflective Foci in SD-OCT With Diabetic Retinopathy

The presence of hyperreflective foci (HFs) is related to retinal disease progression, and the quantity has proven to be a prognostic factor of visual and anatomical outcome in various retinal diseases. However, lack of efficient quantitative tools for evaluating the HFs has deprived ophthalmologist of assessing the volume of HFs. For this reason, we propose an automated quantification algorithm to segment and quantify HFs in spectral domain optical coherence tomography (SD-OCT). The proposed algorithm consists of two parallel processes namely: region of interest (ROI) generation and HFs estimation. To generate the ROI, we use morphological reconstruction to obtain the reconstructed image and histogram constructed for data distributions and clustering. In parallel, we estimate the HFs by extracting the extremal regions from the connected regions obtained from a component tree. Finally, both the ROI and the HFs estimation process are merged to obtain the segmented HFs. The proposed algorithm was tested on 40 3D SD-OCT volumes from 40 patients diagnosed with non-proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR), and diabetic macular edema (DME). The average dice similarity coefficient (DSC) and correlation coefficient (r) are 69.70%, 0.99 for NPDR, 70.31%, 0.99 for PDR, and 71.30%, 0.99 for DME, respectively. The proposed algorithm can provide ophthalmologist with good HFs quantitative information, such as volume, size, and location of the HFs.

Macular Atrophy of the Retinal Pigment Epithelium in Patients with Neovascular Age-Related Macular Degeneration: What is the Link? Part I: A Review of Disease Characterization and Morphological Associations

Introduction

The purpose of this review was to explore the potential link between macular atrophy (MA) of the retinal pigment epithelium in patients with neovascular age-related macular degeneration (nAMD) with the disease characteristics and morphological features.

Methods

To this end, we performed a search of peer-reviewed articles published on the PubMed database and included all relevant papers. We then examined these papers for possible risk factors for MA development in the context of nAMD treated with anti-vascular endothelial growth factor drugs, as well as possible protective factors.

Results

Our review of the relevant publications revealed that areas of MA can be directly visualized through multiple imaging modalities. Associations have been identified between MA of the retinal pigment epithelium and choroidal neovascular membrane characteristics, intra- and subretinal fluid, pigment epithelial detachment, choroidal thickness, subretinal hyperreflective material, outer retinal tubulations, hemorrhage, subretinal drusenoid deposits, refractile drusen, hyperreflective foci, retinal angiomatous proliferation, polypoidal choroidal vasculopathy, geographic atrophy in the fellow eye, genetic factors, and age.

Conclusion

The findings of this review indicate that a multimodal approach is recommended for the assessment of MA. The conclusions drawn to date on the correlation between MA development or progression of MA and specific risk factors and possible protective factors are mixed. More clinical research is needed to reach a better understanding of this association.

Vascular Response to Sildenafil Citrate in Aging and Age-Related Macular Degeneration

Age-related macular degeneration (AMD) - the leading cause of vision loss in the elderly - share many risks factors as atherosclerosis, which exhibits loss of vascular compliance resulting from aging and oxidative stress. Here, we attempt to explore choroidal and retinal vascular compliance in patients with AMD by evaluating dynamic vascular changes using live ocular imaging following treatment with oral sildenafil citrate, a phosphodiesterase type 5 (PDE5) inhibitor and potent vasodilator. Enhanced-depth imaging optical coherence tomography (EDI-OCT) and OCT angiography (OCT-A) were performed on 46 eyes of 23 subjects, including 15 patients with non-exudative AMD in one eye and exudative AMD in the fellow eye, and 8 age-matched control subjects. Choroidal thickness, choroidal vascularity, and retinal vessel density were measured across the central macula at 1 and 3 hours after a 100 mg oral dose of sildenafil citrate. Baseline choroidal thickness was 172.1 ± 60.0 μm in non-exudative AMD eyes, 196.4 ± 89.8 μm in exudative AMD eyes, and 207.4 ± 77.7 μm in control eyes, with no difference between the 3 groups (P = 0.116). After sildenafil, choroidal thickness increased by 6.0% to 9.0% at 1 and 3 hours in all groups (P = 0.001-0.014). Eyes from older subjects were associated with choroidal thinning at baseline (P = 0.005) and showed less choroidal expansion at 1 hour and 3 hours after sildenafil (P = 0.001) regardless of AMD status (P = 0.666). The choroidal thickening appeared to be primarily attributed to expansion of the stroma rather than luminal component. Retinal vascular density remained unchanged after sildenafil in all 3 groups (P = 0.281-0.587). Together, our studies suggest that vascular response of the choroid to sildenafil decreases with age, but is not affected by the presence of non-exudative or exudative AMD, providing insight into changes in vessel compliance in aging and AMD.

Microglia in the Retina: Roles in Development, Maturity, and Disease

Microglia, the primary resident immune cell type, constitute a key population of glia in the retina. Recent evidence indicates that microglia play significant functional roles in the retina at different life stages. During development, retinal microglia regulate neuronal survival by exerting trophic influences and influencing programmed cell death. During adulthood, ramified microglia in the plexiform layers interact closely with synapses to maintain synaptic structure and function that underlie the retina's electrophysiological response to light. Under pathological conditions, retinal microglia participate in potentiating neurodegeneration in diseases such as glaucoma, retinitis pigmentosa, and age-related neurodegeneration by producing proinflammatory neurotoxic cytokines and removing living neurons via phagocytosis. Modulation of pathogenic microglial activation states and effector mechanisms has been linked to neuroprotection in animal models of retinal diseases. These findings have led to the design of early proof-of-concept clinical trials with microglial modulation as a therapeutic strategy.

Retinal Neuroprotection: Overcoming the Translational Roadblocks

PURPOSE

To elucidate the issues that have prevented successful translation of neuroprotective therapeutic modalities for retinal disease from the preclinical to the clinical realm and to suggest strategies to circumvent these barriers in order to develop novel treatments to prevent vision loss.

DESIGN

Interpretive essay.

METHODS

Review and synthesis of selected reports of neuroprotective approaches for retinal disease, with interpretation and perspective.

RESULTS

Retinal neuroprotection is defined as any measure that reduces the death of retinal cells or axonal extensions into the optic nerve, and there is a great unmet need for such therapeutic modalities. Despite encouraging preclinical data, the translation of neuroprotective therapies to the clinic has been fraught with failure. Fundamental issues that have plagued this transition include the animal models used in preclinical studies, the reproducibility of the preclinical data, and the choice of meaningful clinical trial endpoints. Developing animal models that more aptly mimic human disease, defining a set of guidelines for preclinical evaluation of neuroprotective therapies in retinal disease, and identifying and validating biomarkers as surrogate clinical endpoints that shorten and optimize drug development timelines may circumvent some of these barriers to translation.

CONCLUSIONS

Neuroprotective therapeutic approaches have the potential to prevent vision loss in millions of people affected with eye diseases worldwide. However, a stigma currently accompanies the concept of neuroprotection because of the many past failures to bridge the gap between the preclinical and clinical realms. Understanding and addressing the fundamental reasons for the failure of translatable research provides hope for the future development of neuroprotective therapies.

Progression of Geographic Atrophy in Age-related Macular Degeneration: AREDS2 Report Number 16

PURPOSE

To analyze the prevalence, incidence, and clinical characteristics of eyes with geographic atrophy (GA) in age-related macular degeneration (AMD), including clinical and genetic factors affecting enlargement.

DESIGN

Prospective cohort study within a controlled clinical trial.

PARTICIPANTS

Age-Related Eye Disease Study 2 (AREDS2) participants, aged 50-85 years.

METHODS

Baseline and annual stereoscopic color fundus photographs were evaluated for GA presence and area. Analyses included GA prevalence and incidence rates, Kaplan-Meier rates, mixed-model regression, and multivariable analysis of the square root of GA, area adjusted for covariates, including clinical/imaging characteristics and genotype.

MAIN OUTCOME MEASURES

(1) Presence or development of GA; (2) change in the square root of GA area over time.

RESULTS

At baseline, 517 eyes (6.2%) of 411 participants (9.8%) had pre-existing GA (without neovascular AMD), with the following characteristics: 33% central, 67% noncentral; and the following configurations: 36% small, 26% solid/unifocal, 24% multifocal, 9% horseshoe/ring, and 6% indeterminate. Of the remaining 6530 eyes at risk, 1099 eyes (17.3%) of 883 participants developed incident GA without prior neovascular disease during mean follow-up of 4.4 years. The Kaplan-Meier rate of incident GA was 19% of eyes at 5 years. In eyes with incident GA, 4-year risk of subsequent neovascular AMD was 29%. In eyes with incident noncentral GA, 4-year risk of central involvement was 57%. GA enlargement rate (following square root transformation) was similar in eyes with pre-existing GA (0.29 mm/year; 95% confidence interval 0.27-0.30) and incident GA (0.28 mm/year; 0.27-0.30). In the combined group, GA enlargement was significantly faster with noncentrality, multifocality, intermediate baseline size, and bilateral GA (P < 0.0001 for interaction in each case) but not with AREDS2 treatment assignment (P = 0.33) or smoking status (P = 0.05). Enlargement was significantly faster with ARMS2 risk (P < 0.0001), C3 non-risk (P = 0.0002), and APOE non-risk (P = 0.001) genotypes.

CONCLUSIONS

Analyses of AREDS2 data on natural history of GA provide representative data on GA evolution and enlargement. GA enlargement, which was influenced by lesion features, was relentless, resulting in rapid central vision loss. The genetic variants associated with faster enlargement were partially distinct from those associated with risk of incident GA. These findings are relevant to further investigations of GA pathogenesis and clinical trial planning.