Drusen and RPE atrophy automated quantification by optical coherence tomography in an elderly population

Six-year incidence of age-related macular degeneration and correlation to OCT-derived drusen volume measurements in a Chinese population

AIMS

To report the 6-year incidence of optical coherence tomography (OCT)-derived age-related changes in drusen volume and related systemic and ocular associations.

METHODS

Chinese adults aged 40 years and older were assessed at baseline and 6 years with colour fundus photography (CFP) and spectral domain (SD) OCT. CFPs were graded for age-related macular degeneration (AMD) features and drusen volume was generated using commercially available automated software.

RESULTS

A total of 4172 eyes of 2580 participants (mean age 58.12±9.03 years; 51.12% women) had baseline and 6-year follow-up CFP for grading, of these, 2130 eyes of 1305 participants had gradable SD-OCT images, available for analysis. Based on CFP grading, 136 (3.39%) participants developed incident early AMD and 10 (0.25%) late AMD. Concurrently, retinal pigment epithelial-Bruch's membrane (RPE-BrC) volumes decreased, remained stable and increased in 6.8%, 78.5% and 14.7%, respectively, over 6 years. In eyes where RPE-BrC volumes were >0 mm³ at baseline, this was associated with two-fold higher prevalence rate of any AMD at baseline (p<0.001). Multivariable analysis showed that when compared with eyes where RPE-BrC volume was unchanged, volume decrease was significantly associated with older age (OR=1.30; p<0.001), smoking (OR=2.21; p=0.001) and chronic kidney disease (OR=3.4, p=0.008), while increase was associated with older age (OR=1.36; p<0.001) and hypertension (OR=1.43; p=0.016).

CONCLUSION

AMD incidence detected at 6 years on CFP and correlated OCT-derived drusen volume measurement change is low. Older age and some systemic risk factors are associated with drusen volume change, and our data provide new insights into relationship between systemic risk factors and outer retinal morphology in Asian eyes.

Retinal Progression Biomarkers of Early and Intermediate Age-Related Macular Degeneration

Early and intermediate AMD patients represent a heterogeneous population with an important but variable risk of progression to more advanced stages of the disease. The five-year progression from early and intermediate AMD to late disease is known to range from 0.4% to 53%. This wide variation explains the particular interest in searching predictive AMD biomarkers. Clinical parameters such as drusen size, presence of pigmentary abnormalities, and fellow eye status were, traditionally, the more important predictive elements. Multimodal retinal assessment (Color Fundus Photography, Optical Coherence Tomography, Optical Coherence Angiography and Fundus Autofluorescence) is providing new and accurate image biomarkers, useful in research and in daily practice. If individual progression risk could be anticipated, then management plans should be adapted accordingly, considering follow-up intervals and therapeutic interventions. Here, we reviewed the most important image progression biomarkers of early and intermediate AMD with relevant interest in clinical practice.

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.

Cell-specific expression of ENACα gene by FOXA1 in the glucocorticoid receptor pathway

Introduction:

The glucocorticoid receptor (GR) is one of the most widely studied ligand-dependent nuclear receptors. The combination of transcriptional regulatory factors required for the expression of individual genes targeted by GR varies across cell types; however, the mechanisms underlying this cell type–specific regulation of gene expression are not yet clear.

Methods:

Here, we investigated genes regulated by GR in two different cell lines, A549 and ARPE-19, and examined how gene expression varied according to the effect of pioneer factors using RNA-seq and RT-qPCR.

Results:

Our RNA-seq results identified 19 and 63 genes regulated by GR that are ARPE-19-specific and A549-specific, respectively, suggesting that GR induces the expression of different sets of genes in a cell type–specific manner. RT-qPCR confirmed that the epithelial sodium channel (ENACα) gene is an ARPE-19 cell-specific GR target gene, whereas the FK506 binding protein 5 (FKBP5) gene was A549 cell-specific. There was a significant decrease in ENACα expression in FOXA1-deficient ARPE-19 cells, suggesting that FOXA1 might function as a pioneer factor enabling the selective expression of ENACα in ARPE-19 cells but not in A549 cells.

Conclusion:

These findings indicate that ENACα expression in ARPE-19 cells is regulated by FOXA1 and provide insights into the molecular mechanisms of cell type–specific expression of GR-regulated genes.

AMISH EYE STUDY: Baseline Spectral Domain Optical Coherence Tomography Characteristics of Age-Related Macular Degeneration

PURPOSE

To describe spectral domain optical coherence tomography (SD-OCT) findings in an Amish cohort to assess SD-OCT markers for early age-related macular degeneration (AMD).

METHODS

The authors performed a family-based prospective cohort study of 1,146 elderly Amish subjects (age range 50-99 years) (2,292 eyes) who had a family history of at least 1 individual with AMD. All subjects underwent complete ophthalmic examinations, SD-OCT using both Cirrus and Spectralis (20 × 20° scan area) instruments, fundus autofluorescence, infrared imaging, and color fundus photography. Spectral domain optical coherence tomography characteristics were analyzed in subjects with AMD (with and without subretinal drusenoid deposits [SDDs]) and normal healthy cohorts.

RESULTS

Participants' mean age was 65.2 years (SD ± 11). Color fundus photographic findings in 596 (53%) subjects (1,009 eyes) were consistent with AMD; the remaining 478 (43%) subjects showed no signs of AMD. The choroid was significantly thinner on OCT (242 ± 76 µm, P < 0.001) in those with AMD compared with those without (263 ± 63 µm). Subretinal drusenoid deposits were found in 143 eyes (7%); 11 of the 143 eyes (8%) had no other manifestations of AMD. Drusen volume (P < 0.001) and area of geographic atrophy (P < 0.001) were significantly greater, and choroid was significantly (P < 0.001) thinner in subjects with SDDs versus those without SDDs.

CONCLUSION

The authors describe spectral domain optical coherence tomography characteristics in an elderly Amish population with and without AMD, including the frequency of SDD. Although relatively uncommon in this population, the authors confirmed that SDDs can be found in the absence of other features of AMD and that eyes with SDDs have thinner choroids.

Comparison of Drusen Volume Assessed by Two Different OCT Devices

To compare drusen volume between Heidelberg Spectral Domain (SD-) and Zeiss Swept-Source (SS) PlexElite Optical Coherence Tomography (OCT) determined by manual and automated segmentation methods. Thirty-two eyes of 24 patients with Age-Related Macular Degeneration (AMD) and drusen maculopathy were included. In the central 1 and 3 mm ETDRS circle drusen volumes were calculated and compared. Drusen segmentation was performed using automated manufacturer algorithms of the two OCT devices. Then, the automated segmentation was manually corrected and compared and finally analyzed using customized software. Though on SD-OCT, there was a significant difference of mean drusen volume prior to and after manual correction (mean difference: 0.0188 ± 0.0269 mm³, p < 0.001, corr. p < 0.001, correlation of r = 0.90), there was no difference found on SS-OCT (mean difference: 0.0001 ± 0.0003 mm³, p = 0.262, corr. p = 0.524, r = 1.0). Heidelberg-acquired mean drusen volume after manual correction was significantly different from Zeiss-acquired drusen volume after manual correction (mean difference: 0.1231 ± 0.0371 mm³, p < 0.001, corr. p < 0.001, r = 0.68). Using customized software, the difference of measurements between both devices decreased and correlation among the measurements improved (mean difference: 0.0547 ± 0.0744 mm³, p = 0.02, corr. p = 0.08, r = 0.937). Heidelberg SD-OCT, the Zeiss PlexElite SS-OCT, and customized software all measured significantly different drusen volumes. Therefore, devices/algorithms may not be interchangeable. Third-party customized software helps to minimize differences, which may allow a pooling of data of different devices, e.g., in multicenter trials.

Correlation of Color Fundus Photograph Grading with Risks of Early Age-related Macular Degeneration by using Automated OCT-derived Drusen Measurements

We evaluated automated OCT-derived drusen volume measures in a population-based study (n = 4,512) aged ≥40 years, and its correlation with conventional color fundus photographs (CFP)-derived early AMD features. Participants had protocol-based assessment to capture medical and ocular history, genotyping for SNPs in CFH, ARMS2, and CETP, CFP-based AMD grading and automated drusen volume based on SD-OCT using built-in software (Cirrus OCT advanced RPE analysis software). Significantly fewer eyes with early AMD features (drusen, hyperpigmentation, soft or reticular drusen) had drusen volume = 0 mm³ (p < 0.001). In eyes with drusen volume > 0 mm³, increasing AMD severity was associated with increase in drusen volume (correlation coefficient 0.17, p < 0.001). However 220 (59.14%) of 372 participants with AMD based on CFP grading had drusen volume = 0 mm³. Factors associated with drusen volume included age (OR 1.42 per 5 years, 95% confidence interval [CI] 2.76, 4.48), systolic blood pressure (OR1.00, 95% CI 1.00, 1.01), ethnic Malay (OR 1.54, 95% CI 1.29, 1.83) and Chinese (OR 1.66, 95% CI 1.37, 2.01) compared to Indian. The ARMS2 rs10490924 T allele was associated with increased drusen volume in subjects with AMD (multivariable adjusted OR1.54, 95% CI 1.08, 2.19). Automated OCT-derived drusen volume is correlated with CFP-based AMD grading in many, but not all subjects. However the agreement is not good. These two modalities provide complementary information and should be incorporated into future studies.

Automated segmentation of mouse OCT volumes (ASiMOV): Validation & clinical study of a light damage model

The use of spectral-domain optical coherence tomography (SD-OCT) is becoming commonplace for the in vivo longitudinal study of murine models of ophthalmic disease. Longitudinal studies, however, generate large quantities of data, the manual analysis of which is very challenging due to the time-consuming nature of generating delineations. Thus, it is of importance that automated algorithms be developed to facilitate accurate and timely analysis of these large datasets. Furthermore, as the models target a variety of diseases, the associated structural changes can also be extremely disparate. For instance, in the light damage (LD) model, which is frequently used to study photoreceptor degeneration, the outer retina appears dramatically different from the normal retina. To address these concerns, we have developed a flexible graph-based algorithm for the automated segmentation of mouse OCT volumes (ASiMOV). This approach incorporates a machine-learning component that can be easily trained for different disease models. To validate ASiMOV, the automated results were compared to manual delineations obtained from three raters on healthy and BALB/cJ mice post LD. It was also used to study a longitudinal LD model, where five control and five LD mice were imaged at four timepoints post LD. The total retinal thickness and the outer retina (comprising the outer nuclear layer, and inner and outer segments of the photoreceptors) were unchanged the day after the LD, but subsequently thinned significantly (p < 0.01). The retinal nerve fiber-ganglion cell complex and the inner plexiform layers, however, remained unchanged for the duration of the study.

Algorithms for the Automated Analysis of Age-Related Macular Degeneration Biomarkers on Optical Coherence Tomography: A Systematic Review

PURPOSE

To assess the quality of optical coherence tomography (OCT) grading algorithms for retinal biomarkers of age-related macular degeneration (AMD).

METHODS

Following a systematic review of the literature data on detection and quantification of AMD retinal biomarkers by available algorithms were extracted and descriptively synthesized. Algorithm quality was assessed using a modified version of the Quality Assessment of Diagnostic Accuracy Studies 2 checklist with a focus on accuracy against established reference standards and risk of bias.

RESULTS

Thirty five studies reporting computer-aided diagnosis (CAD) tools for qualitative analysis or algorithms for quantitative analysis were identified. Compared with manual assessment in reference standards correlation coefficients ranged from 0.54 to 0.97 for drusen, 0.80 to 0.98 for geographic atrophy (GA), and 0.30 to 0.98 for intra- or subretinal fluid and pigment epithelial detachment (PED) detection by automated algorithms. CAD tools achieved area under the curve (AUC) values of 0.94 to 0.99, sensitivity of 0.90 to 1.00, and specificity of 0.89 to 0.92.

CONCLUSIONS

Automated analysis of AMD biomarkers on OCT is promising. However, most of the algorithm validation was performed in preselected patients, exhibiting the targeted biomarker only. In addition, type and quality of reported algorithm validation varied substantially.

TRANSLATIONAL RELEVANCE

The development of algorithms for combined, simultaneous analysis of multiple AMD biomarkers including AMD staging and the agreement on standardized validation procedures would be of considerable translational value for the clinician and the clinical researcher.

En Face Optical Coherence Tomography Imaging for the Detection of Nascent Geographic Atrophy

PURPOSE

To determine if en face optical coherence tomography (OCT) imaging can identify nascent geographic atrophy (nGA) in eyes with intermediate age-related macular degeneration (iAMD).

DESIGN

Retrospective observational case series.

METHODS

Patients with iAMD from the COMPLETE study at the Bascom Palmer Eye Institute were evaluated to determine if nGA was present at baseline and at follow-up using high-density Spectralis OCT B-scans and en face OCT images from the Cirrus OCT instrument. If available, additional en face OCT images and B-scans were analyzed at follow-up times beyond the 52-week period.

RESULTS

A total of 37 eyes (27 patients) were evaluated for at least 1 year using both B-scans and en face images. Two drusen suspicious for nGA at baseline were identified, but neither druse developed GA after 24 and 62 months of follow-up, respectively. Another druse displayed hypertransmission into the choroid at week 52 on B-scan imaging and was classified as nGA. En face OCT imaging identified this druse as a focal bright area. Drusen breakdown occurred during a follow-up of 39 months.

CONCLUSIONS

En face OCT imaging appeared to be as useful as routine B-scan imaging for identifying areas suspicious for nGA in this population from the COMPLETE Study. Additional longitudinal follow-up of eyes with drusen is needed to determine if en face OCT imaging can replace the evaluation of individual B-scans for the detection of nGA.

Genetic Association Analysis of Drusen Progression

PURPOSE

Age-related macular degeneration is a common form of vision loss affecting older adults. The etiology of AMD is multifactorial and is influenced by environmental and genetic risk factors. In this study, we examine how 19 common risk variants contribute to drusen progression, a hallmark of AMD pathogenesis.

METHODS

Exome chip data was made available through the International AMD Genomics Consortium (IAMDGC). Drusen quantification was carried out with color fundus photographs using an automated drusen detection and quantification algorithm. A genetic risk score (GRS) was calculated per subject by summing risk allele counts at 19 common genetic risk variants weighted by their respective effect sizes. Pathway analysis of drusen progression was carried out with the software package Pathway Analysis by Randomization Incorporating Structure.

RESULTS

We observed significant correlation with drusen baseline area and the GRS in the age-related eye disease study (AREDS) dataset (ρ = 0.175, P = 0.006). Measures of association were not statistically significant between drusen progression and the GRS (P = 0.54). Pathway analysis revealed the cell adhesion molecules pathway as the most highly significant pathway associated with drusen progression (corrected P = 0.02).

CONCLUSIONS

In this study, we explored the potential influence of known common AMD genetic risk factors on drusen progression. Our results from the GRS analysis showed association of increasing genetic burden (from 19 AMD associated loci) to baseline drusen load but not drusen progression in the AREDS dataset while pathway analysis suggests additional genetic contributors to AMD risk.

Drusen Volume and Retinal Pigment Epithelium Abnormal Thinning Volume Predict 2-Year Progression of Age-Related Macular Degeneration

PURPOSE

To analyze the value of novel measures of retinal pigment epithelium-drusen complex (RPEDC) volume to predict 2-year disease progression of intermediate age-related macular degeneration (AMD).

DESIGN

Prospective, observational study.

PARTICIPANTS

Three hundred forty-five AMD and 122 non-AMD participants enrolled in the Age Related Eye Disease Study 2 Ancillary Spectral-Domain (SD) Optical Coherence Tomography (OCT) study.

METHODS

High-density SD OCT macular volumes were obtained at yearly study visits. The RPEDC abnormal thickening (henceforth, OCT drusen) and RPEDC abnormal thinning (RAT) volumes were generated by semiautomated segmentation of total RPEDC within a 5-mm-diameter macular field.

MAIN OUTCOME MEASURES

Volume change and odds ratio (OR) with 95% confidence intervals (CI) for progression to advanced AMD with choroidal neovascularization (CNV) or central geographic atrophy (GA).

RESULTS

Complete volumes were obtained in 265 and 266 AMD eyes and in 115 and 97 control eyes at baseline and at year 2, respectively. In AMD eyes, mean (standard deviation) OCT drusen volume increased from 0.08 mm(3) (0.16 mm(3)) to 0.10 mm(3) (0.23 mm(3); P < 0.001), and RAT volume increased from 8.3 × 10(-4) mm(3) (20.8 × 10(-4) mm(3)) to 18.4 × 10(-4) mm(3) (46.6 × 10(-4) mm(3); P < 0.001). Greater baseline OCT drusen volume was associated with 2-year progression to CNV (P = 0.002). Odds of developing CNV increased by 31% for every 0.1-mm(3) increase in baseline OCT drusen volume (OR, 1.31; 95% CI, 1.06-1.63; P = 0.013). Greater baseline RAT volume was associated with significant 2-year increase in RAT volume (P < 0.001), noncentral GA (P < 0.001), and progression to central GA (P < 0.001). Odds of developing central GA increased by 32% for every 0.001-mm(3) increase in baseline RAT volume (OR, 1.32; 95% CI, 1.14-1.53; P < 0.001). In non-AMD eyes, all volumes were significantly lower than AMD eyes and showed no significant 2-year change.

CONCLUSIONS

Macular OCT drusen and RAT volumes increased significantly in AMD eyes over 2 years. These quantitative SD OCT biomarkers predict 2-year AMD progression and may serve as useful biomarkers for future clinical trials.

Association of OCT derived drusen measurements with AMD associated-genotypic SNPs in Amish population

Purpose: To investigate the association of optical coherence tomography (OCT)-derived drusen measures in Amish age-related macular degeneration (AMD) patients with known loci for macular degeneration. Methods: Members of the Old Order Amish community in Pennsylvania ages 50 and older were assessed for drusen area, volume and regions of retinal pigment epithelium (RPE) atrophy using a Cirrus High-Definition OCT. Measurements were obtained in the macula region within a central circle (CC) of 3 mm in diameter and a surrounding perifoveal ring (PR) of 3 to 5 mm in diameter using the Cirrus OCT RPE analysis software. Other demographic information, including age, gender and smoking status, were collected. Study subjects were further genotyped to determine their risk for the AMD-associated SNPs in the SYN3, LIPC, ARMS2, C3, CFB, CETP, CFI and CFH genes using TaqMan genotyping assays. The association of genotypes with OCT measures were assessed using linear trend p-values calculated from univariate and multivariate generalized linear models. Results: 432 eyes were included in the analysis. Multivariate analysis (adjusted by age, gender and smoking status) confirmed the known significant association between AMD and macular drusen with the number of CFH risk alleles for the drusen area (the area increased 0.12 mm² for a risk allele increase, p < 0.01), drusen volume (the volume increased 0.01 mm³ for a risk allele increase, p ≤ 0.05) and the area of RPE atrophy (the area increased 0.43 mm² for a risk allele increase, p = 0.003). SYN3 risk allele G is significantly associated with larger area PR (the area increased 0.09 mm² for a risk allele increase, p = 0.03) and larger drusen volume in the central circle (the volume increased 0.01 mm³ for a risk allele increase, p = 0.04). Conclusion: Among the genotyped SNPs tested, the CFH risk genotype appears to play a major role in determining the drusen phenotype in the Amish AMD population.