Geographic Atrophy in Age-Related Macular Degeneration: A Tale of Two Stages

An overview of retinal light damage models for preclinical studies on age-related macular degeneration: identifying molecular hallmarks and therapeutic targets

Age-related macular degeneration (AMD) is a complex, multifactorial disease leading to progressive and irreversible retinal degeneration, whose pathogenesis has not been fully elucidated yet. Due to the complexity and to the multiple features of the disease, many efforts have been made to develop animal models which faithfully reproduce the overall AMD hallmarks or that are able to mimic the different AMD stages. In this context, light damage (LD) rodent models of AMD represent a suitable and reliable approach to mimic the different AMD forms (dry, wet and geographic atrophy) while maintaining the time-dependent progression of the disease. In this review, we comprehensively reported how the LD paradigms reproduce the main features of human AMD. We discuss the capability of these models to broaden the knowledge in AMD research, with a focus on the mechanisms and the molecular hallmarks underlying the pathogenesis of the disease. We also critically revise the remaining challenges and future directions for the use of LD models.

An Updated Simplified Severity Scale for Age-Related Macular Degeneration Incorporating Reticular Pseudodrusen: Age-Related Eye Disease Study Report Number 42

PURPOSE

To update the Age-Related Eye Disease Study (AREDS) simplified severity scale for risk of late age-related macular degeneration (AMD), including incorporation of reticular pseudodrusen (RPD), and to perform external validation on the Age-Related Eye Disease Study 2 (AREDS2).

DESIGN

Post hoc analysis of 2 clinical trial cohorts: AREDS and AREDS2.

PARTICIPANTS

Participants with no late AMD in either eye at baseline in AREDS (n = 2719) and AREDS2 (n = 1472).

METHODS

Five-year rates of progression to late AMD were calculated according to levels 0 to 4 on the simplified severity scale after 2 updates: (1) noncentral geographic atrophy (GA) considered part of the outcome, rather than a risk feature, and (2) scale separation according to RPD status (determined by validated deep learning grading of color fundus photographs).

MAIN OUTCOME MEASURES

Five-year rate of progression to late AMD (defined as neovascular AMD or any GA).

RESULTS

In the AREDS, after the first scale update, the 5-year rates of progression to late AMD for levels 0 to 4 were 0.3%, 4.5%, 12.9%, 32.2%, and 55.6%, respectively. As the final simplified severity scale, the 5-year progression rates for levels 0 to 4 were 0.3%, 4.3%, 11.6%, 26.7%, and 50.0%, respectively, for participants without RPD at baseline and 2.8%, 8.0%, 29.0%, 58.7%, and 72.2%, respectively, for participants with RPD at baseline. In external validation on the AREDS2, for levels 2 to 4, the progression rates were similar: 15.0%, 27.7%, and 45.7% (RPD absent) and 26.2%, 46.0%, and 73.0% (RPD present), respectively.

CONCLUSIONS

The AREDS AMD simplified severity scale has been modernized with 2 important updates. The new scale for individuals without RPD has 5-year progression rates of approximately 0.5%, 4%, 12%, 25%, and 50%, such that the rates on the original scale remain accurate. The new scale for individuals with RPD has 5-year progression rates of approximately 3%, 8%, 30%, 60%, and 70%, that is, approximately double for most levels. This scale fits updated definitions of late AMD, has increased prognostic accuracy, seems generalizable to similar populations, but remains simple for broad risk categorization.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Expert Consensus on Geographic Atrophy in the EU: A Call for Urgent Policy Action

Geographic atrophy is an eye disease that greatly interferes with the daily lives of patients and their families, posing a serious threat to the aging European demographic. Over the past 30 months, this initiative has assembled leading experts in the field of ophthalmology to share insights on the necessary policy steps that need to be taken to overcome this challenge on an EU-wide scale. Through analyzing best practices in Germany, Italy, France, and Spain, this consensus paper sets out a series of policy recommendations, which, if implemented, could greatly benefit all individuals affected by geographic atrophy. Amongst other features, these countries have provided valuable examples of awareness campaigns and an overall commitment to inclusive and comprehensive policies. The policy recommendations emerging from this paper include the adoption of comprehensive screening programs, retinal disease screening in the EU Driving License Directive, the development of a white paper at the European Commission, and the creation of Council recommendations on eye health screening. Given the significant improvements made at the national level throughout the EU, countries will require unitary support at the European level to further develop their policies and successfully address the burden of geographic atrophy.

Critical Dependence on Area in Relationship between ARMS2/HTRA1 Genotype and Faster Geographic Atrophy Enlargement: Age-Related Eye Disease Study 2 Report Number 33

PURPOSE

To analyze ARMS2/HTRA1 as a risk factor for faster geographic atrophy (GA) enlargement according to (1) GA area and (2) contiguous enlargement versus progression to multifocality.

DESIGN

Age-Related Eye Disease Study 2 (AREDS2) cohort analysis.

PARTICIPANTS

Eyes with GA: 546 eyes of 406 participants.

METHODS

Geographic atrophy area was measured from color fundus photographs at annual visits. Mixed-model regression of square root of GA area and proportional hazards regression of progression to multifocality were analyzed by ARMS2 genotype.

MAIN OUTCOME MEASURES

Change in square root GA area and progression to multifocality.

RESULTS

Geographic atrophy enlargement was significantly faster with ARMS2 risk alleles (P < 0.0001) at 0.224 mm/year (95% CI, 0.195-0.252 mm/year), 0.298 mm/year (95% CI, 0.271-0.324 mm/year), and 0.317 mm/year (95% CI, 0.279-0.355 mm/year), for 0 to 2 risk alleles, respectively. However, a significant interaction (P = 0.011) was observed between genotype and baseline area. In eyes with very small area (< 1.9 mm2), enlargement was significantly faster with ARMS2 risk alleles (P < 0.0001) at 0.193 mm/year (95% CI, 0.162-0.225 mm/year) versus 0.304 mm/year (95% CI, 0.280-0.329 mm/year) for 0 versus 1 to 2 risk alleles, respectively. With moderately small (1.9-3.8 mm2) or medium to large (≥ 3.8 mm2) area, enlargement was not significantly faster with ARMS2 risk alleles (P = 0.66 and P = 0.70, respectively). In nonmultifocal GA, enlargement was significantly faster with ARMS2 risk alleles (P = 0.001) at 0.175 mm/year (95% CI, 0.142-0.209 mm/year), 0.226 mm/year (95% CI, 0.193-0.259 mm/year), and 0.287 mm/year (95% CI, 0.237-0.337 mm/year) with 0 to 2 risk alleles, respectively. ARMS2 genotype was not associated significantly with progression to multifocal GA.

CONCLUSIONS

The relationship between ARMS2/HTRA1 genotype and faster GA enlargement depends critically on GA area: risk alleles represent a strong risk factor for faster enlargement only in eyes with very small area. They increase the growth rate more through contiguous enlargement than progression to multifocality. ARMS2/HTRA1 genotype is more important in increasing risk of progression to GA and initial GA enlargement (contiguously) than in subsequent enlargement or progression to multifocality. These findings may explain some discrepancies between previous studies and have implications for both research and clinical practice.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Genetic and molecular biomarkers for geographic atrophy

Geographic atrophy (GA) is characterized by atrophy of the retina, retinal pigment epithelium and choriocapillaris, causing a gradual loss of vision over time. Treatment options to prevent initiation or progression of GA are limited; two recently FDA-approved inhibitors of the complement system (pegcetacoplan, avacincaptad pegol) showed a modest decrease in GA lesion growth in phase 3 clinical trials. Exploration of genetic and molecular biomarkers in GA plays a critical role in our battle against this blinding disease to improve early disease detection, to find more effective therapies, and to provide personalized care to patients. In this review, we provide a comprehensive overview of the current literature investigating genetic and molecular biomarkers for GA. Genetic studies identified multiple genes and variants that play a role in progression to GA and GA lesion growth, involving pathways such as complement activation, extracellular matrix interaction and lipid metabolism. The number of published studies assessing molecular biomarkers for GA initiation and progression in ocular matrices is limited. Several studies evaluated molecular biomarkers in the systemic circulation, showing higher levels of complement activation and a causal role of lipid subfractions in GA. Larger, well-powered studies are needed to identify novel and validate existing biomarkers, and to investigate the potential of combining genetic and molecular markers with imaging techniques for more accurate diagnosis and monitoring of GA. The development of personalized medicine approaches based on individual genetic and molecular profiles could hold promise for more effective and targeted treatments for this devastating disease.