Outer Retinal Layer Thickening Predicts the Onset of Exudative Neovascular Age-Related Macular Degeneration

Exploring the Therapeutic Potential of Elastase Inhibition in Age-Related Macular Degeneration in Mouse and Human

Abnormal turnover of the extracellular matrix (ECM) protein elastin has been linked to AMD pathology. Elastin is a critical component of Bruch's membrane (BrM), an ECM layer that separates the retinal pigment epithelium (RPE) from the underlying choriocapillaris. Reduced integrity of BrM's elastin layer corresponds to areas of choroidal neovascularization (CNV) in wet AMD. Serum levels of elastin-derived peptides and anti-elastin antibodies are significantly elevated in AMD patients along with the prevalence of polymorphisms of genes regulating elastin turnover. Despite these results indicating significant associations between abnormal elastin turnover and AMD, very little is known about its exact role in AMD pathogenesis. Here we report on results that suggest that elastase enzymes could play a direct role in the pathogenesis of AMD. We found significantly increased elastase activity in the retinas and RPE cells of AMD mouse models, and AMD patient-iPSC-derived RPE cells. A1AT, a protease inhibitor that inactivates elastase, reduced CNV lesion sizes in mouse models. A1AT completely inhibited elastase-induced VEGFA expression and secretion, and restored RPE monolayer integrity in ARPE-19 monolayers. A1AT also mitigated RPE thickening, an early AMD phenotype, in HTRA1 overexpressing mice, HTRA1 being a serine protease with elastase activity. Finally, in an exploratory study, examining archival records from large patient data sets, we identified an association between A1AT use, age and AMD risk. Our results suggest that repurposing A1AT may have therapeutic potential in modifying the progression to AMD.

[Diagnosis and clinical features of non-exudative macular neovascularization]

Macular neovascularization (MNV) is the process of new abnormal blood vessels formation in the choroid and/or retina. The widespread adoption of optical coherence tomography angiography (OCTA) has significantly expanded the possibilities of not only detecting pathological blood flow before the development of exudation and deterioration of visual acuity, but also determining its characteristics. The purpose of this review is to substantiate the criteria for choosing terminology and diagnostic markers of MNV. The term "non-exudative MNV" refers to type 1 neovascularization without intraretinal or subretinal exudation detected on repeated OCT scans in the course of at least 6 months. This type of MNV may include previously untreated, non-exudative membranes with a low tendency to exudate, as well as previously treated membranes that have become inactive or dormant and no longer require anti-angiogenic therapy. The criterion for dividing the non-exudative form of MNV into inactive (with a low growth rate and vascular density (VD) at baseline) and subclinical (with a high growth rate and VD) is the time of its activation, generally recognized as 6 months. The diagnostic criteria is the visualized "double layer" sign on OCT scans (retinal pigment epithelium and Bruch's membrane), as well as patterns of neovascular membranes of varying sizes, morphology and localization on OCTA scans. The cumulative risk of conversion from subclinical to exudative at two years of follow-up is 13.6 times higher than in eyes without detectable neovascularization, which highlights the importance of frequent monitoring in this healthy eye population for early detection of MNV signs.

Towards a better understanding of non-exudative choroidal and macular neovascularization

Non-exudative macular and choroidal neovascularization (MNV and CNV) usually refers to the entity of treatment-naïve type 1 neovascularization in the absence of associated signs of exudation. Histopathological studies, dating back in the early 70s, identified the presence of non-exudative MNV, but the first clinical report of this finding was in the late 90s using indocyanine green angiography in eyes with age-related macular degeneration (AMD). With more advanced retinal imaging, there has been an ever increasing appreciation of non-exudative MNV associated with AMD and CNV with other macular disorders. However, consensus regarding the exact definition and the clinical management of this entity is lacking. Furthermore, there may be variation in the imaging features and clinical course suggesting that a spectrum of disease may exist. Herein, we review the large body of published work that has provided a better understanding of non-exudative MNV and CNV in the last decade. The prevalence, multimodal imaging features, clinical course, and response to treatment are discussed to elucidate further key insights about this entity. Based on these observations, this review also proposes a new theory about the origin and course of different sub-types of non-exudative MNV/CNV which can have different etiologies and pathways according to the clinical context of disease.

Rapid Macular Thinning is an Early Indicator of Hydroxychloroquine Retinal Toxicity

PURPOSE

To demonstrate rapid macular thinning as an early and objective sign of hydroxychloroquine (HCQ) retinopathy.

DESIGN

Retrospective case cohort.

SUBJECTS

Cohort of 301 long-term HCQ therapy patients at Kaiser Permanente Northern California who had a minimum of four optical coherence tomography (OCT) studies which included Early Treatment Diabetic Retinopathy Study (ETDRS) retinal thickness values over a minimum interval of four years.

METHODS

Creation of sequential retinal thickness plots to show the rate of change in macular thickness within ETDRS regions.

MAIN OUTCOME MEASURES

1) Identification of rapid macular thinning, 2) Comparison of patients with rapid thinning to those with stable macular thickness, and 3) Comparison of rapid thinning patients with and without conventional OCT or 10-2 visual field signs of HCQ toxicity.

RESULTS

Retina thinning in 219 stable patients on long-term HCQ therapy averaged 0.62 ± 0.45 (mean ± standard deviation) microns per year, while 82 patients showed a period of relatively linear rapid thinning with a loss of 3.75 ± 1.34 microns per year. Of the patients with rapid thinning, 38 eventually developed conventional OCT or 10-2 visual field signs of HCQ retinal toxicity. The cumulative retinal thinning in these patients was 25.1 ± 6.2 microns compared to 15.7 ± 4.0 microns in those without conventional toxicity (p < 0.01).

CONCLUSIONS

Retinal thickness remains stable for many years in most patients on long-term HCQ therapy, but after a critical point the retina may begin to thin rapidly. Sequential plots of inner and outer ETDRS ring macular thickness provide objective evidence of this early structural change several years before conventional signs appear. This approach can alert patients and prescribing physicians to potential retinal damage and uses readily available OCT measurements that could be automated by manufacturers for use in comprehensive eyecare settings.