Calcified nodules in retinal drusen are associated with disease progression in age-related macular degeneration

Pathological Mineralization: The Potential of Mineralomics

Pathological mineralization has been reported countless times in the literature and is a well-known phenomenon in the medical field for its connections to a wide range of diseases, including cancer, cardiovascular, and neurodegenerative diseases. The minerals involved in calcification, however, have not been directly studied as extensively as the organic components of each of the pathologies. These have been studied in isolation and, for most of them, physicochemical properties are hitherto not fully known. In a parallel development, materials science methods such as electron microscopy, spectroscopy, thermal analysis, and others have been used in biology mainly for the study of hard tissues and biomaterials and have only recently been incorporated in the study of other biological systems. This review connects a range of soft tissue diseases, including breast cancer, age-related macular degeneration, aortic valve stenosis, kidney stone diseases, and Fahr’s syndrome, all of which have been associated with mineralization processes. Furthermore, it describes how physicochemical material characterization methods have been used to provide new information on such pathologies. Here, we focus on diseases that are associated with calcium-composed minerals to discuss how understanding the properties of these minerals can provide new insights on their origins, considering that different conditions and biological features are required for each type of mineral to be formed. We show that mineralomics, or the study of the properties and roles of minerals, can provide information which will help to improve prevention methods against pathological mineral build-up, which in the cases of most of the diseases mentioned in this review, will ultimately lead to new prevention or treatment methods for the diseases. Importantly, this review aims to highlight that chemical composition alone cannot fully support conclusions drawn on the nature of these minerals.

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.

Metabolomics and Age-Related Macular Degeneration

Age-related macular degeneration (AMD) leads to irreversible visual loss, therefore, early intervention is desirable, but due to its multifactorial nature, diagnosis of early disease might be challenging. Identification of early markers for disease development and progression is key for disease diagnosis. Suitable biomarkers can potentially provide opportunities for clinical intervention at a stage of the disease when irreversible changes are yet to take place. One of the most metabolically active tissues in the human body is the retina, making the use of hypothesis-free techniques, like metabolomics, to measure molecular changes in AMD appealing. Indeed, there is increasing evidence that metabolic dysfunction has an important role in the development and progression of AMD. Therefore, metabolomics appears to be an appropriate platform to investigate disease-associated biomarkers. In this review, we explored what is known about metabolic changes in the retina, in conjunction with the emerging literature in AMD metabolomics research. Methods for metabolic biomarker identification in the eye have also been discussed, including the use of tears, vitreous, and aqueous humor, as well as imaging methods, like fluorescence lifetime imaging, that could be translated into a clinical diagnostic tool with molecular level resolution.