This review will focus on the molecular organisation of the adult vitreous and how it undergoes ageing changes throughout life that result in vitreous liquefaction and a predisposition towards posterior vitreous detachment and retinal break formation. At birth, the vitreous humour is in a gel state due to the presence of a network of fine collagen fibrils. With ageing, these collagen fibrils progressively aggregate due to a loss of type IX collagen from their surfaces. The aggregation of collagen fibrils may cause vitreous liquefaction which, when combined with an age-related weakening of postbasal vitreoretinal adhesion, predisposes to posterior vitreous detachment. Throughout postnatal life, the posterior border of the vitreous base migrates posteriorly from the ora serrata into the peripheral retina. This is due to new collagen synthesis by the peripheral retina. This new collagen intertwines with pre-existing cortical vitreous collagen to create new adhesions and thereby extends the vitreous base posteriorly. If irregularities in the posterior border of the vitreous base arise from this process, there is a predisposition towards retinal break formation during posterior vitreous detachment and subsequent rhegmatogenous retinal detachment.

Opticin is a class III member of the extracellular matrix small leucine-rich repeat protein (SLRP) family that was initially identified in the eye in association with the collagen fibrils of the vitreous humor. Recombinant and tissue-extracted forms of bovine opticin were subjected to biochemical and biophysical characterization. Following SDS-PAGE the predominant component produced by both forms was a broad band between 45-52 kDa. There was evidence for two-stage processing and, additionally, a proteolytic cleavage product of ϳ25 kDa. Deconvolution of circular dichroism spectra revealed ␤-sheet (41%), ␤-turn (21%), and ␣-helix (10%), and thermal denaturation experiments showed a transition with a midpoint of 47°C. Weight-averaged molecular mass measurements using both light scattering and analytical ultracentrifugation demonstrated that opticin exists in solution as a stable dimer of ϳ90 kDa, which can be dissociated into a monomer by denaturation with 2.5 M guanidine hydrochloride or during SDS-polyacrylamide electrophoresis. Opticin remains a dimer after removal of the amino-terminal region by O-sialoglycoprotein endopeptidase digestion, suggesting that dimer formation is mediated by the leucine-rich repeats. Dimerization could have a number of functional consequences, including divalent ligand interactions.The extracellular matrix small leucine-rich repeat proteins (SLRPs) 1 are a family of molecules to which various functions have been ascribed, including regulation of matrix assembly, binding to growth factors, and suppression of cell growth (for review, see Ref. 1). They contain a varying number of leucinerich repeats (LRRs) that contain the consensus sequence LXX-LXLXXNXL, where X is any amino acid, L is leucine, isoleucine or valine, and N can be asparagine, cysteine or threonine. The LRRs are generally flanked by 4 cysteine residues at the amino-terminal end and two at the carboxyl-terminal end. The SLRPs have been subdivided into three classes depending upon the number of LRRs, the spacing of the four amino-terminal cysteine residues, and the number of exons encoding the gene (1, 2). The class I and II SLRPs possess ϳ12 LRRs, whereas the class III members, including opticin (3), epiphycan/PG-Lb (4, 5) and osteoglycin/mimecan (6, 7), have ϳ7 LRRs.Opticin was first identified in a 4 M guanidine hydrochloride (GdnHCl) extract of collagen fibrils from the vitreous humor of the eye (3). Opticin expression is largely confined to the eye and, in the mouse, was localized specifically to the non-pigmented epithelium of the ciliary body (8). However, expressed sequence tag analyses of adult human iris and retinal pigment epithelium/choroid (available at neibank.nei.nih.gov/index. shtml) suggest that opticin is a very common transcript in these tissues (9 -11). Furthermore, recently published immunolocalization data suggests the presence of opticin in a number of ocular tissues, including the cornea, iris, ciliary body, vitreous, choroid, and retina (12). Friedman et al. (12) also suggest that mutations in th...

This paper develops the argument that post-COVID-19 recovery strategies need to focus on building back fairer cities and communities, and that this requires a strong embedding of ‘ age-friendly’ principles to support marginalised groups of older people, especially those living in deprived urban neighbourhoods, trapped in poor quality housing. It shows that older people living in such areas are likely to experience a ‘double lockdown’ as a result of restrictions imposed by social distancing combined with the intensification of social and spatial inequalities. This argument is presented as follows: first, the paper examines the disproportionate impact of COVID-19 on older people, highlighting how the pandemic is both creating new and reinforcing existing inequalities in ageing along the lines of gender, class, ethnicity, race, ability and sexuality. Second, the paper explores the role of spatial inequalities in the context of COVID-19, highlighting how the pandemic is having a disproportionate impact on deprived urban areas already affected by cuts to public services, the loss of social infrastructure and pressures on the voluntary sector. Finally, the paper examines how interrelated social inequalities at both the individual and spatial level are affecting the lives of older people living in deprived urban neighbourhoods during the pandemic. The paper concludes by developing six principles for ‘age-friendly’ community recovery planning aimed at maintaining and improving the quality of life and wellbeing of older residents in the post-pandemic city.