The retinal pigment epithelium (RPE) is located between the neuroretina and the choroid, and plays a critical role in vision. RPE cells internalise outer segments (OS) from overlying photoreceptors in the daily photoreceptor renewal. Changes to RPE structure are linked with age and retinopathy, which has been described in the past by conventional 2D electron microscopy. We used serial block face scanning electron microscopy (SBF-SEM) to reconstruct RPE cells from the central mouse retina. Three-dimensional-reconstructed OS revealed the RPE to support large numbers of photoreceptors (90–216 per RPE cell). Larger bi-nucleate RPE maintained more photoreceptors, although their cytoplasmic volume was comparable to smaller mono-nucleate RPE supporting fewer photoreceptors. Scrutiny of RPE microvilli and interdigitating OS revealed the angle and surface area of contact between RPE and photoreceptors. Bi-nucleate RPE contained more mitochondria compared to mono-nucleate RPE. Furthermore, bi-nucleate cells contained larger sub-RPE spaces, supporting a likely association with disease. Use of perfusion-fixed tissues ensured the highest possible standard of preservation, providing novel insights into the 3D RPE architecture and changes linked with retinopathy. This study serves as a benchmark for comparing retinal tissues from donor eyes with age-related macular degeneration (AMD) and other retinopathies.
Refractive correction of aphakia in childhood can be a complex management issue following lensectomy for congenital cataract or ectopia lentis. Some children have inadequate capsular support to allow an 'in the bag' or sulcus fixated intra-ocular lens (IOL). In such cases, options for refractive correction include spectacles, contact lenses, or surgically fixed IOLs. Many methods of IOL fixation have been described, but none are widely adopted in children. In recent years, the iris-fixated Artisan Aphakic IOL has gained popularity, but there is still significant concern about the rate of corneal endothelial cell loss and IOL de-enclavation. Here, we review the current literature on the use of iris-fixated IOLs in children, the published data on endothelial cell loss and de-enclavation rates. We present a case illustrating the significant improvements in quality of life, which can be seen in selected children, and also the rate of endothelial cell loss, which can be encountered after initial surgery, and a re-enclavation event. We make the case that until more data are available on normal endothelial cell decline in early childhood, in addition to age-specific rates of endothelial cell loss and de-enclavation rates following surgery, the use of iris-fixated IOLs in children will continue to be a moot point and is unlikely to be widely adopted.
Previous studies have suggested that central corneal endothelial cell density (ECD) decreases from 6,100 cells/mm in neonates to 3,100 cells/mm in 10-year-olds. Currently data on ECD in young children as well as the trend for ECD decrease during childhood is sparse because of the difficulty of examination using existing clinic-based specular microscopes. We developed a novel method of imaging young children intraoperatively with the goal of beginning to establish age-specific normative data for ECD and hexagonality of cells (%HEX). Children were imaged using our novel technique under general anesthesia or awake in clinic using a child-friendly technique. A total of 58 children were recruited (mean age, 5.50; range, 0.44-10.36). Our cohort displayed a significant linear decrease in ECD with age (r = -0.56, P < 0.001). No correlation was found between %HEX and age (r = -0.10, P = 0.48).
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