KDIGO clinical practice guideline for the diagnosis, evaluation, prevention, and treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD)

The complex interactions of retinal, optical and environmental factors in myopia aetiology

Purpose
To evaluate refractive error, axial length, and relative peripheral refractive error before, during the year of, and after the onset of myopia in children who became myopic compared with emmetropes.

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Refractive Error, Axial Length, and Relative Peripheral Refractive Error before and after the Onset of Myopia

PURPOSE—Given the prominence of central vision in humans, it has been assumed that visual signals from the fovea dominate emmetropization. The purpose of this study was to examine the impact of peripheral vision on emmetropization. METHODS—Bilateral, peripheral form deprivation was produced in 12 infant monkeys by rearing them with diffusers that had either 4- or 8-mm apertures centered on the pupils of each eye, to allow 24° or 37° of unrestricted central vision, respectively. At the end of the lens-rearing period, an argon laser was used to ablate the fovea in one eye of each of seven monkeys. Subsequently, all the animals were allowed unrestricted vision. Refractive error and axial dimensions were measured along the pupillary axis by retinoscopy and A-scan ultrasonography, respectively. Control data were obtained from 21 normal monkeys and 3 infants reared with binocular plano lenses. RESULTS—Nine of the 12 treated monkeys had refractive errors that fell outside the 10th- and 90th-percentile limits for the age-matched control subjects, and the average refractive error for the treated animals was more variable and significantly less hyperopic/more myopic (+0.03 ± 2.39 D vs. +2.39 ± 0.92 D). The refractive changes were symmetric in the two eyes of a given animal and axial in nature. After lens removal, all the treated monkeys recovered from the induced refractive errors. No interocular differences in the recovery process were observed in the animals with monocular foveal lesions.

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Peripheral vision can influence eye growth and refractive development in infant monkeys.

Japanese Journal of Applied Physicsの創刊

PURPOSES: To determine axial, vertical, and horizontal eye dimensions in myopic and emmetropic eyes by using magnetic resonance imaging (MRI) and to relate these to different ocular expansion models of myopia development. METHODS: The internal length (cornea to retina), height and width (both retina to retina) were measured in emmetropic and myopic eyes (up to -12 D) of 88 participants aged 18 to 36 years. Participants were positioned supine in a clinical MRI scanner. The fixation target was imaged straight ahead of the subject by an overhead 45 degrees inclined mirror. Eye images were acquired with a 7.5-cm receive-only radio frequency surface coil. Axial (horizontal through middle of eye) and sagittal (vertical through visual axis) sections were taken with a T(1)-weighted fast spin-echo sequence. RESULTS: With an increase in myopic refractive correction, myopic eyes became much larger in all three dimensions, but more so in length (0.35 mm/D, 95% confidence interval [CI] 0.28-0.40) than in height (0.19 mm/D, 95% CI 0.09-0.29) and more so in height than in width (0.10 mm/D, 95% CI 0.01-0.20). Based on height and length dimensions, 25% and 29% of myopic eyes exclusively fitted global expansion and axial elongation models, respectively. Based on width and length dimensions, 17% and 39% of myopic eyes exclusively fitted the global expansion and axial elongation models, respectively. CONCLUSIONS: Although there are considerable individual variations, in general myopic eyes are elongated relative to emmetropic eyes, more in length than in height and even less in width. Approximately a quarter of the myopic participants fitted each of the global expansion or axial elongation model exclusively. The small proportions are due primarily to the large variability in the dimensions of emmetropic eyes.

Eye Shape in Emmetropia and Myopia

PURPOSE: To determine and compare the shapes of the retinas of emmetropic and myopic eyes METHODS: Nonrotationally symmetrical ellipsoids were mathematically fitted to the retinal surfaces of 21 emmetropic and 66 myopic eyes (up to -12 D) of participants aged 18 to 36 years (mean, 255) using transverse axial and sagittal images derived from magnetic resonance imaging RESULTS: The shapes of the ellipsoids varied considerably between subjects with similar refractive errors The shapes were oblate (steepening toward the equator) in most of the emmetropic eyes (ie, the axial dimensions of the ellipsoids were smaller than both the vertical and horizontal dimensions) As myopia increased, all ellipsoid dimensions increased with the axial dimension increasing more than the vertical dimension, which in turn increased more than the horizontal dimension (increases in approximate ratios 3:2:1) The relative difference in the increase of these dimensions meant that as the degree of myopia increased the retinal shape decreased in oblateness However, few myopic eyes were prolate (flattening toward the equator) Independent of myopia, the ellipsoids were tilted about the vertical axis by 11 degrees +/- 13 degrees , and ellipsoid centers were decentered horizontally by 05 +/- 04 mm nasally and 02 +/- 05 mm inferiorly, relative to the fovea CONCLUSIONS: In general both emmetropic and myopic retinas are oblate in shape, although myopic eyes less so This finding may be relevant to theories implicating the peripheral retina in the development of myopia

Shape of the retinal surface in emmetropia and myopia.

Refractive index distribution and optical properties of the isolated human lens measured using magnetic resonance imaging (MRI)

PURPOSE: To determine and compare the shapes of the retinas of emmetropic and myopic eyes. METHODS: Nonrotationally symmetrical ellipsoids were mathematically fitted to the retinal surfaces of 21 emmetropic and 66 myopic eyes (up to -12 D) of participants aged 18 to 36 years (mean, 25.5) using transverse axial and sagittal images derived from magnetic resonance imaging. RESULTS: The shapes of the ellipsoids varied considerably between subjects with similar refractive errors. The shapes were oblate (steepening toward the equator) in most of the emmetropic eyes (i.e., the axial dimensions of the ellipsoids were smaller than both the vertical and horizontal dimensions). As myopia increased, all ellipsoid dimensions increased with the axial dimension increasing more than the vertical dimension, which in turn increased more than the horizontal dimension (increases in approximate ratios 3:2:1). The relative difference in the increase of these dimensions meant that as the degree of myopia increased the retinal shape decreased in oblateness. However, few myopic eyes were prolate (flattening toward the equator). Independent of myopia, the ellipsoids were tilted about the vertical axis by 11 degrees +/- 13 degrees , and ellipsoid centers were decentered horizontally by 0.5 +/- 0.4 mm nasally and 0.2 +/- 0.5 mm inferiorly, relative to the fovea. CONCLUSIONS: In general both emmetropic and myopic retinas are oblate in shape, although myopic eyes less so. This finding may be relevant to theories implicating the peripheral retina in the development of myopia.

Shape of the retinal surface in emmetropia and myopia

Introduction: Estrogen depletion after menopause is accompanied by bone loss and architectural deterioration of trabecular bone. The hypothesis underlying this work is that the μMRI-based virtual bone biopsy can capture the temporal changes of scale and topology of the trabecular network and that estrogen supplementation preserves the integrity of the trabecular network.



Materials and Methods: Subjects studied were early postmenopausal women, 45–55 yr of age (N = 65), of whom 32 were on estrogen (estradiol group), and the remainder were not (control group). Early menopause was defined by amenorrhea for 6–24 mo and elevated serum follicle-stimulating hormone (FSH) concentration. The subjects were evaluated with three imaging modalities at baseline and 12 and 24 mo to determine the temporal changes in trabecular and cortical architecture and density. μMRI of the distal radius and tibia was performed at 137 × 137 × 410-μm3 voxel size. The resulting bone volume fraction maps were Fourier interpolated to a final voxel size of 45.7 × 45.7 × 136.7 μm3, binarized, skeletonized, and subjected to 3D digital topological analysis (DTA). Skeletonization converts trabecular rods to curves and plates to surfaces. Parameters quantifying scale included BV/TV, whereas DTA parameters included the volume densities of curves (C) and surface (S)-type voxels, as well as composite parameters: the surface/curve ratio (S/C), and erosion index (EI, ratio of the sum of parameters expected to increase with osteoclastic resorption divided by the sum of those expected to decrease). For comparison, pQCT of the same peripheral locations was conducted, and trabecular density and cortical structural parameters were measured. Areal BMD of the lumbar vertebrae and hip was also measured.



Results: Substantial changes in trabecular architecture of the distal tibia, in particular as they relate to topology of the network, were detected after 12 mo in the control group. S/C decreased 5.6% (p < 0.0005), and EI increased 7.1% (p < 0.0005). Most curve- and profile-type voxels (representative of trabecular struts), increased significantly (p < 0.001). Curve and profile edges resulting from disconnection of rod-like trabeculae increased by 9.8% and 5.1% (p = 0.0001 and <0.001, respectively). Similarly, DXA BMD in the spine and hip decreased 2.6% and 1.3% (p < 0.0001 and <0.005, respectively), and pQCT cortical area decreased 3.6% (p = 0.0001). However, neither trabecular density nor BV/TV changed. Furthermore, none of the parameters measured in the estradiol group were significantly different after 12 mo. Substantial differences in the mean changes from baseline between the estradiol treatment and control groups, in particular after 24 mo, were observed, with relative group differences as large as 13% (S/C, p = 0.005), and the relative changes in the two groups had the opposite sign for most parameters. The observed temporal alterations in architecture are consistent with remodeling changes that involve gradual conversion of plate-like to rod-like trabecular bone along with disconnection of trabecular elements, even in the absence of a net loss of trabecular bone. The high-resolution 3D rendered images provide direct evidence of the above remodeling changes in individual subjects. The radius structural data indicated similar trends but offered no definitive conclusions.



Conclusions: The short-term temporal changes in trabecular architecture after menopause, and the protective effects of estradiol ensuring maintenance of a more plate-like TB architecture, reported here, have not previously been observed in vivo. This work suggests that MRI-based in vivo micromorphometry of trabecular bone has promise as a tool for monitoring osteoporosis treatment.

In vivo magnetic resonance detects rapid remodeling changes in the topology of the trabecular bone network after menopause and the protective effect of estradiol.

Catherine E. Jones

Papers

Eye Shape in Emmetropia and Myopia

Shape of the retinal surface in emmetropia and myopia.

Refractive index distribution and optical properties of the isolated human lens measured using magnetic resonance imaging (MRI)

Shape of the retinal surface in emmetropia and myopia

In vivo magnetic resonance detects rapid remodeling changes in the topology of the trabecular bone network after menopause and the protective effect of estradiol.