Retinal Pigment Epithelium In Eyes Research Articles

Retinal Imaging Using a Confocal Scanning Laser Ophthalmoscope-Based High-Magnification Module

To evaluate the usefulness of a high-magnification module (HMM) lens to visualize retinal photoreceptors, retinal nerve fiber layer (RNFL), and superficial retinal vasculature in physiologic and pathologic retinal conditions. Observational descriptive study. Thirty-two participants with normal and pathologic retina examination results. Normal and pathologic maculae were imaged invivo using still and video HMM lens modes, with fixation and contrast adjustments to enhance visualization. The HMM images were classified qualitatively based on structures identified as either good (photoreceptors seen), average (photoreceptor mosaic cannot be visualized clearly, retinal vessels and other retinal changes can be seen), or poor (no identifiable structures). Selected eyes were imaged with fundus photography, OCT, OCT angiography, indocyanine green angiography, and fluorescein angiography for comparison with the pathologic maculae. Description of HMM module-obtained macula images. From 32 eyes imaged (16 normal and 16 pathologic retinas), 12 of 16 normal and 11 of 16 pathologic retinas demonstrated at least average image quality, in which retinal vasculature and landmarks could be visualized. The mosaic pattern of hexagonal shapes representing photoreceptors could not be resolved in most pathologic retinas. For the retinas in which the photoreceptor mosaics were visualized (12 of 16 normal and 2 of 16 pathologic retinas), parafoveal mosaic patterns appeared denser with better image quality for all participants compared with foveal photoreceptors. Difficulty in resolving the photoreceptors in the umbo, fovea, and perifovea was encountered, similar to what has been reported with adaptive optics devices. The RNFL was seen as arcuate hyperreflective bundles. Flow was observed in the macular microvasculature. Poorly resolved photoreceptors and scattered hyperreflective foci were correlated with changes in the retinal pigment epithelium in eyes with age-related macular degeneration or central serous chorioretinopathy. Macular striae were seen in eyes with epiretinal membrane. In most eyes, regardless of whether retinal pathologic features were present, it was challenging to obtain average quality (or better) images. In the few participants with good-quality imaging, the parafoveal photoreceptor mosaic, vascular flow, and various features of pathologic eyes could be visualized.

Retinol dehydrogenase 11 is essential for the maintenance of retinol homeostasis in liver and testis in mice

Retinol dehydrogenase 11 (RDH11) is a microsomal short-chain dehydrogenase/reductase that recognizes all-trans- and cis-retinoids as substrates and prefers NADPH as a cofactor. Previous work has suggested that RDH11 contributes to the oxidation of 11-cis-retinol to 11-cis-retinaldehyde during the visual cycle in the eye's retinal pigment epithelium. However, the role of RDH11 in metabolism of all-trans-retinoids remains obscure. Here, we report that microsomes isolated from the testes and livers of Rdh11-/- mice fed a regular diet exhibited a 3- and 1.7-fold lower rate of all-trans-retinaldehyde conversion to all-trans-retinol, respectively, than the microsomes of WT littermates. Testes and livers of Rdh11-/- mice fed a vitamin A-deficient diet had ∼35% lower levels of all-trans-retinol than those of WT mice. Furthermore, the conversion of β-carotene to retinol via retinaldehyde as an intermediate appeared to be impaired in the testes of Rdh11-/-/retinol-binding protein 4-/-(Rbp4-/-) mice, which lack circulating holo RBP4 and rely on dietary supplementation with β-carotene for maintenance of their retinoid stores. Together, these results indicate that in mouse testis and liver, RDH11 functions as an all-trans-retinaldehyde reductase essential for the maintenance of physiological levels of all-trans-retinol under reduced vitamin A availability.

Amphiregulin Antibody and Reduction of Axial Elongation in Experimental Myopia

To examine the mechanism of ocular axial elongation in myopia, guinea pigs (age: 2–3weeks) which either underwent unilateral or bilateral lens-induced myopization (group 1) or which were primarily myopic at baseline (group 2) received unilateral intraocular injections of amphiregulin antibody (doses: 5, 10, or 15μg) three times in intervals of 9days. A third group of emmetropic guinea pigs got intraocular unilateral injections of amphiregulin (doses: 0.25, 0.50 or 1.00ng, respectively). In each group, the contralateral eyes received intraocular injections of Ringer's solution. In intra-animal inter-eye comparison and intra-eye follow-up comparison in groups 1 and 2, the study eyes as compared to the contralateral eyes showed a dose-dependent reduction in axial elongation. In group 3, study eyes and control eyes did not differ significantly in axial elongation. Immunohistochemistry revealed amphiregulin labelling at the retinal pigment epithelium in eyes with lens-induced myopization and Ringer's solution injection, but not in eyes with amphiregulin antibody injection. Intraocular injections of amphiregulin-antibody led to a reduction of lens-induced axial myopic elongation and of the physiological eye enlargement in young guinea pigs. In contrast, intraocularly injected amphiregulin in a dose of ≤1ng did not show a significant effect. Amphiregulin may be one of several essential molecular factors for axial elongation.

Imaging drusens using Spectral Domain Optical Coherence Tomography

PurposeThe purpose was to evaluate pathological changes of photoreceptor layer and retinal pigment epithelium in eyes with drusens using Spectral Domain Optical Coherence Tomography (SD-OCT). MethodsTwenty-nine eyes of 29 patients with (drusens) dry age-related macular degeneration and 43 eyes of 43 controls were included in this study. All subjects underwent complete ophthalmic examination including SD-OCT. Central foveal thickness (CFT), photoreceptor layer (PRL) thickness and retinal pigment epithelial (RPE) thickness were measured and compared between the groups. P value<0.05 was considered statistically significant. ResultsBest corrected visual acuity (BCVA) ranged between 20/20 and 20/200. RPE (36.10±5.48μm Vs 39.27±4.30) and PRL thickness (53.93±7.36μm Vs 61.20±4.50μm) were significantly reduced in patients with drusens compared to controls. Increase in age was a significant risk factor for drusens (OR: 1.22, p<0.001) and increased PRL thickness was a protective factor (OR: 0.720, p=0.002). PRL thickness was significantly associated with BCVA (p=0.019). ConclusionWith an increased resolution of SD-OCT, the involvement of the outer retinal layers was more clearly defined. SD-OCT may allow for the early detection of exudative changes.

Lipofuscin redistribution and loss accompanied by cytoskeletal stress in retinal pigment epithelium of eyes with age-related macular degeneration.

Lipofuscin (LF) and melanolipofuscin (MLF) of the retinal pigment epithelium (RPE) are the principal sources of autofluorescence (AF) signals in clinical fundus-AF imaging. Few details about the subcellular distribution of AF organelles in AMD are available. We describe the impact of aging and AMD on RPE morphology revealed by the distribution of AF LF/MLF granules and actin cytoskeleton in human tissues. Thirty-five RPE-Bruch's membrane flatmounts from 35 donors were prepared (postmortem: ≤4 hours). Ex vivo fundus examination at the time of accession revealed either absence of chorioretinal pathologies (10 tissues; mean age: 83.0 ± 2.6 years) or stages of AMD (25 tissues; 85.0 ± 5.8 years): early AMD, geographic atrophy, and late exudative AMD. Retinal pigment epithelium cytoskeleton was labeled with AlexaFluor647-Phalloidin. Tissues were imaged on a spinning-disk fluorescence microscope and a high-resolution structured illumination microscope. Age-related macular degeneration impacts individual RPE cells by (1) lipofuscin redistribution by (i) degranulation (granule-by-granule loss) and/or (ii) aggregation and apparent shedding into the extracellular space; (2) enlarged RPE cell area and conversion from convex to irregular and sometimes concave polygons; and (3) cytoskeleton derangement including separations and breaks around subretinal deposits, thickening, and stress fibers. We report an extensive and systematic en face analysis of LF/MLF-AF in AMD eyes. Redistribution and loss of AF granules are among the earliest AMD changes and could reduce fundus AF signal attributable to RPE at these locations. Data can enhance the interpretation of clinical fundus-AF and provide a basis for future quantitative studies.

IMPROVED VISUALIZATION OF POLYPOIDAL CHOROIDAL VASCULOPATHY LESIONS USING SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY

To report the tomographic features of vascular lesions beneath the retinal pigment epithelium in eyes with polypoidal choroidal vasculopathy by using spectral-domain optical coherence tomography (SD-OCT). Retrospective observational case series. Angiograms and images obtained using the prototype SD-OCT system were compared for 21 eyes of 21 patients with polypoidal choroidal vasculopathy to identify sub-retinal pigment epithelium abnormalities visible on three-dimensional and enhanced SD-OCT images. On angiography, a branching vascular network and at least 1 polypoidal lesion were visible in all 21 eyes; 10 eyes also had pigment epithelial detachment (PED). SD-OCT revealed a thin straight line of high reflectivity-Bruch's membrane-associated with the branching vascular network in all 21 eyes, polypoidal lesions, 19 (90%) of the 21 eyes; and PED, 9 (90%) of the 10 eyes with PED. The vascular abnormalities of polypoidal choroidal vasculopathy (polypoidal lesion and branching vascular network) identified with angiograms were visualized on SD-OCT images in 20 of the 21 eyes (95%) as areas of moderate reflectivity between the clearly delineated abnormal section of retinal pigment epithelium and Bruch's membrane. Enhanced SD-OCT imaging clearly depicted Bruch's membrane beneath areas of abnormal retinal pigment epithelium in the same locations where the vascular abnormalities of polypoidal choroidal vasculopathy were evident on angiography.

Alterations of retinal pigment epithelium in central serous chorioretinopathy

To examine with en face optical coherence tomography (OCT) the alterations of retinal pigment epithelium (RPE) in central serous chorioretinopathy (CSC) and their role in the pathophysiology of CSC. We examined retrospectively 30 consecutive eyes of 30 patients with various phases of CSC. All patients underwent fluorescein angiography, indocyanine green angiography, and en face and longitudinal OCT examinations. Of 25 eyes with acute CSC, en face OCT showed RPE abnormalities in 22 eyes (88%) with pigment epithelial detachment (PED) in nine eyes (36%) and a small bulge of RPE in the posterior pole in 15 eyes (60%). Of four eyes with chronic CSC, OCT showed PED in one eye (25%) and a small bulge of RPE in other three eyes (75%). Of 29 eyes with acute or chronic CSC, fluorescein angiography showed characteristic pinpoint leakage in 20 eyes (69%). Of these 20 eyes, a leaking point was located within PEDs in five eyes (25%) and was consistent with the bulge of RPE in nine eyes (45%). With indocyanine green angiography, 28 (97%) eyes showed choroidal vascular hyperpermeability. Ten of the 11 eyes with PED (91%) showed PED within the areas of choroidal vascular hyperpermeability. Sixteen of the 18 eyes with a bulge of RPE (89%) showed the bulge within areas of choroidal vascular hyperpermeability. The one eye in the quiescent CSC exhibited multiple small PEDs within the areas of choroidal vascular hyperpermeability by en face OCT. En face OCT enables us to detect alterations of RPE in eyes with CSC. Most alterations of RPE were associated with choroidal abnormalities.

Retinal Pigment Epithelium Tear After Intravitreal Bevacizumab for Exudative Age-related Macular Degeneration

To report on the development of retinal pigment epithelium tears after intravitreal injections of bevacizumab as treatment of exudative age-related macular degeneration (AMD). Interventional case series. The study included 63 patients who received an intravitreal injection of 1.5 mg bevacizumab as treatment of a detachment of the retinal pigment epithelium attributable to AMD and who had a follow-up of at least two months. Four patients (6%) developed a tear of the retinal pigment epithelium in the parafoveal region. Compared with the baseline value, visual acuity at the end of follow-up remained stable in three patients and declined in the fourth patient. Intravitreal injections of bevacizumab may be followed by a tear of the retinal pigment epithelium in eyes with exudative AMD and a retinal pigment epithelium detachment.

CORRELATION OF OPTICAL COHERENCE TOMOGRAPHY WITH ANGIOGRAPHY IN RETINAL PIGMENT EPITHELIAL DETACHMENT ASSOCIATED WITH AGE-RELATED MACULAR DEGENERATION

To correlate optical coherence tomography (OCT) with angiographic signs of choroidal neovascularization (CNV) in retinal pigment epithelial detachment (PED) associated with age-related macular degeneration (ARMD). Prospectively, the authors performed OCT in 35 eyes of 35 patients (30 men and 5 women with a mean age of 71.6 years [range, 56-76 years]) with ARMD. All 35 eyes had CNV in the area of PED or adjacent to it, which was shown by fluorescein or indocyanine green angiography. Cross-sectional images were obtained by the OCT scanning line through the CNV and PED. In 10 (56%) of 18 eyes in which the CNV was at the margin of the PED, a small PED was adjacent to the central, dome-shaped PED. There was a notch between the central and small mounds of PED. In 13 (76%) of 17 eyes in which the CNV was within the PED, a notch was seen in the dome-shaped PED, resulting in a contour with 2 mounds. One of the 2 mounds contained a highly reflective mass immediately beneath the detached retinal pigment epithelium in 8 (62%) of the 13 eyes. A tomographic notch in the PED may be diagnostically important as an indication of CNV beneath the detached retinal pigment epithelium in eyes with ARMD.

Transplantation of autologous retinal pigment epithelium in eyes with foveal neovascularization resulting from age-related macular degeneration: a pilot study

PURPOSE: To describe the indications, surgical technique, and clinical results of 14 eyes in 13 patients with age-related macular degeneration and foveal choroidal neovascularization, in which subretinal surgery was combined with simultaneous transplantation of autologous retinal pigment epithelial cells.METHODS: Between March 1999 and February 2000, in a prospective study, 14 eyes (13 patients) with age-related macular degeneration underwent subretinal surgery because of foveal choroidal neovascularization with simultaneous transplantation of retinal pigment epithelium harvested from the nasal subretinal area of the same eye. Preoperatively, 1 month postoperatively, 3 months postoperatively and at 3-month intervals thereafter, examinations were performed including best-corrected visual acuity, visual field, biomicroscopy of anterior and posterior segment, tonometry, fluorescein and indocyanine angiographies, autofluorescence, scotometry, and fixation tests.RESULTS: Postoperatively, after median observation of 17 months (range, 12 to 24 months) best-corrected visual acuity was improved 2 or more lines in eight eyes (57.1%), remained the same (± 1 line) in five eyes (35%), and decreased by more than 2 lines in one eye (7.1%). Pairwise t test showed significant improvement after 1 month (P = .0031, P = .0062) as well as 1 year (P = .0066, P = .0105). Satisfactory reading vision between Jaeger 1 and 4 was achieved in three eyes (21.2%). No significant intraoperative or postoperative complications occurred in any eye. No recurrence of choroidal neovascularization was observed during the observation period.CONCLUSIONS: In eyes with age-related macular degeneration and foveal choroidal neovascularization, autotransplantation of retinal pigment epithelium was performed in addition to conventional removal of the choroidal neovascularization without significant intraoperative or postoperative complications. Visual acuity improvement of 2 or more lines in 57% of the eyes was achieved. No recurrent choroidal neovascularization formation was observed during the observation period. The results of this pilot study suggest that autologous transplantation of retinal pigment epithelium combined with submacular surgery might be a reasonable treatment option for patients with foveal choroidal neovascularization secondary to age-related macular degeneration.

Antioxidant enzymes in the macular retinal pigment epithelium of eyes with neovascular age-related macular degeneration

PURPOSE: To test the hypothesis that neovascular age-related macular degeneration is related to oxidative stress involving the macular retinal pigment epithelium. This study investigated, as a function of age, levels of enzymes that defend tissues against oxidative stress in the macular retinal pigment epithelium of human eyes with this disease. METHODS: Surgical specimens of macular choroidal neovascular membranes from eyes with age-related macular degeneration and the macular regions of whole donor eyes with neovascular age-related macular degeneration or without evident ocular disease were studied by quantitative electron microscopic immunocytochemistry with colloidal gold–labeled second antibodies. Relative levels in retinal pigment epithelium cell cytoplasm and lysosomes were determined of five enzymes believed to protect cells from oxidative stress, as well as levels of the retinal pigment epithelium marker cytoplasmic retinaldehyde-binding protein, for comparison with the enzymes. RESULTS: Copper, zinc superoxide dismutase immunoreactivity increased and catalase immunoreactivity decreased with age in cytoplasm and lysosomes from macular retinal pigment epithelium cells of normal eyes and eyes with age-related macular degeneration. Cytoplasmic retinaldehyde-binding protein immunoreactivity showed no significant relationship to age or the presence of neovascular age-related macular degeneration. Glutathione peroxidase immunoreactivity was absent from human retinal pigment epithelium cells. Both heme oxygenase-1 and heme oxygenase-2 had highly significantly greater immunoreactivity in retinal pigment epithelium cell lysosomes than in cytoplasm, differing from the much greater cytoplasmic immunoreactivity of the other proteins studied. This immunoreactivity decreased with age, particularly in the lysosomes of retinal pigment epithelium cells from eyes with neovascular age-related macular degeneration. These decreases were of borderline significance ( P = .067 for heme oxygenase-1; P = .12 for heme oxygenase-2) when eyes with age-related macular degeneration were compared with normal eyes by multivariable logistic regression. CONCLUSIONS: The high heme oxygenase-1 and heme oxygenase-2 lysosomal antigen levels in macular retinal pigment epithelium cells of eyes with neovascular age-related macular degeneration suggest that oxidative stress causes a pathologic upregulation of these enzymes. Increased lysosomal disposal may indicate that the reparative functions of these enzymes are accompanied by deleterious effects, necessitating their rapid removal from the cell. The much higher heme oxygenase-1 and heme oxygenase-2 antigen levels in macular retinal pigment epithelium cells from younger individuals suggest that protective mechanisms against oxidation and, hence, presumably to the development of age-related macular degeneration, decrease with age.

Zinc content of human retinal pigment epithelium decreases with age and macular degeneration, but superoxide dismutase activity increases

We previously reported an age-related decline of catalase activity and metallothionein (MT) in human retinal pigment epithelium (RPE) isolated from donor eyes. MT content and catalase activity also were shown to decrease in RPE cells cultured in zinc-deficient medium. We now sought to determine whether zinc content and superoxide dismutase activity change with age and signs of macular degenerative disease in isolated human RPE. Eyes from 57 donors were graded with respect to disease by the presence or absence of visible drusen and macular pigment changes. RPE was collected from macular and peripheral regions. Tissues from 39 donors were separated into soluble and pigment granule fractions and zinc content determined by flame atomic absorption spectroscopy. RPE from 18 separate donors was used for SOD activity analysis. Total RPE zinc was 9% lower in eyes from donors >70 years of age compared to that from donors <age 70. Soluble macular zinc was 45% less in eyes >age 70 and showed a greater decline in the soluble fraction of macular RPE in eyes with signs of macular disease. Total SOD activity increased significantly (P < .05) with donor age. We conclude that zinc content decreased dramatically in the soluble fraction of macular RPE with age and signs of macular degeneration. Total SOD activity correlated negatively with changes in zinc content. It remains to be determined whether the age-related decline in macular zinc is causal with respect to previously observed decreases in cellular MT and catalase. © 1996 Wiley-Liss, Inc.

Zinc content of human retinal pigment epithelium decreases with age and macular degeneration, but superoxide dismutase activity increases

We previously reported an age-related decline of catalase activity and metallothionein (MT) in human retinal pigment epithelium (RPE) isolated from donor eyes. MT content and catalase activity also were shown to decrease in RPE cells cultured in zinc-deficient medium. We now sought to determine whether zinc content and superoxide dismutase activity change with age and signs of macular degenerative disease in isolated human RPE. Eyes from 57 donors were graded with respect to disease by the presence or absence of visible drusen and macular pigment changes. RPE was collected from macular and peripheral regions. Tissues from 39 donors were separated into soluble and pigment granule fractions and zinc content determined by flame atomic absorption spectroscopy. RPE from 18 separate donors was used for SOD activity analysis. Total RPE zinc was 9% lower in eyes from donors >70 years of age compared to that from donors <age 70. Soluble macular zinc was 45% less in eyes >age 70 and showed a greater decline in the soluble fraction of macular RPE in eyes with signs of macular disease. Total SOD activity increased significantly (P < .05) with donor age. We conclude that zinc content decreased dramatically in the soluble fraction of macular RPE with age and signs of macular degeneration. Total SOD activity correlated negatively with changes in zinc content. It remains to be determined whether the age-related decline in macular zinc is causal with respect to previously observed decreases in cellular MT and catalase. © 1996 Wiley-Liss, Inc.