Retinal Pigment Epithelium Abnormalities Research Articles

AMD Drusenoid deposits “P”, Protein‐Cellular Type: Characterization and Evolution. Multimodal imaging and OCT, OCT en Face, Evaluation and Interest

PurposeTo study AMD drusenoid deposits “P”, Protein‐Cellular Type with multimodal imaging,to characterize their morphologic type, evolution, to consider etiopathogeny, biomarker featuresMethods148 eyes of 74 AMD patients. AMD drusenoid deposits “P”,Protein‐Cellular Type:Cuticular drusen,Drusenoid PED “P”, Subretinal drusenoid deposits (SDD),Pseudovitellifom AMD were evaluated by Autofluorescence,IR imaging,ETDRS visual acuity (VA),ophthalmic examination with Ocular Fundus,Ocular Confocal Tomography exam(spectral domain OCT, OCT en Face software). Size, characteristics, number, topography of the lesions, growth way were evaluated, also their environment above, below and evolution. Each element was studied, compared cut to cut,layer to layer,time to time.ResultsVA stabilized in 90%. Pseudovitelliform AMD are little, irregular upper limit drusenoid PED. Cuticular drusen appear, uniform, round, white, under retinal pigment epithelium (RPE). SDD deposits are white, homogeneous,quite similar in all cross‐section, FA and ICG too, nearby upper side RPE layer. Drusenoid PED “P” were dense,white, granular,different in all cross‐sections,heterogeneous PED, below RPE,with abnormal RPE above,heavily unstructured.Multimodal imaging,especially OCT en Face, let individualize “P” drusenoid deposits.Evolution was‐choriocapillaris change‐pigment epithelium involution:more dense, irregular, inhomogeneous, crumbled‐inflammation‐neovascular signs even net.Specific metabolic defect outcome, etiopathogenic pathways appear: “P” drusenoid deposit is mostly enrolled in protein‐cellular metabolic pathway dysfunction with rather evolution to neovascular complication. So it would build up its biomarker feature.ConclusionsAMD Drusenoid deposits “P”, Protein‐Cellular type study,knowledge,evolution,notably with multimodal imaging, OCT en Face contribute to and improve AMD understanding, prognosis, etiopathogic concept.

Incidence, Progression, and Associated Risk Factors of Medium Drusen in Age-Related Macular Degeneration: Findings From the 15-Year Follow-up of an Australian Cohort.

The natural course and prognosis of medium drusen and risk factors associated with the incidence and progression of this lesion type in age-related macular degeneration (AMD) are not well understood. To assess the 15-year incidence and progression of medium drusen and associated risk factors. Population-based cohort in the Blue Mountains region, west of Sydney, Australia. Included in the study were 3654 participants 49 years or older who attended baseline examinations of the Blue Mountains Eye Study (1992-1994), and 75.8%, 76.7%, and 56.1% of survivors who attended the 5-year, 10-year, and 15-year follow-up examinations, respectively. Color retinal fundus photographs were obtained at each examination. The incidence and progression of medium drusen (maximum diameter, 63 to <125 µm) were assessed using Kaplan-Meier product-limit survival methods, controlling for competing risk of death. Factors associated with a 15-year incidence of medium drusen were assessed using discrete logistic regression models after adjusting for age, sex, smoking status, serum lipid levels, systemic and dietary factors, and CFH rs1061170 and ARMS2 rs10490924 polymorphisms. Associations between lesion characteristics and the progression to late AMD were assessed using generalized estimating equation models and eye-specific data. Among 1317 participants at risk, the 15-year cumulative incidence of medium drusen was 13.9% (n = 281). Increasing age (per decade older) (odds ratio [OR], 1.4; 95% CI, 1.2-1.8) and the presence of at least 3 risk alleles of the CFH rs1061170 or ARMS2 rs10490924 genes (OR, 2.1; 95% CI, 1.1-4.1) were associated with a higher incidence. There was no association between past smoking (OR, 0.8; 95% CI, 0.6-1.1) or current smoking (OR, 0.6; 95% CI, 0.4-1.1) and the development of medium drusen. The progression rate to late AMD in eyes with both medium drusen and retinal pigmentary abnormalities was 4-fold higher than that in eyes with medium drusen alone. Larger total area and central location of medium drusen were associated with a greater likelihood of the progression to worse stages of AMD. Older age and the presence of CFH and ARMS2 risk alleles are 2 main risk factors associated with the development of medium drusen. The copresence of medium drusen plus retinal pigment epithelium abnormalities signals a greater risk of the progression to late AMD than the presence of medium drusen alone.

The Project MACULA Retinal Pigment Epithelium Grading System for Histology and Optical Coherence Tomography in Age-Related Macular Degeneration.

To seek pathways of retinal pigment epithelium (RPE) fate in age-related macular degeneration via a morphology grading system; provide nomenclature, visualization targets, and metrics for clinical imaging and model systems. Donor eyes with geographic atrophy (GA) or choroidal neovascularization (CNV) and one GA eye with previous clinical spectral-domain optical coherence tomography (SDOCT) imaging were processed for histology, photodocumented, and annotated at predefined locations. Retinal pigment epithelial cells contained spindle-shaped melanosomes, apposed a basal lamina or basal laminar deposit (BLamD), and exhibited recognizable morphologies. Thicknesses and unbiased estimates of frequencies were obtained. In 13 GA eyes (449 locations), 'Shedding,' 'Sloughed,' and 'Dissociated' morphologies were abundant; 22.2% of atrophic locations had 'Dissociated' RPE. In 39 CNV eyes (1363 locations), 37.3% of locations with fibrovascular/fibrocellular scar had 'Entombed' RPE; 'Sloughed,' 'Dissociated,' and 'Bilaminar' morphologies were abundant. Of abnormal RPE, CNV and GA both had ~35% 'Sloughed'/'Intraretinal,' with more Intraretinal in CNV (9.5% vs. 1.8%). 'Shedding' cells associated with granule aggregations in BLamD. The RPE layer did not thin, and BLamD remained thick, with progression. Granule-containing material consistent with three morphologies correlated to SDOCT hyperreflective foci in the previously examined GA patient. Retinal pigment epithelium morphology indicates multiple pathways in GA and CNV. Atrophic/scarred areas have numerous cells capable of transcribing genes and generating imaging signals. Shed granule aggregates, possibly apoptotic, are visible in SDOCT, as are 'Dissociated' and 'Sloughed' cells. The significance of RPE phenotypes is addressable in longitudinal, high-resolution imaging in clinic populations. Data can motivate future molecular phenotyping studies.

The gene mutation in a Taiwanese family with X-linked retinoschisis

X-linked retinoschisis (XLRS) is one of the leading causes of macular degeneration in male children. The purpose of this study is to describe the clinical characteristics of a Taiwanese family with X-linked retinoschisis (XLRS) and to investigate the genetic mutation in the retinoschisin 1 (RS1) gene. A total of four participants in this XLRS family were analyzed. Complete ophthalmic examinations were performed, including best corrected visual acuity, optical coherence tomography (OCT), and electroretinogram (ERG). Direct DNA sequence of the RS1 gene identified one affected male and one female carrier. The affected male, had a cartwheel-like macular appearance and abnormal retinal pigment epithelium pigmentation in his bilateral eyes. The mixed scotopic ERG b-wave was more reduced than a-wave. OCT revealed typical macular microcystic schisis cavities. Direct DNA sequence analysis revealed a single base pair substitution in Exon 4, 304C > T, resulting in Arg102Trp. Our results show a RS1 (304C > T) mutation in a Taiwanese family with XLRS. This finding expands the clinical profiles of RS1 mutation and may help to further understand its pathogenesis.

NHE8 is essential for RPE cell polarity and photoreceptor survival.

A new N-ethyl-N-nitrosourea (ENU)-induced mouse recessive mutation, identified by fundus examination of the eye, develops depigmented patches, indicating retinal disorder. Histology data show aberrant retinal pigment epithelium (RPE) and late-onset photoreceptor cell loss in the mutant retina. Chromosomal mapping and DNA sequencing reveal a point mutation (T to A) of the Slc9a8 gene, resulting in mutant sodium/proton exchanger 8 (NHE8)-M120K protein. The lysine substitution decreases the probability of forming the 3rd transmembrane helix, which impairs the pore structure of the Na+/H+ exchanger. Various RPE defects, including mislocalization of the apical marker ezrin, and disrupted apical microvilli and basal infoldings are observed in mutant mice. We have further generated NHE8 knockout mice and confirmed similar phenotypes, including abnormal RPE cells and late-onset photoreceptor cell loss. Both in vivo and in vitro data indicate that NHE8 co-localizes with ER, Golgi and intracellular vesicles in RPE cells. Thus, NHE8 function is necessary for the survival of photoreceptor cells and NHE8 is important for RPE cell polarity and function. Dysfunctional RPE may ultimately lead to photoreceptor cell death in the NHE8 mutants. Further studies will be needed to elucidate whether or not NHE8 regulates pH homeostasis in the protein secretory pathways of RPE.

Structural and Functional Outcomes in Chronic Central Serous Chorioretinopathy Treated with Photodynamic Therapy.

PurposeTo study the retinal pigment epithelium (RPE) and retinal alterations in chronic central serous chorioretinopathy treated with photodynamic therapy, and its correlation with functional parameters such as best-corrected visual acuity (BCVA) and contrast sensitivity (CS).MethodsRetrospective, noncomparative, consecutive evaluation by optical coherence tomography and its correlation with BCVA and CS in 31 eyes of 26 patients.ResultsIn all affected patients, 88.5% were male with a mean age of 42.9 years. The right eye was involved in 64.5% of cases, bilateral in 19% and 73.9% were hyperopic (spherical refraction between 0 and +5.0 diopters). Of these cases, 51.5% had peri-RPE abnormalities, 17.3% hyperreflective substances at RPE, 19.4% RPE atrophy, 55.3% foveolar atrophy, 3.1% pigment epithelial detachment, 5.2% subretinal fluid persistence, 8.3% fibrin deposits, 68.4% photoreceptor inner and outer segment line interruption and 31.1% external limiting membrane interruption.ConclusionsTime evolution and number of outbreaks were related to the decrease in foveal and chorodial thickness and in those with worse BCVA and CS. RPE abnormalities and atrophy were related to the age of onset of symptoms. Photoreceptor elongation has been correlated with poor BCVA and inner and outer segment line destructuring and interruption with poor CS.

Differential Light-induced Responses in Sectorial Inherited Retinal Degeneration

Retinitis pigmentosa (RP) is a group of genetically and clinically heterogeneous inherited degenerative retinopathies caused by abnormalities of photoreceptors or retinal pigment epithelium in the retina leading to progressive sight loss. Rhodopsin is the prototypical G-protein-coupled receptor located in the vertebrate retina and is responsible for dim light vision. Here, novel M39R and N55K variants were identified as causing an intriguing sector phenotype of RP in affected patients, with selective degeneration in the inferior retina. To gain insights into the molecular aspects associated with this sector RP phenotype, whose molecular mechanism remains elusive, the mutations were constructed by site-directed mutagenesis, expressed in heterologous systems, and studied by biochemical, spectroscopic, and functional assays. M39R and N55K opsins had variable degrees of chromophore regeneration when compared with WT opsin but showed no gross structural misfolding or altered trafficking. M39R showed a faster rate for transducin activation than WT rhodopsin with a faster metarhodopsinII decay, whereas N55K presented a reduced activation rate and an altered photobleaching pattern. N55K also showed an altered retinal release from the opsin binding pocket upon light exposure, affecting its optimal functional response. Our data suggest that these sector RP mutations cause different protein phenotypes that may be related to their different clinical progression. Overall, these findings illuminate the molecular mechanisms of sector RP associated with rhodopsin mutations.

The effect of cobalt on the human eye.

The effect of elevated serum cobalt on the human visual system has not yet been established. In light of recent reports of visual problems with elevated cobalt in association with hip prostheses, this review examines the literature for evidence regarding the effects of cobalt on human visual function. A systematic literature review was undertaken in July 2013. The electronic databases of PubMed (1955 to July week 1 2013), Cochrane Library and EMBASE were searched. Only human studies or case reports written in English were included. Eight case reports were identified. Five case reports involved patients with metal hip arthroplasties, two cases involved patients exposed to environmental cobalt, and one case involved a patient treated medically for anaemia with cobalt chloride. No human prospective studies were identified. Several case reports showed that high serum cobalt may be associated with both irreversible and reversible visual loss, optic neuropathy and atrophy, electrophysiological evidence of abnormal retinal and retinal pigment epithelium function and fluorescein angiographic evidence of abnormal choroidal perfusion.

Mutations in Pre-mRNA Processing Factors 3, 8, and 31 Cause Dysfunction of the Retinal Pigment Epithelium

Mutations in the ubiquitously expressed pre-mRNA processing factors 3, 8, and 31 (PRPF3, PRPF8, and PRPF31) cause nonsyndromic dominant retinitis pigmentosa in humans, an inherited retinal degeneration. It is unclear what mechanisms, or which cell types of the retina, are affected. Transgenic mice with the human mutations in these genes display late-onset morphological changes in the retinal pigment epithelium (RPE). To determine whether the observed morphological changes are preceded by abnormal RPE function, we investigated its phagocytic function in Prpf3(T494M/T494M), Prpf8(H2309P/H2309P), and Prpf31(+/-) mice. We observe decreased phagocytosis in primary RPE cultures from mutant mice, and this is replicated by shRNA-mediated knockdown of PRPF31 in human ARPE-19 cells. The diurnal rhythmicity of phagocytosis is almost lost, indicated by the marked attenuation of the phagocytic burst 2 hours after light onset. The strength of adhesion between RPE apical microvilli and photoreceptor outer segments also declined during peak adhesion in all mutants. In all models, at least one of the receptors involved in binding and internalization of shed photoreceptor outer segments was subjected to changes in localization. Although the mechanism underlying these changes in RPE function is yet to be elucidated, these data are consistent with the mouse RPE being the primary cell affected by mutations in the RNA splicing factors, and these changes occur at an early age.

Enhanced depth imaging optical coherence tomography of choroidal metastasis in 14 eyes.

To describe the imaging features of choroidal metastasis using enhanced depth imaging optical coherence tomography (EDI-OCT). This retrospective observational case series included 31 eyes with choroidal metastasis. Spectral domain EDI-OCT was performed using Heidelberg Spectralis HRA + OCT. The main outcome measures were imaging features by EDI-OCT. Of 31 eyes with choroidal metastasis imaged with EDI-OCT, 14 (45%) eyes displayed image detail suitable for study. The metastasis originated from carcinoma of the breast (n = 7, 50%), lung (n = 5, 36%), pancreas (n = 1, 7%), and thyroid gland (n = 1, 7%). The mean tumor basal diameter was 6.4 mm, and mean thickness was 2.3 mm by B-scan ultrasonography. The tumor location was submacular in 6 (43%) eyes and extramacular in 8 (57%) eyes. By EDI-OCT, the mean tumor thickness was 987 μm. The most salient EDI-OCT features of the metastasis included anterior compression/obliteration of the overlying choriocapillaris (n = 13, 93%), an irregular (lumpy bumpy) anterior contour (n = 9, 64%), and posterior shadowing (n = 12, 86%). Overlying retinal pigment epithelial abnormalities were noted (n = 11, 78%). Outer retinal features included structural loss of the interdigitation of the cone outer segment tips (n = 9, 64%), the ellipsoid portion of photoreceptors (n = 8, 57%), external limiting membrane (n = 4, 29%), outer nuclear layer (n = 1, 7%), and outer plexiform layer (n = 1, 7%). The inner retinal layers (inner nuclear layer to nerve fiber layer) were normal. Subretinal fluid (n = 11, 79%), subretinal lipofuscin pigment (n = 1, 7%), and intraretinal edema (n = 2, 14%) were identified. The EDI-OCT of choroidal metastasis shows a characteristic lumpy bumpy anterior tumor surface and outer retinal layer disruption with preservation of inner retinal layers.

Study of Subretinal Exudation and Consequent Changes in Acute Central Serous Chorioretinopathy by Optical Coherence Tomography

To investigate the characteristics of subretinal exudation and consequent morphologic changes in acute central serous chorioretinopathy (CSC) using spectral-domain optical coherence tomography (OCT). Prospective, observational, cross-sectional case series. Patients with CSC with symptom duration of fewer than 3 months underwent visual acuity measurement, fundus observation and spectral-domain OCT examinations and then were evaluated for subretinal exudation and other changes. A total of 123 patients (123 eyes) were included, all showing various retinal pigment epithelium (RPE) abnormalities on OCT. OCT also showed subretinal exudation (65 eyes, 52.8%); retinal dipping (14 eyes, 11.4%); and photoreceptor layer defects (88 eyes, 71.5%). Without exception, the locations of these pathologic changes were closely related to the abnormal sites in the RPE. Those with subretinal exudation showed shorter durations of symptoms, whereas those with photoreceptor layer defects showed longer durations. In most eyes with retinal dipping, exudation connected it to RPE abnormalities. The defects of the photoreceptor layer, which involved the photoreceptor outer segment in 68 eyes, the photoreceptor inner segment in 20 eyes, and the outer nuclear layer as well, were likely to be the consequence of retinal dipping. OCT findings suggested that in eyes with acute CSC subretinal exudation, which indicated fibrin leakage through the RPE defects, might cause retinal dipping, thus leading to photoreceptor layer defects, and that spectral-domain OCT could provide a better understanding of the pathologic changes in acute CSC.

Age- and Gene-Dosage–Dependent Cre-Induced Abnormalities in the Retinal Pigment Epithelium

To conditionally inactivate genes in the retinal pigment epithelium (RPE) transgenic mouse strains have been developed, in which Cre recombinase (Cre) expression is driven by an RPE-specific gene promoter. The RPE is a quiescent epithelium, and continuous expression of Cre could affect its function. Here, we tested the hypothesis that continuous postnatal Cre expression in the RPE may lead to cellular abnormalities, which may depend on both age and Cre gene dosage. We therefore examined the eyes of homozygous and heterozygous VMD2-Cre mice at various ages. In VMD2-Cre heterozygous mice variable progressive age-dependent RPE abnormalities were noticed, including attenuation of phalloidin and cytoplasmic active β-catenin staining, reduced cell size, and loss of the typical honeycomb pattern of RPE morphology in those RPE cells that stained for Cre. These morphological RPE abnormalities were not noticed in Cre-negative RPE cells in VMD2-Cre or age-matched control mice. In addition, an abnormal number and morphology of cell nuclei were noticed in a subset of Cre-expressing RPE cells in aged heterozygous VMD2-Cre mice, whereas more severe nuclear abnormalities were observed already in young homozygous VMD2-Cre mice. Thus, continuous postnatal expression of Cre causes abnormalities in the RPE in an age- and Cre gene dosage-dependent manner, which needs to be considered in the interpretation of gene targeting studies in the RPE.

Progressive dysfunction of the retinal pigment epithelium and retina due to increased VEGF‐A levels

Patients with nonexudative ("dry") age-related macular degeneration (AMD) frequently also develop neovascular ("wet") AMD, suggesting a common pathomechanism. Increased vascular endothelial growth factor A (VEGF-A) has been implicated in the pathogenesis of choroidal neovascularization (CNV) in neovascular AMD, while its role in nonexudative AMD that manifests with progressive retinal pigment epithelium (RPE) and photoreceptor degeneration is not well defined. Mice with overall increased VEGF-A levels develop progressive morphological features of both forms of AMD, suggesting that an increase in VEGF-A has a direct age-dependent adverse effect on RPE and photoreceptor function independently of its CNV-promoting proangiogenic effect. Here we provide evidence for this hypothesis and show that morphological RPE abnormalities and retinal thinning in mice with increased VEGF-A levels correlate with progressive age-dependent attenuation of visual function with abnormal electroretinograms and reduced retinal rhodopsin levels. Retinoid profiling revealed a progressive reduction of 11-cis and all-trans retinal in the retinas of these mice, consistent with an impaired retinoid transport between the RPE and photoreceptors. These findings suggest that increased VEGF-A leads to an age-dependent RPE and retinal dysfunction that occurs also at sites where no CNV lesions form. The data support a central role of increased VEGF-A not only in the pathogenesis of neovascular but also of nonexudative AMD.

A novel gene mutation in a family with X-linked retinoschisis

To describe the clinical characteristics of a Taiwanese family with X-linked retinoschisis (XLRS) and to investigate the molecular genetics of a novel mutation in the retinoschisin 1 (RS1) gene. A total of 15 participants in this XLRS family were analyzed. Complete ophthalmic examinations and fundus photography were performed on 15 family members. These tests identified five affected males and two female carriers. Blood samples were collected, and genomic DNA was extracted. Best-corrected visual acuity, optical coherence tomography (OCT), electroretinogram (ERG), and direct DNA sequence analysis of the RS1 gene were performed on 15 family members. Five affected males, with visual acuity ranging from 0.2 to 0.7, had macular schisis and abnormal retinal pigment epithelium pigmentation. The mixed scotopic ERG "b" wave was more reduced than the "a" wave. OCT revealed typical microcystic schisis cavities within the macula area. Direct DNA sequence analysis revealed a single base pair deletion, 97delT, in all the affected individuals. This deletion resulted in a frameshift mutation of the RS1 gene, causing protein truncation. The affected males in this family showed moderately decreased visual acuity and dysfunction in both cone cells and phototransduction. We identified a novel RS1 (97delT) mutation in a Taiwanese family with XLRS. This finding expands the RS1 mutation spectrum and may help to further understand the molecular pathogenesis of XLRS.

En Face Enhanced-Depth Swept-Source Optical Coherence Tomography Features of Chronic Central Serous Chorioretinopathy

To characterize en face features of the retinal pigment epithelium (RPE) and choroid in eyes with chronic central serous chorioretinopathy (CSCR) using a high-speed, enhanced-depth swept-source optical coherence tomography (SS-OCT) prototype. Consecutive patients with chronic CSCR were prospectively examined with SS-OCT. Fifteen eyes of 13 patients. Three-dimensional 6×6 mm macular cube raster scans were obtained with SS-OCT operating at 1050 nm wavelength and 100000 A-lines/sec with 6 μm axial resolution. Segmentation of the RPE generated a reference surface; en face SS-OCT images of the RPE and choroid were extracted at varying depths every 3.5 μm (1 pixel). Abnormal features were characterized by systematic analysis of multimodal fundus imaging, including color photographs, fundus autofluorescence, fluorescein angiography, and indocyanine-green angiography (ICGA). En face SS-OCT morphology of the RPE and individual choroidal layers. En face SS-OCT imaging at the RPE level revealed absence of signal corresponding to RPE detachment or RPE loss in 15 of 15 (100%) eyes. En face SS-OCT imaging at the choriocapillaris level showed focally enlarged vessels in 8 of 15 eyes (53%). At the level of Sattler's layer, en face SS-OCT documented focal choroidal dilation in 8 of 15 eyes (53%) and diffuse choroidal dilation in 7 of 15 eyes (47%). At the level of Haller's layer, these same features were observed in 3 of 15 eyes (20%) and 12 of 15 eyes (80%), respectively. In all affected eyes, these choroidal vascular abnormalities were seen just below areas of RPE abnormalities. In 2 eyes with secondary choroidal neovascularization (CNV), distinct en face SS-OCT features corresponded to the neovascular lesions. High-speed, enhanced-depth SS-OCT at 1050 nm wavelength enables the visualization of pathologic features of the RPE and choroid in eyes with chronic CSCR not usually appreciated with standard spectral domain (SD) OCT. En face SS-OCT imaging seems to be a useful tool in the identification of CNV without the use of angiography. This in vivo documentation of the RPE and choroidal vasculature at variable depths may help elucidate the pathophysiology of disease and can contribute to the diagnosis and management of chronic CSCR.

A Constitutively Active Gαi3 Protein Corrects the Abnormal Retinal Pigment Epithelium Phenotype of Oa1−/− mice

PurposeOcular Albinism type 1 (OA1) is a disease caused by mutations in the OA1 gene and characterized by the presence of macromelanosomes in the retinal pigment epithelium (RPE) as well as abnormal crossing of the optic axons at the optic chiasm. We showed in our previous studies in mice that Oa1 activates specifically Gαi3 in its signaling pathway and thus, hypothesized that a constitutively active Gαi3 in the RPE of Oa1−/− mice might keep on the Oa1 signaling cascade and prevent the formation of macromelanosomes. To test this hypothesis, we have generated transgenic mice that carry the constitutively active Gαi3 (Q204L) protein in the RPE of Oa1−/− mice and are now reporting the effects that the transgene produced on the Oa1−/− RPE phenotype.MethodsTransgenic mice carrying RPE-specific expression of the constitutively active Gαi3 (Q204L) were generated by injecting fertilized eggs of Oa1−/− females with a lentivirus containing the Gαi3 (Q204L) cDNA. PCR, Southern blots, Western blots and confocal microscopy were used to confirm the presence of the transgene in the RPE of positive transgenic mice. Morphometrical analyses were performed using electron microscopy to compare the size and number of melanosomes per RPE area in putative Oa1−/−, Gαi3 (Q204L) transgenic mice with those of wild-type NCrl and Oa1−/− mice.ResultsWe found a correlation between the presence of the constitutively active Gαi3 (Q204L) transgene and the rescue of the normal phenotype of RPE melanosomes in Oa1−/−, Gαi3 (Q204L) mice. These mice have higher density of melanosomes per RPE area and a larger number of small melanosomes than Oa1−/− mice, and their RPE phenotype is similar to that of wild-type mice.ConclusionsOur results show that a constitutively active Gαi3 protein can by-pass the lack of Oa1 protein in Oa1−/− mice and consequently rescue the RPE melanosomal phenotype.

In vivo Optical Coherence Tomography of Light-Driven Melanosome Translocation in Retinal Pigment Epithelium

Optical coherence tomography (OCT) may revolutionize fundamental investigation and clinical management of age-related macular degeneration and other eye diseases. However, quantitative OCT interpretation is hampered due to uncertain sub-cellular correlates of reflectivity in the retinal pigment epithelium (RPE) and photoreceptor. The purpose of this study was twofold: 1) to test OCT correlates in the RPE, and 2) to demonstrate the feasibility of longitudinal OCT monitoring of sub-cellular RPE dynamics. A high resolution OCT was constructed to achieve dynamic imaging of frog eyes, in which light-driven translocation of RPE melanosomes occurred within the RPE cell body and apical processes. Comparative histological examination of dark- and light-adapted eyes indicated that the RPE melanin granule, i.e., melanosome, was a primary OCT correlate. In vivo OCT imaging of RPE melanosomes opens the opportunity for quantitative assessment of RPE abnormalities associated with disease, and enables longitudinal investigation of RPE kinetics correlated with visual function.

PACHYCHOROID PIGMENT EPITHELIOPATHY

To report nine cases of pachychoroid pigment epitheliopathy. An observational case series of nine patients who underwent comprehensive ophthalmic examination, fundus photography, fundus autofluorescence, spectral-domain optical coherence tomography, and enhanced depth imaging optical coherence tomography. Eighteen eyes of 9 patients, aged 27 years to 89 years, were diagnosed with pachychoroid pigment epitheliopathy based on the characteristic funduscopic appearance of reduced fundus tessellation with overlying retinal pigment epithelial changes in one or both eyes, fundus autofluorescence abnormalities, and increased subfoveal choroidal thickness confirmed by enhanced depth imaging optical coherence tomography (mean, 460.2 μm). The five older patients had been previously diagnosed with age-related macular degeneration, while the four younger subjects were referred for possible inflammatory chorioretinitis, pattern dystrophy, or nonspecific drusen. No subjects had a history of or subsequently developed subretinal fluid. Pachychoroid pigment epitheliopathy falls within a spectrum of diseases associated with choroidal thickening that includes central serous chorioretinopathy and polypoidal choroidal vasculopathy, and it should be suspected in eyes with a characteristic fundus appearance related to choroidal thickening and associated retinal pigment epithelial abnormalities but no history of subretinal fluid. Enhanced depth imaging optical coherence tomography confirming an abnormally thick choroid and characteristic retinal pigment epithelial changes on fundus autofluorescence support the diagnosis. Because these patients are frequently misdiagnosed, the recognition of pachychoroid pigment epitheliopathy may avoid unnecessary diagnostic testing and interventions.

Questioning photostasis

Photostasis is a phenomenon where the photoreceptor outer segment (OS) length and its rhodopsin content vary depending on environmental lighting. When light is reduced for extended periods, it is argued that OS lengthen and its rhodopsin concentration rises to increase photon capture in darker environment. Increases in OS length may occur because the retinal pigment epithelium (RPE) cells reduce OS consumption in prolonged darkness. But sample sizes in assessing changes in OS length have been small, and results highly varied with no statistical analysis ever offered. Further, animals used were often albinos, which have abnormal RPE cells. Here we keep pigmented and albino mice for 21 days in darkness and compare OS length with those in a normal 12:12 light/dark environment. We measured approximately 1300 OS but found no statistically significant difference in their lengths between light and dark groups in either pigmentation phenotype, although there was a small trend in the data favoring OS extension in the dark. Given that earlier studies were undertaken on limited samples with no statistical analysis, our data pose serious questions for the notion of mammalian photostasis in terms of significant OS plasticity.

Multifocal electroretinographic evaluation of macular function in acute posterior multifocal placoid pigment epitheliopathy

In acute posterior multifocal placoid pigment epitheliopathy (APMPPE), little is known about the long-term outcome of electroretinographic macular function. The purpose of this study was to report 2-year follow-up results of multifocal electroretinography (mfERG) in a 26-year-old Japanese woman diagnosed with APMPPE. Clinical and electrophysiological investigations of a single patient. Best-corrected visual acuity at initial examination was 1.5 and 0.5 in her right and left eyes, respectively. In addition to characteristic fundus lesions bilaterally, fluorescein angiography demonstrated diagnostic early blockage and late staining of the lesions. Optical coherence tomography revealed a hyperreflective spot (corresponding to the lesion) in the outer retinal layer in the right eye and intraretinal fluid in the left eye. On mfERG, the amplitudes were generally preserved, but markedly reduced amplitudes were detected in the central region of the left eye and in the paracentral region of the right eye. Five days later, visual acuity improved to 1.0, and the intraretinal fluid spontaneously disappeared without medication in the left eye. Light-to-dark ratios on electrooculography were 2.68 and 2.23 in the right and left eyes, respectively, both within the normal range. Two years later, visual acuity was 2.0 in both eyes, and ophthalmoscopically, there were neither retinal nor retinal pigment epithelial (RPE) abnormalities. mfERG revealed that the amplitudes were considerably improved (nearly normal level) in both eyes. The outcome suggests that longitudinal macular function in both visual acuity and mfERG may be favorable, unless areas of retinal or RPE alteration remain.