Single flash electroretinograms of mature cataractous and fellow eyes.

BACKGROUND: It is generally stated that opacities of the ocular media, including senile cataract, have little effect on the electrical responses of the retina. However, lower amplitudes and longer implicit times are sometimes observed in electroretinograms (ERGs) of patients with mature cataract. METHODS: Single flash ERGs of mature cataractous eyes with decimal visual acuity less than 0.1 were compared with those of the fellow eyes with decimal visual acuity better than 0.5, in 105 senile cataract patients. RESULTS: The mean amplitudes and implicit times of ERG a-waves were, respectively, 323.6±95.8 µV and 14.7±3.5 ms in the cataractous eyes and 352.3±96.6 µV and 12.0±1.5 ms in the fellow eyes. The mean amplitudes and implicit times of ERG b-waves were, respectively, 390.1±108.7 µV and 63.4±27.9 ms in the cataractous eyes and 415.3±119.1 µV and 59.0±9.3 ms in the fellow eyes. The mean amplitudes of the a- and b-waves were significantly lower and the mean implicit times of the a- and b-wave were significantly longer in the cataractous eyes as compared to those of the fellow eyes. Postoperative visual acuity was similar in cataractous and fellow eyes. CONCLUSION: Even though single flash ERG was influenced due to mature cataract, eyes revealed good postoperative visual acuity. Single flash ERG does not always reflect the foveal function and the visual pathway; nevertheless, it remains a reliable guide to evaluate visual prognosis before cataract surgery.

Profile of intraocular immune mediators in patients with age-related macular degeneration and the effect of intravitreal bevacizumab injection.

PURPOSE: To measure intraocular cytokine levels in patients with exudative age-related macular degeneration and analyze changes in the cytokine profile 2 days after intravitreal bevacizumab injection. METHODS: This prospective case-control study enrolled 37 patients (37 eyes) with age-related macular degeneration including polypoidal choroidal vasculopathy. Twenty-eight age-matched patients (28 eyes) who underwent cataract surgery were used as controls. Undiluted aqueous humor samples were collected after intravitreal bevacizumab injection. Two days after intravitreal bevacizumab injection, cataract surgery was performed and undiluted aqueous humor samples were collected at the beginning of surgery (10 eyes). Twenty-three cytokines were measured using flow cytometry. P values were corrected in multiple comparisons using the conservative Bonferroni-Holm method. The level of significance was set at 0.0022 (0.05/23). RESULTS: At baseline, aqueous humor levels of vascular endothelial growth factor, angiogenin, interferon gamma-inducible protein (IP)-10, macrophage inflammatory protein (MIP)-1ß, monokine induced by interferon γ (Mig), and monocyte chemotactic protein (MCP)-1 were significantly higher in the age-related macular degeneration group than in the control group (P < 0.0022). The result of exploratory multivariate analysis showed that elevated angiogenin level was an important factor that discriminates the two groups (P = 0.0004). Two days after intravitreal bevacizumab injection, vascular endothelial growth factor levels tended to be reduced (P = 0.049), whereas interleukin (IL)-6 and IL-8 levels increased significantly (P < 0.0022). CONCLUSION: Vascular endothelial growth factor and also angiogenin, IP-10, MCP-1, MIP-1ß, and Mig may be related to the pathogenesis of age-related macular degeneration. Intravitreal bevacizumab injection increases inflammatory cytokine levels, suggesting the induction of an inflammatory process.

Novel automated screening of age-related macular degeneration.

PURPOSE: To determine the objective and quantitative hyperspectral parameters for distinguishing between age-related macular degeneration (AMD) and a normal macula. METHODS: Near-infrared hyperspectral images were taken of 71 eyes of 62 AMD patients with exudative AMD and 21 eyes of 12 control subjects without AMD. The spatial information included a 480 × 321-pixel image in a 50° field located at the ocular fundus and a 720-950-nm-per-pixel reflectance spectrum. Macular vectors were determined as the average spectrum for each macula, and reference vectors were used as average macular vectors for healthy volunteers. Variations in vector length and angle were calculated based on comparison with the reference vector. The AMD differentiation index was a parameter that minimized the plot overlap between AMD patients and controls. RESULTS: Statistically significant differences between the AMD patients and controls were noted. Receiver-operating characteristic curve analysis revealed an area under the curve of 0.888. The appropriate threshold values were attained for the proposed discrimination index, including 68 % sensitivity, 95 % specificity and 74 % accuracy. CONCLUSIONS: This study presents a simplified diagnostic index for the determination of age-related macular degeneration based on near-infrared spectra.

Biological activity is the likely origin of the intersection between the photoreceptor inner and outer segments of the rat retina as determined by optical coherence tomography.

BACKGROUND: Recent research on macular diseases has prompted investigations into the condition of the intersection between the photoreceptor inner and outer segments (IS/OS) and the relationship with retinal photoreceptor abnormalities. Although the origin of the IS/OS in optical coherence tomography (OCT) images is unclear, it may be related to either the cellular activity of the photoreceptors or the structure of the OS disks. To address this question, we compared the IS/OS status in OCT images of rat retinas before and after euthanasia. METHODS: OCT images were taken before and after euthanasia in four eyes of two Brown Norway rats. After the OCT images were taken, the rats were used for histopathological studies to confirm that retinal structures were intact. RESULTS: Before euthanasia, the IS/OS and external limiting membrane (ELM) line were clearly identifiable on the OCT images. However, after euthanasia, neither the IS/OS nor the ELM line was evident in three out of four eyes, and a faint IS/OS and an ELM line were identified in one eye. Histopathological analysis did not show any abnormalities in the retina in any of the four eyes. CONCLUSION: The origin of the IS/OS identified in OCT images is likely related to the biological activities of the photoreceptor cells.

Correlation between high-resolution optical coherence tomography (OCT) images and histopathology in an N-methyl-N-nitrosourea-induced retinal degeneration rat model.

BACKGROUND: Recent research on macular diseases has prompted investigations into the condition of the intersection between the inner and outer segments (IS/OS), and its relationship with retinal photoreceptor abnormalities. Because the correlation between optical coherence tomography (OCT) images and histopathology is unclear, the authors compared them in an N-methyl-N-nitrosourea (MNU)-induced photoreceptor degeneration rat model. METHODS: MNU (60 mg/kg), which is toxic to photoreceptors, was injected in 12 Brown Norway rats. After MNU administration, three rats were used per histopathological study 3 h, 6 h, 24 h and 1 week after the injections. Two healthy rats served as controls. OCT images were taken before euthanisation. RESULTS: 3 h after the MNU injections, the IS and OS were oedematous, but the IS/OS borderline was recognised histopathologically, and the IS/OS was depicted on the OCT images. Six hours after injections, the OS were preserved, but the IS structures were destroyed or partially disorganised histopathologically, and the IS/OS was not observed on the OCT images. Twenty-four hours after the injections, the IS and OS were totally disorganised histopathologically, and the IS/OS was not depicted on the OCT images. CONCLUSION: The IS structure might be the origin of the IS/OS on OCT images.

Correlation between high-resolution optical coherence tomography (OCT) images and histopathology in an iodoacetic acid-induced model of retinal degeneration in rabbits.

BACKGROUND: Recent research on macular disease has prompted investigation into the condition of the intersection of the inner and outer segments (IS/OS) and its relationship with retinal photoreceptor abnormalities. Because the relationship between optical coherence tomography (OCT) images and histopathology is unclear, we compared these in an iodoacetic acid (IAA)-induced model of photoreceptor degeneration in rabbits. METHODS: IAA (20 mg/kg), which is toxic to photoreceptors, was injected into six coloured rabbits. After IAA administration, nine retinas were used for histopathological study: three from rabbits surviving for 1 day and six from rabbits surviving for 4 months. Four healthy rabbit retinas served as controls. OCT images were taken before euthanasia. RESULTS: In the controls, OCT images revealed the IS/OS as a clear, straight line. In rabbits surviving for 1 day, the structure of the photoreceptor IS/OS was destroyed and the IS/OS boundary was not visible. In rabbits surviving for 4 months, the IS was still preserved, but the structure of the OS was destroyed or partially disorganised, and the IS/OS was observed as a wavy, broken line on the OCT images. CONCLUSION: The IS/OS on the OCT images reflected the histopathology of the inner and outer segments in a photoreceptor degeneration model.

[Pars plana vitrectomy in patients with acute retinal necrosis syndrome: surgical results in 52 patients].

PURPOSE: To analyze results of pars plana vitrectomy for acute retinal necrosis (ARN) syndrome. METHODS: We reviewed the records of 52 eyes with ARN syndrome who underwent pars plana vitrectomy at the Tokyo Medical University Hospital from 1989 to 2007. The mean age was 50.1 +/- 10.2 years and the mean follow-up duration was 75.3 months. The causative virus was herpes simplex virus in 7 cases and varicella zoster virus in 45 cases. In all cases, treatment with acyclovir and corticosteroids was started from presentation. During the follow-up period, vitrectomy was done in patients who developed retinal detachment, and in those who developed posterior vitreous detachment exerting marked traction on the retina, even though retinal detachment had not occurred. In these cases, preoperative and postoperative visual acuities were compared and reoperation, retinal detachment preventive surgery and age-stratified visual prognosis after vitrectomy were analyzed. RESULTS: Visual acuity was improved by 2 lines or more in 13 eyes (25.0%), remained unchanged in 16 eyes (30.8%), and deteriorated by 2 lines or more in 23 eyes (44.2%). Thirty-seven of 52 eyes (71.2%) required re-operation. No significant differences were detected when the patients were stratified according to whether they were treated either with or without combined use of silicon oil, or according to whether they were treated either with or without prophylactic surgery for retinal detachment, as well as by age of vitrectomy. A combination of lens extraction, silicon oil and encircling sclera buckling procedure was associated with a significantly higher frequency of final visual acuity. CONCLUSION: Despite the advances in vitrectomy achieved today, the visual prognosis of acute retinal necrosis remains unsatisfactory. The present study found no significant improvement in the prognostic relevance of prophylactic vitrectomy. Improvement in pharmacotherapy may help improve the prognosis. Further prospective large-scale studies to compare other treatment modalities are also required.

Long-term cellular and regional specificity of the photoreceptor toxin, iodoacetic acid (IAA), in the rabbit retina.

This study investigated the anatomical consequences of a photoreceptor toxin, iodoacetic acid (IAA), in the rabbit retina. Retinae were examined 2 weeks, 1, 3, and 6 months after systemic IAA injection. The retinae were processed using standard histological methods to assess the gross morphology and topographical distribution of damage, and by immunohistochemistry to examine specific cell populations in the retina. Degeneration was restricted to the photoreceptors and was most common in the ventral retina and visual streak. In damaged regions, the outer nuclear layer was reduced in thickness or eliminated entirely, with a concomitant loss of immunoreactivity for rhodopsin. However, the magnitude of the effect varied between animals with the same IAA dose and survival time, suggesting individual differences in the bioavailability of the toxin. In all eyes, the inner retina remained intact, as judged by the thickness of the inner nuclear layer, and by the pattern of immunoreactivity for protein kinase C-alpha (rod bipolar cells) and calbindin D-28 (horizontal cells). Müller cell stalks became immunoreactive for glial fibrillary acidic protein (GFAP) even in IAA-treated retinae that had no signs of cell loss, indicating a response of the retina to the toxin. However, no marked hypertrophy or proliferation of Müller cells was observed with either GFAP or vimentin immunohistochemistry. Thus the selective, long lasting damage to the photoreceptors produced by this toxin did not lead to a reorganization of the surviving cells, at least with survival as long as 6 months, in contrast to the remodeling of the inner retina that is observed in inherited retinal degenerations such as retinitis pigmentosa and retinal injuries such as retinal detachment.

A case of hypertensive keratouveitis with endotheliitis associated with cytomegalovirus.

AIM: While cytomegalovirus is well known as a pathogenic organism of retinitis, especially associated with human immunodeficiency virus infection, there are few reports of anterior uveitis associated with cytomegalovirus. METHODS: The authors present a case of keratouveitis associated with cytomegalovirus. RESULTS: A 70-year-old Japanese man was referred to the authors because of poorly controlled hypertensive keratouveitis in the left eye. The patient had a history of recurrent hypertensive anterior uveitis. At presentation, the corneal stroma was edematous, with Descemet's folds and pigmented keratic precipitates. The anterior chamber angle was depigmented compared to the fellow eye. Even though pupil dilation and posterior synechiae were absent, iris atrophy was not evident. His right eye appeared normal except for moderate cataract. Funduscopy of the left eye was hazy, with the optic disc showing a normal color but poorly defined details, and no apparent exdative retinitis. The best-corrected decimal visual acuity of the right and left eyes was 0.4 and 0.02, respectively. Intraocular pressure was 11 mmHg in the right eye and 35 mmHg in the left, despite maximum medical therapy. Systemic acyclovir and prednisolone for a month did not improve the hypertensive keratouveitis. The aqueous humor was investigated for herpes simplex virus, varicella-zoster virus and cytomegalovirus. Cytomegalovius genome was detected by polymerase chain reaction analysis. Oral valganciclovir rapidly reduced ocular hypertension within a week. CMV DNA disappeared 3 months after the initiation of valganciclovir. CONCLUSION: The authors reported a case of hypertensive keratouveitis with endotheliitis associated with cytomegalovirus.

Relationship between retinal vein occlusion and carotid artery lesions.

PURPOSE: To investigate the relationship between retinal vein occlusion (RVO) and carotid artery lesions. METHODS: For patients with RVO who presented to the Ophthalmology Department of Tokyo Medical University Hospital between 2000 and 2003, carotid artery evaluation was possible on 58 eyes of 57 patients aged 51 years to 88 years (mean, 70.1 years). Thirty-nine patients (40 eyes) had central RVO (CRVO), and 18 patients (18 eyes) had branch RVO (BRVO). The observation period ranged from 6 months to 28 months (mean, 14 months). A diagnostic ultrasound device was used to detect carotid artery lesions. RESULTS: Carotid artery lesions were detected in 19 (49%) of 39 patients with CRVO and in 4 (22%) of 18 patients with BRVO. In CRVO, 6 eyes without carotid artery lesions but no eye with carotid artery lesions had good decimal visual acuity of >or=0.8 (P < 0.05). Fluorescein angiographic findings identified a significantly (P < 0.01) higher incidence of the ischemic type in cases with carotid lesions (15 eyes; 79%) than in cases without carotid lesions (8 eyes; 40%). CONCLUSIONS: The findings suggest that the presence of a carotid artery lesion has a considerable association with the development and prognosis of CRVO.

Systemically transferred hematopoietic stem cells home to the subretinal space and express RPE-65 in a mouse model of retinal pigment epithelium damage.

Stem cell regeneration of damaged tissue has recently been reported in many different organs. Since the loss of retinal pigment epithelium (RPE) in the eye is associated with a major cause of visual loss - specifically, age-related macular degeneration - we investigated whether hematopoietic stem cells (HSC) given systemically can home to the damaged subretinal space and express markers of RPE lineage. Green fluorescent protein (GFP) cells of bone marrow origin were used in a sodium iodate (NaIO(3)) model of RPE damage in the mouse. The optimal time for adoptive transfer of bone marrow-derived stem cells relative to the time of injury and the optimal cell type [whole bone marrow, mobilized peripheral blood, HSC, facilitating cells (FC)] were determined by counting the number of GFP(+) cells in whole eye flat mounts. Immunocytochemistry was performed to identify the bone marrow origin of the cells in the RPE using antibodies for CD45, Sca-1, and c-kit, as well as the expression of the RPE-specific marker, RPE-65. The time at which bone marrow-derived cells were adoptively transferred relative to the time of NaIO(3) injection did not significantly influence the number of cells that homed to the subretinal space. At both one and two weeks after intravenous (i.v.) injection, GFP(+) cells of bone marrow origin were observed in the damaged subretinal space, at sites of RPE loss, but not in the normal subretinal space. The combined transplantation of HSC+FC cells appeared to favor the survival of the homed stem cells at two weeks, and RPE-65 was expressed by adoptively transferred HSC by four weeks. We have shown that systemically injected HSC homed to the subretinal space in the presence of RPE damage and that FC promoted survival of these cells. Furthermore, the RPE-specific marker RPE-65 was expressed on adoptively transferred HSC in the denuded areas.

Behavioral and anatomical abnormalities in a sodium iodate-induced model of retinal pigment epithelium degeneration.

We characterized changes in the visual behavior of mice in which a loss of the retinal pigment epithelium (RPE) was experimentally induced with intravenous (i.v.) administration of sodium iodate (NaIO3). We compared and correlated these changes with alterations in neural retinal structure and function. RPE loss was induced in 4-6 week old male C57BL/6 mice with an i.v. injection of 1% NaIO3 at three concentrations: 35, 50, or 70 mg/kg. At 1, 3, 7, 14, 21, and 28 days (d) as well as 6 months post injection (PI) a behavioral test was performed in previously trained mice to evaluate visual function. Eye morphology was then assessed for changes in both the RPE and neural retina. NaIO3-induced RPE degeneration was both dose and PI time dependent. Our low dose showed no effects, while our high dose caused the most damage, as did longer PI times at our intermediate dose. Using the intermediate dose, no changes were detectable in either visual behavior or retinal morphology at 1 d PI. However, at 3 d PI visual behavior became abnormal and patchy RPE cell loss was observed. From 7 d PI onward, changes in retinal morphology and visual behavior became more severe. At 6 months PI, no recovery was seen in any of these measures in mice administered the intermediate dose. These results show that NaIO3 dosage and/or time PI can be varied to produce different, yet permanent deficits in retinal morphology and visual function. Thus, this approach should provide a unique system in which the onset and severity of RPE damage, and its consequences can be manipulated. As such, it should be useful in the assessment of rescue or mitigating effects of retinal or stem cell transplantation on visual function.

Suspected simultaneous bilateral anterior ischemic optic neuropathy in a patient with Behçet's disease.

AIM: To report a 47-year-old Japanese woman with a one-year history of Behçet's disease who complained of sudden bilateral visual loss with concurrent anterior ischemic optic neuropathy (AION). CASE REPORT: The patient's Snellen visual acuity was 0.1 (OD) and 0.3 (OS) of onset. There was bilateral mild anterior chamber inflammation. Bilateral optic disc pale swelling was observed without retinal exudates and edema. Fluorescein angiography demonstrated bilateral hypofluorescence of the optic disc in early frames but with no distinct retinal vasculitis. Visual field showed bilateral relative central scotoma and right altitudinal hemianopsia. Laboratory examination revealed an ESR of 26 mm in the first hour with a C-reactive protein level of < 0.3 mg/dl. Periocular injection of triamcinolone acetonide in both eyes without systemic corticosteroid administration improved her visual acuity to 0.7 (OD) and 1.2 (OS) within 45 days of onset. Bilateral optic disc swelling gradually resolved. In the early stages, fluorescein angiography demonstrated normal optic disc filling in both eyes. There was a residual right central scotoma on visual field. CONCLUSION: We observed an extremely rare case of simultaneous bilateral AION with Behçet's disease with marked visual recovery within 45 days of onset.

Conjunctival flora in patients with human immunodeficiency virus infection.

PURPOSE: To compare the conjunctival flora of human immunodeficiency virus (HIV)-positive and HIV-negative patients. Also, to assess the prophylactic effect of oral clarithromycin against Mycobacterium avium complex on the conjunctival flora of HIV-positive patients. METHODS: Ninety-four eyes of 47 HIV-positive patients and 122 eyes of 61 control patients were examined. All participants had a detailed anterior segment examination, including conjunctival cultures and laboratory blood tests. Culture results for different organisms were evaluated by chi-square analysis between the groups. The effect of systemic antibiotic treatment on the conjunctival flora of patients with HIV infection was evaluated by chi-square analysis. RESULTS: Bacterial organisms in the conjunctival sac were detected in four out of 28 (14.3%) eyes of HIV-positive patients treated with systemic clarithromycin and in 32 out of 66 (48.5%) eyes of HIV-positive patients without systemic clarithromycin treatment (p < 0.01). The CD4-positive T-cell counts in these groups were 158/microl and 416/microl, respectively (p < 0.01). Bacterial organisms were also detected in 46 of 122 (37.7%) control eyes. No difference was observed in the types and proportions of organisms isolated from the conjunctiva between HIV-positive patients without systemic clarithromycin treatment and controls. CONCLUSION: There was no difference between the conjunctival flora of HIV-negative and HIV-positive patients. Systemic clarithromycin treatment decreased the conjunctival flora of HIV patients, including those who had a CD4 count that was less than 50/microl.

Comparison of electrically evoked cortical potential thresholds generated with subretinal or suprachoroidal placement of a microelectrode array in the rabbit.

The aim of the study was to directly compare the threshold electrical charge density of the retina (retinal threshold) in rabbits for the generation of electrical evoked potentials (EEP) by delivering electrical stimulation with a custom-made microelectrode array (MEA) implanted into either the subretinal or suprachoroidal space. Nine eyes of seven Dutch-belted rabbits were studied. The electroretinogram (ERG), visual evoked potentials (VEP) and EEP were recorded. Electrodes for the VEP and EEP were placed on the dura mater overlying the visual cortex. The EEP was recorded following electrical stimulation of the MEA placed either subretinally beneath the visual streak of the retina or in the suprachoroidal space in the rabbit eye. An ab externo approach was used for placement of the MEA. Liquid perfluorodecaline (PFCL; 0.4 ml) was placed within the vitreous cavity to flatten the neurosensory retina on the MEA after subretinal implantation. The retinal threshold for generation of an EEP was determined for each MEA placement by three consecutive measurements consisting of 100 computer-averaged recordings. Animals were sacrificed at the conclusion of the experiment and the eyes were enucleated for histological examination. The retinal threshold to generate an EEP was 9 +/- 7 nC (0.023 +/- 0.016 mC cm(-2)) within the subretinal space and 150 +/- 122 nC (0.375 +/- 0.306 mC cm(-2)) within the suprachoroidal space. Histology showed disruption of the outer retina with subretinal but not suprachoroidal placement. The retinal threshold to elicit an EEP is significantly lower with subretinal placement of the MEA compared to suprachoroidal placement (P < 0.05). The retinal threshold charge density with a subretinal MEA is well below the published charge limit of 1 mC cm(-2), which is the level below which chronic stimulation of the retina is considered necessary to avoid tissue damage (Shannon 1992 IEEE Trans. Biomed. Eng. 39 424-6).

[Histopathological findings in cytomegalovirus retinitis].

PURPOSE: We examined eyeballs collected from autopsied acquired immunodeficiency syndrome patients with cytomegalovirus (CMV) retinitis, and analyzed the precise pathogenesis of CMV retinitis. MATERIAL AND METHODS: Eyeballs were fixed with 10% buffered formalin embedded in paraffin. CMV antigens were investigated by histopathological and immunohistochemical analyses. Histopathological findings were compared with funduscopic images. RESULTS: CMV antigens remained in the necrotic area of the retina and many CMV immediate early antigens existed in intact parts of the inner retina showing almost intact structure, and around retinal vessels. CONCLUSIONS: The results suggest that CMV infects the inner retina first via the retinal vessels, although funduscopic examination may appear normal. It extends through the neuronal cells and glial cells horizontally and Muller cells vertically. CMV severely damages the retinal structure.

Enhanced induction of RPE lineage markers in pluripotent neural stem cells engrafted into the adult rat subretinal space.

PURPOSE: To investigate the differentiation of rat neural stem cells (rNSCs) into cells of retinal pigment epithelial (RPE) lineage both in vitro and in vivo, after subretinal transplantation into normal rats and in a sodium iodate (NaIO(3)) model of RPE loss. METHODS: rNSCs prepared from the cortex of embryonic day (E)14 Fisher F344 rats were cocultured with different concentrations of vasoactive intestinal peptide (VIP), adult rat RPE cells, or neurosensory retina (NSR) for 5 days. Cell morphology and expression of RPE-specific markers (cytokeratin, CD68, microphthalmia-inducing transcription factor [MITF]) were studied. Additional antibodies used to characterize the rNSCs were markers for stem cells (nestin), immature neurons (betaIII-tubulin), astrocytes (glial fibrillary acidic protein [GFAP]), and oligodendrocytes (Rip). In in vivo studies, 10(6) green fluorescent protein [GFP]-labeled rNSCs were injected subretinally in either normal adult Lewis rats or NaIO(3)-treated rats (70 mg/mL NaIO(3) administered intravenously 7 days before transplantation). RESULTS: In vitro VIP-treated rNSCs changed from round cells to glia-like cells with processes that stained for both GFAP and nestin. In addition, small clusters of flattened, polygonal cells with an epithelial-cell-like shape that stained for cytokeratin and CD68 were observed. Coculture of rNSCs with RPE cells, but not with NSR, also led to cells of this phenotype. After transplantation, nestin(+) and GFP(+) rNSCs were visible subretinally as a transplant. In addition, more than 50% of transplanted rNSCs were cytokeratin(+) and CD68(+). CONCLUSIONS: Very few rNSCs differentiate in vitro into epithelial-like cells that express RPE-specific markers. In vivo, this differentiation is remarkably enhanced after subretinal engraftment. Thus, transplantation of NSCs into the subretinal space may be a therapy for retinal diseases involving an RPE abnormality.