RNA-seq analysis of ageing human retinal pigment epithelium: Unexpected up-regulation of visual cycle gene transcription

Ageing presents adverse effects on the retina and is the primary risk factor for age‐related macular degeneration (AMD). We report the first RNA‐seq analysis of age‐related transcriptional changes in the human retinal pigment epithelium (RPE), the primary site of AMD pathogenesis. Whole transcriptome sequencing of RPE from human donors ranging in age from 31 to 93 reveals that ageing is associated with increasing transcription of main RPE‐associated visual cycle genes (including LRAT, RPE65, RDH5, RDH10, RDH11; pathway enrichment BH‐adjusted P = 4.6 × 10(−6)). This positive correlation is replicated in an independent set of 28 donors and a microarray dataset of 50 donors previously published. LRAT expression is positively regulated by retinoid by‐products of the visual cycle (A2E and all‐trans‐retinal) involving modulation by retinoic acid receptor alpha transcription factor. The results substantiate a novel age‐related positive feedback mechanism between accumulation of retinoid by‐products in the RPE and the up‐regulation of visual cycle genes

Scanning Laser Ophthalmoscopy (SLO)

Since the first scanning laser ophthalmoscope (SLO) was introduced in the early 1980s, this imaging technique has been adapted and optimized for various clinical applications based on different contrast mechanism. Reflectance imaging, where the back scattered light is detected, is widely used for eye tracking and as reference image for OCT applications. But also the reflectance modality itself has several important diagnostic applications: laser scanning tomography (SLT), imaging with different laser wavelengths (Multicolor contrast) and others. Fluorescence imaging channels with different excitation wavelengths were introduced to SLOs for angiography, i.e. for the visualization of the vascular system after intravenously injecting an appropriate dye, as well as for autofluorescence imaging of endogenous fluorophores within the retina

Near-infrared reflectance imaging of neovascular age-related macular degeneration

Contains fulltext : 81007.pdf (publisher's version ) (Closed access)PURPOSE: To evaluate various types of neovascular age-related macular degeneration (AMD) by near-infrared fundus reflectance (NIR) as compared to fundus fluorescein angiography (FFA) and to test NIR for assessment of leakage due to choroidal neovascularization (CNV). PATIENTS AND METHODS: Thirty-three patients with neovascular AMD (cases) and 20 age-matched patients with non-exudative AMD and healthy subjects (controls) were examined with a confocal scanning laser ophthalmoscope (Heidelberg Retina Angiograph 2). NIR images of neovascular AMD were qualitatively compared to the corresponding FFA and to age-matched controls. CNV membranes and exudation areas were manually segmented on FFA and NIR and analyzed quantitatively. Results : Of all cases included, five eyes had classic CNV, six had minimal classic lesions, 15 occult CNV's and seven eyes had retinal angiomatous proliferation (RAP). A dark halo on NIR was found in all cases and showed high correspondence to leakage on FFA (r (2) = 0.93; p < 0,0005). In classic CNV and minimal classic CNV, the classic part of the lesion on FFA revealed strong correlation to a dark core surrounded by a bright reflecting ring on NIR (r (2) = 0.88; p < 0.0005). Occult parts on FFA of minimal classic CNV and occult CNV lesions appeared as poorly demarcated, jagged areas of increased NIR. RAP was characterized by speckled NIR located at the intraretinal neovascular complex. CONCLUSIONS: NIR imaging in neovascular AMD revealed characteristic alterations depending on the type of CNV. These changes may reflect histological differences of the lesions. Leakage caused local darkening of NIR, presumably originating from increased light-scattering and absorbance by fluid accumulation and sub-cellular structure alterations

Hyperspectral Computed Tomographic Imaging Spectroscopy of Vascular Oxygen Gradients in the Rabbit Retina In Vivo

Diagnosis of retinal vascular diseases depends on ophthalmoscopic findings that most often occur after severe visual loss (as in vein occlusions) or chronic changes that are irreversible (as in diabetic retinopathy). Despite recent advances, diagnostic imaging currently reveals very little about the vascular function and local oxygen delivery. One potentially useful measure of vascular function is measurement of hemoglobin oxygen content. In this paper, we demonstrate a novel method of accurately, rapidly and easily measuring oxygen saturation within retinal vessels using in vivo imaging spectroscopy. This method uses a commercially available fundus camera coupled to two-dimensional diffracting optics that scatter the incident light onto a focal plane array in a calibrated pattern. Computed tomographic algorithms are used to reconstruct the diffracted spectral patterns into wavelength components of the original image. In this paper the spectral components of oxy- and deoxyhemoglobin are analyzed from the vessels within the image. Up to 76 spectral measurements can be made in only a few milliseconds and used to quantify the oxygen saturation within the retinal vessels over a 10–15 degree field. The method described here can acquire 10-fold more spectral data in much less time than conventional oximetry systems (while utilizing the commonly accepted fundus camera platform). Application of this method to animal models of retinal vascular disease and clinical subjects will provide useful and novel information about retinal vascular disease and physiology

Photovoltaic restoration of sight with high visual acuity

Patients with retinal degeneration lose sight due to the gradual demise of photoreceptors. Electrical stimulation of surviving retinal neurons provides an alternative route for the delivery of visual information. We demonstrate that subretinal implants with 70-μm-wide photovoltaic pixels provide highly localized stimulation of retinal neurons in rats. The electrical receptive fields recorded in retinal ganglion cells were similar in size to the natural visual receptive fields. Similarly to normal vision, the retinal response to prosthetic stimulation exhibited flicker fusion at high frequencies, adaptation to static images and nonlinear spatial summation. In rats with retinal degeneration, these photovoltaic arrays elicited retinal responses with a spatial resolution of 64 ± 11 μm, corresponding to half of the normal visual acuity in healthy rats. The ease of implantation of these wireless and modular arrays, combined with their high resolution, opens the door to the functional restoration of sight in patients blinded by retinal degeneration