The retina is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create visual perception. The retina serves a function analogous to that of the film or image sensor in a camera.
Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision. As peripheral vision worsens, people may experience "tunnel vision". Complete blindness is uncommon. Onset of symptoms is generally gradual and often begins in childhood.
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential.
A retinal ganglion cell (RGC) is a type of neuron located near the inner surface of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and retina amacrine cells. Retina amacrine cells, particularly narrow field cells, are important for creating functional subunits within the ganglion cell layer and making it so that ganglion cells can observe a small dot moving a small distance. Retinal ganglion cells collectively transmit image-forming and non-image forming visual information from the retina in the form of action potential to several regions in the thalamus, hypothalamus, and mesencephalon, or midbrain.
Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene Opn4. In the mammalian retina, there are two additional categories of opsins, both involved in the formation of visual images: rhodopsin and photopsin in the rod and cone photoreceptor cells, respectively.
Intrinsically photosensitive retinal ganglion cells (ipRGCs), also called photosensitive retinal ganglion cells (pRGC), or melanopsin-containing retinal ganglion cells (mRGCs), are a type of neuron in the retina of the mammalian eye. The presence of ipRGCs was first suspected in 1927 when rodless, coneless mice still responded to a light stimulus through pupil constriction, This implied that rods and cones are not the only light-sensitive neurons in the retina. Yet research on these cells did not advance until the 1980s. Recent research has shown that these retinal ganglion cells, unlike other retinal ganglion cells, are intrinsically photosensitive due to the presence of melanopsin, a light-sensitive protein. Therefore they constitute a third class of photoreceptors, in addition to rod and cone cells.
Progressive retinal atrophy (PRA) is a group of genetic diseases seen in certain breeds of dogs and, more rarely, cats. Similar to retinitis pigmentosa in humans, it is characterized by the bilateral degeneration of the retina, causing progressive vision loss culminating in blindness. The condition in nearly all breeds is inherited as an autosomal recessive trait, with the exception of the Siberian Husky and the Bullmastiff. There is no treatment.
Eye formation in the human embryo begins at approximately three weeks into embryonic development and continues through the tenth week. Cells from both the mesodermal and the ectodermal tissues contribute to the formation of the eye. Specifically, the eye is derived from the neuroepithelium, surface ectoderm, and the extracellular mesenchyme which consists of both the neural crest and mesoderm.
Congenital stationary night blindness (CSNB) is a rare non-progressive retinal disorder. People with CSNB often have difficulty adapting to low light situations due to impaired photoreceptor transmission. These patients may also have reduced visual acuity, myopia, nystagmus, and strabismus. CSNB has two forms -- complete, also known as type-1 (CSNB1), and incomplete, also known as type-2 (CSNB2), which are distinguished by the involvement of different retinal pathways. In CSNB1, downstream neurons called bipolar cells are unable to detect neurotransmission from photoreceptor cells. CSNB1 can be caused by mutations in various genes involved in neurotransmitter detection, including NYX. In CSNB2, the photoreceptors themselves have impaired neurotransmission function; this is caused primarily by mutations in the gene CACNA1F, which encodes a voltage-gated calcium channel important for neurotransmitter release. CSNB has been identified in horses and dogs as the result of mutations in TRPM1, GRM6, and LRIT3 .
Müller glia, or Müller cells, are a type of retinal glial cells, first recognized and described by Heinrich Müller. They are found in the vertebrate retina, which serve as support cells for the neurons, as all glial cells do. They are the most common type of glial cell found in the retina. While their cell bodies are located in the inner nuclear layer of the retina, they span across the entire retina.
Homeobox protein OTX2 is a protein that in humans is encoded by the OTX2 gene.
Retinal gene therapy holds a promise in treating different forms of non-inherited and inherited blindness.
Adam David Rutherford is a British geneticist, author, and broadcaster. He was an audio-visual content editor for the journal Nature for a decade, and is a frequent contributor to the newspaper The Guardian. He hosts the BBC Radio 4 programmes Inside Science and The Curious Cases of Rutherford and Fry; has produced several science documentaries; and has published books related to genetics and the origin of life.
Retinal regeneration refers to the restoration of vision in vertebrates that have suffered retinal lesions or retinal degeneration.
Retinal precursor cells are biological cells that differentiate into the various cell types of the retina during development. In the vertebrate, these retinal cells differentiate into seven cell types, including retinal ganglion cells, amacrine cells, bipolar cells, horizontal cells, rod photoreceptors, cone photoreceptors, and Müller glia cells. During embryogenesis, retinal cells originate from the anterior portion of the neural plate termed the eye field. Eye field cells with a retinal fate express several transcription factor markers including Rx1, Pax6, and Lhx2. The eye field gives rise to the optic vesicle and then to the optic cup. The retina is generated from the precursor cells within the inner layer of the optic cup, as opposed to the retinal pigment epithelium that originate from the outer layer of the optic cup. In general, the developing retina is organized so that the least-committed precursor cells are located in the periphery of the retina, while the committed cells are located in the center of the retina. The differentiation of retinal precursor cells into the mature cell types found in the retina is coordinated in time and space by factors within the cell as well as factors in the environment of the cell. One example of an intrinsic regulator of this process is the transcription factor Ath5. Ath5 expression in retinal progenitor cells biases their differentiation into a retinal ganglion cell fate. An example of an environmental factor is the morphogen sonic hedge hog (Shh). Shh has been shown to repress the differentiation of precursor cells into retinal ganglion cells.
José-Alain Sahel is a French ophthalmologist and scientist. He is currently the chair of the Department of Ophthalmology at the University of Pittsburgh School of Medicine, director of the UPMC Eye Center, and the Eye and Ear Foundation Chair of Ophthalmology. Dr. Sahel previously led the Vision Institute in Paris, a research center associated with the one of the oldest eye hospitals of Europe - Quinze-Vingts National Eye Hospital in Paris, founded in 1260. He is a pioneer in the field of artificial retina and eye regenerative therapies. He is a member of the French Academy of Sciences.
Robert E. MacLaren FMedSci FRCOphth FRCS FACS VR is a British ophthalmologist who has led pioneering work in the treatment of blindness caused by diseases of the retina. He is Professor of Ophthalmology at the University of Oxford and Honorary Professor of Ophthalmology at the UCL Institute of Ophthalmology. He is a Consultant Ophthalmologist at the Oxford Eye Hospital and an Honorary Consultant Ophthalmologist at the Great Ormond Street Hospital. He is also an Honorary Consultant Vitreo-retinal Surgeon at the Moorfields Eye Hospital. MacLaren is an NIHR Senior Investigator, or lead researcher, for the speciality of Ophthalmology. In addition, he is a member of the research committee of Euretina: the European Society of Retina specialists, Fellow of Merton College, in Oxford and a Fellow of the Higher Education Academy.
Masayo Takahashi is a Japanese medical physician, ophthalmologist and stem cell researcher.
Stem cell therapy for macular degeneration is the use of stem cells to heal, replace dead or damaged cells of the macula in the retina. Stem cell based therapies using bone marrow stem cells as well as retinal pigment epithelial transplantation are being studied. A number of trials have occurred in humans with encouraging results.
Caren Norden is a German biophysicist who is Deputy Director for Science at the Instituto Gulbenkian de Ciência. She works as a group leader at the Max Planck Institute of Molecular Cell Biology and Genetics. Her research considers the cell biology of tissue morphogenesis.
