Retinitis pigmentosa and Usher syndrome currently do not have a cure, though there are some genetic therapies and innovative treatments (such as bionic eyes for retinitis pigmentosa) that show promise for treating these conditions.Ĭolor blindness also does not have a cure, but colorblind glasses can help people see color better with the use of special filters in the lenses. Photokeratitis (snow blindness) – a painful but temporary loss of vision due to overexposure to ultraviolet (UV) rays. Usher syndrome – a rare genetic disorder that affects vision, hearing and balance - this is often associated with retinitis pigmentosa.Ĭolor blindness – a color vision deficiency that affects the way the eye sees color. Retinitis pigmentosa – a genetic disorder that affects how the retina responds to light. Various vision conditions involve the photoreceptors - many of which have to do with how light enters the eye. Vision conditions that involve photoreceptors Unlike cones, rods are not found in the fovea portion of the retina. There are over 100 million rod cells in the eye. This type of photoreceptor does not have any subtypes, and does not help the eye see color - which is why when you view objects at night (or in otherwise dark environments), everything appears in a gray scale. These photoreceptors contain a protein called rhodopsin (also called visual purple) that provide the eye with pigmentation in low-light conditions. Rod photoreceptors are sensitive in dimly-lit environments, and assist the eye in night vision and seeing in black and white. The eye has approximately 6 million cones, which are mostly located in the fovea, a pit-like structure located in the center of the retina that sharpens the details of images you see. For example, a yellow object - such as a banana - stimulates the red and green cones simultaneously, as red and green combine to create a yellow hue. More than one color cone is stimulated to see the colors in between. Red light and objects stimulate the red cones, while green light and objects stimulate the green cones and so on. There are three subtypes of cones: blue, red and green cones - each is sensitive to various wavelengths of light, which allows the eye to see multiple colors. This type of photoreceptor contains proteins called photopsins (or cone opsins) that help create color pigments for the eye to view. Cone photoreceptorsĬone photoreceptors are activated by bright lighting and help the eye to see color. The human eye contains more rod photoreceptors than cone photoreceptors. Rods aid in night vision and identifying black and white hues.īoth cones and rods contain special proteins that assist in their functionality. While cone photoreceptors detect color through bright light, rod photoreceptors are sensitive to low-light levels. These cells function by sensing light and/or color and delivering the message back to the brain through the optic nerve. There are two types of photoreceptors: cone photoreceptors and rod photoreceptors. Each type of photoreceptor works to convert different levels of light into signals that are then sent to the brain to form a visual representation. There are two kinds of photoreceptor cells: cones and rods. Photoreceptor cells are located in the retina, which is the light-sensitive tissue that lines the back of the eye. Finally, we will analyse the evidence for and against optogenetic tool mediated toxicity and will discuss the challenges associated with clinical translation of this promising therapeutic concept.Small cells called photoreceptors in the eye play a vital role in night vision and also affect how the eye sees color. Possible cellular targets will be discussed and we will address the question how retinal remodelling may affect the choice of the target and to what extent it may limit the outcomes of optogenetic vision restoration. We discuss the currently available optogenetic tools and their relative advantages and disadvantages. In this article, we provide a review of optogenetic approaches for vision restoration. Since proof-of-concept almost fifteen years ago, this field has rapidly evolved and a detailed first report on a treated patient has recently been published. By rendering surviving retinal neurons light sensitive optogenetic gene therapy now offers a feasible treatment option that can restore lost vision, even in late disease stages and widely independent of the underlying cause of degeneration. Over recent years, innovative gene replacement therapies aiming to halt the progression of certain inherited retinal disorders have made their way into clinics. Degenerative retinal disorders are a diverse family of diseases commonly leading to irreversible photoreceptor death, while leaving the inner retina relatively intact.
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