{"id":1851,"date":"2026-10-20T08:53:02","date_gmt":"2026-10-20T08:53:02","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/retina\/"},"modified":"2026-10-20T12:57:15","modified_gmt":"2026-10-20T12:57:15","slug":"retina","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/retina\/","title":{"rendered":"Retina: What It Is, How It Works and What Can Go Wrong"},"content":{"rendered":"\n
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  1. Home<\/a><\/li>
  2. Knowledge centre<\/a><\/li>
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  4. Retina: What It Is, How It Works and What Can Go Wrong<\/span><\/li><\/ol><\/div>\t\t\t

    Retina: What It Is, How It Works and What Can Go Wrong<\/h1>\n\t\t\t\t\t\t

    Medically reviewed by {{surgeon}}<\/span><\/strong>, {{surgeon’s title and specialty}}<\/span>, on {{review date}}<\/span>. Last updated {{date}}<\/span>.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

    \"Retina<\/figure><\/div>\n\t\t\t<\/div><\/div>\n<\/section>\n\n\n\n\n
    \n\t\t<\/svg>Definition<\/span>\n\t\t\t

    Retina<\/strong> (noun, plural retinas or retinae)<\/em>: the retina is the thin, light-sensitive layer of nerve tissue that lines the inside of the back of the eye. It acts like the sensor of a camera: light-sensing cells called rods and cones turn the image focused by the cornea and lens into electrical signals, and the optic nerve carries those signals to the brain, which turns them into what you see. Retinal diseases such as retinal detachment, macular degeneration and diabetic retinopathy can cause permanent sight loss if they are not found and treated in time.<\/p>\n\t\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Retina: key facts<\/h2><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t
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    <\/svg>Where it is<\/span><\/dt>
    The inner lining of the back wall of the eye, behind the vitreous gel and in front of the choroid (the blood-rich layer beneath it)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Thickness<\/span><\/dt>
    About 0.5 mm<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Main cells<\/span><\/dt>
    Photoreceptors: rods (dim light, side vision) and cones (detail and colour); then bipolar, horizontal and amacrine cells and ganglion cells<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Centre of sharp vision<\/span><\/dt>
    The macula, with the fovea at its centre (the fovea is less than a quarter of a millimetre, about 200 \u00b5m, across)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Exit to the brain<\/span><\/dt>
    The optic nerve, at the optic disc<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Layers<\/span><\/dt>
    Ten, counting the pigment epithelium and the inner limiting membrane<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Blood supply<\/span><\/dt>
    Two sources: the central retinal artery feeds the inner retina, and the choroid feeds the photoreceptors (it receives the larger share of the eye’s blood flow)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Specialist<\/span><\/dt>
    Retina specialist (ophthalmologist); at Laser Istanbul Clinic, Do\u00e7. Dr. Muhammet Derda \u00d6zer and Op. Dr. Aysan Bayram<\/dd><\/dl><\/div>\n\t\t\t<\/div>\n\t\t<\/div><\/div><\/div><\/section>\n\n\n\n\n
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    \"Eye<\/div><\/div>\n\t\t
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    What is the retina, and where is it in the eye?<\/h2>\n\t\t\t\t\t\t

    The retina is the layer of cells lining the back wall inside the eye that senses light and sends signals to the brain so that you can see, as the American Academy of Ophthalmology (AAO) puts it. It is only about 0.5 mm thick, yet it holds the first stages of the whole visual system: light capture, early image processing and the cables (nerve fibres) that leave the eye.<\/p>\n\t\t\t\t\t\t

    The retina sits at the very back of the eyeball. In front of it is the vitreous<\/strong>, the clear gel that fills the middle of the eye. Behind it is the choroid<\/strong>, a layer of blood vessels that feeds the outer retina, and then the white outer wall of the eye, the sclera. Light enters through the cornea, passes through the pupil and the lens, crosses the vitreous and has to travel through the thickness of the retina before it reaches the rods and cones, which lie at the back against the pigment layer.<\/p>\n

    Retina, macula and fovea: what is the difference?<\/strong> The retina is the whole lining. The macula<\/strong> is its small central area, responsible for the sharp, straight-ahead vision you use to read, recognise faces and see colour. The fovea<\/strong> is the tiny pit at the very centre of the macula, less than a quarter of a millimetre across, where cones are packed most tightly. Everything outside the macula is the peripheral retina<\/strong>, which gives side vision and helps you see in dim light.<\/p>

    Glossary: Macula and fovea <\/svg><\/a><\/div><\/div>\n\t\t\t\t\t\t\t\t\t\t\t<\/div>\n<\/div><\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

    Retina function: how the retina creates vision<\/h2><\/div>

    The retina does four jobs, in this order.<\/p>\n

    1. It captures light.<\/strong> The photoreceptors convert light into electrical signals. There are two kinds. Rods<\/strong> work in dim light; they contain the pigment rhodopsin and give you night vision and side vision. Cones<\/strong> work in bright light, give sharp detail and let you see colour; people normally have three types, sensitive mainly to red, green and blue light. Cones dominate the centre of the retina and rods dominate the periphery.<\/p>\n

    2. It processes the signal.<\/strong> Before anything leaves the eye, bipolar, horizontal and amacrine cells begin sorting the information, for example picking out edges and contrast.<\/p>\n

    3. It sends the result to the brain.<\/strong> The output cells, the ganglion cells, send their long fibres across the surface of the retina and gather at the optic disc, where they leave the eye as the optic nerve. The optic disc has no light-sensing cells, which is why everyone has a natural blind spot there.<\/p>

    Glossary: Optic nerve <\/svg><\/a><\/div>

    4. It is fed by a dedicated blood supply.<\/strong> The retina is a very energy-hungry tissue. According to the Webvision retina textbook, the choroid receives the greatest share of the eye’s blood flow (65\u201385%) and nourishes the photoreceptors, while the central retinal artery supplies the inner retina with 20\u201330%. That is why blood-vessel disease, such as diabetes or a blocked retinal vein, shows up in the retina, and why a detached retina, cut off from the choroid beneath it, is an emergency.<\/p><\/div><\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    The layers of the retina<\/h2>\n\t\t\t

    Under a microscope, and on an OCT scan, the retina shows ten layers. Listed from the back of the eye (outermost) to the front (innermost, facing the vitreous):<\/p>\n\t\t\t

    #<\/th>Layer<\/th>What it contains or does<\/th><\/tr><\/thead>
    1<\/th>Retinal pigment epithelium (RPE)<\/td>A single layer of pigmented cells that supports and nourishes the rods and cones<\/td><\/tr>
    2<\/th>Photoreceptor layer<\/td>The light-sensing outer parts of the rods and cones<\/td><\/tr>
    3<\/th>Outer (external) limiting membrane<\/td>Junctions between M\u00fcller support cells and the photoreceptors<\/td><\/tr>
    4<\/th>Outer nuclear layer<\/td>Cell bodies of the rods and cones<\/td><\/tr>
    5<\/th>Outer plexiform layer<\/td>Connections between photoreceptors and bipolar and horizontal cells<\/td><\/tr>
    6<\/th>Inner nuclear layer<\/td>Cell bodies of bipolar, horizontal and amacrine cells<\/td><\/tr>
    7<\/th>Inner plexiform layer<\/td>Connections between bipolar cells and ganglion cells<\/td><\/tr>
    8<\/th>Ganglion cell layer<\/td>Cell bodies of the ganglion cells, the output neurons of the retina<\/td><\/tr>
    9<\/th>Nerve fibre layer<\/td>Ganglion cell fibres running to the optic nerve<\/td><\/tr>
    10<\/th>Inner limiting membrane (ILM)<\/td>A thin membrane facing the vitreous<\/td><\/tr><\/tbody><\/table><\/div>

    Strictly speaking, the RPE is the outer wall on which the nerve retina rests. A retinal detachment<\/strong> is a separation between layers 1 and 2: the nerve retina lifts away from the pigment layer that feeds it. In macular hole surgery, the surgeon often peels the inner limiting membrane around the hole to help it close.<\/p><\/div>\t<\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Retinal diseases: common conditions that affect the retina<\/h2><\/div><\/div>
    <\/svg><\/span>

    Retinal tear and retinal detachment<\/h3>

    With age, the vitreous gel shrinks and pulls away from the retina (posterior vitreous detachment). This is common and usually harmless, but sometimes the gel sticks and pulls hard enough to tear the retina, letting fluid pass behind it so the retina peels away. According to the AAO, you are at higher risk if you are short-sighted, have had cataract or other eye surgery or a serious eye injury, or have a family history of detachment. EyeWiki (AAO) gives an incidence of about 1 in 10,000 people. Retinal detachment is an emergency: untreated, it can lead to permanent vision loss.<\/p><\/div><\/div>

    <\/svg><\/span>

    Age-related macular degeneration (AMD)<\/h3>

    AMD damages the macula and blurs central vision while side vision is kept. The US National Eye Institute (NEI) says about 11 million people in the United States have it. Dry AMD<\/strong> is the more common form: the macula thins slowly over years, and there is no treatment for late-stage dry AMD. Wet AMD<\/strong> is less common and faster: abnormal blood vessels grow under the macula and damage it, and it can be treated with anti-VEGF injections. Risk factors are age (55 and over), a family history and smoking.<\/p><\/div><\/div>

    <\/svg><\/span>

    Diabetic retinopathy<\/h3>

    High blood sugar damages the tiny blood vessels in the retina. Early stages usually cause no symptoms, which is why screening matters; later the vessels leak or new, fragile ones grow, causing blurred vision, floaters and bleeding inside the eye. The NEI notes that anyone with type 1, type 2 or gestational diabetes is at risk, and that about 1 in 15 people with diabetes will develop diabetic macular oedema (swelling of the macula). The NHS invites people with diabetes aged 12 and over for eye screening every 1\u20132 years.<\/p><\/div><\/div>

    <\/svg><\/span>

    Retinal vein occlusion<\/h3>

    A blockage in the central retinal vein or one of its branches causes bleeding and swelling in the retina, usually with sudden loss of vision in one eye. According to EyeWiki, high blood pressure, diabetes, glaucoma and cardiovascular disease are the main risk factors.<\/p><\/div><\/div>

    <\/svg><\/span>

    Macular hole and epiretinal membrane (macular pucker)<\/h3>

    A macular hole is a small break in the macula, causing blurred or distorted central vision; an epiretinal membrane is a thin scar-like film on the macula that wrinkles it. Both are usually treated with vitrectomy surgery.<\/p><\/div><\/div>

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    Retinitis pigmentosa and inherited retinal disease<\/h3>

    Retinitis pigmentosa is a group of rare inherited conditions in which retinal cells gradually deteriorate. Night vision is usually lost first, often in childhood, followed by a narrowing of side vision (“tunnel vision”). The NEI states there is no cure for retinitis pigmentosa; vision aids, regular monitoring and genetic counselling help.<\/p><\/div><\/div>

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    Other conditions<\/h3>

    Central serous chorioretinopathy, cytomegalovirus retinitis, retinopathy of prematurity, retinoblastoma (a rare childhood eye cancer) and Usher syndrome are also listed by the AAO among retinal diseases.<\/p><\/div><\/div><\/div>\t<\/div><\/div><\/div>\n<\/section>\n\n\n\n\n

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    Damaged retina symptoms: warning signs to know<\/h2>\n\t\t\t

    Many retinal diseases cause no pain, and early diabetic retinopathy and early AMD cause no symptoms at all. Watch for these signs:<\/p>\n\t\t\t

    Symptom<\/th>What it can point to<\/th><\/tr><\/thead>
    New floaters (dots, lines, cobwebs), especially a sudden shower<\/th>Posterior vitreous detachment, retinal tear or detachment, bleeding<\/td><\/tr>
    Flashes of light<\/th>Vitreous pulling on the retina; tear or detachment<\/td><\/tr>
    A dark curtain, shadow or grey area spreading across your vision<\/th>Retinal detachment: emergency<\/td><\/tr>
    Blurred or distorted central vision; straight lines look wavy<\/th>Macular disease: AMD, macular hole, epiretinal membrane, macular oedema<\/td><\/tr>
    Sudden painless loss of vision in one eye<\/th>Retinal vein or artery blockage, bleeding, detachment: emergency<\/td><\/tr>
    Trouble seeing at night, narrowing of side vision<\/th>Retinitis pigmentosa and other inherited conditions<\/td><\/tr>
    Worsening vision with long-standing diabetes<\/th>Diabetic retinopathy or macular oedema<\/td><\/tr><\/tbody><\/table><\/div>

    The NHS and the AAO give the same advice for the first three rows: new flashes, floaters or a shadow need an eye examination straight away.<\/p><\/div>\t<\/div><\/div><\/div><\/section>\n\n\n\n\n

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    How is the retina examined?<\/h2><\/div>

    An eye specialist uses a mix of examinations and scans, most of them quick and painless:<\/p><\/div><\/div>\t\t\t\t