Facts from the Foundation of the ASRS
Retina Health Series
Committed to improving the quality of life of all people with retinal disease


Amblyopia (pronounced am blee OPE ee ah): A condition also known as lazy eye. This loss or lack of normal development in central vision during infancy and early childhood is a leading cause of decreased vision among children.   

Anti-VEGF medications: Elevated vascular endothelial growth factor (VEGF), a soluble factor that can be produced in eyes with poor circulation can lead to swelling and the growth of abnormal new blood vessels in the eye. Leaky blood vessels cause swelling such as macular edema and  are prone to bleeding, both of which cause decreased vision. Anti-VEGF drugs which inactivate VEGF have revolutionized treatment allowing retina specialists to reduce new blood vessel growth and swelling with periodic injections of anti-VEGF drugs including bevacizumab (Avastin®), ranibizumab (Lucentis®), and aflibercept (Eylea®).

Asteroid hyalosis: Degenerative condition characterized by spherical-shaped opacities within the clear gel (vitreous humor) that fills the eye cavity between the lens (front) and the retina, which lines the back wall of the eye. This can cause floaters and blurred vision.

Cataract: A clouding of the eye’s lens causing a decrease in vision. Cataracts are the most common cause of vision loss for those over the age of 40.

Choroid (pronounced CORE oid): The layer of blood vessels and connective tissue between the retina and the white of the eye, also known as the sclera.

Contractile membrane: Scar tissue on the surface of the retina that can wrinkle, distorting the retina and causing blurred vision. In some cases, the scar tissue can pull hard enough on the retina to create a retinal hole.

Cornea: Transparent coating of the front part of the eye that covers the iris and pupil.

Corneal edema: Swelling of the cornea which is the transparent coating of the eye that covers the iris and pupil. The cornea becomes cloudy like a dirty windshield and this may cause decreased vision. 

Cryotherapy: A technique in which a pencil-like probe is placed on the white of the eye (sclera). The tip of the probe becomes very cold and can freeze structures inside the eye. This can be used to create a seal around a retinal tear. 

Cystoid macular edema: A painless disorder in which the macula becomes swollen with fluid (edema), that presents in cyst-like patterns.

Choroidal neovascularization (CNV): Growth of abnormal new blood vessels in the choroid layer of the eye that grow under the retina and macula and disrupt vision. 

CT scan: A computed tomography scan is a sophisticated X-ray device that capture cross- sectional images of the body revealing internal structures that cannot be viewed through traditional X-rays.  

Diabetic macular edema: The term used for swelling in the macula in eyes with diabetic retinopathy, or the center part of the retina which is responsible for providing the sharp, straight-ahead vision used for reading and recognizing faces. 

Diabetic retinopathy: A complication of diabetes that causes damage to the blood vessels of the retina—the light-sensitive tissue that lines the back part of the eye, allowing you to see fine detail.  Read more >>

Disciform scar: A scar that develops in the macula area of the retina resulting from leakage and bleeding from abnormal blood vessels (neovascularization) in the eye.    

Dynamic B-scan ultrasound: Sound waves are used to form an image of the back of the eye during ocular movements. This allows identification of spatial relationships of structures within the eye.

Ehlers-Danlos – A genetic connective tissue disease where joints are hyper-extendable and skin is abnormally elastic. This disease is associated with an increased risk of lattice degeneration and retinal detachment.

EKG (electrocardiogram): An EKG is a non-invasive screening that monitors the electrical activity of the heart. 

Electroretinogram (ERG): Non-invasive test that measures the electrical “circuitry” of the eye by assessing the response of the retina’s light-sensitive cells to stimulus.

Endophthalmitis: An infection inside the eye. It is characterized by decreased vision and sometimes severe pain and increased floaters. This can lead to severe vision loss if not treated promptly. 

Endolaser: A laser attached to a fiberoptic light probe that can be placed inside the eye to seal blood vessels and coagulate (clot) tissue. 

Epiretinal membrane: A layer of scar tissue that forms over the macula that reduces vision and can warp and contract causing a wrinkling of the retina known as macular pucker. Read more >

Eyelid speculum: Medical device used to keep the eyelid open during ocular procedures and surgeries.  It typically has two blades that hold the upper and lower lid apart.

Flashes: Streaks of light, usually appearing at the side of vision. 

Floater: Mobile blurry shadow that partially obscures vision. Floaters are most bothersome when near the center of vision and less annoying when they settle to the side of the vision. They may appear like cobwebs, dust, or a swarm of insects--or in the shape of a circle or oval, called a Weiss ring.  

Fluorescein angiography (FA): An imaging technique where a yellow dye called sodium fluorescein is injected into a vein in the arm, allowing a special camera to record circulation in the retina and choroid in the back of the eye. This test can be very useful in diagnosing a number of retinal disorders. 

Focal and grid laser photocoagulation: A surgical technique that uses a highly targeted laser light to seal retinal blood vessels and reduce macular edema (swelling).

Fovea: A small pit at the center of the retina’s macula that is responsible for producing the sharp central vision required for reading and driving.  

Fundus: The back of the eye where the retina, macula, vitreous, choroid, and optic nerve are located.

Fundus autofluorescence (FAF): An imaging modality that uses naturally occurring fluorescence from the retina to provide an indicator of retinal health.

Fundus photography: Involves the use of specialized cameras equipped with lenses that capture images of the back of the eye where the retina, macula, vitreous, choroid and optic nerve are located. 

General anesthesia: The patient is put to sleep using intravenous or inhaled anesthetic drugs. The patient remains unconscious throughout the procedure until the anesthesia is reversed, waking the patient up. This type of anesthesia is typically used for major/prolonged surgical procedures or in patients who cannot tolerate remaining awake during surgery.  

Glaucoma: A condition where fluid buildup in the eye causes an increase in eye pressure that damages the optic nerve. 

Hypopyon: Accumulation of white blood cells in the anterior chamber of the eye. 

Indirect ophthalmoscope: Medical instrument used to examine the interior of the eye.  This looks a bit like a miner’s helmet.

Indocyanine green angiography (ICGA): A diagnostic procedure that uses a green dye to illuminate blood flow in the choroid, which is a layer of blood vessels located between the white of the eye (sclera) and the retina that supplies nutrients to the inner eye. 

Internal limiting membrane: A very thin membrane on the innermost surface of the retina. Sometimes this membrane is removed at the time of vitrectomy.

Intraocular pressure (IOP): The pressure in the eye. The eye must have a positive pressure or it would collapse like a hot air balloon without hot air. If the pressure is too high, this can damage the optic nerve as in glaucoma.

Intravitreal injections: Treatment where a medication is injected into the vitreous cavity in the middle of the eye. 

Ischemia: Insufficient blood supply to an organ or part of the body such as the retina.

IV (intravenous):  A device used to administer fluids (blood, saline, medicine, nutrients, etc.) to patients intravenously (through the veins).

Laser photocoagulation: A surgical technique that uses a highly targeted laser light to seal blood vessels and coagulate (clot) tissue. 

Lattice degeneration: A condition that involves abnormal thinning of the retina, most often around the edge. The condition makes patients more vulnerable to developing retinal tears, breaks or holes that could lead to a visually debilitating retinal detachment. Lattice degeneration is characterized by oval or straight patches of thinned retina, sometimes accompanied by pigment clumps or a crosshatching pattern formed by sclerotic vessels.

Macula: A small area at the center of the retina where light is sharply focused to produce the detailed color vision needed for tasks such as reading and driving.

Macular edema: The term used for swelling in the macula in eyes, or the center part of the retina which is responsible for providing the sharp, straight-ahead vision used for reading and recognizing faces as well as color vision. Read more >

Macular hole: The macula is the small area at the center of the retina where light is sharply focused to produce the detailed color vision needed for tasks like reading. A full-thickness defect in the macula is referred to as a macular hole. Read more >

Macular pucker: An epiretinal membrane is a layer of scar tissue that forms over the macula that reduces vision and can warp and contract causing a wrinkling of the retina known as macular pucker. 

Marfan syndrome: A connective tissue disease where those affected are abnormally tall with long limbs, fingers and toes. Some with this disease develop life-threatening problems with their aorta and have an increased risk of lattice degeneration and retinal detachment.

Metamorphopsia: A symptom causing visual distortion that makes things that are normally straight, like window blinds or a door frame, appear wavy or crooked.

MRI (magnetic resonance imaging):  A non-invasive imaging technique that uses magnetic fields and radio waves to create images of body tissues and organs that cannot be normally visualized. The patient receives no radiation with this imaging procedure.  

Microperimetry: A test that measures the sensitivity to brightness at various locations in the macula.

Myopia: Nearsightedness or the ability to see clearly close up, but not at a distance. 

Neovascularization: Excessive growth of new blood vessels on abnormal tissue as a result of oxygen deprivation that can cause vision loss.

Nystagmus (pronounced nis TAG mus): A condition defined by abnormal oscillatory eye movement.

Ocular ultrasound: A non-invasive imaging technique that uses high-frequency sound waves to produce images of the eye’s structure for physician evaluation.

Optical coherence tomography (OCT): A non-invasive imaging technique that uses light to create a 3-dimensional image of your eye for physician evaluation. 

Optical coherence tomography angiography (OCTA): A noninvasive imaging technique that uses light to image the blood vessels in different layers of the retina and choroid.  

Perfluorocarbon liquid: A heavier than water clear liquid that can be injected into the eye to help push the retina back against the eye wall. It is typically placed temporarily into the vitreous during vitrectomy to hold the retina while the retinal surgeon repairs the retina. 

Peripheral retina: The area outside of the central retina. This includes the equatorial and anterior retina. 

Photodynamic therapy (PDT): A treatment for macular degeneration in which a light-activated medicine (verteporfin) is injected into the bloodstream followed by application of a cold laser which targets abnormal blood vessels growing in the macula at the center of the retina.   

Photopsias:  Flashes of light that occur spontaneously within the eye. These are best seen when the surroundings are dark and can appear like lightning flashes, usually in the peripheral vision.

Photoreceptors: The light sensing cells found in the outer retina known as the rods (important for night vision) and cones (important for color vision during the day).

Posterior vitreous detachment (PVD): A natural change that occurs during adulthood, when the vitreous gel that fills the eye separates from the retina, which is the light-sensing nerve layer at the back of the eye responsible for sight. Read more >

Posterior capsule: A thin membrane that comprises the back surface of the eye’s lens.

Primary tumor: The first, or original tumor in the body. Also called primary cancer.

Proliferative diabetic retinopathy (PDR): An advanced stage of diabetic retinopathy in which new abnormal blood vessels and scar tissue form on the surface of the retina. The scar tissue can pull on the retina and cause retinal detachment and loss of vision. If blood vessels grow on the iris it can clog the drainage system of the eye causing glaucoma (high pressure in the eye), pain and vision loss. 

Pseudoexfoliation syndrome (PEX):  Also called exfoliation glaucoma, pseudoexfoliation glaucoma, pseudoexfoliation of the lens, and exfoliation syndrome. An age-related condition in which microscopic white protein ‘flakes’ are deposited primarily on the lens of the eye. These deposits can build up and cause blockage of the eye’s drainage system leading to increased ocular (eye) pressure and glaucoma. 

Retina: A thin layer of light-sensitive nerve tissue that lines the back of the eye (or vitreous cavity). Images are focused at its center (known as the macula) and converted to electrical impulses that are carried to the brain by the optic nerve, resulting in sight.

Retinal detachment: A condition where the retina separates from the back of the eye cavity. This may be caused by vitreous gel or fluid leaking through a retinal tear or hole and collecting under the retina causing it to separate from the tissue around it. Read more >

Retinal pigment epithelium (RPE): A pigmented layer of the retina lying just outside the retinal photoreceptors that transmit light to the brain. 

Retinal prosthesis: A method to restore vision in eyes using microelectronic chip technologies to convert light rays to neuronal impulses that can be conveyed to the brain via preserved connections. This method is also referred to as artificial vision, retinal chip, and bionic eye. Read more > 

Retinal tear: A rip or discontinuity in the retina, which is the thin layer of light-sensitive nerve tissue that lines the back of the eye and is responsible for sight. Read more > 

Retinal vein occlusions:  Complication that occurs when there is a blockage of veins carrying deoxygenated blood back from the retinal arteries to the optic nerve. A blockage in the retina’s main draining vein is referred to as a central retinal vein occlusion (CRVO), while a blockage in a smaller vein is called a branch retinal vein occlusion (BRVO).  Read more >

Retinectomy: Surgical removal of a portion of retinal tissue. This is sometimes required where there is severe scar tissue contracting the retina that cannot be peeled from the surface of the retina. 

Retinitis pigmentosa (RP): A group of inherited (passed down from parents) diseases causing retinal degeneration and blindness. Individuals with RP lose their vision because photoreceptor (light-sensing) cells of the retina gradually degenerate and then die. In most forms of RP (rod-cone dystrophy), night blindness is one of the earliest and most frequent symptoms. Read more > 

Sclera: The white part of the eye.  

Scleral buckle: A piece of silicone rubber or sponge sutured to the outer wall of the eye posterior to the rectus eye muscles. The scleral buckle helps to indent the eye to support the peripheral retina and pushes the outer eye against the retina in eyes with a retinal detachment. 

Scleral depression: A diagnostic technique where a pencil-like tool is used to press on the outside of the eye while the retina specialist looks inside the eye with an indirect ophthalmoscope. The pressure can be mildly uncomfortable, but allows the retina specialist to see portions of the peripheral retina that cannot otherwise be visualized. 

Sclerotic vessels: blood vessels that are often thin and white rather than red due to lack of blood flow or tissue damage. These types of vessels are often found in patches of lattice degeneration. 

Sedation: A drug-induced state of deep relaxation, sometimes called “twilight sleep,“ where patients are able to respond to commands. This can vary from minimal to deeper sedation, depending on the requirements of the procedure. This type of anesthesia is typically used for shorter surgical procedures if the body tissue being operated can be adequately anesthetized to prevent pain. 

Slit lamp: An instrument that combines a high-intensity light source with a microscope to examine the external and internal structures of the eye, including the optic nerve and retina. 

Stickler syndrome: A genetic disorder characterized by flattened nose and cheekbones, problems with the skeletal system, hearing loss and lattice degeneration. The vitreous jelly is abnormally liquified which can lead to early onset retinal detachment.

Strabismus (pronounced stra BIS mus): A condition also known as crossed eyes.  

Spectral Domain Optical Coherence Tomography (SD-OCT): A non-invasive test where light rays are bounced off the retina like sonar off the ocean floor or the way ultrasound is used to image structures in the body. The reflected light rays form an image of the layers of the retina and show any abnormalities that may exist.

Ultrasound: An imaging technique that uses high-frequency sound waves to produce images of structures inside the body.

Vaso-occlusive crisis: A painful episode that occurs when sickle-shaped red blood cells in the small blood vessels block the oxygen supply to tissues in the body. This causes inadequate blood flow and permanent injury to that tissue.

Visual hallucinations: A visual perception that has the sense of reality but occurs without external stimulation of the visual system.
• Formed visual hallucination: Includes seeing objects such as people, animals, buildings, etc.

• Unformed visual hallucination: Includes seeing flashes of light, patterns, colors, etc.

Vitrectomy surgery: A procedure undertaken by a specialist where the vitreous gel that fills the eye cavity is removed to provide better access to the retina. This allows for a variety of repairs, including the removal of scar tissue, laser repair of retinal detachments and treatment of macular holes. Once surgery is complete, saline, a gas bubble or silicone oil may be injected into the vitreous cavity to help hold the retina in position while the eye heals. 

There are different types of vitrectomy:

  • Pars plana vitrectomy is performed by retina specialists to address diseases of the ‘posterior’ (back) segment of the eye cavity, also referred to as the pars plana.
  • Anterior vitrectomy is performed by ophthalmologists or retina specialists to address leakage of vitreous gel into the front (anterior) chamber of the eye.   
    Read more >

Vitreomacular traction: Shrinking and pulling away of the eye’s vitreous gel from the macula. This condition, which appears with normal aging, can create a loss of vision if the traction persists in the macula. 

Vitreous or vitreous humor: The "gel" that fills the inside of the eye or vitreous cavity. 

Vitreous cavity: The area between the lens at the front of the eye and the retina which lines the back of the eye. The vitreous cavity is filled with a clear gel called vitreous humor.

Vitreous hemorrhage: A leakage of blood into the gel that fills the eye cavity (also called vitreous humor) that is often the result of blockage or damage to blood vessels in the retina. 

Weiss ring: A circular or oval floater in the eye that partially obstructs vision.

YAG laser capsulotomy: Laser procedure used to make a small hole in the posterior capsule which sits directly behind an intraocular lens after cataract surgery. The posterior capsule may become spontaneously cloudy and this procedure can help clear up the vision.