Eye Glossary | Terminology from A-Z

  • Amblyopia : Also known as lazy eye, is a vision development disorder in which an eye fails to achieve normal visual acuity, even with prescription eyeglasses or contact lenses. Amblyopia begins during infancy and early childhood. In most cases, only one eye is affected.
  • Age Related Macular Degeneration : This is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, some people experience a gradual worsening of vision that may affect one or both eyes. While it does not result in complete blindness, loss of central vision can make it hard to recognize faces, drive, read, or perform other activities of daily life. They are of two types: Dry & Wet. Dry is the formation of deposits known as drusen on and around the macula where as in wet (more severe type) has growth of abnormal blood vessels under the macula. The wet kind can be treated by surgical intervention whereas the dry kind has no treatment.
  • Astigmatism : Like nearsightedness and farsightedness, astigmatism is a refractive error, meaning it is not an eye disease or eye health problem; it's simply a problem with how the eye focuses light. In an eye with astigmatism, light fails to come to a single focus on the retina to produce clear vision. Instead, multiple focus points occur, either in front of the retina or behind it (or both).
  • Cataract : A cataract is clouding of the lens in the eye leading to a decrease in vision. It can affect one or both eyes. Often it develops slowly. Symptoms may include faded colors, blurry vision, haloes around light, trouble with bright lights, and trouble seeing at night. This can easily be corrected using surgical intervention to restore eye sight.
  • Computer Vision Syndrome : Computer vision syndrome (CVS) is a condition, often temporary, resulting from focusing the eyes on a computer or other display device for protracted, uninterrupted periods of time. Some symptoms of CVS include headaches, blurred vision, neck pain, redness in the eyes, fatigue, eye strain, dry eyes, irritated eyes, double vision, vertigo/dizziness, polyopia, and difficulty refocusing the eyes. These symptoms can be further aggravated by improper lighting conditions (i.e. glare or bright overhead lighting) or air moving past the eyes (e.g. overhead vents, direct air from a fan).
  • Conjunctivitis : Conjunctivitis, also known as pink eye, is inflammation of the outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. There may also be pain, burning, scratchiness, or itchiness.This may be viral, bacterial or allergic and are diagnosed based on symptoms.
  • Diabetic Retinopathy : Diabetic retinopathy, also known as diabetic eye disease, is when damage occurs to the retina due to diabetes. It can eventually lead to blindness.
  • Emmetropia : This is the normal refractive condition of the eye, in which the rays of light are accurately focused on the retina and a clear image is seen.
  • Entropion : This is a medical condition in which the eyelid (usually the lower lid) folds inward. It is very uncomfortable, as the eyelashes constantly rub against the cornea and irritate it. Entropion is usually caused by genetic factors.
  • Ectropion : This is a medical condition in which the lower eyelid turns outwards, typically a consequence of advanced age.
  • Epiblepharon : This is characterized by a congenital horizontal fold of skin near the margin of the upper or lower eyelid caused by the abnormal insertion of muscle fibres. This extra fold of skin redirects the lashes into a vertical position, where they may contact the globe.
  • Hyperopia : Hyperopia or hypermetropia, commonly known as farsightedness or longsightedness is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or the lens cannot become round enough), causing the eye to not have enough power to see close or nearby objects. Correction is usually achieved by the use of spectacle lenses or refractive surgery. For near objects, the eye has to accommodate even more.
  • Keratoconus : This is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than the more normal gradual curve. Keratoconus can cause substantial distortion of vision, with multiple images, streaking and sensitivity to light all often reported by the person. It is typically diagnosed in the person's adolescent years.
  • Macular Edema : Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye (a yellow central area of the retina) and causes it to thicken and swell (edema). The swelling may distort a person's central vision, because the macula holds tightly packed receptors that provide sharp, clear, central vision to enable a person to see detail, form, and color that is directly in the center of the field of view.
  • Macular Hole : A macular hole is a small break in the macula, located in the center of the eye's light-sensitive tissue called the retina. The macula provides the sharp, central vision we need for reading, driving, and seeing fine detail. A macular hole can cause blurred and distorted central vision.
  • Presbyopia : This is a condition associated with aging in which the eye exhibits a progressively diminished ability to focus on near objects. The first signs of presbyopia – eyestrain, difficulty seeing in dim light, problems focusing on small objects and fine print – are usually first noticed between the ages of 40 and 50. This can be corrected using reading glasses or refractive surgery.
  • Myopia : Myopia, also known as near-sightedness or short-sightedness, is a condition of the eye where the light that comes in does not directly focus on the retina (back of the eye) but in front of it, causing the image that one sees when looking at a distant object to be out of focus. Correction is achieved by spectacle lenses or refractive surgery.
  • Cornea : The transparent layer forming the front of the eye. Also known as “the window” allowing light to pass through to the back of the eye.
  • Pupil : The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil
  • Lens : The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. This adjustment of the lens is known as accommodation.
  • Vitreous : The vitreous body is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates. It is often referred to as the vitreous humour or simply "the vitreous".
  • Retina : This is the inner most coat of the eye which is a light sensitive layer of tissue.
  • Macula : This is an oval-shaped pigmented area near the center of the retina of the human eye. The macula is thus responsible for the central, high-resolution, color vision that is possible in good light; and this kind of vision is impaired if the macula is damaged, for example in macular degeneration.
  • Refractive Errors : A refractive error, or refraction error, is an error in the focusing of light by the eye and a frequent reason for reduced vision. Can be corrected using spectacles, contact lenses or refractive surgery.
  • Squint/ Strabismus : Strabismus is a condition that interferes with binocular vision because it prevents a person from directing both eyes simultaneously towards the same fixation point; the eyes do not properly align with each other.
  • Ptosis : This is a drooping or falling of the upper eye lid. May be seen in both eyes and one eye.
  • Uveitis : This is the inflammation of the uvea, the pigmented layer that lies between the inner retina and the outer fibrous layer composed of the sclera and cornea.
  • Retinal Detachment : This is whereby the retina detaches from the base of the eye. This can be caused by fluid leaking behind the retina through tears, by traction on the retina, or by fluid exuding from the retina. The visual prognosis of a retinal detachment is dependent on the duration of the detachment, whether the macula was detached, and the underlying health of both the retina and circulatory system of the eye.
  • Retinitis Pigmentosa : Retinitis pigmentosa (RP) is a group of genetic disorders that affect the retina’s ability to respond to light. This inherited disease causes a slow loss of vision, beginning with decreased night vision and loss of peripheral (side) vision. Eventually, blindness results. Unfortunately, there is no cure for RP.
  • Retinal Vein Oclusion : This is a blockage of the small veins that carry blood away from the retina.
  • Retinal Arterial Oclusion : Retinal artery occlusion is a blockage in one of the small arteries that carry blood to the retina.

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