Ocular terms

• Anatomy is the identification and description of the structures of living things, a branch of biology and medicine that goes back over 2,000 years to the Ancient Greeks.
• Human anatomy is the study of the structures of the human body, understanding of which is key to the practice of health and medicine.
• The word “ anatomy ” comes from the Greek words “ ana ,” meaning “ up ,” and “ tome ,” meaning “ a cutting .”
• Vitreous Humor is a clear, jelly-like substance that fills the middle of the eye.
• Sagittal or Antero-Posterior (A-P) Diameter measures the length along the geometric axis of the eye, which is typically 22-27mm, with an average of 24mm.
• Vertical Diameter measures the height of the eyeball at the equator, which is 23.5mm.
• Transverse or Horizontal Diameter measures the width of the eyeball, which is 24.5mm.
• Studies of anatomy have traditionally depended on cutting up, or dissection, but now, with imaging technology, it is increasingly possible to see how a body is made up without dissection.
• The anterior chamber is a fluid-filled space inside the eye between the iris and cornea, filled with a watery substance called the aqueous humor that maintains the pressure within the eye.
• The aqueous humor is the clear, watery fluid between your lens and cornea.
• The angle (drainage angle) is a drainage area of the eye formed between the cornea and the iris, named for its angular shape, which is why you see the word "angle" in the different glaucoma names.
• The anterior pole is the center of curvature of the cornea.
• The blind spot is a small area in the visual field corresponding to the retina’s optic disc or optic nerve head (where the optic nerve emerges), where no photoreceptors are present and where there is no sensitivity to light, not noticed with both eyes open because the part of the visual field containing the blind spot of one eye is overlapped by a light-sensitive area in the other eye.
• The conjunctiva is the thin, moist tissue that lines the inner surfaces of the eyelids and the outer surface of the sclera.
• The cornea is the transparent, anterior, dome-shaped portion of the eyeball that covers the iris and pupil, acting like a window which admits light into the eye.
• The crystalline lens is the highly transparent biconvex, lens-shaped or nearly spherical body in the eye, situated immediately behind the pupil, focuses light rays entering the eye typically onto the retina.
• Cupping is an enlargement of the cup or central depression in the optic nerve head, visible when viewing the back of the eye with an ophthalmoscope, and is a clinical sign that indicates that a large number of nerve fibers in the optic nerve have been lost.
• Night Blindness: When you have trouble seeing in dim or darkened conditions, it may result from a lack of vitamin A or less often, it’s a sign of retinitis pigmentosa, a genetic retinal disease.
• Optic Disc (or Disk): Optic nerve head in the eye, in which no photoreceptors are present, thus, resulting in a blind spot in the visual field.
• Foveola: The center of the fovea – about 0.2 mm in diameter – where only cone photoreceptors are present.
• Limbus: Junction between the cornea and the sclera.
• Macular Edema: A swelling of the macula that makes it hard to see, usually resulting from injury or disease.
• The lens accounts for approximately one-third of the eye’s total focusing power.
• Eyelid: Either of the movable lids of skin and muscle that can be closed over the eyeball, providing eye protection and distribution of tears over the cornea while blinking.
• Iris: Contains pigment that determines the color of the eye and helps regulate the amount of light that enters the eye.
• The central fovea consists of very compact cones, thinner and more rod-like in appearance than cones elsewhere.
• Meridian: Any line encircling the surface of the eyeball that passes through both poles and crosses the equator at a right angle from the limbus to the posterior pole passing the meridian (32mm).
• Glands located near the eye and in the eyelids which produce the lipid, lacrimal, and mucoid layers of the tear film coating the surface of the cornea.
• Lens: Curved surface of the eye that brings rays of light to a focus in the retina.
• Fovea: In the human eye, the term fovea (or fovea centralis) is the "pit" in the retina that allows for maximum acuity of vision.
• Tear gland: About the size and shape of an almond, the major producer of a watery secretion which forms the middle (lacrimal), thickest layer of the tear film.
• Human Eye: Specialized sense organ that is capable of receiving visual images, which are then carried to the brain.
• Macula: The central portion of your retina, which is required for high resolution vision.
• The human fovea has a diameter of about 1.0 mm with a high concentration of cone photoreceptors.
• Nyctalopia: Night blindness.
• Equator: Line encircling the eyeball equidistant from the two poles dividing the eyeball into anterior and posterior hemisphere.
• Geometric Axis: Connects the anterior and posterior pole and it lies along the line drawn from the fovea centralis through the center of the rotation of the eyeball to a point on the cornea slightly nasal.
• Photocoagulation is most often used to treat retinal conditions like complications from diabetes.
• Retina is an extension of the brain, formed embryonically from brain tissue and connected to the brain proper by the optic nerve.
• Orbit is the bony cavity of the skull that contains the eye.