Medical terms connected to Keratoconus

  • Astigmatism A difference in the focal point of the eye in one meridian from another (eg between the horizontal and vertical planes). It can usually be corrected with a cylindrical (toric) lens.
  • Bowman’s Layer is a smooth nonregenerating layer, located between the superficial epithelium and the stroma in the cornea of the eye
  • Cornea The “front window” of the eye.
  • CXL (Corneal Collagen Crosslinking) uses ultraviolet light with riboflavin dye to stiffen the cornea
  • DALK (Deep anterior lamellar keratoplasty) is a partial thickness graft that preserves the TWO inner most layers of the cornea.
  • Descemet’s membrane A layer of the cornea which lies just forward of the endothelium.
  • Dioptre A unit of power of a lens, the reciprocal of the focal length of the lens.
  • Endothelium The layer of the cornea closest to the anterior chamber. It is a single layer of cells which does not regenerate after birth. Its function is to pump fluid out of the cornea. If it fails, the cornea becomes hazy (decompensates).
  • Endothelial Keratoplasty (EK) – replacing the deeper (back) layers of the cornea 
  • Epithelium (of the cornea) The layer of the cornea closest to the tear film.
  • Excimer laser A type of laser which emits in the ultraviolet range of the spectrum. In ophthalmology, it is used for removing tissue from the cornea, particularly in refractive surgery.
  • Ferrara rings Perspex ring implants placed in the cornea to flatten and make more regular the shape of a keratoconic cornea
  • Hydrops Limbus The posterior membrane of the cornea suddenly splits and water from inside the eye cascades into the corneal stroma.
  • Intacs are very small clear plastic arcs that are designed to be inserted into the substance of the cornea
  • Limbus The region where the cornea and the sclera meet.
  • Microkeratome A device which cuts a flap of the cornea prior to removal some of the thickness of the underlying corneal stroma with the excimer laser during refractive surgery.
  • Mydriatic An eye drop or ointment which dilates the pupil.
    Myopia Short-sightedness, requiring a concave lens to focus the vision.
  • NICE National Institute for Health and Care Excellence
  • PK (Penetrating Keratoplasty) surgery, that involves removal of the whole cornea and replacement with a full thickness cornea from a donor.
  • RGP (Ridged Gas Permeable Contact Lenses) hard contact lenses made of silicone-containing compounds that allow oxygen to pass through the lens material to the eye.
  • Sclera The “white” of the eye. It forms the wall of the eye, except in the region of the cornea.
  • Stroma The central layer of the cornea between the epithelium and endothelium. It makes up the majority of the thickness of the cornea.
  • Toric A type of lens required to correct astigmatism.

Many of these terms have been copied from the Royal College of Ophthalmologists website. You can see the full glossary – Here