RT Book, Section
A1 Biswell, Roderick
A2 Riordan-Eva, Paul
A2 Cunningham, Emmett T.
SR Print(0)
ID 55781951
T1 Chapter 6. Cornea
T2 Vaughan & Asbury's General Ophthalmology, 18e
YR 2011
FD 2011
PB The McGraw-Hill Companies
PP New York, NY
SN 978-0-07-163420-5
LK accessmedicine.mhmedical.com/content.aspx?aid=55781951
RD 2024/04/24
AB The  cornea  functions  both  as  a  protective  barrier  and  as  a  “window”  through  which  light  rays  pass  to  the  retina.  Its  transparency  is  due  to  its  uniform  structure,  avascularity,  and  deturgescence  (see  Chapter  1).  Deturgescence,  or  the  state  of  relative  dehydration  of  the  corneal  tissue,  is  maintained  by  the  bicarbonate  “pump”  provided  by  the  endothelium  and  the  barrier  function  of  the  epithelium  and  endothelium.  The  endothelium  is  more  important  than  the  epithelium  in  the  mechanism  of  dehydration,  and  damage  to  the  endothelium  is  far  more  serious  than  damage  to  the  epithelium.  Destruction  of  the  endothelial  cells  causes  edema  of  the  cornea  and  loss  of  transparency,  which  is  more  likely  to  persist  because  of  the  limited  potential  for  recovery  of  endothelial  function.  Damage  to  the  epithelium  usually  causes  only  transient,  localized  edema  of  the  corneal  stroma  that  clears  with  the  rapid  regeneration  of  epithelial  cells.  Evaporation  of  water  from  the  precorneal  tear  film  produces  hypertonicity  of  the  film.  Together  with  direct  evaporation,  this  draws  water  from  the  superficial  corneal  stroma  in  order  to  maintain  the  state  of  dehydration.