title: What pressure is exerted on the retina by heavy tamponade agents?
abstract: BACKGROUND
  Histological changes in the retina during the use of heavy tamponade agents have been linked with the pressure on the retina caused by the increased specific gravity of the agent. This paper calculates the possible increases in pressure due to these agents and questions the validity of this argument.
  
  
  METHODS
  A model eye chamber was used to make measurements of the shape of F6H8 bubbles, with incrementally increasing volumes, and thus calculate the maximum possible increase in pressure under the tamponade agent.
  
  
  RESULTS
  The maximum increase in pressure under an F6H8 tamponade which completely fills an eye with a diameter of 2.2 cm would be 0.52 mmHg.
  
  
  CONCLUSIONS
  This increase in pressure is within normal diurnal pressure changes in the eye; therefore, it would seem unlikely that such an increase could cause the histological changes observed. With increasing volumes of a heavy tamponade agent, aqueous is excluded from a greater area of retina. This could account for the pathological changes reported.
authors.affiliation: St Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, UK.
authors.forename: David
authors.initials: D
authors.lastname: Wong
authors.forename: Rachel
authors.initials: R
authors.lastname: Williams
authors.forename: Theodor
authors.initials: T
authors.lastname: Stappler
authors.forename: Carl
authors.initials: C
authors.lastname: Groenewald
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005466:Fluorocarbons / Q000737:chemistry*; D006801:Humans; D008953:Models, Anatomic; D019904:Polymethyl Methacrylate; D011312:Pressure; D012160:Retina / Q000502:physiology*; D013046:Specific Gravity; D013499:Surface Properties; D014783:Viscosity
chemical_list: D005466:Fluorocarbons; C118616:perfluorohexyl-octan; D019904:Polymethyl Methacrylate