title: Tonopen measurement of intraocular pressure in mice.
abstract: OBJECTIVE
  To standardize a method of non-invasive measurement of intraocular pressure (IOP) in mice.
  
  
  METHODS
  Cannulated-eye study: IOP was measured simultaneously with a Tonopen and by direct cannulation of the vitreous compartment while pressure was manipulated in steps between 10 and 45 mmHg by a saline reservoir via a second vitreal cannula (five mice, one rat). Non-cannulated-eye study: Tonopen and servo-null measurements were performed in independent groups (48 mice) to verify Tonopen measurements in non-cannulated-eyes. Topical brimonidine (0.15%) was used to decrease IOP.
  
  
  RESULTS
  In the rat, there was a similar relationship between Tonopen readings and direct measurements via cannulation of the eye as previously reported. Although readings from mice eyes were higher in variability than those obtained from the rat, the measurements were reproducible and the correlation between the invasive and the non-invasive methods was good (r = 0.97). The IOP lowering effect of brimonidine was detected with Tonopen as well as servo-null measurements (p < 0.001) and the results with both techniques were similar.
  
  
  CONCLUSIONS
  The Tonopen can be used for rapid and reproducible measurements of IOP in mice. The method is easy to apply and can provide a useful means for IOP measurement in mouse models of induced ocular hypertension, in knock-out and transgenic mice, or in pharmacological studies.
authors.affiliation: Department of Ophthalmology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, M/C 6230, San Antonio, TX 78229-3900, USA.
authors.forename: Herbert A
authors.initials: HA
authors.lastname: Reitsamer
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Kiel
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Harrison
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Ransom
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: McKinnon
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D000068438:Brimonidine Tartrate; D002404:Catheterization; D007429:Intraocular Pressure; D008365:Manometry / Q000295:instrumentation / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D011914:Rats, Inbred BN; D015203:Reproducibility of Results
chemical_list: D000959:Antihypertensive Agents; D011810:Quinoxalines; D000068438:Brimonidine Tartrate