title: Estimation of ocular rigidity based on measurement of pulse amplitude using pneumotonometry and fundus pulse using laser interferometry in glaucoma.
abstract: OBJECTIVE
  There is evidence from theoretical models and animal studies that the biomechanical properties of the optic nerve head and the sclera play a role in the pathophysiology of glaucoma. There are, however, only a few data available that demonstrate such biomechanical alterations in vivo. In this study, the hypothesis was that patients with primary open-angle glaucoma (POAG) have an abnormal ocular structural stiffness based on measurements of intraocular pressure amplitude and ocular fundus pulsation amplitude (FPA).
  
  
  METHODS
  Seventy patients with POAG and 70 healthy control subjects matched for age, sex, intraocular pressure and systemic blood pressure were included. The ocular PA and pulsatile ocular blood flow were assessed with pneumotonometry. The FPA was measured by using laser interferometry. Based on the Friedenwald equation, a coefficient of ocular rigidity (E1) was calculated relating PA to FPA.
  
  
  RESULTS
  There was no difference in systemic blood pressure, intraocular pressure, and ocular perfusion pressure (OPP) between the patients with glaucoma and the healthy control subjects. Both, FPA and PA were lower in the patients with glaucoma than in the control subjects. The calculated factor E1 was significantly higher in the patients with POAG (0.0454 +/- 0.0085 AU) than in the control subjects (0.0427 +/- 0.0058 AU, P = 0.03). Multiple regression analysis revealed that E1 was independent of age and sex, and correlated only slightly with OPP.
  
  
  CONCLUSIONS
  The present study indicates increased ocular rigidity in patients with POAG. This is compatible with a number of previous animal experiments and supports the concepts that the biomechanical properties of ocular tissues play a role in the diseases process.
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Anton
authors.initials: A
authors.lastname: Hommer
authors.forename: Gabriele
authors.initials: G
authors.lastname: Fuchsjäger-Mayrl
authors.forename: Hemma
authors.initials: H
authors.lastname: Resch
authors.forename: Clemens
authors.initials: C
authors.lastname: Vass
authors.forename: Gerhard
authors.initials: G
authors.lastname: Garhofer
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000368:Aged; D001794:Blood Pressure; D004359:Drug Therapy, Combination; D005260:Female; D005654:Fundus Oculi; D005902:Glaucoma, Open-Angle / Q000188:drug therapy / Q000503:physiopathology*; D006801:Humans; D007368:Interferometry; D007429:Intraocular Pressure; D007834:Lasers; D000077338:Latanoprost; D008027:Light; D008297:Male; D008875:Middle Aged; D011461:Prostaglandins F, Synthetic / Q000627:therapeutic use; D011674:Pulse; D012016:Reference Values; D013449:Sulfonamides / Q000627:therapeutic use; D013876:Thiophenes / Q000627:therapeutic use; D013999:Timolol / Q000627:therapeutic use; D014065:Tonometry, Ocular
chemical_list: D011461:Prostaglandins F, Synthetic; D013449:Sulfonamides; D013876:Thiophenes; D000077338:Latanoprost; D013999:Timolol; C062765:dorzolamide