title: Effects of topical anaesthetics and repeated tonometry on intraocular pressure.
abstract: OBJECTIVE
  To investigate the effects of repeated measurements of intraocular pressure (IOP) using Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) to identify mechanisms contributing to the expected IOP reduction.
  
  
  METHODS
  A prospective, single-centre study with six healthy volunteers. Consecutive repeated series (six measurements/serie/method) were made alternately on both eyes for 1 hr with oxybuprocaine/fluorescein in the right eye and tetracaine in the left. The left eye was Pentacam(®) photographed before and repeatedly for 20 min after the IOP measurements. On a separate occasion, the same volunteers received the same amount of anaesthetic drops for 1 hr but without repeated IOP measurements.
  
  
  RESULTS
  A significant IOP reduction occurred with both ART and GAT in the oxybuprocaine-treated eye, -4.4 mmHg and -3.8 mmHg, respectively and with ART in the tetracaine eye, -2.1 mmHg. There was a significant difference in IOP reduction between the oxybuprocaine and tetracaine eyes with ART. There was a significant drop in anterior chamber volume (ACV) immediately after the IOP measurements, -12.6 μl that returned to pretrial level after 2 min. After 1 hr of receiving anaesthetic eye drops (without IOP measurements), the IOP decreased significantly in the oxybuprocaine eye for both ART and GAT, -3.1 and -1.7 mmHg, respectively, but not in the tetracaine eye (p = 0.72).
  
  
  CONCLUSIONS
  The IOP reduction cannot be explained solely by aqueous humor being pressed out of the anterior chamber. While significant IOP reduction occurred with both tetracaine and oxybuprocaine after repeated mechanical applanation, the IOP reduction was significantly greater with oxybuprocaine.
authors: Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, SwedenDepartment of Radiation Sciences, Biomedical Engineering and Informatics, Umeå University, Umeå, Sweden.
authors: Gauti
authors: G
authors: Jóhannesson
authors: Per
authors: P
authors: Hallberg
authors: Anders
authors: A
authors: Eklund
authors: Anders
authors: A
authors: Behndig
authors: Christina
authors: C
authors: Lindén
mesh_terms: D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions; D011343:Procaine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D011446:Prospective Studies; D013748:Tetracaine / Q000008:administration & dosage*; D014065:Tonometry, Ocular / Q000295:instrumentation*
chemical_list: D000779:Anesthetics, Local; D009883:Ophthalmic Solutions; D013748:Tetracaine; D011343:Procaine; C005298:benoxinate
keywords: Goldmann applanation tonometry; applanation resonance tonometry; aqueous humor; intraocular pressure; repeated tonometry