title: Intraoperative assessment of intraocular pressure in vitrectomized air-filled and fluid-filled eyes.
abstract: OBJECTIVE
  To ascertain the difference of intraocular pressure (IOP) measurement between vitrectomized air-filled and fluid-filled eyes.
  
  
  METHODS
  Thirty-one eyes of 31 consecutive patients who underwent conventional vitrectomy and intraocular gas tamponade were assessed. After vitrectomy, IOP of the fluid-filled eyes was measured by Tono-Pen. Thereafter, fluid-air exchange was performed, and IOP of the air-filled eyes was measured again. The IOP within each fluid- and air-filled eye was varied by selecting settings on the vitrectomy system, from 10 to 50 mmHg with 5-mmHg increments. Postoperatively, IOP was assessed by both Tono-Pen and Goldmann applanation tonometry (GAT). Linear and nonlinear regression analyses were conducted between intraoperatively measured Tono-Pen readings and actual IOPs. Bland-Altman plot was used to assess the agreements between postoperatively measured Tono-Pen readings and GAT readings.
  
  
  RESULTS
  The discrepancy between Tono-Pen readings and actual IOP in fluid-filled eyes was not significant, except for the profound high pressures over 45 mmHg. However, Tono-Pen readings in air-filled eyes were significantly lower than actual IOPs in all ranges, and Tono-Pen increasingly underestimates IOP at higher levels. Intraoperative Tono-Pen readings were correlated significantly with actual IOP and a quadratic equation evidenced the best fit (R(2) = 0.996). Postoperatively, difference of the measurements between Tono-Pen and GAT was not significant.
  
  
  CONCLUSIONS
  Tono-Pen and GAT significantly underestimate actual IOP in air-filled eyes. It should be considered that actual IOP would be greater than the measured IOP in gas-filled eyes, even though the IOP is measured as normal.
authors.affiliation: Department of Ophthalmology, College of Medicine, Soonchunhyang University, Seoul, KoreaMyeong Eye Clinic, Seoul, Korea.
authors.forename: Chan Hee
authors.initials: CH
authors.lastname: Moon
authors.forename: Kyung Seek
authors.initials: KS
authors.lastname: Choi
authors.forename: Mi Ri
authors.initials: MR
authors.lastname: Rhee
authors.forename: Sung Jin
authors.initials: SJ
authors.lastname: Lee
mesh_terms: D000085:Acetates; D000388:Air; D004338:Drug Combinations; D058450:Endotamponade; D005466:Fluorocarbons / Q000008:administration & dosage; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D007432:Intraoperative Period; D008875:Middle Aged; D008903:Minerals; D018918:Phacoemulsification; D011184:Postoperative Period; D015203:Reproducibility of Results; D012163:Retinal Detachment / Q000601:surgery; D012965:Sodium Chloride; D013459:Sulfur Hexafluoride / Q000008:administration & dosage; D014065:Tonometry, Ocular / Q000592:standards*; D014821:Vitrectomy
chemical_list: D000085:Acetates; C030660:BSS solution; D004338:Drug Combinations; D005466:Fluorocarbons; D008903:Minerals; D012965:Sodium Chloride; C042852:perflutren; D013459:Sulfur Hexafluoride
keywords: Tono-Pen; intraocular gas; intraocular pressure; pars plana vitrectomy