title: Deviations between transpalpebral tonometry using TGDc-01 and Goldmann applanation tonometry depending on the IOP level.
abstract: BACKGROUND
  Recent comparisons between transpalpebral tonometry using TGDc-01 and Goldmann applanation tonometry were performed in populations with IOPs between 10 and 20 mmHg. The purpose of this study was to evaluate device deviations depending on different IOP levels (range 5-40 mmHg).
  
  
  METHODS
  A total of 68 eyes of 68 patients were included and assigned to four IOP levels according to an initial applanation tonometry assessment: level I, <10 mmHg (n=8); level II, 10-19 mmHg (n=20); level III, 20-29 mmHg (n=20); and level IV, > or =30 mmHg (n=20). Two independent and randomized observers performed three replicate measurements per eye-observer 1 using TGDc-01 tonometry, and observer 2 using Goldmann applanation tonometry. Intraindividual deviations between measurement results were investigated concerning clinical relevance by medians and quartiles, concerning statistical significance by pairwise sign tests; p values <0.05 indicate local statistical significance.
  
  
  RESULTS
  In patients with initial IOP > or =20 mmHg, TGDc-01-based tonometry significantly underestimated the IOP as based on Goldmann applanation tonometry (p<0.001). This effect increased with increasing IOP: IOP level III median difference (TGDc-01 - Goldmann) -1.3 mmHg (interquartile range, -2.5, -0.4), IOP level IV median difference -2.7 mmHg (-3.7, -1.0). In patients with initial IOP <10 mmHg, an at least gradual underestimation by TGDc-01 tonometry (p=0.219; median difference, -0.6, -1.6, 0) was observed. A total 18% of patients showed device deviations > +/-3 mmHg, and even 35% of those patients with initial IOP > or =30 mmHg.
  
  
  CONCLUSIONS
  TGDc-01-based tonometry demonstrated an increasing underestimation of IOP with increasing IOP levels when compared with the current standard method of Goldmann applanation tonometry.
authors.affiliation: Department of Ophthalmology, Johannes Gutenberg University, Langenbeckstr. 1, 55131 Mainz, Germany. Annette.Troost@gmx.de
authors.forename: Annette
authors.initials: A
authors.lastname: Troost
authors.forename: Kathrin
authors.initials: K
authors.lastname: Specht
authors.forename: Frank
authors.initials: F
authors.lastname: Krummenauer
authors.forename: Sung Hyun
authors.initials: SH
authors.lastname: Yun
authors.forename: Oliver
authors.initials: O
authors.lastname: Schwenn
mesh_terms: D000368:Aged; D005143:Eyelids; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation / Q000592:standards*