In VivoValidation of the New Tonopen AVIA Tonometer using Manometers placed in the Anterior chamber and the Vitreous Cavity under Various Vitreous Conditions

PURPOSE: To validate intraocular pressure (IOP) measurements using the new Tonopen AVIA® tonometer by comparing values obtained with those measured by manometers placed in the anterior chamber (AC) and the vitreous cavity (VC). MATERIALS AND METHODS: Seventy-nine consecutive patients awaiting phacovitrectomy for epiretinal membrane (ERM) or macular hole (MH) (n=29), vitreous hemorrhage (DMVH) (n=27) or silicone oil removal (n=23) were included in this prospective observational study. A clinician masked to patient information performed a complete ophthalmologic examination, including measurements of corneal thickness (CT), AC depth and axial length. Another examiner simultaneously measured conventional IOP using the Tonopen AVIA® (TIOP) and AC and VC IOPs (ACIOP and VCIOP) using two transducers. RESULTS: The mean TIOP, ACIOP and VCIOP were 16.1 ± 3.8, 16.1 ± 4.4 and 15.5 ± 4.6 mmHg, respectively. There was a good agreement between the TIOP and ACIOP; however, the agreement between TIOP and VCIOP was relatively poor in subgroup analysis. VCIOP was significantly higher than TIOP in the ERM and MH group, with a mean difference of 1.0 mmHg (p=0.042); however, they were significantly lower in the DMVH group, with a mean difference of -0.7 mmHg (p=0.026) and in the silicone oil group (mean difference, -2.3 mmHg) (p<0.0001). In multivariate analysis, TIOP correlated significantly only with CT (p<0.037) and increased by 2.7 mmHg per 100 μm increase in CT. CONCLUSIONS: IOP measurements using the Tonopen AVIA® tonometer showed good agreement with ACIOP values, although TIOP measurements were affected by CT. However, the VCIOP values using the transducer may have over- or underestimated IOP relative to TIOP and ACIOP under various vitreous conditions. Further validation of VCIOP using a cannular type of manometer should be considered.