In Vivo Agreement of Intraocular Pressures Simultaneously Measured Using Tonometer and Manometers Placed in Anterior and Vitreous Cavity under General Anesthesia

Abstract

 

Purpose

 

To analyze the agreement between three intraocular pressure (IOP) measurements obtained using tonometer and manometers placed in anterior chamber (AC) and vitreous cavity (VC) in various vitreous conditions and their association with ocular properties.

 

Methods

 

Sixty nine patients who were planning to have vitreous surgery for epiretinal membrane or macular hole (ERM and MH; n=26), vitreous hemorrhage (DMVH; n=24), or silicone oil removal (n=19) were included consecutively in this prospective study. One examiner, who was blinded to the patient’s information, performed a complete ophthalmologic examination, including the corneal thickness (CT), anterior chamber depth (ACD), and axial length (AL). Another examiner simultaneously measured IOP using Tonopen AVIA® and 2 automated transducers during the surgery (Fig. 1).

 

Results

 

The mean POAIOP, ACIOP and VCIOP were 16.7±3.7 mmHg, 16.7±3.8 mmHg and 16.0±4.6mmHg, respectively. The correlations between POAIOP and ACIOP, between ACIOP and VCIOP, and between POAIOP and VCIOP were all very good (R=0.92, 0.65, and 0.76, respectively). However, the VCIOP was significantly higher compared with POAIOP or ACIOP in the ERM and MH group (by 1.4 and 1.5 mmHg, respectively), butsignificantly lower in the DMVH (by -1.0 and -1.1 mmHg, respectively) and the silicone oil groups (by -2.8 and -2.7 mmHg, respectively) (Fig.2). In the multivariate analysis, only CT among ocular properties was significantly correlated with POAIOP (p<0.037) and the increase in POAIOP per 100 um of CT was about 2.7 mmHg.

 

Conclusions

 

Generally, transducers in AC and VC provide IOP measurements that correlate well with those offered by tonopen and are not affected by the patient’s individual ocular properties such as CT, ACD and AL, though CT affected Tono-pen AVIA® measurement. However, the VCIOP using transducer overestimated the ACIOP or POAIOP in normal vitreous condition, whereas significantly underestimated depending on the associated pathologic vitreous conditions especially in silicone-oil filled eyes. Thus, IOP measured by VC transducer in certain vitreous conditions needs further validation about the real IOP difference or measurement error.

 

 

Fig 1. Schematic drawing of setup for the simultaneous measurement of IOP.

 

 

Fig 2. Box plots of IOP measured by tonopen and two transducers located in AC and VC in 3 groups.

 

Keywords: 568 intraocular pressure • 763 vitreous