A pilot study of the precision of digital intraocular pressure measurement during vitrectomy

To evaluate the precision of digital intraocular pressure (IOP) measurement in silicone oil (SO) filled eyes during vitrectomy.

This is a retrospective, single-blind study. Patients who were diagnosed with retinal detachment and scheduled for vitrectomy with SO injection were consecutively enrolled. During the vitrectomy, IOP was digitally measured and then by a rebound tonometer (IcarePRO). The rebound tonometer readings were masked to the surgeons. The digitally measured IOP and that of rebound tonometer were compared, and the inter-methods agreement was assessed. The absolute deviation in IOP values between these two methods (ΔIOP) was also calculated, and correlations between ΔIOP and refractive status, lens status and levels of surgeons' experience were analyzed.

A total of 131 patients (131 eyes) were recruited, with a mean age of 51.0±16.1y. There was no significant difference in IOPs between digital measurement and the rebound tonometer (15.6±4.3 vs 15.7±5.1 mm Hg; t=0.406, P=0.686). Intraclass correlation coefficients (ICC) analysis indicated a strong correlation between these two measurements (ICC=0.830, P<0.001). The mean ΔIOP was 2.0±1.9 mm Hg (range: 0-12.8 mm Hg), with 98 eyes (74.8%) had the ΔIOP within 3 mm Hg. ΔIOP was found to be negatively correlated with levels of surgeons' experience (r=-0.183; P=0.037), but not with the refractive status or lens status of the patients (both P>0.05).

For experienced surgeons, the digital IOP measurement may be an acceptable technique for IOP measurement in SO filled eyes during vitrectomy. However, its use by inexperienced surgeons should be taken with caution.