Hand-held dynamic contour tonometry

Purpose: We present a prototype of the hand-held dynamic contour tonometer (HH-DCT) and prospectively compare this HH-DCT with the well-established Perkins applanation tonometer (PAT) and the TonoPenXL (TPXL). Methods: In a prospective, single-centre, randomized study, intraocular pressure (IOP) readings were taken in random order using HH-DCT, PAT and TPXL tonometers. Intra-observer variability was calculated for each observer and compared between three experienced ophthalmologists and an inexperienced medical student. Results: Ninety-two corneas of 92 healthy participants were enrolled. IOP [mean mmHg +/- standard deviation (SD)] as measured by HH-DCT was 16.97 +/- 2.71, by PAT 13.98 +/- 2.52 and by TPXL 13.34 +/- 2.68. The range of three consecutive IOP readings differed significantly between the devices [p < 0.001; mean range: 1.45 +/- 1.07 (HH-DCT), 1.87 +/- 0.97 (PAT) and 2.08 +/- 1.77 (TPXL)]. There was no difference of the range in all devices between the ophthalmologists and the medical student (HH-DCT p = 0.68, PAT p = 0.54, TPXL p = 0.48). Conclusion: IOP readings measured by HH-DCT are significantly higher than by PAT and TPXL. The differences of IOP measurements are in good accordance with previous studies using the slit-lamp-mounted DCT (SL-DCT) and Goldmann Applanation Tonometry, where SL-DCT readings were 1-3.2 mmHg higher. HH-DCT seems to give more constant results, which can be seen in the lower intra-observer variability compared to PAT and TPXL.