Analysis of reproducibility, evaluation, and preference of the new iC100 rebound tonometer versus iCare PRO and Perkins portable applanation tonometry

Objectives: To analyze the reproducibility of the new iC100 rebound tonometer, to compare its results with the applanation tonometry and iCare PRO and to evaluate the preference between them. Materials and methods: For the study of reproducibility, 15 eyes of 15 healthy Caucasian subjects were included. Three measurements were taken each day in three separate sessions. For the comparative study, 150 eyes of 150 Caucasian subjects were included (75 normal subjects and 75 patients with glaucoma). Three consecutive measurements were collected with each tonometer, randomizing the order of use. The discomfort caused by each tonometer was evaluated using the visual analogue scale. Results: No statistically significant differences were detected between sessions. In the comparison between tonometers, the measurements with iC100 were statistically lower than those of Perkins (-1.35 +/- 0.417, p = 0.004) and that iCare PRO (-1.41 +/- 0.417, p = 0.002). The difference between PRO and Perkins was not statistically significant (p = 0.990). The mean time of measurement (in seconds) with iC100 was significantly lower than with Perkins (6.74 +/- 1.46 vs 15.53 +/- 2.01, p < 0.001) and that PRO (6.74 +/- 1.46 vs 11.53 +/- 1.85, p < 0.001). Visual analogue scale score with iC100 was lower than Perkins (1.33 +/- 0.99 vs 1.73 +/- 1.10, p < 0.05). In total, 61.7% preferred iC100 against Perkins. Conclusion: The reproducibility of this instrument has been proven good. iC100 underestimates intraocular pressure compared to applanation tonometry at normal values and tends to overestimate it in high intraocular pressure values. Most of the subjects preferred iC100 tonometer.