Abstract
Purpose: :
: to asses the correlation of intraocular pressure (IOP) measurements obtained from two different methods, the Rebound tonometer (i-care) and the Tono Pen XL (TP), with the Goldmann applanation tonometer (GAT).
Methods: :
two hundred sixty nine eyes from 135 consecutive patients were involved in this cross-sectional study. All IOP and pachymetry measurements were made by the same examiner, who was masked to the observed result. I-care tonometry was performed first, followed by TP, GAT and pachymetry in a randomly order.
Results: :
one hundred twenty one patients were normal, 12 had ocular hypertension, and two glaucoma. Mean IOP was 16.89, 17.87, and 15.88 mmHg for i-care, TP and GAT respectively. The difference between the measurements obtained with all the three methods was statistically significant (Duncan test, p< .05). There was a good correlation between IOP readings obtained using the i-care and GAT (r = 0.76, p=.00) and between TP and GAT (r = 0.75, p=.00). A Bland-Altman plot indicated that the 95% limits of agreement between TP and GAT were -7.10 to 3.50 mmHg, and between i-care and GAT were -7.01 to 5.0 mmHg. In corneas thinner than 500 µ, the difference between GAT and TP (2.16 mmHg) was statistically significant (Duncan test, p= .73), but not between GAT and i-care (0.26 mmHg, p<.05). In corneas thicker than 560 µ a difference of 1.50 and 1.58 mmHg was obtained between GAT and i-care and between GAT and TP respectively, and both were statistically significant (Duncan test, p=.92).
Conclusions: :
both i-care and TP correlates well with GAT, and provide an overestimation of IOP measured by GAT. Tono-Pen XL overestimate IOP obtained by GAT in thinner corneas, and both i-care and TP overestimate IOP obtained by GAT in thicker corneas.
Keywords: intraocular pressure • reading