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Abstract #18980 Published in IGR 3-1
Tonometry in normal and scarred corneas, and in postkeratoplasty eyes: a comparative study of the Goldmann, the ProTon and the Schiotz tonometers
Jain AK; Saini JS; Gupta RIndian Journal of Ophthalmology 2000; 48: 25-32
PURPOSE: Clinical comparison of intraocular pressure (IOP) measured with the Goldmann applanation tonometer (GAT), ProTon tonometer (PT), and Schiotz tonometer (ST), in normal eyes, eyes with scarred corneas, and postkeratoplasty eyes. MATERIAL AND METHODS: The IOP readings with GAT, PT, and ST were compared in 125 eyes with normal corneas (Group A), 17 eyes with scarred corneas (Group B), and in 21 postkeratoplasty eyes (Group C). The data were statistically analyzed at a 95% confidence interval; linear regression analysis and paired t-test were performed. RESULTS: The mean differences and their standard deviation (SD) between GAT and PT readings, and GAT and ST readings, respectively, were: (1) Group A: -0.23 (SD 2.75) mmHg and +0.24 (SD 3.18) mmHg, respectively; (2) Group B: -1.8 (SD 12.67) mmHg and -4.5 (SD 9.95) mmHg; and (3) Group C: +0.24 (SD 8.72) mmHg and -0.12 (SD 8.7) mmHg. These were not statistically significant. In Group A, the 95% confidence interval between GAT and PT readings was -5.27 to 5.73 mmHg, and between GAT and ST readings, -6.12 to 6.59 mmHg. Ninety-six (77%) eyes with PT and 84 (69%) eyes with ST measurements were within 3 mmHg of GAT pressure. The correlation coefficients (r) for PT and ST were 0.93 (p = 0.0000) and 0.88 (p = 0.0000), respectively. In Group B, the 95% confidence interval between GAT and PT readings was -27.17 to 23.51 mmHg, and between GAT and ST measurement, -24.37 to 15.44 mmHg. The correlation coefficients (r) for PT and ST were 0.112 (p = 0.660) and 0.630 (p = 0.006), respectively. In group C, the 95% confidence interval between GAT and PT measurements was -17.20 to 17.67 mmHg, and between GAT and ST measurements, -17.51 to 17.27 mmHg. The correlation coefficients (r) for PT and ST were 0.780 (p = 0.0000) and 0.740 (p = 0.0001), respectively. CONCLUSIONS: In clinical practice, PT appears to have a higher level of accuracy than ST in normal corneas. In scarred corneas and post-penetrating keratoplasty eyes, because of high SD for mean differences and the wide confidence interval of 95%, both PT and ST are inaccurate in measuring IOP compared to GAT in such eyes.
Dr A.K. Jain, Department of Ophthalmology, Post-Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
Classification:
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)