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C. G. Vasconcelos, A. S. Reis, M. E. Sano, A. K. Barreira, R. M. Vessani, R. Susanna, Jr.; Intraocular Pressure Profile During the Modified Diurnal Tension Curve Using Goldman Applanation Tonometry and Dynamic Contour Tonometry in Glaucomatous Eyes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1055.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of this paper is to compare the IOP profile during the modified diurnal tension curve (DTC) using Goldman Aplanation Tonometry (GAT) and Dynamic Contour Tonometry (DCT) in glaucomatous eyes under topical treatment.
Patients were diagnosed with Primary Open Angle Glaucoma (POAG) based on glaucomatous optic neuropathy and typical Standard Automated Perimetry visual field defects. All patients were under the use topical treatment. All eligible patients were submitted to the mDTC using GAT and DCT, in this sequence. Tonometry was performed at 8 am, 10 am, 2 pm and 4 pm .Only DCT measurements with Q scores of 1 or 2 were considered for analysis. Agreement between IOP measurements using GAT and DCT was analyzed using Bland- Altman Plot. Comparison between means was performed using paired student t-test.
Forty eyes were included in the study. The mean difference between IOP measurements (DCT - GAT) was 0.9 mmHg. The 95% limits of agreement between methods ranged from -5.0 mmHg to 6.7 mmHg .The mean IOP measurements during the mDTC were 19.68 (±4.68), 17.63 (±4.44), 17.25 (±5.41) and 17.32 (±4.25) using GAT and 19.97 (±4.75), 18.79 (±4.61), 19.53 (±5.30) and 19.43 (±5.45) using DCT. The differences between DCT and GAT measurements were lower in the morning and increased throughout the day. Short-term IOP variability (SD) was higher using GAT than DCT (2.20 ±0.80 and 1.80 ±1.28, respectively, p=0.035).
The mean IOP values using DCT were higher than GAT at all times during the mDTC, which is consistent with previous reports. This difference was smaller in the morning, and tended to increase throughout the day. Previous reports have demonstrated a fluctuation of the Central Corneal Thickness (CCT) during the day (Kida and Weinreb). Also, previous reports have shown that under acute hypoxia, increased CCT may result in overestimation of GAT measurements (Lu et cols; Hamilton et cols). Considering that the factors involved in the IOP circadian rhythm were the same in this group of patients for both tonometers, and that their differences were lower in the morning and increased throughout the day, we suggest that an artifact variable contributes to such difference. Since both tonometers show measurement differences that are related to the corneal biomechanical properties, we believe that this variable might be one of the contributing factors for these findings.
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