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M. Babic, J. Barreto, Jr., R.M. Vessani, L.M. Alencar, M. Hatanaka, C.G. V. Moraes, R. Susanna, Jr.; Dynamic Contour Tonometry and Goldman Applanation Tonometry in Eyes with Keratoconus . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4448.
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The dynamic contour tonometer (DCT) is a non–applanation contact tonometer designed to be largely independent of the structural properties of the cornea. Theoretically, it may measure IOP most accurately in abnormally thinner corneas. This study compares IOP measurements by DCT with Goldman applanation tonometry (GAT) in eyes with normal corneas and eyes with advanced keratoconus (KC).
A prospective comparative case series. Subjects were submitted to IOP measurement by GAT, DCT, ultrassonic pachymetry and slit scanning topography (Orbscan IIz). Exclusion criteria: any ocular pathology other than KC, previous corneal or refractive surgery, stromal scarring due to acute hydrops or any other corneal opacities.
Ten patients with KC were included in Group A and 12 normal patients composed Group B according to the pre–established criteria. The mean GAT measurement in group A was 10.3±1.8 mmHg and group B was14.3±0.75 mmHg. (p = 0,024). In group A, the mean DCT measurement was 14.6±2,09 mmHg and, in group B, the mean DCT measurement was 17,4±3,1 mmHg (p = 0,026). The difference between GAT and DCT measurements in group A was statistically significant (p < 0.0002).
IOP readings with the DCT in the keratoconus group were significantly higher than GAT measurements and lower when comparing to the control group. As there are no published manometric studies in eyes with KC, these lower IOP readings with the DCT could be related to the discrepancy between the radius of corneal curvature and DCT tip, the important thinning of the cornea, or other corneal biomechanical abnormalities related to advanced KC.
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