Comparing GAT with DCT

Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) do not produce identical results when measuring intraocular pressure (IOP), according to study results published in the September 2008 issue of the Journal of Glaucoma.

Michele Lanza, MD of the Department of Ophthalmology at the Second University of Naples, Italy and colleagues used DCT and then, ten minutes later, GAT to assess subjects aged 20–77 years who showed no signs of glaucoma (n=118) and compared the results.

As measured with GAT, the median IOP value was 15.49±2.43 mmHg (range: 11–22 mmHg); when measured with DCT, the median value was 17.59±2.9 mmHg (range: 10.5–25.1 mmHg).

As the median IOP value was statistically significantly higher when measured with DCT when compared with GAT measurements, the researchers concluded that it is not advisable to interchange these instruments and that, when measured with DCT, higher apparent IOP values may in fact be within the normal range.