[A comparative study of a disposable non-prismatic cone versus the biprismatic cone over 100 IOP measurements]

In 2009, we developed a non-prismatic cone in accordance with Goldmann tonometer standards. We undertook a prospective comparative clinical study of the non-prismatic cone versus the traditional biprismatic cone.

The disposable non-prismatic Plexiglas cone contains, on the inner side of its applanating end, a raised circular pattern 3.06 mm in diameter. Patient recruitment was performed in the setting of diurnal intraocular pressure (IOP) measurement for all comers including medically treated glaucoma patients. Two operators clinically tested the non-prismatic cone, with each operator measuring his or her own series of 50 eyes, for a total of 100 IOP measurements.

For the first operator, the mean IOP measurement with the non-prismatic cone was 17.92 mmHg, range 13 to 26 mmHg; the mean IOP measurement with the biprismatic cone was 17.40 mmHg; the difference between mean IOP measurements was 0.52 mmHg, with a correlation coefficient of 0.98. For the second operator, with a series ranging from 10 to 19 mmHg, similar results were observed.

Disposable cones, including the non-prismatic cone, adapted for the Goldmann tonometer are superior to other strategies for infection prophylaxis, such as chemical disinfection or condoms.

This study demonstrates the reliability of the disposable non-prismatic cone adapted for the Goldmann tonometer. Other features unique to the non-prismatic cone are evoked at the end of this paper.