A clinical evaluation of XPERT^tm NCT^tm (Reichert) for glaucoma screening by optometrists

Abstract

XPERT^tm NCT^tm advanced logic pneumotonometer (Reichert) was studied for its reliability and use in glaucoma screening. The evaluated 2400 NCT measurements on 300 eyes were compared to the results of Goldmann applanation tonometry (GAT) from the same eyes. Repeated NCT tonometry had no significant effect on IOP. Local anesthesia reduced mean NCT-GAT difference and standard deviation significantly (p < 0.05), i.e. feeling due to the diminished air pulse force provided by the instrument had still considerable influence on IOP. NCT-GAT regression was significant (p < 0.01). Mean IOP readings provided by NCT were four mmHg higher than GAT values. Although accuracy was not satisfactory for exact measuring, it was satisfactory for screening. The results suggested that four mmHg less than the mean IOP value seen on the display is acceptable for screening when the difference between the minimal and maximal individual readings on the display is less than 2SD i.e. six mmHg. In the case of a greater difference, the maximal value is to be replaced, as NCT tends to read higher values than GAT.