Measurement of the intraocular pressure with the "transpalpebral tonometer" TGDc-01 in comparison with applanation tonometry.

BACKGROUND

An irregular corneal surface compromises IOP measurement by Goldmann applanation tonometry. In such cases accurate measurement without corneal contact would be desirable. The new eyelid tonometer TGDc-01 measures IOP without corneal contact through the eyelid. The aim of the study was to evaluate the accuracy of the eyelid tonometer compared with Goldmann applanation tonometry (cornea thickness-corrected values) in subjects without corneal alterations.

METHODS

IOP was measured in 199 eyes of 103 subjects without corneal alterations by means of two different methods. Measurements with the transpalpebral tonometer TGDc-01 and the Goldmann applanation tonometer were performed within 5 min in random order.

RESULTS

The mean difference between lid tonometry and Goldmann applanation tonometry was 0.71 mmHg, SD +/-2.467 mmHg. In the reliability analysis the intraclass correlation coefficient was 0.8620. Compared with Goldmann applanation tonometry 66.4% of the IOP readings measured by lid tonometry were in an interval of +/-2 mmHg, 81.0% in an interval of +/-3 mmHg. The maximum of deviation was -6 mmHg and +6 mmHg, respectively. The Bland and Altman plots are shown.

CONCLUSIONS

Lid tonometry correlates sufficiently with Goldmann applanation tonometry, but in more than 10% of the measurements the IOP readings differed by more than 3 mmHg. The eyelid tonometer may be helpful as a screening tool when Goldmann applanation tonometry is not applicable.