Purpose:
Sensitivity (SN) and specificity (SP) of intraocular pressure (IOP) measurements were compared by three methods, by Goldmann applanation tonometry (GAT), Ocular Response Analyzer (ORA) and Dynamic Contour Tonometry (DCT).
Methods:
IOP was measured in 840 eyes of 420 patients sequentially by GAT, ORA and DCT. GAT was corrected for CCT and corneal curvatures (K’s) to calculate "presumed" reference IOP (R–IOP) as benchmark for comparison. SP and SN were compared using R–IOP 21 mmHg as threshold of elevated and not elevated IOP.
Results:
Mean GAT was 15.8 ± 4.2 mmHg, IOP by ORA (ORA–P) 14.4 ± 3.3 mmHg, IOP by DCT (DCT–P) 18.2 ± 4.5 mmHg. R–IOP correlates most with GAT ( R2 = 0.69), next with ORA–P ( R2 =0.61) and least with DCT–P ( R2 = 0.23). GAT correlates most with ORA–P ( R2 = 0.91), next with R–IOP ( R2 = 0.69) and least with DCT–P ( R2 = 0.32). ORA–P correlates most with GAT ( R2 = 0.91), next with R–IOP ( R2 = 0.60) and least with DCT–P ( R2 =0.34)). DCT–P correlates moderately with ORA–P next with GAT and least with R–IOP. SP and SN using R–IOP 21 mmHg as threshold of elevated and not elevated IOP is shown in Table 1. Highest product of SP x SN with integer IOP threshold was defined as Optimum threshold IOP as shown in the Table 1. .
Conclusions:
IOP measured indirectly by corneal deformation is influenced by dimensions of corneal structure and elasticity of corneal tissue. GAT correlates most with R–IOP, then with ORA–P and least with Pas–P. Highest optimum product of SP and SN of these tests were seen when GAT threshold was 19 mmHg, ORA–P was 16 mmHg and DCT–P was 19 mmHg. These values may be used as new thresholds in screening elevated IOP with these instruments.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: systems/equipment/techniques • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology