Abstract
Purpose: :
To identify the mean of corneal hysteresis(CH) and corneal resistance factor(CRF), and to investigate the agreement between Goldmann correlated IOP(IOPg), Corneal-compensated IOP(IOPcc) and Goldmann applanation tonomter(GAT) in normal(N) and normal tension glaucoma/normal tension glaucoma suspect(NTG/S) patients in Korea.
Methods: :
The study consisted of 71 eyes in N group and 63 eyes in NTG/NTGS group. After CH, CRF, IOPg and IOPcc were measured with the Ocular response analyzer(ORA; Reichert Inc., Depew, NY), central corneal thickness(CCT) with ultrasound pachymetry and GAT were also measured. The association between the measured IOP and other parameters was analyzed.
Results: :
There was a statistically significant difference in mean CRF(10.8 vs 9.6mmHg, p=0.001), but not in mean CH(10.9 vs 10.4mmHg, p=0.10). Of the patients in NTG/S group, patients who used topical glaucoma medications had lower CH and CRF than who did not use medications(CH: 10.8 vs 10.4mmHg(p=0.03); CRF: 9.3 vs 10.2mmHg(p=0.01)). CH and CRF showed significant correlation with CCT in both groups(CH : r=0.338 in N, r=0.380 in NTG/S; CRF: r=0.348 in N, r=0.559 in NTG/S).Mean differences between GAT-IOPg, GAT-IOPcc and IOPcc-IOPg were 0.54, 0.25, 0.29mmHg in N group, and 0.41, -0.42, 0.83mmHg in NTG/S group respectively. Only IOPcc - IOPg in NTG/S group was significantly different from zero(p<0.001), so IOPcc overestimates IOPg in NTG/S group. IOPcc-IOPg was not influenced by the magnitude of IOP, but significantly correlated with CCT in both groups(p=0.02 in N, p<0.001 in NTG/S group), that is, IOPg overestimates IOPcc when CCT increases.In multivariate regression analysis, GAT, IOPg and IOPcc in N group were significantly correlated with CCT(p<0.001, all), but not with CH or CRF. On the contrary in NTG/S group, GAT, IOPg and IOPcc were correlated with lower CH and higher CRF(p<0.001, all), but not with CCT.
Conclusions: :
CRF was significantly lower in NTG/S group, especially who used topical glaucoma medications than N group. Both CH and CRF were significantly correlated with CCT. IOP obtained with ORA(IOPg, IOPcc) has good agreement with GAT, but biomechanical factors affecting these parameters were different between the groups.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: systems/equipment/techniques