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Yun Jeong Choi, Roo Min Jun, Kyu-Ryong Choi; Corneal Biomechanical Properties and Intraocular Pressure with the Ocular Response Analyzer in Normal Tension Glaucoma and Normal Tension Glaucoma Suspect Patients in Korea. Invest. Ophthalmol. Vis. Sci. 2011;52(14):667.
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© ARVO (1962-2015); The Authors (2016-present)
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.
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.
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.
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.
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