Estimated Trans-Lamina Cribrosa Pressure Differences in Low-Teen and High-Teen Intraocular Pressure Normal Tension Glaucoma: The Korean National Health and Nutrition Examination Survey

Background To investigate the association between estimated trans-lamina cribrosa pressure difference (TLCPD) and prevalence of normal tension glaucoma (NTG) with low-teen and high-teen intraocular pressure (IOP) using a population-based study design. Methods A total of 12,743 adults (>= 40 years of age) who participated in the Korean National Health and Nutrition Examination Survey (KNHANES) from 2009 to 2012 were included. Using a previously developed formula, cerebrospinal fluid pressure (CSFP) in mmHg was estimated as 0.55 x body mass index (kg/m(2)) + 0.16 x diastolic blood pressure (mmHg)-0.18 x age (years)-1.91. TLCPD was calculated as IOP-CSFP. The NTG subjects were divided into two groups according to IOP level: low-teen NTG (IOP <= 15 mmHg) and high-teen NTG (15 mmHg < IOP <= 21 mmHg) groups. The association between TLCPD and the prevalence of NTG was assessed in the low-and high-teen IOP groups. Results In the normal population (n = 12,069), the weighted mean estimated CSFP was 11.69 +/- 0.04 mmHg and the weighted mean TLCPD 2.31 +/- 0.06 mmHg. Significantly higher TLCPD (p < 0.001; 6.48 +/- 0.27 mmHg) was found in the high-teen NTG compared with the normal group. On the other hand, there was no significant difference in TLCPD between normal and low-teen NTG subjects (p = 0.395; 2.31 +/- 0.06 vs. 2.11 +/- 0.24 mmHg). Multivariate logistic regression analysis revealed that TLCPD was significantly associated with the prevalence of NTG in the high-teen IOP group (p = 0.006; OR: 1.09; 95% CI: 1.02, 1.15), but not the low-teen IOP group (p = 0.636). Instead, the presence of hypertension was significantly associated with the prevalence of NTGin the low-teen IOP group (p < 0.001; OR: 1.65; 95% CI: 1.26, 2.16). Conclusions TLCPD was significantly associated with the prevalence of NTG in high-teen IOP subjects, but not low-teen IOP subjects, in whom hypertension may be more closely associated. This study suggests that the underlying mechanisms may differ between low-teen and high-teen NTG patients.