Ocular Pulse Amplitude With Normal Tension Glaucoma in Japan

Abstract

Abstract: : Purpose:To investigate factors to affect ocular pulse amplitude (OPA) with NTG, using Dynamic Observing Tonometry (DOT; Ophthalmic development CO). The intraocular pressure (IOP) is not constant value and is fluctuating with cardiac beat. The fluctuated amplitude is called OPA which is understood to be the peak–to–peak difference between average systolic and diastolic IOP. OPA has been thought to reflect choroidal circulation. Therefore, OPA can possibly give some information about the choroidal circulation. In normal tension glaucoma (NTG), the abnormality of intraocular circulation have been reported (V Klingmüller, 2000, P Gasser, 1994). Knowing the OPA in NTG may be useful for the elucidation of pathology in NTG. Methods:60 NTG patients (mean 61.3±13.5 y.o.) and 64 age matched healthy control (mean 54.7±17.2 y.o.) were enrolled in this study. NTG; refractive error (mean –2.3±3.03D). MD of Humphrey Field Analyzer (HFA) 30–2 (mean –7.6±7.01dB). Control; refractive error (mean –1.01±2.7D). ODT was used to measure base line pressure (Po; dialated ocular pressure) and OPA in all participants by same examiner. The followings were analyzed in NTG and control groups. i) Comparison of OPA (Student’s t–test). ii) The correlation between OPA and following parameters (age, refractive error, applanation IOP, systolic blood pressure, diastolic blood pressure, average blood pressure, pulse pressure, ocular perfusion pressure, Po, MD of HFA 30–2) (Pearson’s correlation coefficient). iii) The exploration of determinants to OPA (Multiple regression analysis). Results:i)OPA in NTG (1.8±0.5mmHg), OPA in control (2.2±0.7mmHg) (p<0.05). ii)In NTG, Po (r=0.34, p=0.005) and Pulse pressure (r=0.34, p=0.0063 were significantly associated with OPA. In Control, Pulse pressure (r=0.46, p<0.0001), Po (r=0.41, p=0.005) and refraction (r=0.294, p=0.013) were associated with OPA. iii) Po (p=0.0165) and Pulse pressure (p=0.0197) influenced OPA in NTG. Pulse pressure (p=0.0137), Po (p=0.002), and refractive error (p=0.0009) influenced OPA in controls (NTG; R²=0.19, Control; R²=0.39). Conclusions: NTG patients showed reduced OPA. These results may associate with deficiency of ocular blood flow in NTG. Parameters we implied showed lower coefficient determination (R²=0.19) in NTG, than control (R²=0.39). We need to explore the further parameters to affect to OPA in NTG.

Keywords: choroid • clinical research methodology • intraocular pressure