[Reproducibility and comparison study of two methods evaluating the optic nerve subarachnoid space sectional area using MRI].

Objective: To optimize the method of acquiring the ONSAS parameter and to access the repeatability of the new method comparing with the traditional one. Methods: This is a cross-sectional study. Standard operation procedure of an optimized method of acquiring the ONSAS sectional area was made against the defect of the traditional method. Ten healthy volunteers (20 eyes) in different ages were recruited from March 2016 to October. Two times of MRI scan were proceeded with the interval of one week. The optimized and traditional methods were both applied for each scanning. The images were analyzed by two ophthalmologists. The rate of high quality images between two groups was compared with matching chi-square test. The orbital subarachnoid space areas between groups at different locations were compared using analysis of variance of repeated measurement data. The ICC between different scans and different ophthalmologists was calculated. Results: The mean age of the volunteers was 43.8±13.1 years old. Male/Female was 1∶1. The rates of high quality images from the optimized method (100%, 83%, 78%) was higher than those of the traditional method(80%, 78%, 70%). The orbital subarachnoid space area at 3 mm, 9 mm and 15 mm behind the eye ball acquired from the new method(7.2±1.8, 6.1±1.8, 5.9±1.4 mm(2)) were bigger than those of the traditional method (9.0±2.9, 7.6±2.4, 7.1±1.6 mm(2)). Statistical significances were found at 9 mm(F=4.30, P=0.048) and 15 mm(F=5.67, P=0.026) behind the eye ball. The ICC between two different scans (0.879, 0.857, 0.857 vs 0.741, 0.762, 0.639) and two different ophthalmologists (0.864, 0.890, 0.894 vs 0.785, 0.609, 0.753) were higher in the new method group than in the traditional method group. Conclusions: The optimized method of acquiring the parameters of optic nerve subarachnoid space is easier to get the sectional cross area. The measuring reproducibility is better than the traditional one. (Chin J Ophthalmol, 2017, 53: 440-444).