Comparison and interchangeability of macular thickness measured with Cirrus OCT and Stratus OCT in myopic eyes.

AIM: To investigate the difference of macular thickness measurements between stratus optical coherence tomography (OCT) and Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA) in the same myopic patient and to develop a conversion equation to interchange macular thickness obtained with these two OCT devices. METHODS: Eighty-nine healthy Chinese adults with spherical equivalent (SE) ranging from -1.13 D to -9.63 D were recruited. The macular thickness was measured by Cirrus OCT and Stratus OCT. The correlation between macular thickness and axial length and the agreement between two OCT measurements were evaluated. A formula was generated to interchange macular thickness obtained with two OCT devices. RESULTS: Average macular thickness measured with Stratus OCT (r=-0.280, P=0.008) and Cirrus OCT (r=-0.224, P=0.034) were found to be negatively correlated with axial length. No statistically significant correlation was found between axial length and central subfield macular thickness (CMT) measured with Stratus OCT (r=0.191, P=0.073) and Cirrus OCT (r=0.169, P=0.113). The mean CMT measured with Cirrus OCT was 53.63±7.94 µm thicker than with Stratus OCT. The formula CMTCirrus OCT=78.328+0.874×CMTStratus OCT was generated to interchange macular thickness obtained with two OCT devices. CONCLUSION: Macular thickness measured with Cirrus OCT were thicker than with Stratus OCT in myopic eyes. A formula can be used to interchange macular thickness measured with two OCT devices in myopic eyes. Studies with different OCT devices and larger samples are warranted to enable the comparison of macular values measured with different OCT devices.

[Research on monitoring land subsidence in Beijing plain area using PS-InSAR technology].

In the present paper, the authors use permanent scatterers synthetic aperture radar interferometry (PS-InSAR) technique and 29 acquisitions by Envisat during 2003 to 2009 to monitor and analyze the spatial-temporal distribution and mechanism characterize of land subsidence in Beijing plain area. The results show that subsidence bowls have been bounded together in Beijing plain area, which covers Chaoyang, Changping, Shunyi and Tongzhou area, and the range of subsidence has an eastward trend. The most serious regional subsidence is mainly distributed by the quaternary depression in Beijing plain area. PS-Insar results also show a new subsidence bowl in Pinggu. What's more, the spatial and temporal distribution of deformation is controlled mainly by faults, such as Liangxiang-Shunyi fault, Huangzhuang-Gaoliying fault, and Nankou-Sunhe fault. The subsidence and level of groundwater in study area shows a good correlation, and the subsidence shows seasonal ups trend during November to March and seasonal downs trend during March to June along with changes in groundwater levels. The contribution of land subsidence is also influenced by stress-strain behavior of aquitards. The compaction of aquitards shows an elastic, plastic, viscoelastic pattern.

Diagnostic classification of retinal nerve fiber layer measurement in myopic eyes: a comparison between time-domain and spectral-domain optical coherence tomography.

PURPOSE: To evaluate and compare the diagnostic classification of retinal nerve fiber layer (RNFL) measurement between time-domain and spectral-domain optical coherence tomography (OCT) in myopic eyes. DESIGN: Prospective, observational study. METHODS: A total of 97 eyes from 97 healthy myopic subjects were included. The RNFL in each eye was imaged sequentially with the Stratus OCT and the Cirrus HD-OCT (Carl Zeiss Meditec). With reference to the built-in normative database, the number of abnormal diagnostic classifications (borderline or outside normal limits) in each OCT device was analyzed and compared using the likelihood ratio chi-square test. Multiple logistic regression analysis was performed to evaluate factors associated with abnormal diagnostic classification. RESULTS: The Cirrus HD-OCT classified a significantly higher percentage of eyes as outside normal limits/borderline in at least 1 clock hour (Stratus, 14.4%/24.8%; Cirrus, 21.6%/34.1%; all P < .01). RNFL measurement at 1 (23.6%) and 2 o'clock (23.5%) of all eyes was the most frequent location classified as abnormal by the Cirrus HD-OCT and the Stratus OCT, respectively. Eyes with smaller optic disc and longer axial length were more likely to have abnormal diagnostic classification. CONCLUSIONS: In myopic eyes, Cirrus HD-OCT was more likely to have abnormal diagnostic classification than the Stratus OCT.