Comparative study of corneal thickness and thinnest point position of keratoconus measured by Pentacam HR and RTVue OCT / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To investigate the difference, correlation, and consistency of corneal thickness and the thinnest point position detected by Pentacam HR corneal topography map and RTVue optical coherence tomography(OCT)in patients with keratoconus.METHODS: Cross-sectional comparative study. The corneal curvature map, corneal thickness map, thinnest point position, and thinnest point thickness were detected by Pentacam HR and RTVue OCT. Paired sample t-test was used for data consistent with normal distribution, and paired sample rank sum test was used for data inconsistent with normal distribution. Spearman correlation analysis and Bland-Altman analysis were used for the correlation and consistency of the two measurement methods.RESULTS: A total of 63 patients(105 eyes)with keratoconus were included in this study, including 49 males(77.8%)and 14 females(22.2%), aged 22.24±6.19 years; among them, relevant data of Pentacam HR topographic map: Km was 47.85±4.73D and Kmax was 55.43±8.72D. In measuring central corneal thickness and the thinnest point thickness of keratoconus, the Pentacam HR was 4.70μm and 19.46μm thicker than the mean value measured by RTVue OCT(P<0.05). There was no significant difference between the horizontal and vertical coordinates of the thinnest points measured by the two devices(P>0.05). The central corneal thickness and the thinnest point thickness measured by the two devices were highly correlated, the horizontal coordinate of the thinnest point was moderately correlated, and the vertical coordinate of the thinnest point was weakly correlated. Bland-Altman analysis showed that the central corneal thickness, the thinnest point thickness, the horizontal coordinate of the thinnest point, and the vertical coordinate of the thinnest point were 95.2%(100/105)and 93.3%(98/105), 95.2%(100/105), 95.2%(100/105)respectively, which were within the 95% consistency limit, while the consistency ranges were -36.00～+26.62μm, -42.27～+3.36μm, -0.80～+0.84mm, and -1.95～+1.06mm, respectively.CONCLUSION: In keratoconus, the central corneal thickness and the thinnest point thickness measured by Pentacam HR were higher than those measured by RTVue OCT. It is not recommended that the central corneal thickness and the thinnest point thickness measured by the two instruments be interchangeable in clinical use because of the wide range of consistency between the two instruments' results. The position of the thinnest corneal point measured by the two instruments is similar and consistent, so it could be considered to replace the measured values of the two instruments in clinical use.

Thickness Determination of Silicon Coating for Glass Injection Bottles by Scanning Electron Microscopy / 中国药师

Objective: To detect the thickness of silicon coating film for glass injection bottles by focused ion beam (FIB) emission scanning electron microscopy and investigate the stability and uniformity of the film.Methods: The boron silicon coating injection bottles were selected as the experimental samples and treated with such stability experiments as ultrasonic cleaning, high temperature resistance, heat resistance, water resistance, acid resistance and alkali resistance.The samples were vertically cut by the ion beam from an FIB field emission scanning electron microscope, and the thickness of the cutting face was measured by the built-in measuring module of the scanning electron microscope.Results: The thickness of silicon film was stable and uniform.Conclusion: The film thickness of glass bottles can be accurately detected, and the film stability and uniformity can be reflected directly and objectively by using an FIB double beam field emission scanning electron microscope.

The Comparison of Macular Thickness Measurements and Repeatabilities Between Time Domain and Spectral Domain OCT

PURPOSE: To compare macular thickness measurements obtained from time domain optical coherence tomography (TD-OCT) and 2 spectral domain (SD) OCTs and to evaluate their repeatability and agreement in normal subjects and diabetic macular edema patients. METHODS: Fifty-four healthy, normal subjects and 26 diabetic macular edema patients were participated in this study. In a randomly selected eye from each subject, two serial macular measurements were obtained from TD-OCT (Stratus OCT) and SD-OCTs (Cirrus HD-OCT, Spectralis HRA+OCT) by an experienced technician in random order. Nine areas of macular thickness map and repeatabilities obtained by the 3 OCTs were compared. RESULTS: In relative repeatability, SD-OCT showed better results overall compared to TD-OCT. Macular thickness was greatest in the Spectralis HRA+OCT in both normal subjects and diabetic macular edema patients, followed by Cirrus HD-OCT and Stratus OCT. In normal subjects, regardless of the type of comparison between the machines there was a statistically significant difference in all 9 areas. CONCLUSIONS: While the TD-OCT and the 2 SD-OCTs are reliable for macular thickness measurement, SD-OCT has better measurement repeatability compared with TD-OCT. Because macular measurements obtained from the 3 OCT systems cannot be interchanged, an effort should be made to standardize the measurement of each system.