Lens thickness assessment : anterior segment optical coherence tomography versus A-scan ultrasonography

AIMTo assess lens thickness measurements with anterior segment-optical coherence tomography (AS-OCT) in comparison with A-scan ultrasonography (A-scan US).METHODSThere were 218 adult subjects (218 eyes) aged 59.2±9.2y enrolled in this prospective cross-sectional study. Forty-three eyes had open angles and 175 eyes had narrow angles. Routine ophthalmic exam was performed and nuclear opacity was graded using the Lens Opacities Classification System III (LOCS III). Lens thickness was measured by AS-OCT (Visante OCT, Carl Zeiss Meditec, Dublin, CA, USA). The highest quality image was selected for each eye and lens thickness was calculated using ImageJ software. Lens thickness was also measured by A-scan US.RESULTSInterclass correlations showed a value of 99.7% for intra-visit measurements and 95.3% for inter-visit measurements. The mean lens thickness measured by AS-OCT was not significantly different from that of A-scan US (4.861±0.404 vs 4.866±0.351 mm, P=0.74). Lens thickness values obtained from the two instruments were highly correlated overall (Pearson correlation coefficient=0.81, P<0.001), and in all LOCS III specific subgroups except in grade 5 of nuclear opacity. Bland-Altman analysis revealed a 95% limit of agreement from -0.45 to 0.46 mm. Lens thickness difference between the two instruments became smaller as the lens thickness increased and AS-OCT yielded smaller values than A-scan US in thicker lens (β=-0.29, P<0.001)CONCLUSIONAS-OCT-derived lens thickness measurement is valid and comparable to the results obtained by A-scan US. It can be used as a reliable noncontact method for measuring lens thickness in adults with or without significant cataract.

Preoperative evaluation of human crystalline lens hardness using A-scan ultrasound biometry： a pilot study

Dear Editor,I write to present the results of a study on the correlation between the ultrasound energy consumed during phacoemulsification with various preoperative parameters,including best corrected distance visual acuity（BCDVA）,the signal to noise ratio（SNR）obtained by partial coherence laser interferometry and primarily,lens spikes measurements derived by A-scan ultrasound biometry.Quantification of crystalline lens hardness before cataract removal has been attempted by several researchers in the past.These have been in humans and in animals,in vivo and in vitro,and have used a variety of imaging modalities.

Automatic Discontinuity Classification of Wind-turbine Blades Using A-scan-based Convolutional Neural Network

Recent development trends in wind power generation have increased the importance of the safe operation of wind-turbine blades(WTBs). To realize this objective, it is essential to inspect WTBs for any defects before they are placed into operation. However, conventional methods of fault inspection in WTBs can be rather difficult to implement, since complex curvatures that characterize the WTB structures must ensure accurate and reliable inspection. Moreover, it is considered useful if inspection results can be objectively and consistently classified and analyzed by an automated system and not by the subjective judgment of an inspector. To address this concern,the construction of a pressure-and shape-adaptive phased-array ultrasonic testing platform, which is controlled by a nanoengine operation system to inspect WTBs for internal defects, has been presented in this paper. An automatic classifier has been designed to detect discontinuities in WTBs by using an A-scanimaging-based convolutional neural network(CNN). The proposed CNN classifier design demonstrates a classification accuracy of nearly 99%. Results of the study demonstrate that the proposed CNN classifier is capable of automatically classifying the discontinuities of WTB with high accuracy, all of which could be considered as defect candidates.

Differences in intraocular lens power calculation in patients with sub-foveal choroidal neovascularization

Dear Editor,I am Dr Xing-Chao Shentu,from the Eye Center of the Second Affiliated Hospital,Medical College of Zhejiang University,Hangzhou,China.I write to present case series of differences in intraocular lens (IOL)power calculation by partial coherence interferometry (PCI)and ultrasound A-scan biometry with sub-foveal choroidal neovascularization (CNV).

RTM复合材料中分层缺陷的超声表征及量化分析

以ZT7H/QY8911碳纤维增强树脂基RTM工艺成型复合材料为研究对象,通过预埋单层聚四氟乙烯薄膜(PTFE)模拟不同尺寸(φ=3 mm,6 mm,10 mm)和不同深度(近上表面、中间深度、近下表明)的分层缺陷,制备了RTM复合材料超声检测试样。基于水浸式超声反射法对缺陷进行超声A-Scan、B-Scan和C-Scan检测表征,并对检测结果进行量化分析。结果表明:超声反射法对RTM复合材料层压板中分层缺陷具有定性、定量检测能力,超声A-Scan检测信号中幅值、相位、时域渡越等特征量与缺陷的尺寸、深度、性质等具有相关性,超声B-Scan检测可以对缺陷深度进行表征,超声C-Scan可以对缺陷尺寸进行表征,深度方向检测分辨率达1个铺层厚度,缺陷尺寸的检测偏差≤1.0 mm。

Changes in anterior chamber depth following vitrectomy

Background Anterior segment morphometry is crucial for ophthalmologists to understand the visual outcomes of cataract surgery,keratorefractive surgery,as well as some other anterior segment disorders.Previous reports in literature have shown that anterior chamber depth （ACD） may shift slightly after vitrectomy.This study aimed to characterize the shortterm changes in ACD in eyes after vitrectomy by means of A-scan ultrasound.Methods A prospective case series study was carried out on 29 eyes of 29 patients who underwent vitrectomy as the sole procedure.ACD was measured using A-scan ultrasound biometry shortly before vitrectomy and 1 week,1 month,and 3 months after the surgery.Postoperative ACDs were compared with baseline.Results Twenty-nine patients （16 males and 13 females） were enrolled in the study,with mean age of （50±11） （25-65） years.Twenty-three eyes of 23 patients were vitrectomized for vitreous hemorrhage （VH） and the other six were operated for idiopathic epiretinal membrane （ERM）.The mean preoperative ACD of the VH eyes was （2.98±0.38） mm.No significant difference was found between the ACD of the VH eyes and their fellow eyes （P=0.058）.The average preoperative ACD in the ERM eyes was （2.94±0.31） mm,which was statistically deeper than that of their fellow eyes （（2.85±0.28） mm,P=0.008）.No statistical difference was found in the postoperative average ACD of the VH eyes compared with baseline.In the ERM group,the postoperative ACD in the surgical eyes was still statistically deeper than the fellow eyes 1 week after surgery （P=0.034）.However,such statistical difference disappeared at 1 or 3 months postoperative （P=0.186 and 0.682）.Conclusions ERM may induce deepening of the ACD,which can be recovered by uneventful vitrectomy.VH does not cause shift of ACD,neither does vitrectomy.