Evaluation of anterior and posterior surfaces of the cornea using a dual Scheimpflug analyzer in keratoconus patients implanted with intrastromal corneal ring segments

AIM：To evaluate corneal parameters measured with a dual Scheimpflug analyzer in keratoconus patients implanted with intrastromal corneal ring segments（ICRS）.METHODS：Fifty eyes of 40 keratoconus patients had Ferrara ICRS implantation from November 2010 to April2014.Uncorrected visual acuity（UCVA）,best corrected visual acuity（BCVA）,refraction,keratometry,asphericity,elevation,pachymetry,root mean square（RMS）,spherical aberration and coma were studied.All patients were evaluated using a dual Scheimpflug system.RESULTS：The mean follow-up time after the procedure was 12.7mo.The mean UCVA improved from0.82 to 0.31（P〈0.001）;the mean BCVA improved from0.42 to 0.05（P〈0.0001）,the mean spherical refraction changed from-3.06 ±3.80 D to-0.80 ±2.5 D（P〈0.0001）and the mean refraction astigmatism reduced from-4.51 ±2.08 D to-2.26±1.18 D（P〈0.0001）.The changes from preoperative to postoperative,in parameters of the anterior and posterior surface of the cornea,were statistically significant except the elevation posterior at the apex of the cornea and posterior asphericity.CONCLUSION：The implantation of Ferrara ICRS induces changes in both anterior and posterior surfaces of the cornea.

极小盲区双视场沙氏激光雷达研究

沙氏激光雷达是一种可实现近距离高分辨率探测的系统,而室内气溶胶的扩散研究对其探测范围提出了严苛的要求。以沙氏激光雷达技术为基础,提出对远场和近场的气溶胶后向散射信号进行同时探测的双视场技术方案。该方案通过融合双视场的信号获取极小盲区的全路径信号廓线。在室内环境下,利用人工施放的气溶胶对所研制的双视场沙氏激光雷达系统进行了测试实验。实验中,在路径末端7.1 m处设置硬靶,提供边界值标定,从而反演得到气溶胶消光系数。实验结果表明:相比单视场探测系统,双视场探测系统的盲区由1.26 m缩小到0.36 m;同时,系统距离分辨率在最近处为0.1 mm,在最远处为15 mm;通过对两个视场信号的定标融合,全距离范围内气溶胶反演结果具有较好的时空连续性。