Lohmann C P, Timberlake G T, Fitzke F W, Gartry D S, Muir M K, Marshall J
Department of Clinical Ophthalmology, Institute of Ophthalmology, London, UK.
Refract Corneal Surg. 1992 Mar-Apr;8(2):114-21.
After photorefractive keratectomy using excimer lasers (193 nm), most corneas show a marginal loss of transparency (haze) and the assessment of its magnitude in clinical studies has been subjective. To address this problem, we have developed a new device for the objective measurement of haze by measuring corneal light scattering.
A CCD-camera was fixed at 40 degrees to a slit-lamp microscope and connected via frame-grabber to a computer. By incorporating polarizing filters, the system could discriminate between reflected and scattered light. The intensity of light coming from the cornea was measured in gray scale levels using in-house image analysis software. The system was calibrated against three different sizes of microspheres (0.25, 0.50, and 5.00 microns) which corresponded to the size of cellular and extracellular elements known to occur at sites of corneal surgery. Data were obtained from three treated human eyes with measurements before treatment and at five different postoperative intervals with a maximum follow up of 4 months.
All three sizes of microspheres caused disturbances in gray scale levels (36 to 255 units) in the same range of those observed in corneal measurements. Disturbances in corneal light scattering were noted from 1 week postoperatively and persisted throughout the period of observation. We observed an increase in reflected and scattered light until the 2nd postoperative month followed by a subsequent decline.
It appears that this device is very useful to defect and measure objectively disturbances in corneal transparency after excimer laser photorefractive keratectomy.
使用准分子激光（193纳米）进行光性屈光性角膜切削术后，大多数角膜会出现边缘透明度丧失（ haze），而在临床研究中对其程度的评估一直是主观的。为了解决这个问题，我们开发了一种通过测量角膜光散射来客观测量 haze的新装置。
将一台CCD相机固定在裂隙灯显微镜上40度角处，并通过图像采集卡连接到计算机。通过加入偏振滤光片，该系统可以区分反射光和散射光。使用内部图像分析软件以灰度级测量来自角膜的光强度。该系统针对三种不同大小的微球（0.25、0.50和5.00微米）进行校准，这些微球对应于已知在角膜手术部位出现的细胞和细胞外成分的大小。从三只接受治疗的人眼中获取数据，在治疗前以及术后五个不同时间间隔进行测量，最长随访4个月。
所有三种大小的微球在角膜测量中观察到的相同范围内引起灰度级（36至255单位）的干扰。术后1周开始出现角膜光散射干扰，并在整个观察期持续存在。我们观察到反射光和散射光在术后第2个月之前增加，随后下降。
看来该装置对于检测和客观测量准分子激光光性屈光性角膜切削术后角膜透明度的干扰非常有用。
