Development of Optical Systems for Retina Evaluation

该仪器评估人类黄斑中存在的类胡萝卜素、叶黄素和玉米黄质的水平。这些色素可以防止老年性黄斑变性，这是老年人失明的主要原因。共振拉曼光谱是一种非侵入性的方法，可以对视网膜中的这些黄斑色素进行量化。 犹他大学开发的共振拉曼光谱仪要求受试者在启动产生拉曼反向散射信号的激光脉冲之前，将模拟Ar离子激发激光束的受照光纤阵列与探测器光瞳的表示对准。对于视力良好的患者来说，这种对齐是一件简单的事情，但黄斑的退化使对齐成为一个困难的问题。为了克服这个问题，仪器进行了改进，以提供以角膜为中心的受试者眼睛的视频演示。在仪器的光路中引入了一个与拉曼激发和发射光路的光轴共线的低能级氦-霓激光。摄像机捕捉从角膜前表面散射和反射的激光束。医生调整受试者眼睛的位置，直到激光束集中在角膜上。这是通过定向到基准标记以及随着角膜前表面变得垂直于入射对准激光而增加反射强度来实现的。使用该仪器的临床试验表明，从每次运行的几个成功图像收集数据的能力增加到几乎100%的成功率。 对眼底相机进行了相关的改装，以进行平行调查，以捕捉激光刺激视网膜选定区域后的视网膜电信号，并拍摄选定区域。这个光学系统有五个主要组成部分。首先，将氦-霓虹激光(633 Nm)与Ar离子激光(488 Nm)或触发的氙灯共线并重合，作为患者对准时的替代光束，用于视网膜电信号刺激脉冲Ar激光或氙灯。其次，在光路的平行光空间内，可变孔可以自由地定位在光路的侧面，使得它允许医生调整视网膜上照明区域的大小和位置。第三，选择适当焦距和f数的最终聚焦透镜，以覆盖最大区域(即全光圈)，在眼睛的晶状体处达到焦点，相当于视神经。第四，玻璃分束器将改进的代理和激励激光的光路引入眼底相机的光路中，使得两条光路重合。第五，在分束器之前的激光路径中引入垂直偏振器，在眼底相机的观察路径中引入第二水平偏振器。这样做的意义在于，它允许观察到来自视网膜的去偏振光，但消除了来自光学表面的不必要的镜面反射，尤其是角膜。如果需要，旋转任何一个偏振器都可以使该反射可见。初步的临床评估正在进行中，以捕捉视网膜正常和病变区域的ERG反应。 建造了一种甘兹菲尔德型照明系统，以允许小动物视野的均匀照明。对直径12英寸的球体进行了改装，以容纳动物支撑平台和相关的记录电极，并在内部涂上了反射涂料。光纤耦合到反射球，引入了来自商业光源的刺激光。该仪器目前正在开发中。

This instrumentation assesses the level of the carotenoid pigments, lutein and zeaxanthin, present in the human macula. These pigments protect against age-related macula degeneration, the leading cause of blindness in the elderly. Resonance Raman spectroscopy is a non-invasive methodology that allows quantification of these macular pigments in the retina. The Resonance Raman Spectrometer, which was developed at the University of Utah, requires the subject to align an illuminated fiber optic array, which simulates the argon ion excitation laser beam, with a representation of the detector optical pupil prior to initiating the laser pulse that produces the Raman backscattered signal. This alignment is a simple matter with patients who possess good visual acuity, but degeneration of the macula makes the alignment a difficult problem. To overcome this problem, the instrument was modified to provide a video presentation of the subject's eye centered on the cornea. A low-level helium-neon laser was introduced into the instrument's optical path co-linear with the optical axis of the Raman excitation and emission pathways. The video camera captures the scattered and reflected laser beam from the front surface of the cornea. The physician adjusts the position of the subject's eye until the laser beam is centered on the cornea. This is accomplished by orienting to fiducial marks and by the increase in reflected intensity as the front surface of the cornea becomes perpendicular to the incident alignment laser beam. Clinical trials using the instrumentations have shown an increase of the ability to gather data from a few successful images per run to almost a 100% success rate. A related modification of a fundus camera was performed for a parallel investigation to capture an electro-retinogram following laser stimulation of selected areas of the retina and to photograph the selected area. There are five main components to this optical system. First, a helium neon laser (633 nm) was made collinear and coincident with an argon ion laser (488 nm) or triggered xenon flashlamp and serves as a surrogate light beam during patient alignment for the electro-retinogram stimulating pulsed argon laser or xenon flashlamp. Second, within the parallel light space of the optical path, a variable aperture can be freely positioned laterally to the light path such that it allows the physician to adjust the size and position of the area of illumination on the retina. Third, a final focusing lens of appropriate focal length and f-number is chosen to cover a maximum area (i.e. at full aperture), after reaching a focus at the lens of the eye, equivalent to the optic nerve. Fourth, a glass beamsplitter introduces the modified optical path of the surrogate and stimulating lasers into the optical path of the fundus camera such that both pathways are coincident. Fifth, a vertical polarizer is introduced into the laser path prior to the beamsplitter and a second horizontal polarizer is introduced into the observation pathway of the fundus camera. The significance of this is that it allows depolarized light from the retina to be observed, but eliminates unwanted specular reflections from optical surfaces, most particularly the cornea. Rotation of either polarizer renders this reflection visible if required. A preliminary clinical evaluation is on-going to capture ERG responses in normal and diseased areas of the retina. A Ganzfeld-type illumination system has been constructed to permit uniform illumination of the visual field of small animals. A 12-inch diameter sphere was modified to accommodate the animal support platform and associated recording electrodes, and internally coated with reflectance paint. Fiber optic coupling to the reflecting sphere introduced the stimulating light from a commercial source. This instrument is presently under development.