Miller D
Ann Ophthalmol. 1982 Dec;14(12):1107-10.
The history and basic optical principles of the direct ophthalmoscope are reviewed, and new developments, including the halogen-tungsten bulb, are explored. To counter the problem of trying to discern retinal details through an immature cataract or an edematous cornea, a system has been designed that sends a thin light annulus along the outer edge of a dilated pupil, avoiding the middle of the cornea or lens. Recent studies suggest that the direct ophthalmoscope with a standard bulb at design voltage can safely be used steadily for only about a minute and a half, and occasional pausing during prolonged viewing is recommended.
回顾了直接检眼镜的历史和基本光学原理，并探讨了包括卤钨灯泡在内的新进展。为解决透过未成熟白内障或水肿角膜辨别视网膜细节的问题，设计了一种系统，该系统沿散瞳的外边缘发送细光环，避开角膜或晶状体中部。最近的研究表明，在设计电压下使用标准灯泡的直接检眼镜仅能安全稳定地使用约一分半钟，建议在长时间观察时偶尔停顿。
