Clinical Application of Binocular Indirect Ophthalmoscope

Author: Chief Editor: Wei Wenbin
Publisher:
Publish Date: 1999-02-01
Features:
Fragment: Before the invention of the electric light in 1878, the reflective ophthalmoscope had undergone little change. The introduction of longer-lasting small bulbs and dry batteries in 1910 revolutionized the direct ophthalmoscope. In the United States, after the invention of the monocular direct ophthalmoscope, the indirect ophthalmoscope was not widely accepted by physicians at the time, whereas in Europe, this technology was still applied quite extensively. In 1883, Adams invented a monocular indirect ophthalmoscope with a headband, allowing the examiner to save the trouble of holding the ophthalmoscope, freeing up one hand, and not having to put down the ophthalmoscope to draw a fundus map. Allvar Gullstrand, a Swedish Nobel laureate, expressed the laws of light reflection of the ophthalmoscope in a formula. In 1920, Zeiss Optical Company manufactured a small binocular indirect ophthalmoscope based on Gullstrand's theory. From 1931 to 1970, Bausch and Lomb produced a benchtop binocular indirect ophthalmoscope based on Allvar Gullstrand's early design. The images obtained by this ophthalmoscope were upright fundus images, which were very helpful for teaching. However, due to the cumbersome and time-consuming process of adjusting the instrument and the difficulty of observing the anterior part of the fundus, it was not widely adopted. In 1947, Schepens developed a binocular indirect ophthalmoscope. His early model was similar to Adams' monocular indirect ophthalmoscope. After multiple improvements, the binocular indirect ophthalmoscope demonstrated outstanding superiority in fundus examination and once again attracted interest in the United States. This was the prototype of the modern binocular indirect ophthalmoscope, and with the advancement of science and technology, continuous improvements have been made on this basis. For example, fiber optics were placed in the illumination system of the ophthalmoscope to reduce heat generation; the use of miniature halogen tungsten bulbs and dichromatic filters increased the intensity of fundus illumination; monochromatic light sources made significant progress in increasing contrast, reducing chromatic aberration, and facilitating the localization of retinal and choroidal lesions. Other advancements include the integration of filters with light sources, used in intravenous fluorescein fundus angiography and oral fluorescein fundus angiography, and so on. In recent years, lightweight binocular indirect ophthalmoscope systems for clinical use have been developed, and miniature color television cameras have been combined with standard binocular indirect ophthalmoscopes for continuous imaging, or with color fundus cameras for taking fundus photographs. In terms of the condenser lens (objective lens), significant improvements have been made, producing objective lenses of various diameters and refractive powers to reduce chromatic aberration and achieve clear imaging, such as 13D, 20D, 28D, 30D, etc. Coated lenses reduce reflective interference, while yellow condenser lenses absorb shorter-wavelength blue and violet light, preventing retinal damage caused by the ophthalmoscope's light source. Additionally, Trantas (in 1900) first invented the scleral indentation method to examine the peripheral fundus, but at the time, he used his thumb nail to press the eye and used a direct ophthalmoscope. In 1951, Schepens invented a finger-cup-like indenter. However, some scholars believe that pressing the sclera may cause retinal tears or increase intraocular pressure. With the widespread use of binocular indirect ophthalmoscopes, it has been found that appropriate scleral pressure is harmless to eyes without wounds and is a safe and effective examination method. Currently, the binocular indirect ophthalmoscope is being increasingly accepted by ophthalmologists due to its advantages over the direct ophthalmoscope. It can be said that a clinically trained physician who has not mastered this examination method is already behind the times. In Western countries, the proficient use of the binocular indirect ophthalmoscope has become one of the fundamental skills for clinical ophthalmologists.