Which fundus lens has an approximate magnification of 1x when used with Slit Lamp?

Study for the NBEO Physiological Optics Test. Prepare with flashcards and multiple-choice questions, each question has hints and explanations. Ace your exam!

Multiple Choice

Which fundus lens has an approximate magnification of 1x when used with Slit Lamp?

Explanation:
In slit-lamp fundus viewing, magnification depends on the lens power and how the eye-to-lens setup is arranged. The 60D lens has the longest focal length among the commonly used slit-lamp condensing lenses, so at the standard working distance it produces a retinal image that appears about the same size as the actual retina—roughly 1x magnification. The higher-power lenses (78D, 90D, 100D) have shorter focal lengths and, in the same setup, yield a retinal image that is smaller in angular size (magnification less than 1x) even though they can give a brighter or more magnified view of a smaller area. So, for an approximate 1x magnification, the 60D is the best choice.

In slit-lamp fundus viewing, magnification depends on the lens power and how the eye-to-lens setup is arranged. The 60D lens has the longest focal length among the commonly used slit-lamp condensing lenses, so at the standard working distance it produces a retinal image that appears about the same size as the actual retina—roughly 1x magnification. The higher-power lenses (78D, 90D, 100D) have shorter focal lengths and, in the same setup, yield a retinal image that is smaller in angular size (magnification less than 1x) even though they can give a brighter or more magnified view of a smaller area. So, for an approximate 1x magnification, the 60D is the best choice.

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