The following device shown in the figure used for indirect ophthalmoscopy. What is the power of the lens that should be used with it to visualize the retina?
A. -58 D
B. +20 D
C. +60 D
D. +90 D
Ans: B. +20 D
(Ref Yanoff and Duker 4/e p69; Khurana 6/e p586-587. 5/e p600; Parson’s 22/e p136. 21/e p134).
- With indirect ophthalmoscope, most commonly a lens of +20 D is used.
- Gives a magnification of about 3x (Magnification = power of eye (+60D)/ power of lens).