If the refractive power of the unaccommodated eye of an emmetropic woman is 60 diopters (D), the axial length of her eye is closest to?: (A) 14.5mm, (B) 15.5mm, (C) 16.5mm, (D) 17.5mm
Answer is C. The focal point of an optical system (in meters) is the reciprocal of the refractive power of the system. Therefore, the focal point is 1/60 diopter (D), or 16.7 mm. An emmetropic eye forms a focused image of a distant object on the retina without accommodation. If the axial length is 16.5 mm, the image will be focused on the retina. Ref: Chang D.F. (2011). Chapter 2. Ophthalmologic Examination. In P. Riordan-Eva, E.T. Cunningham, Jr. (Eds), Vaughan & Asbury's General Ophthalmology, 18e.