An ophthalmologist visiting the Uffizi Museum in Florence admires the "Birth of Venus" by Bortecelli through a +3.50 D cylinder lens. The views of Venus through the lens at two different orientation are shown below. What is the axis of the lens in:

a. View I and 

b. View II?

View I

z

View II

 

Answer 
In view I, the lens is at  90 degrees and in view II, the lens is at 180 degrees. 

The image in view I is elongated horizontally and therefore the axis is at 90 degrees.

In view II, the image is elongated vertically and therefore the axis is at 180 degrees. 
Remember that the axis is 90 degrees to the power. Try this with the trial lenses in the clinic.