Hello everyone! In studying for the ABO exam I came across a question and I have no idea how to arrive at the answer.
"What is the actual intermediate power of the Rx using this lensomerter reading: OD -1.00, Add +1.50, intermediate +0.50?"
I know the answer is -0.50 but I have no idea how to arrive at that answer. I am comfortable using the lensometer to find sphere, cylinder and reading power, and I would think knowing that I could find the intermediate (usually half the add) but I am thrown by this particular question.
Any help would be much appreciated. Thanks!
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