In the past, the measurement of accommodation was measured by looking at the lens with an ophthalmoscope and using the lens to view a chart with large letters. The lens would be moved closer and further away from the eye until the patient could read the largest letters on the chart.
The answer to this question depends on the measurement system that you use. If you are using the metric system, then you would measure the waist circumference at the midpoint between the lower rib and the iliac crest. If you are using the imperial system, then you would measure around the natural waist at the smallest point.