What is the Interval of Sturm for a spherocylindrical lens with a power of +6.00-2.00x090?

To determine the Interval of Sturm for a spherocylindrical lens, it is important to consider the nature of the lens and how the powers contribute to the formation of different focal points for each meridian involved. The power of the spherocylindrical lens is given as +6.00 diopters in the spherical component and -2.00 diopters in the cylindrical component at an axis of 90 degrees.

The Interval of Sturm is calculated as the distance between the two focal points of the astigmatic lens, which occurs at the two principal meridians. The distance is derived from the difference in power between the two meridians. To calculate it:

1. The power in one meridian (for the regular axis of the sphere) is +6.00 D, while in the perpendicular meridian (due to the cylinder) it is +6.00 D - 2.00 D = +4.00 D.

2. The difference in power between the two principal meridians (the powers of +6.00 D and +4.00 D) is therefore 2.00 D.

3. The focal length (in meters) can be found using the formula ( f =