Sturm's Conoid

Sturm's Conoid Useful and Descriptive Information.

1. Sturm’s Conoid Mayuri Mohite 1 st Year B.Optometry

2. STURM’S CONOID It is an optical condition in which the refractive power of cornea and lens is not the same in all meridians. Therefore, instead of single focal point there are two focal points separated by interval of sturm This condition is called a sturm’s conoid .

3. Cont.. At point A – the vertical rays are converging more than the horizontal rays, so the section here is horizontal oval At point B – (first focus) the vertical rays have come to a focus while the horizontal rays are still converging therefore it forms a horizontal line. At point C – the vertical rays are diverging and their divergence is less than the convergence of the horizontal rays, so a horizontal oval is formed here.

4. Cont.. At point D – the divergence of vertical rays is exactly equal to the convergence of the horizontal rays from the axis. So here the section is a circle which is called the CIRCLE OF LEAST CONFUSION. Diagram showing circles of confusion for point source too close in focus too far

5. Cont.. At point E – the divergence of vertical rays is more than the convergence of horizontal rays, so the section here is a vertical oval . At point F – (second focus) the horizontal rays have come to a focus while the vertical rays are divergent. Therefore a vertical line is formed. Beyond F (at point G) – both horizontal and vertical rays are diverging and so the section will always be a vertical oval.