What is the difference between cylindrical and spherical eye lenses?-Dr. Elankumaran P

It is difficult to explain the difference between a spherical and a cylindrical lens. Spherical lenses are those lenses where the power is the same throughout the 360 degrees, that is throughout the lens. However when we talk about the cylindrical lens, we also talk about the axis in terms of degrees. So remember that this particular axis is more or less, that is it is different from the rest of the areas. The rest of the area can be a zero and this particular axis would be a plano cylinder or the rest of the area can also be a sphere, a spherical power and that can be an additional power called as the sphenocylindrical power. Any irregular surface has a cylindrical power and in ophthalmology we call it astigmatism, however of it is a regular smooth surface then it is only a spherical power.

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