Factors affecting the thickness of eyeglass lenses

On the issue of the thinness of eyeglass lenses, many friends with eyeglasses are more concerned, on the one hand, consider the aesthetic, on the other hand, the weight. To help you simply popularize a few factors that affect the thickness of the lens:

Factor 1, the center of the lens thickness (degree)

Factors affecting the thickness of eyeglass lenses is the brunt of the degree of the lens, we know that myopia is a concave lens, the middle of the thin circumference of the thick, the deeper the degree of the lens edge of the thickness of the lens is also the thicker; hyperopia or presbyopia lens is a convex lens, the edge of the lens is thin in the middle of the thick, the degree of the lens is deeper the center of the thickness of the thicker the lens, the center of the lens the thinner the lens is also the thinner. However, the center thickness of the lens is not the thinner the better, too thin the center thickness will reduce the strength of the lens and may make the lens curvature degree change, affecting the accuracy of the lens degree, so choose a compromise between the appropriate lens, the center thickness of the lens is very important to the effect of the thickness of the lens.

Factor 2, Refractive index of the lens

The higher the refractive index of the lens, the thinner the lens will be for the same number of diopters. Refractive index is the ratio of the speed of propagation of light in air to the speed of propagation of light in the lens (N). The refractive index of common resin lenses: 1.56, 1.60, 1.67, 1.74, etc.. (At present, the refractive index of glass lenses is generally between 1.523 and 1.9)

Factor 3, Curvature Design of Lenses

Myopia and hyperopia lenses are made up of two curved spherical surfaces inside and outside to produce the degree of myopia. For myopia lenses with the same data, the smaller the outer curvature of the lens, the thinner the lens is, and the larger the outer curvature is, the thicker the lens is.

Factor 4, the type and size of the frame

Frames are divided into four categories: full frame, half frame, rimless, and sheet, and the type of frame has a great influence on the thickness of the lenses, from the type of frame to the thickness of the lenses, the effect is from thin to thick, in order: sheet – full frame – half frame -Rimless.

If the frame is small and round, the more you grind the shape of the lens to the center of the concave lens, the more you grind the lens, the thinner it will be; conversely, the larger the frame and the more square the shape, the less you grind the lens, the thicker it will be. The opposite is true for farsightedness: the larger the shape of the lens, the thinner the edge of the lens.

Factor 5: Pupillary distance: the larger the pupillary distance, the thinner the lens.