The curvature of a lens's front surface is referred to as its base curve. A lens's optical power increases as its base curve is increased since this produces a steeper curvature, which strengthens the lens's ability to bend light rays.
The amount that a lens material bends light depends on its index of refraction. By choosing a lens material with a greater index of refraction, patients with high refractive defects can have lenses that are lighter, thinner, more aesthetically beautiful, and more comfortable without sacrificing the lens's optical power.
In bifocal lenses, the term "add power" describes the extra magnification that is added to the bottom portion of the lens to help with near vision tasks. This is required for presbyopic patients whose lens flexibility has changed with age, making it impossible for them to focus or adjust for close work.
A lens material's dispersive power is measured by its Abbe value; higher values indicate less light dispersion into constituent colors, which lowers chromatic aberration. Higher abbe value materials provide for sharper, more color-accurate vision.
Blurred distance vision is a result of a myopic (nearsighted) eye's capacity to focus light rays in front of the retina rather than directly on it. A cornea that is excessively curved relative to the length of the eye or a longer axial length of the eye may be the cause of this disorder.
Applying an anti-reflective (AR) coating to ophthalmic lenses is primarily done to decrease reflections, thereby increasing light transmission through the lens. This reduces glare and improves vision. It is especially useful in low light and for cutting down on nighttime glare from headlights and computer screens.
According to the effective Focal Length (EFL) Principle, a lens's effective power varies with the distance it is from the eye. Because the focal length of plus lenses rises when the lens is moved away from the eye, the effective power of the lens decreases.
The effective power of high-minus lenses decreases when the vertex distance—the separation between the lens's rear surface and cornea—increases. This is due to the fact that light rays must travel a greater distance to reach the retina, which lessens the lens's converging
Astigmatism is a refractive error caused by an irregular curvature of the cornea or lens, leading to light being focused at multiple points within the eye, either in front of or behind the retina, or both. This results in a distortion of the retinal image, affecting both horizontal and vertical lines, and can cause blurred or distorted vision at all distances.
In glasses, aspheric lens esigns are utilized to lessen peripheral dstotion. Contrary to spherical lenses, which minimize distortion and offer a broader, clearer field of vision, especially with higher prescriptions, these lenses feature curvatures that alter from the center to the edge.
