The look, weight and impact resistance of your glasses will depend on whether the lens is made from plastic, polycarbonate, high-index plastic or glass.
The lens is designed to suit the wearer’s prescription needs, whether for distance, arm’s length or near vision. Design options include single vision, reading, bifocal, trifocal, progressive and computer lenses.
Either one or both sides of the lens can be treated to extend the longevity of the glasses and improve clarity of vision. Lens treatments options include anti-reflective, scratch resistant and anti-fog benefits, among others.
Normally, light rays bend (refract) evenly onto a small area of the retina to give a clear image. For people with refractive errors like myopia, hyperopia and astigmatism - the light is unable to focus on this area of the retina. Corrective lenses bend the light that passes through to the retina, adjusting its focus and enabling the wearer to see clearly again.
Different lenses are required for different eye conditions:
Light rays are focused on the front of the retina, causing distant objects to blur. The lens to correct this issue is a ‘minus’ lens. The lens shape is concave (thicker at the edge, thinner in the middle) to bend rays outwards, allowing light to focus on the right spot to correct the vision.
Light rays focus behind the retina, causing objects at all distances, especially close up, to blur. In this case, a ‘plus’ lens is needed. The lens shape is convex (thicker in the middle, thinner at the edge) to bend rays inwards, allowing light to focus on the right spot within the eye and correct the vision.
The cornea of the eye is oval, rather than round, so light is unable to find a single focus on the right part of the retina, resulting in a blurred image. Astigmatism can occur by itself or in combination with near-sightedness or far-sightedness. A cylindrical lens is the most common way to correct astigmatism. A cylindrical lens may be minus or plus, depending on the type of astigmatism.
Schedule a comprehensive eye exam with a trusted Eyecare Professional and learn more about the right Essilor lens solutions for you.