Types of Lenses Explained
Single Vision Lenses
Single Vision lenses are the optical industryâ€™s standard for the majority of prescriptions. It is the most basic type of lens for glasses where the whole lens is made to the same prescription. For younger patients this allows clear vision at all distances.
However, when people reach approximately the age of 45, a condition called presbyopia occurs to such an extent that separate prescriptions are often needed for long and short distances. This means either two separate pairs of glasses, or a switch to Bifocal or Multifocal lenses.
A Bifocal lens consists of two parts. An upper part for clear long distance vision (walking, driving, TV etc), and a lower section (usually in a circular or half-moon shape) which is stronger and allows the eye to focus closer up.
These lenses give nice wide viewing areas for both long-distance and close-up, but it might not be easy to focus on middle-distance items, for example computer screens and music stands. Solutions for this include having a separate pair of computer glasses, or using Multifocal.
If you require bifocal eyewear for a particular purpose such as reading, or riding a motorbike, then please let us know at eyekit.co by adding your requirement to the additional details section of the prescription input page. We will then set the lower half moon segment to optimise vision for that purpose.
Should you wish for the segment to be positioned at a particular height then please state this on the additional information box instead.
Multifocals are lenses that combine your distance, reading and intermediate prescriptions into one lens. However, they provide clear vision at all distances, at the expense of some field (or width) of view for reading. They do not have any dividing line, so look just like a standard pair of lenses.
Multifocal lenses have some slight distortion on the lenses because of the way they are made. This means you have to move your head more when using multifocals to avoid catching some of the distorted areas.
However in recent times with great advancement in technologies of multifocal lens design, these distortions are less and less noticeable giving far greater field of view than ever before.
With the almost extinction of glass lenses from the spectacle market, most lenses are made from special resins or plastics.
Almost all lenses have a scratch resistant coating to help prevent permanent scratches and marks appearing on your lenses.
Most lenses are recommended with an anti-reflective coating to hide unwanted surface reflections and reduce glare on the surface of lenses caused by strong light sources like headlights when night driving or computer screens.
Photo chromatic materials may be useful which change colour from light to dark adapting to the brightness of the sun.
High index materials help reduce the thickness and weight of lenses and are especially helpful for people with higher prescriptions when considering the appearance of their spectacles.
Tinted lenses and UV coatings can be added to most lenses to make them into prescription sunglasses. Also polarised lenses can be used to not only reduce the UV and sunlight but also reduce significantly the intense glare that can dazzle the eyes. This is great for fishing to help see into the water or when driving to eliminate mirages from the road.
The optometrist will make recommendations as to what may best suit your needs when considering lens choices, so it is important to discuss what your visual needs are to maximise the performance of your new spectacles.