ALBRIGHT VISION CENTRE

90 Weoley Castle Rd, Weoley Castle, Birmingham B29 5PT 0121 477 2835

Contact Lens Practice,Eye Care & chiropody in Birmingham

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Dispensing Information

How to choose the right spectacle frame

This is always a balanced decision where the desired result gives the best appearance and the best performance of spectacle lenses. To give an example too large a frame may look perfect until a high prescription lens is put in, leaving you looking through goldfish bowls. The main factors to consider, in no particular order are:

Lens power

With powers over 3.5 lens thickness becomes a consideration plus lenses are thicker in the centre (convex) and tend to magnify the eyes, negative powers (concave) are thicker at the edge and tend to minify the eyes. Lens thickness increases with power and with overall size so that for higher powers trying to keep to a minimum spectacle eye size becomes increasingly important.The ideal position for the optical centre of the lens is opposite the pupil centre, meaning that the lens does not need to be decentred and the resulting lens is then thinner. It is very important particularly with high prescriptions to seek advice from a qualified optometrist or dispensing optician. Lens thickness can be further reduced by choosing different lens materials, however choosing an appropriate frame in the first place is more than half the battle.

Multi focal lenses

If you have varifocals or bifocals you need some depth in the eye shape to allow room for the reading portion. Bifocals tend to need less depth than varifocals, how ever varifocals have a great cosmetic advantage as they are invisible.

Lens Materials

Today the vast majority of spectacle lenses are plastic, these are much lighter and tend not to break as easily as the glass alternative. They do, however scratch more easily.

High index materials

By increasing the density of the plastic a marked reduction in thickness can be attained. Optical density starts at 1.49 for standard plastic increasing to 1.74, currently the highest available http://en.wikipedia.org/wiki/Corrective_lens. Generally speaking the higher the index the thinner the lens. Since lens price almost doubles for each 0.1 increase in index so the is invariably some compromise based on frame size lens power and wallet thickness. I do not feel high index is necessary for powers under 4.00 dioptres ( for long or short sight)

For very high prescriptions thickness considerations tend to over take weight so for powers over 10 dioptres glass which can go up to an optical density of 9.0 can be the best choice.

 

Facial characteristics

Heavy faces tend to suit heavy frames and fine features tend the suit thin frames. Noses come in different sizes if the nose is large a broad bridge on the frame is necessary for a good fit, other wise the frame will tend to sit high. If there is not much bridge to the nose as with many children, frequently a pad bridge in a metal frame is the best option.

Pupillary distance

The distance your eyes are apart means that, with a narrow Pd, the lenses need be inset so that the lens centre is opposite the eye, this has lens thickness implications since the greater the decentration necessary, the thicker the lens. Further, from an appearance point of view, spectacles with masses of lens on the temporal side can leave the eyes looking inset and appearance suffers.

Fashion

Usually what looks good, given the constraints above is going to be good. The more extreme styles don't suit every body although some time what is obviously wrong can some times be right, for instance spectacles for Woody Allen are so wrong they look good. There are rules to picking a really nice frame, the real problem is that most people only ever buy about twenty frames in there life times, for us its a living, so in this practice particularly we do take a very hands on approach to helping you decide because if you don't look good, neither do we!

 

 

 

 

 

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