If you have a high negative prescription, you’ll be familiar with thin lens options which are made from high index materials. The higher the index number, the thinner your lenses will be. These materials essentially have an ability to bend light into your eyes at a higher angle which in turn corrects your sight.
There are 2 main material options; glass and plastic.
Glass - up to 1.9 high index
Yes, actual glass lenses. These can be quite pricey, and go all the way up to 1.9 high index. However, they’re not widely recommended for 2 main reasons - safety, and weight. Like all glass, it can smash if for example you get hit by a football, or fall over into something. The glass also adds weight, which can affect comfort, and nose slide.
Plastic - up to 1.76 high index
Plastic lenses are the go-to material that you’ll usually get offered. The benefits of higher index plastic lenses are that they can be made to be thinner and lighter.
A standard optician will usually offer 1.5 - 1.74 options depending on your prescription. A 1.74 lens is going to turn out around 50% thinner than a 1.5 comparatively.
A more specialist lens is also on the market by a Japanese company called Tokai Optical which is 1.76 or ‘the thinnest lens in the world’ which is available through some opticians and lens glazers.
In order to get the slimmest result, the thinnest lens option suited to your prescription should be chosen (advised by your optician), combined with an optimised frame design for lens thickness.
Read more about lens thickness and calculating what your lenses could look like in different frames here: lens thickness calculator.