Whether you are near or farsighted, there are options available to help reduce the thickness of your lenses. First, you should consider using a higher index lens material to help reduce size. Different materials have varying index levels, and since the level is directly related to the corrective ability, a higher index level means less of the material is needed. Choosing the right material is important for limiting the lens thickness of your glasses.
The highest ranked materials are glass lenses with indexes between 1.8 and 1.9. Unfortunately, these high-end lenses are hard to get (only a few manufacturers available), and are expensive. Plastic lenses with indexes between 1.6 and 1.74 are the next best option and are considered to be high index. These plastic lenses are the thinnest available for all plastic lenses and considerably less expensive than the glass options. Below the high end plastic materials, are polycarbonate lenses. The polycarbonate lenses have an index of 1.59, and are very light and durbale. Trivex is the next lowest index material at 1.53. With an index of 1.52 is Crown Glass, which is rather heavy and thicker than the other materials discussed so far. Lastly, there is CR-39, a plastic material with an index of 1.5. CR-39 is lighter than Crown Glass but is the thickest lens type available.
After you’ve selected the proper lens material for your needs, there are other otpions to consider. Having the edges polished will make the glasses look thinner. You may choose to have either a satin, or clear polish. The satin polish will make the edge less visible, therefore making the lens appear noticeably smaller. A glossy polish will have some effect, yet not as drastic as the clear polish.
Having the edges tinted will also help make the overall lens appear less thick. This option works well with plastic frames that are somewhat larger than most. When you match the edge of lens with the frame color, it appears as though the edge is actually part of the frame, therefore making it difficult to distinguish the thickness. The thickness of the frame is important as well. The thicker a frame, the less chance there is of a lens protruding beyond it.
Avoid using rims that do not cover the entire circumference of the lens. Leaving the lens exposed will clearly show the actual thickness of the lens. Again, a plastic frame is ideal for covering the entire lens, as they tend to be thicker than metal ones. Rolling the edges used to be common as well, but is losing popularity with the new lens materials that have become available. The process of rolling edges, simply involves rounding off the edges so that a distinct flat edge is not present.