There are a lot of factors that come with purchasing a pair of glasses or readers. Material (plastic or metal), weight and look are probably three that come to mind quickly.
Another important factor though that you may want to consider is how the glasses match with your eye color. Here are a few good guidelines you may want to consider:
If your eyes are bright and blue a contrasting brown tone frame will help make your eyes pop. A great option would be the Elements Magnetic Readers in Tortoise. You may also want to coordinate with a frame that has a blue and grey tone such as the EcoClear Harmony in Ruthenium/Blue.
For those with hazel eyes, amber frames as well as greenish frames match up well as they emphasize the gold in eyes. Tropic in Apple Tini and Mocha Espresso are two ideal options.
For those with green eyes, frames with rich earthy colors in brown and gold tones should pair perfectly. In this situation a pair of CEO 2013 in tortoise with black temples is your best bet. They are extremely fashionable and make those green eyes shine.
The majority of us in the world have brown eyes. These people have a slew of options, as so many colors can look great with warm brown eyes. From basic black frames such as the CEO in black/crystal to rimless clear readers such as the popular airlite frames make for great glasses/eyes combinations.
As you can see, your eyes can compliment your glasses frames greatly. By knowing what works with what color will lead to lots and lots of compliments!