Benjamin Franklin proved the old adage "Necessity is the Mother of Invention" with his creation of the bifocal lens. Unfortunate enough to be both myopic (near-sighted) and hyperopic (far-sighted), Franklin was frustrated that he had to constantly switch his pairs of glasses, depending on what he was trying to focus on. He longed for the ability to see both near and far with a single frame. In order to accomplish this, Benjamin had the lenses of two pairs of spectacles cut in half and put half of each lens in one sole frame. Today, millions of individuals take advantage of Franklin’s bifocals, giving people a convenient way in which to correct their vision for both distance and reading.

Technology today with regard to reading glasses has come a long way since Benjamin Franklin. The two most common forms of reading glasses are flat-top bifocals or tri-focals and progressive lenses. Flat-top bifocals and trifocals are lenses that have a line on them that differentiate between the distance prescription and near prescription. As the name implies, with a bi-focal there are two points of focus, one in the distance at 20 feet or what is referred to as "optical infinity", and the other at near somewhere between 16-18 inches most commonly. Trifocals have two lines, with three areas to look through. The top is the far distance for driving, the middle is the intermediate distance for computer or just past arms length, and the bottom is the near point at about 14-16 inches. The advantage of what’s optically available today is that the patient can choose the specific focal points he or she desires for distance, reading or computer work or virtually any activity or vocation. So depending on your vocation, your physical size, as well as where you desire the "in focused area” to be, glasses can be designed to meet those requirements. Flat top or lined bifocals and trifocals do have limitations. Those limitations include they have very limited "depth of focus" or "range" with respect to the 2 (bifocals) or 3 (trifocals) focal points or areas of clear vision. Flat top lenses provide a good range of peripheral vision and typically do not limit vision when looking from left to right.

Progressive lenses are another technology that has specific differences compared to flat-tops. Because of the limitations of 2 or 3 points of focus with flat-tops progressive lenses were ultimately designed. Progressive lens technology provides a range of vision from "optical infinity" or 20 feet and beyond all the way up to 14-16 inches at near. Simply by moving your head up and down your eyes travel in the vertical meridian of the glasses. As you look down the lens the point of focus moves from distance to near. This provides the patient with any point of focus from 14 inches to 20 feet and beyond. The limitation of progressive lens technology is that in order to design a lens that allows these multiple areas of focus, the power is all in the vertical meridian of the lens. Therefore, peripheral or side vision is slightly blurred or distorted requiring the patient to point their nose where they would like to see clearly, keeping the vertical meridian of the glasses in line with the desired object. This is easily mastered by most with in a few days to one week. Neither flat-tops nor progressives are easy to use when traveling up and down stairs or off curbs at first however, once mastered vision is clear and comfortable. There are over 130 progressive designs on the market providing a vast selection for all types of patients and activities. If progressives aren’t for you, flat-top bifocals are available in an equally abundant variety.

Please visit our Optical Galleries’ in Stillwater and Pawnee for demonstrations of the various types of lenses available. We can be reached in Stillwater at 405-372-1715 or Pawnee at 918-762-2573. We also invite you to visit our website at www.cockrelleyecare.com