When we are young, the lens inside the eye is soft and flexible. To change focus from near to distant and back again, the muscles surrounding the natural lens contract and relax changing the optical power of the lens. This ability of the lens to change its shape and focus is called accommodation.
Around the age of 40, a condition known as presbyopia becomes noticeable where we lose the ability to change the shape of the lens inside the eye. As this occurs, we become more and more dependent on reading glasses to see close objects.
Benjamin Franklin invented a way to correct this condition with bi-focal lenses back in 1784. Today, progressive lenses are available that have the appearance of single vision lenses while providing you with a full range of vision from near, to intermediate, to distance.
Progressive lenses are created with a gradient of power starting with the patient’s distance prescription at the top of the lens, a stronger intermediate power in the middle of the lens, and the strongest near power at the bottom of the lens.
This seamless gradient of power zones allows patients to easily shift their focus from distance, to intermediate, to near, without the visual interference of lined bifocal or trifocal lenses.
If you experienced trouble in the past choosing a frame that would accommodate a progressive lens, there are now many progressive lens designs available for virtually any style of frame.