Progressive lenses, which are also known as progressive addition lenses, progressive power lenses and graduated prescription lenses, are used in eyeglasses to correct presbyopia. They also correct a number of different conditions where these kinds of lenses can be beneficial. These lenses are typically characterized by a built-in gradient of increasing lens strength.
The gradient will always start at the patient’s distance prescription, which is always at the very top of the lens. As the lens progresses and reaches maximum power, it progresses to the bottom of the lens. The length of the progressive power gradient, which is on the lens surface, is strictly dependent upon the designs of the lens and the needs of the patient.
Advantages of progressive lenses
There are significant advantages to having progressive lenses. The advantages are results from a number of factors, including:
- Adjustment for field of vision
- Avoiding discontinuations
- Looking better
Adjustment for the field of vision
The location of the lenses for the correct additional power for viewing distance, typically only requires a small adjustment of the head position. We use specifically designed lenses to enhance the field of vision. Objects that are closer to a person, like the reading of a form or book, are going to be within the lowest field of vision.
Objects that are far away and require distance correction, are typically higher in the field of vision. Thus, we design the lenses to provide a significant advantage by mimicking normal human visual behavior.
With most lenses, bifocal and trifocal, there is a phenomenon known as discontinuities. This basically means that the image jumps within the visual field because of the different types of lenses. To put it in simple terms, if the patient is looking at something in the distance, and then looks down to read something, there is a potential for them to see blurriness.
The blurriness can cause the object to "jump" and this, in turn, can be very stressful for the eyes. The human eye can make adjustments within the field of vision. Since distance objects as seen from the top of the field of vision, and close objects seen from within the lower part of the field of vision, having a gradual adjustment or progressive adjustment allows for the eye to make the transition without having the jump effect. In other words, using these lenses can completely eliminate discontinuities.
Let’s face it, bifocals and trifocals have long been associated with aging. Seeing somebody wearing bifocals automatically conjures up an image of age and needing glasses. Being the one to need this correction, and hence being perceived as older, can be disturbing to some people, particularly if they are young people.
On the other hand, progressive lenses are smooth and give a youthful appearance. While performing virtually the same function, they help to alleviate the appearance of age and encourage people of all ages to wear their glasses more as prescribed.
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