Progressive Lens - Disadvantages

Disadvantages

Distortion: Progressive lenses suffer the disadvantage of the power progression creating regions of aberration away from the optic axis, yielding poor visual resolution (blur), which varies in relation to the quality of the lens. As the lenses combine a range of powers in a single surface there are also geometric distortions to the visual field, which increase with the addition power. Some wearers find the visual discomfort caused by these distortions outweigh the benefits of wearing PALs, this is known as progressive non-tolerance. However, manufacturers claim acceptance rates of 90%–98%. Clinicians generally agree that in order to avoid adaptation problems it is best to start wearing progressive lenses early in the development of presbyopia (around 40 years of age for most people) while the prescribed addition powers are low. The wearer can then adapt to the increases in a series of steps in addition power over a number of years as their presbyopia progresses.

Peripheral Vision Distortion: Because of the compromise in vertical range of undistorted vision, there is an inherent impact on peripheral vision with progressive lenses which is more obvious than that which is found in single vision lenses. This can affect the intermediate portion of the vision more so than the distance, and wearers who use computers regularly and for prolonged periods of time may benefit from an occupational progressive lens, commonly referred to as an office or extended reading lens.

Fitting: Progressive lenses require careful placement relative to the wearer's pupil centre for a distance-viewing reference position. Incorrect specification of the fitting location can cause problems for the wearer including (depending on the design of the lens) narrow fields of view, clear vision in one eye only, on-axis blur, and the need to alter the natural head position in order to see clearly.

Cost: Progressive lenses are generally dispensed at a higher price than bifocal and single-vision reading spectacles due to the increased manufacture and professional service costs.

When selecting a progressive lens design, an eyecare practitioner will usually ask some lifestyle questions, which coupled with prescription restrictions or recommendations and cost can effectively establish suitability for various models of progressive lens. Different lenses have different glazing restrictions, lens material availabilities, maximum and minimum fitting heights, prescription ranges and as such the variation in quality between higher and lower end varifocal lenses is considerable.