It is commonly known that bifocal reading glasses and trifocal spectacles will probably cause visual side effects like image jump and even headaches. The reason for this is that these forms of eyeglasses take use of prescription lenses that are molded with separate powers. And these powers are fitted into different parts of the lens in an obvious way. So, power transition on the lens is quite sudden. It is these problems that drove experts to develop progressive addition lenses and progressive eyeglasses. By using lenses with smooth power addition, progressive lens glasses are supposed to be completely free from those traditional problems caused by bifocals or trifocals. However, that is not always the case. Progressive addition lenses may also cause similar side effects.
Presbyopic patients who switch from regular reading glasses to multifocal reading glasses like bifocals and trifocals usually need to experience a period of adaption because the lenses are no longer single-vision. They need to get their eyes and the brain used to the power transition within a short time. This is not an easy task. Progressive lens glasses also need a similar process. For those who switch from bifocals or trifocals to progressive glasses, getting themselves adjusted to the new kind of visual correction can be even harder. Some people may be confused by this phenomenon because those progressive reading glasses have long been advertised to get rid of all the bothersome problems associated with bifocals or trifocals.
In fact, the way in which progressive lens glasses provide visual aid is quite different from bifocals or trifocals. A progressive lens with a gradient of addition lens powers will surely cause narrower vertical band of prescriptively accurate optic characteristics at each lens part. For those new users, head movements are often made in order to sight through an appropriate lens section. During this accommodation period which varies from a few hours to a couple weeks, side effects like headaches and visual dizziness are quite possible.
C: Progressive lens glasses can not be completely free from visual side effects. During the accommodation period, some patients will experience headache and visual dizziness.