The relief of presbyopia with single-vision reading glasses, bifocals, and trifocals has obvious disadvantages. Reading glasses, while very effective for a limited range of distances about the near work position, cause progressive blurring with increasing distance of observation beyond that range. Bifocals and trifocals enable the wearer to see clearly at 1 and 2 intermediate positions, but they have the disadvantage of causing discontinuity of the visual field as a result of the segments and their boundaries.
The effects of a discontinuous field, in combination with the abrupt differences in focal power between segments and the surrounding lens, are blurring, distortion, and doubled vision. In some cases there is overlapping of the discontinuous fields within the total field, so that there is always some part of the environment which cannot be seen, while in other cases, though there is no overlapping, there is severe relative displacement of visual areas at
VOLK D, WEINBERG JW. The Omnifocal Lens for Presbyopia. Arch Ophthalmol. 1962;68(6):776-784. doi:10.1001/archopht.1962.00960030780012