I had one pair of 'progressive bifocals' in which i could pick out 7 different viewing regions. A well-designed progressive lens has an optically infinite number of zones which are a straight line in the vertical centre of the lens, with each zone above and below that point being more bell-curve shaped, within the limits of lens shape.
They all come together in the horizontal centre of the lens, at each side. You should notice less distortion that way if you look up or down to the side through the lens.
Though, lens tech has come a long way. I have curved-lens sunglasses, the wrap toward my temples, which have my full astigmatism/presbyobia bifocal in them. Oddly, there's no distortion in the peripheral vision zones of the lens.
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Date: Thursday, 21 September 2006 03:54 pm (UTC)They all come together in the horizontal centre of the lens, at each side. You should notice less distortion that way if you look up or down to the side through the lens.
Though, lens tech has come a long way. I have curved-lens sunglasses, the wrap toward my temples, which have my full astigmatism/presbyobia bifocal in them. Oddly, there's no distortion in the peripheral vision zones of the lens.