Transcript Distortion in Progressive Addition Lenses & Directionalization

Progressive Addition
Lenses: Distortion &
Directionalization
Spectacle Correction of
Presbyopia
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Bifocals
Trifocals
Progressive Addition Lenses (PALs)
(http://www.penrithspectacles.com.)
(http://vectors.usc.edu)
(http://www.eyeglasslensdirect.com)
Progressive Addition Lenses
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Spectacle correction of choice for Presbyopes:
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Bifocal or PALs?
 PALs were preferred by 92 percent of the participants.
(Boroyan, 1995)
 Other studies provide similarly high preference scores.
(Hitzeman, 1985) (Borish, 1983)
PAL designs continue to improve…
Progressive Addition Lenses
Despite high preference scores, some report
adaptation problems (10-15%)
(Pope, 2000; Cho, 1991; Gresset 1991)
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Possible Causes
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Frequent head movements
Higher order aberrations
Excessive unwanted astigmatism
Distortion
Distortion
What is Distortion?
As it applies to optics, distortion is the result of
changes in magnification in a lens system-causing objects to appear different in size and
orientation.
PAL Design Overview
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Eliminating the multifocal segment line
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Achieve:
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blending between the surfaces
steepening in the inferior portion of the lens
Add:
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obliquely oriented cylinder
(Meister, 2008)
PAL Design Overview
Distortion applies to progressive
addition spectacle lenses
•Increasing amounts of obliquely oriented
cylindrical power creates changes in spectacle
magnification; these changes in magnification
cause straight edges to appear tilted or curved
(non-uniform).
(Meister, 2008)
Previous Studies
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Effect of visual distortion on postural balance in a full
immersion stereoscopic environment.
(Faubert, 2004)
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Background:
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The effect of refractive blur on postural stability.
(Anand, 2002)
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Simple visual defocus = increase postural instability (other senses
disrupted)
Previous Studies
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Procedure:
 8x8x8’ CAVE immersion virtual environment
 Stimuli = sinewaves moving in a checkerboard pattern (varying
amplitude and viewing distance)
 Non-linear visual distortions (similar ro PALs)
Previous Studies
Previous Studies
Previous Studies
Previous Studies
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Effect of visual distortion on postural balance in a full
immersion stereoscopic environment
(Faubert, 2004)
 Conclusions:
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When viewing at a distance, postural instability is less affected
by non-linear, progressive-like distortions.
When viewing at near, progressive-like distortions create
significant posture instability.
Lateral movement shows the most postural instability as a
function of wave amplitude
Progressive Addition Lens
Research
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Touch-screen test:
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Using pointing response as a metric for
measuring distortion
w/ miracletouch
(http://pmxaudio.com)
Touch-screen Test
Touch-screen Test
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Pilot Data:
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High ametropes adapt very well to the peripheral
aberrations in their spectacles (ex. -10.00 D
myope)
Touch-screen Test
1) No correction
2) Plano +2.00 D
add progressives
(PAL trial set)
Touch-screen Test
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Hypothesis:
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We expect increased pointing error with non-linear
distortion
Progressive Addition Lens
Research
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Other interests/potential projects:
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Measurements of surface optics for current designs (Using
Rotlex Class Plus Lens Analyzer)
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Individualized vs. Traditional Progressives