Embed Size (px)
Citation preview
UNDERSTANDING
SHORT & LONG
CORRIDOR
PROGRESSIVE
LENSES
Technical Level 2
Jackie O’Keefe, LDO
HOACLS
2015
What Does It Mean?
Greek Origin
”Presby” = old
”opia” = eye.
Presbyopia
When? Hyperopia - late 30’s
Emmetropia - about 40
Myopia - mid-to-late 40’s.
Presbyopia
“My arms aren’t long enough!”Emerging presbyope = 0.75 to 1.00 add
Early presbyope = 1.25 to 1.75 add
Advanced presbyope = 2.00 to 2.75
Late presbyope = 3.00 and higher.
Presbyopia Lens Options
OTC Readers
SV Readers
Bifocals & Blended Bifocals
Trifocals
Occupational Lenses
Progressive Addition Lenses
PALs and Zones
Zone 1
Zone 2
Zone 3
Zone 4.
Earliest Progressives – 1
Sphere based designs from 6/200 model
(+6.00 BC/+2.00 D Add)
Excessive cylinder in progressive zone (4:1)
One lens “rotated” for left and right eye
Linear CorridorMono-Design.
Symmetric Designs
The Next Phase – 2
Sphere based designs from 6/200 model
Less cylinder (2:1 ratio) in progressive zone
One lens rotated in the mold for left & right
Linear CorridorMono-Design.
Mono/Multi Designs
Mono-Design: Same design for all add powers.
Near and intermediate widths shrink as add power increases.
Multi-Design: Design changes as add power increases.
Design becomes progressively harder.
The Next Generation – 3
Partially aspheric &/or
asymmetric designs
Much less cylinder in
progressive zone (1:1)
Each base/add designed
independently
Designed right & leftMulti-Design.
Asymmetrical Designs
Asymmetrical Designs
Short Corridor PALs?
A PAL designed specifically for small “B” dimension frames
Custom designed by optical scientists to shorten a corridor
without sacrificing optical quality
A design that adheres to quality ophthalmic criteria
considering all optical zones.
Longer Shorter
Did We Have It All?
A sufficient minimum corridor length is around 9-10 millimeters
The add must be at least 4-5mm in the vertical dimension
The 85% Factor.
What About The Corridor?
Long
Short
In-Between.
Corridor Mathematics
Minkwitz Theorem.
“The width of the progressive channel*
is proportional to its length
and is inverse (opposite) proportion to
the add power.”
*channel = corridor
Corridor Mathematics
Minkwitz Theorem.
Lower add power = wider corridor
Higher add power = narrower corridor
Corridor Mathematics
Minkwitz Theorem.
Longer channel = wider corridor
Shorter channel = narrower corridor
Fixed Corridor Mathematics
9 + 5 = 14 OC
12 + 5 = 17 OC
Fixed = Mold
NV = 100%.
Variable Corridor Mathematics
9 → 14 Lengths
OC – 5 = Corridor
Per .5 Increments
Variable = DST
NV = 100%.
The Human Factor
Previous Segmented
Wearers
OC to Seg = 5
Seg OC = 5
Total Drop = 10
The Comfort Zone
The Human FactorLarger Faces
Previous Small B
Wearers
Previous Long B
Wearers
Add Power Changes
Posture & Stature
The End-User
What Is The Task?
What Happened Next?
Duel Optics
DST.
100th Diopter In Perfection
Patient Experience
26
