Ophthalmic Optics lab
pg 1
Frames
Frame Pieces
Front
Eyewire
Eyewire groove
Bridge
Endpiece
Shield
Hinge
Temple
Frame Types
Plastic
Metal
Combination
Rimless / 3-Piece
Semi-Rimless, Nylon Suspension
Half-Eyes
Temple Types
Skull
Riding Bow
Comfort Cable
Library
Bridge Types
Saddle
Keyhole
Adjustable Pads
Formfit
Adjustable pads American – twisted horizontal loop
European – single vertical loop
Plastic Frames
Cellulose acetate (zyl)
Optyl
must use heat
Polyamide
must use minimal heat (brand: SPX)
Nylon
Carbon
Metal
Nickel, Monel Alloys
Titanium
Memory Metal (Flexon, etc)
Stainless Steel
Lensometry
Come down from plus (for minus cyl)
Sphere lines (skinny) focus at more plus power than cyl lines (thick)
Add power is only time temples are towards you
Prism
P = hF ex: .5 cm x 2.00 D = 1pd
difference b/w sph and cyl lines is cyl power
Frame PD = A + DBL
Inset = (Frame PD – Pt PD)/2
blank size = A + 2*inset (if no prism)
OC – Optical Center – point on lens with no prism – not centered on pupils if prism
PRP – Prism Reference Point – point on lens with amount of prism prescribed
always at pupils, point pt looks through, separated by PD – if no prism, same as OC
Level PRP – bottom of lens to PRP
Lensometry – Multifocals
Intermediate = written as % of near add
PALs – tradeoff – gradual change in center means poor optics on edges, especially cyl
PAL markings
◦
+
•
○
◦
distance power
+ fitting, pupil center
◦ permanent marking # is add (17 = +1.75), image is mfg
• prism, PRP – if no prism, OC
PALs are easiest glasses to measure prism;
○ add
… just measure at prism dot
Ophthalmic Optics lab
pg 2
Lens Design
Add
glass – higher index – fused (no bump)
plastic – thickness – one-piece (sticks out)
PAL – curvature
Base Curve – curve on front surface (distance part if multifocal)
Lens Blanks
semi-finished
uncut
surfacing – grind RX
edging – cut to fit frame
put add on front
grind cyl on back
+ 4.00 D lens from +8.00 D BC
0.00 D lens from +6.00 D BC
– 4.00 D lens from +4.00 D BC
thick – hockey puck – same thickness across entire lens
thin – only needs to be edged – thinner in center if originally thick
Base Curve – warpage, one-piece add power, slab-off prism (if aniso) (bump up = BU, dip down = BD)
Tints
index
1.50
1.53
1.59
1.523
1.80
plastic
glass
glass
dyed
through-and-through
coated
material
CR-39
Trivex (PPG)
polycarbonate
crown glass
flint glass
impact resistance
agency
FDA
OSHA
OSHA
polariscope
bull’s eye effect
colored reflection from interference (magnesium fluoride)
high index = thinner, but more color aberrations (worse off-axis optics)
impact resistant
impact resistant
has lead in glass, for x-ray protection; so thick, can’t be made impact resistant
drop-ball test
must keep records for 3 years
type of lens
dress
basic impact
high impact
test
5/8” steel ball from 50”
1” steel ball from 50”
1/4” steel ball at 150 ft/sec
untempered
glass – chem
glass – heat
plastic
no pattern (all dark)
no pattern (all dark)
cross with ring around
V shapes at edges
min thickness
N/A
3.0 mm
2.0 mm
label
N/A
mfg
mfg +
standard
ANSI Z80.1
ANSI Z87.1
ANSI Z87.1
[pattern = stress]
very even stress
polycarb = lots of stress
Lensometry – Prism
only measure at an angle (horiz & vert without zeroing other) on PALs because measure at dot
Vert
1. center lens with stronger power in vertical meridian
2. slide to other lens
3. measure prism where horiz prism = 0
if x090, use sph
(+3 DS = +3@90)
if x180, add sph + cyl (+3-2x180 = +1@90)
if b/w, approx (+1@45, +3@135 = +2@90)
Horiz
1. measure PD
2. dot
3. measure prism where vert prism = 0 (center to remove vert prism)
4. same on other eye
auxillary prism used if large amounts of prism, aphakic lenses (deflect target out of field of view)
Ophthalmic Optics lab
pg 3
Approximate Lens Power
Lens Clock
Front
Back
+
–
Front
should be sph
can have cyl (measure max and min)
+
Back
Total
–4.75 (@110)
+9.00
+9.00
+
thicker at
center
edge
+4.25 (@110)
– 6.75 (@20)
Hand Neutralization (shaking) – at arm’s length
1. twist – cyl
2. move back and forth over line
a. against
+
b. with i. inverted
+
ii. erect, minified –
+ lens
– lens
=
low power
high power
any power
obj appears
inverted & clear or blurry
erect & minified
=
+2.25 (@20)
=
+4.25–2.00x110
+ high power
1. arm’s length: with, inverted, clear
2. closer: blurry
3. closer: against motion
person wearing
eyes big
edge of head behind glasses pushed in
Multifocals
Trifocals = 7/25 = vertical height of intermediate / width (at widest of entire add)
trifocal types: double exec, double D, double round, quadrifocal
D / Flat Top
Round
22
22 #1
25
25
28 #1
28
35 #2 (wide FOV: drafter)
45
positioning
Executive
N/A
Market: ½ D28, ½ PAL
seg inset = (dist PD – near PD) / 2 = (dist PRP – seg OC) / 2
need 3 measurements:
type
bifocal
trifocal
PAL
Blended Bif
22
25
28
seg height reference
lower lid margin
lower pupil margin
pupil center
1. dist PD
2. near PD
3. seg height
PAL:
1. split PD (frame center to fitting cross)
2. seg height (fitting height)
already wearing bif/tri = same relative height as hold seg
… depends on frame size (have pt put on old glasses & measure)
verify near PD on exec = no edge = hand neutralization = point where distant line is continuous
exec trifocal
double exec trifocal
stair step
bump
7 mm middle segment
14 mm
Ophthalmic Optics lab
pg 4
Etc
Bevels 1. standard / V
2. hide-a-bevel
roll = edge chopped off to reduce thickness
3. rimless
polish = remove whitish roughened appearance, but reflections
4. rolled, polished, rolled & polished
poly is always polished
5. nylon suspension grooved
6. safety / pin
outer edges chopped off; prevents chipping
ARC – either glass or plastic, usually front and back (reflectance at each surface reduced from 4% to 0.5%)
Interference  colored reflection
transmittance increased from 92% to 99%
SRC – at least front, often both surfaces – hard to tell if lens has
ARC – outside
SRC – middle
lens – inside
tints
#1
#2
#3
#4
transmittance
85%
50%
20-30%
10-15%
cosmetic
too light outside, too light inside
most sunglasses
sunglasses: gray, brown, green (most to least common)
cosmetic: pink, gray, brown
UV – absorb radiation below 400nm (cataracts)
CR-39 must be dyed, other plastics have build in, not on glass
lenses have slight yellow tint
must use for aphakes
photochromatic lenses
1. glass
2. plastic
transmittance:
Photogrey Extra (Corning)
Photobrown Extra
Photosun II
Transitions
Sunsensors (Corning)
LifeRX (Vision-Ease)
Instashades (Sig Arm)
light
87
86
41
dark
22
24
12
new lenses appear greenish
need break-in period
do not need break-in period
wears out after time
~8% lighter after 1.5 yrs
not as dark when hot
High-power lenses
minus
very flat BC for better off-axis optical quality
carrier = outside
1. minus lenticular
edges removed (grind & polish)
ugly
bowl = inside
2. myodisk
(plano concave) flat front
ugly
3. mythinned
(blended minus lenticular)
less ugly; lighter circle from front
4. biconcave
plus (aphakes) aspheric front surface b/c always have poor off-axis optics with spherical BC
1. aspheric lenticular
egg
ugly
2. full-field aspheric
no carrier
less ugly