ANSI Flashcards
occupation and glasses
it is important to know the patients occupation when fitting them for glasses
normal pantoscopic tilt
7 degrees
how does panto change glasses Rx
its rotated around 180 degrees
- induces minus cyl at 180
- induced plus cyl at 180
how does faceform change glasses RX
lens tilted around the 90 axis
- induces minus cyl at 90
- induces plus cyl at 90
how does panto affect the sphere component of glassed
increase the plus and the minus sphere
panto and PALs
patients who wear PALs benefit from panto because it moves the reading portion of the lens closer to the eye, which increased the reading width of the lens
how much does the OC lower when there is added panto
for every 2 degrees of panto, the OC is lowered 1mm
panto and lens distortion
will typically increase and alter the cylindrical effect
how to induce panto
adjusting the angle of the temple
retroscopoc tilt
causes the top of the lens to be close to the face
pantoscopic tilt is helpful if the optical center of the lens is too ____
high
ANSI standard for horizontal prism
2/3 amount prism
ANSI standard for vertical prism
1/3 amount of the prism
ANSI : sphere -6.50 to +6.50
+/- 0.13
ANSI: sphere >+/-6.50
+/- 2% sphere power
ANSI: cyl <2.00D
+/-0.13
ANSI: cyl 2.00-4.50D
+/- 0.15
ANSI: cyl >4.50D
4% of cyl power
ANSI: cyl axis 0.25 or less
+/-14
ANSI: cyl axis >0/25-0.50
+/-7
ANSI: cyl axis >0.50-0.75
+/-5
ANSI: cyl axis 0.75-1.50
+/-3
ANSI: cyl; axis 1.50
+/-2
how to lower the height of the bifocal segment
the glasses need to be lowered on the patients face
increase the distance between the nosepads
raise the vertical portion of the nosepads
widen the bridge of the frame
glasses falling down face
pull in temple
bend down temple tips
pull in nosepads to tighten the fit
one lens feels closer to the face than the other lens
straighten the temples
glasses touching cheeks
reduce panto
narrow bridge or nosepads to raise frame
narrow bridge or nosepads to increase vertex distance
glasses to close to face
narrow the nosepads, shrink the bridge, or decrease faceform to move lenses away from face
frames sit sit too low on the face
narrow the bridge, add nosepads, or lower vertical position of pads to move frames up on face
if the frame is too high on one side
bend temples toward the problem
if the segment is too high
increased panto decrease the vertex distance spread the nosepads move the nosepads up by adjusting the notepad arms stretch the bridge
if the segment is too low
narrow the nosepads move the nosepads down by adjusting the notepad arms increase the vertex distance reduce panto tilt shrink the bridge
abbe value and aberration
increased abbe value=decreased aberration
abbe value of diff lens materials
crown:58.9 CR-39: 58 Trivex: 44 high index: 40 polycarbonate: 30
pros of crown glass
does not scratch
cons of crown glass
heavy, shatters
pros of CR-39
light
cons of CR39
scratches easily
pros of polycarbonate
safety
cons of polycarbonate
high chomratic aberration, scratches
pros of high index
very thin and light
cons of high index
high chromatic aberrations, scratches
pros of trivex
safety, less chromatic aberration
cons of trivex
thicker than poly, more expensive
what powers need aspheric lenses
-23 and higher
+7 and higher
best frames and lenses for high myopia
- small eye and larger bridge
- round shape frame
- high index lenses
- roll and polish lens edges
- aspheric lenses
best frames and lenses for high hyperopia/aphakia
- small eye size (induced prism if too large)
- round shape frmae
- high index lenses
- cable temples
- apsheric lenses
Best frame and lens options for PALs
- adequate panto tilt
- adequate vertical depth and nasal portion
- minimal vertex distance
best frames and lenses for kids
- polycarb lenses for safety
- sturdy frame
- consider transitions
- eye protection for sports
- spring temples
- no rimless frames
safety regulations of lenses
Z87
- 5/8 inch diameter steel ball dropped from 50”
- safety glasses: the steel ball is increased to 1” diameter for testing from the same distance
- the marking for safety lenses is Z87
- RX lenses must have a minimum thickness of 3mm, except for plus lenses >3D
who should get polycarbonate lenses
all children, monocular patients, and patients using glasses for safety or sports
double D bifocal
lined bifocal at the bottom of the lens and at the top of the lens. it is an occupational lens that is most often RXed for patients who perform detailed work above their line of sight, such as electricians and auto mechanics
