RGP Design Flashcards

1
Q

Three things lens design should provide to pt:

A

comfort, vision, minimal surface changes

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2
Q

Four things to look for in evaluating lens fit [PCM] ..and L

A

position, centration, mvmt, lens-to-cornea relationship

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3
Q

Specifications of design Rx: remember your mnemonic!

A

B-CLOS-PC-BETM
-BC/CLP/LD/OZD/Scr @w/Pcr@w/CT/Blend/Edge lift/Tint/Material

OZD: 1.5 more than BC
Blend: 3.0 more than BC

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4
Q

What you’ll select FIRST, then second, third, fourth, other: zone s___, c___, l__ p__, c__ t__, o___

(see other sheet)

A

first: zone SIZE: LD, OZD, SC WIDTH/PC width
second: zone CURVATURE: BC, SCr/PCr
third: lens POWER
fourth: center THICKNESS
last: other - ET, shape, junction blend
last last: material

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5
Q
LENS DIAMETER - choose FIRST! derive others
larger cornea - \_\_\_\_ diameter
     -values for HVIDs of 10, 11, 12?
flatter cornea - \_\_\_\_ diameter
steeper cornea - \_\_\_ diameter
A

larger diameter:
HVID: 10mm - 8.8, 11mm - 9.2, 12mm - 9.6
flatter = larger LD
steeper = smaller LD

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6
Q

OZD - bright/dim light?
-usually how much smaller than LD?
-larger pupil = ____ OZD
NECO starting point?

A

dim light
~1.5mm smaller than LD
larger
7.8mm

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7
Q

SC WIDTH/PC WIDTH

  • larger LD - requires (more/less) curve widths
  • SCw usually __X larger than PCw
  • What’s the purpose of the PCw?
A

-MORE curve widths - tri or tetracurve
-SCw = 2PCw
LD = OZD + 2(SCw) + 2(PCw)
PCw - tear exchange!

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8
Q

BASE CURVE - based on what 3 things? [KTT]

A

KERATOMETRY: Kavg - 0.50 (standard LD =9.2)
-1.00 for 9.6/8.2, -1.50 for 10.0/8.6
TORICITY -more toricity requires STEEPER lens
TOPO - rare - takes ave of 4 readings, 3mm away from apex

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9
Q

T/F: alignment = on-K

-what DOES = on-K?

A

FALSE

-flat K! - “On-K” = BC equal to flat K

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10
Q

T/F: SCr and PCr are always flatter than the BC

-equation? Add or subtract addnl size?

A

TRUE - ADD! Larger number = flatter

  • SCr = BCr + 1.5mm
  • PCr = BCr + 3.0mm
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11
Q

CENTER THICKNESS:
Increased thickness: (better/worse) durability/stability, (increased/decreased) O2 transmission -comfort, (more/less) fitting problems - why?

-What about decreased thickness?

A

better stability/durability, DECREASED O2 transmission (and comfort), MORE fit problems d/t excessive weight

decreased thickness: worse durability (more fragility), increased O2/comfort, better positioning (lighter)

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12
Q

T/F: You must change the center thickness as the lens power changes in order to maintain the edge thickness

A

true. absolutely true. Gotta keep that edge the same.

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13
Q

Center thickness increases as the peripheral curves become (flatter/steeper)

  • minus carrier lenticular - (thicker/thinner) CT?
  • what should you do to CT w/ DK>40?
A

flatter
thinner (for - lenticular)
increase CT by .03-.04 to increase O2 permeability

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14
Q

EDGE thickness - ideally what range?
Powers greater than -6.00D - what lenticular?
Powers less than -2.00D - what lenticular?
ANY PLUS POWER - what lenticular?

A

.1-.12mm (happens @ -3.00D); -2–>-6D: single
plus
minus
minus

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15
Q

what’s the ideal edge shape? (t___ edge, r___ tip)

A

tapered edge, rounded tip

-apex either a) centered or b) more posterior (closer to cornea)

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16
Q

junction blend: smoothes t___ b/w zones
-how to specify:

-(increases/decreases) flare:

A

transitions
-light (visible), medium, heavy (can’t see transition zones)
DECREASES flare

17
Q

Material: name some considerations you must take when selecting

A

Dk (O2 perm - low, high, hyper +100), Wettability, durability, weight, tints/UV absorbtion

18
Q

In minus lenticular lenses, it’s ok to make AOZd = BOZd

A

FALSE. Makes JT too thin/fragile and it can easily break

19
Q

It is important to make your AOZd large enough on a plus lenticular lens to prevent ___ from occuring

A

flare (more minus your lens is, the SMALLER the AOZD will be)

20
Q

Name 5 characteristics of good GP material

A

transparent, optical quality, stable (1-2 yrs), biocompatible, wettable, durable, gas permeable, machinable/moldable, affordable

21
Q

structural component: M__ m__
oxygen component: f__, s__, (make it hydrophilic or hydrophobic?)
wettability component: M___ acid

A

methyl methacrylate, itaconate
fluorine, silicone (hydroPHOBIC)
methacrylic acid