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CL 1 > Soft toric lens design clinical perspective > Flashcards

Soft toric lens design clinical perspective Flashcards

1
Q

incidence of astig. in general pop.

A
  1. 75 = 45%
  2. 00 = 34%
  3. 50 = 20%
  4. 00 = 10%
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2
Q

spheroequivalent complacency

A

use toric when refractive cyl is 0.75 or greaater

use torics when BVA with spherical hydrogels is one or more lines less than best spec acuity

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3
Q

toric cl lens principles

A

lens conform to shape of cornea

correcting cyl provide proper in vivo meridonial powers

lens should remain in correct orientation and relocate rapidly

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4
Q

toric lens fitting criteria

A

criteria

  • full corneal centration and coverage
  • lens edge and conforms to eye shape
  • movement in primary and upward gaze, approx 0.5mm
  • keratometric mires => clear stable
  • comfort => good
  • VA => good, stable
  • rotation and stablity => stable rotation with consistent return after off axis rotation
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5
Q

spherical vs. toric proper fits

A

spherical:

  • proper movement
  • proper centration

toric:

  • proper movement
  • proper centration
  • base mark stability
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6
Q

fitting from dx lens

A
  • base mark position
  • lens comfort
  • equilibration
  • proper drift axis
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7
Q

prism base

A

prism base marks axial realignment

3 base marks, 30 degrees apart
-center is primary

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8
Q

fitting toric lens

A

select closest to pt’s rx

  • cyl within 10 deg
  • sphere within 1D

allow lens to equilibrate for 2-3 min

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9
Q

fitting procedure

A
  1. meet basic criteria?
    - good centration
    - adequate mvmt
    - corneal coverage
    - stability on eye in lateral and upgaze
    - rotational stability of base mark
  2. over-refraction
    - perform spherical over-refraction and measure VA
    - determine final lens spherical power
  3. compensate for axial realingment
    - locate toric base mark
    - estimate rotational displacement from center line
    - compensate axis of spec rx to determine correct toric soft lens axis
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10
Q

lars formula

A 
LARS
left
add
right
subtract

CW
add
CCW
sub

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11
Q

axis compensation

A

optical principle that ensures toric lens, in natural position, keeps CL toric axis aligned with patient’s spec axis

cyl axis only correct if lens continue to orieent at position compensated for

do not expect compensated toric lens will have base mark appear at 6 oclock = NOT COMPENSATION

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12
Q

use clockwork

A

each hour = 30 degrees

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13
Q

refractive considerations

A

spherical overrefraction

spherocylindrical overrefraction

dec. cyl to dec. variable vision

importance of refractive components:

  • axis
  • cyl power
  • sphere power

vertex must be calculated for each power meridian

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14
Q

undercorrect cyl power why?

A

undercorrecting cyl is often needed simply due to vertex consideration

vertex applies to RX > 4D

additional slight undercorrection in cyl also beneficial => less distortion if lens rotate away

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15
Q

toric lens observation

A

full corneal coverage, with 0.25 - 0.5 mm movement

  • good fit: quick return to axis
  • tight fit: slow return to axis

loose fit: lens orientation unstable and inconsistent

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16
Q

tight fit toric

A

show large degrees of angular mislocation > 20 degrees

little to no movement with blink

dont bother compensating for rotation if drift angles large

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17
Q

diagnostic lens method toric fitting

A

advantages:
immediately observe lens behavior
-result in BVA in difficult-to-fit pt

18
Q

problem solving toric lens

A

fitting consideration

refractive considerations

19
Q

when lens moved out of position, does it return to original position?

A

1) check base mark position

2) if not where anticipated => rotate to proper position

20
Q

refractive considerations (SCO) spherocylindrical overrefraction

A

reduced VA response

accurate SCO improve VA means CL power is off, spec rx is off, lens rotate

SCO does not improve VA means fit of lens is poor, quality of lens is poor, must rule out pathology

overrefraction results

OR axis = refraction axis -> inc. lens cyl power

OR axis = 90 deg away -> dec. lens cyl power

OR sph/cyl at oblique -> adjust axis

OR cyl = lens cyl power -> lens 30 deg off

OR cyl = 1/3 lens cyl power -> lens is 10 deg off

21
Q

checking lens optics

A

if reflex bad:
optics bad, defective lens -> reorder

if reflex good:
blur cause unknown -> check refraction, tear quality, new lens

22
Q

why do toric hydrogels mislocate

A

natural vector forces of the lids

lens fit too tightly or too loosely

effects of nonuniform meridonal edge thickness

excessive inferior edge thickness

effects of tight lids/narrow palpebral apertures

23
Q

prism ballast

A

increases likelyhood of rotation
-balanced by bottom weighting

-blink stabilized design: balanced with four zones of stability

24
Q

rotation dependent

A

on differences in meridional edge thickness -> rotats to thicker meridian

25
Q

stabilization methods and design

A

prism ballast

truncation with prism ballast

thin zone slab-off

periballast and eccentric lenticulation

combination

26
Q

prism ballast

A

method of stabilixation
-addition of 0.75 - 2.0 D base down prism reducing rotation

-require inferior chamfering or slab-off for good comfort

27
Q

chamfer or lenticulation

A

provides nearly equal thicness around lens periphery - reduces torsional effects from differntial lens thickness

provides better comfort

minimizes lens compression at periphery

28
Q

disadvantages of prism-ballas

A

thickness variation

lens mass

localized pressure on cornea @prism base

resulting: inc. centra, temporal, and inferior corneal thickness

29
Q

eccentric lenticulation

A

material removed from anterior lenticular surface

upper and lower thin zones equal thickness

edge thickness uniform thorughout lens circumference

high cyl and oblique axes

30
Q

combination stabilization

A

incorporates eccentric lenticulation, thin zones, and back surface toricity

edge thicness uniform throughout lens circumference

no prism in optic zone

minimal rotation allows empirical fitting

31
Q

modern stabilization method

A

blink stabilized

  • balanced with four zone of stability
  • more gaze independence
  • accelerated slopes: more lid power
  • symmetrical weighting : limit gravity
  • thin lens
32
Q

toric brands

A

cooper: biofinity toric, avaira toric, and proclear toric

J&J: acuvue oasys for astig

B+L: purevision toric

alcon: air optix for astigmatism

33
Q

acuvue oasys for astig

A

silicone hydrogel

2 week replaceent

scribe marks vertical

comes in 0.75, 1.25, 1.75, 2.25, 2,75 cyl powers

34
Q

pure vision toric

A

anterior aspheric optics to reduce inherent and induced spherical aberration

prism ballasting geometry with 360 comfort chamfer for enhanced rotational stability across all powers

balanced vertical thickness profile for excellent axis stabilization and exceptional vision

35
Q

air optix for astig

A

powers: +6 to -6 in 0.25 step
- 6.50 to -10 in 0.5 steps
cyl: 0.75,1.25,1.75,2.25
axe: 10 deg steps

material lotrafilcon B

bc 87
dia: 14.5

water content 33%
DK, Dk/t: 110, 108 @ -3.00

surface: permanet plasma treatment
back surface: toric

36
Q

proclear XR

preference XR

A

extended range torics offered by cooper vision

cost higher
4 pack options

37
Q

improvement in hypoxia related signs of corneal health

A

silicone hydrogel toric lens offer high oxygen transmissibility to help protect patients from signs and symptoms of corneal oxygen deficiency for whiter healthy-looking eyes

38
Q

customized lens

A

specialeyes corp will make custom spherical or custom toric

great for oblique axes or high powers not avaialble

39
Q

daily disposable torics

A

clearsight 1day

aqua comfort plus toric dailies

1 day acuvue moist for astigmatism

B+L purevision daily disposable for astigmatism

40
Q

proclear multifocal toric

A

bc 8.3 to 8.0
spher pwoer -20 to +20
cyl -0.75 to -2.75
add powrs: +1.00 to +3.5

41
Q

custoom toric multifocals

A

intelliwave multifocal and multifocal toric

  • supply keratometr readings
  • spec refraction including spher, cyl, axis and add

HVID

dominant eye; pupil diameter in normal light

Sihy-any rx

CL 1 (5 decks)

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