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Contact lenses year 3 > Therapeutic and cosmetic contact lenses > Flashcards

Therapeutic and cosmetic contact lenses Flashcards

1
Q

list 8 indications for using therapeutic CLs

A
  • Pain relief
  • Promotion of healing
  • Mechanical protection of ocular surface
  • Maintenance of ocular surface hydration
  • Apposition of wound edges
  • Maintenance of fornices
  • Ptosis prop
  • Drug delivery
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2
Q

why is CLs indicated for apposition of wound edges

A

if a wound has been broken down.

to avoid resuturing or doing more surgery, use CLs instead to resolve it

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3
Q

how is CLs indicated for the maintenance of fornices

A

it is incorporated in scleral CLs

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4
Q

name a condition where you will need to use CLs as ptosis props

A

steven johnson syndrom

a condition where you get some blepharon and adhesions of the conjunctiva fornices

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5
Q

list the 4 advantages to a therapeutic lens mechanism

A
  • Protection from shearing force of eyelid
  • Retention of tears
  • Reduction in neutrophil infiltrate (from tears)
  • Retention of fibrin matrix on surface of injured cornea
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6
Q

list 5 disadvantages to a therapeutic lens mechanism

A
  • Mechanical - CL rigidity and poor CL fit
  • Corneal desiccation
  • Toxicity, inflammatory
  • Corneal hypoxia
  • Complications – high risk for ocular infection in this ‘group’
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7
Q

list 8 properties an ideal therapeutic lens should have

A
  • Minimal movement
  • Low modulus of elasticity
  • High wettability/ “lubricity”
  • High oxygen transmission (Dk/t)
  • Facilitates wound healing
  • Retain tears - minimise corneal desiccation
  • Biocompatible material
  • Reduce the risk of ocular infection…
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8
Q

why would you want minimal movement in a ideal therapeutic CL

A

if the ocular surface is fragile, to dont want a lens that moves excessively

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9
Q

what is contradicting about a therapeutic lens being able to reduce the risk of ocular infection

A

a CL can increase the likelihood of that anyways, so must be mindful of that

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10
Q

which 3 materials of therapeutic CLs are used

A
  • Hydrogel (soft):
    silicone hydrogel
  • Rigid:
    scleral (haptic) PMMA and RGP
    corneal PMMA and RGP
  • Collagen shield
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11
Q

what are the 6 advantages of using hydrogel lenses for therapeutic use

A
  • Comfort (low modulus and wraps around cornea well)
  • Easy fit
  • Readily available
  • Large range of parameters and materials (also custom made)
  • Cost
  • Tint possible
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12
Q

what are the 6 disadvantages of using hydrogel lenses for therapeutic use

A
  • Oxygen transmission (Dk/t) not as good
  • Dry eyes - as increases tear evaporation, so will make worse
  • Rapid spoilage - as attracts deposits
  • Require frequent replacement
  • VA not improved - as will mould itself to regular topography
  • Not licensed for 24hr therapeutic use - so EW use will be off label
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13
Q

why are hydrogel and Sihydrogel lenses used as bandage CLs

A
  • Corneal coverage, centration and stability
  • Corneal coverage: diameter
  • Fornices: diameter
  • Corneal shape: thickness, radius, diameter
  • Irregular thin lens (drapes)
  • Dry eye/ exposure: thickness, water content, bound H2O, non-ionic
  • Corneal perforation
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14
Q

list 4 examples of hydrogel therapeutic CLs

A
  • proclear: drapes well
  • bespoke lens
  • Igel select
    Both drape well, large range of TD and BOZR
  • Acuvue: Ionic
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15
Q

list 7 advantages to the silicone hydrogel lens: purevision night and day for therapeutic use

A 
- Comfort
High Dk/t = 110 & 170
ct = 0.09mm
- Easy to fit
- Readily available
- Cost
- Low water content (good for dry eye px as does not depend on tears of px)
- Dry eyes
- Licensed use
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16
Q

list 5 disadvantages to the silicone hydrogel lens: purevision night and day for therapeutic use

A
  • Limited BOZR and TD
  • Poor flexure (c.f. hydrogel modulus)
  • Reduced tear exchange
  • Increased mucous deposits
  • Papillary conjunctivitis from still material
    2nd and 3rd generation lenses
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17
Q

what implications does reduced tear exchange of the silicone hydrogel lens: purevision night and day for therapeutic use have

A

reduced tear exchange beneath the lens, is important to eradicate waste metabolites especially CO2 building up beneath the lens = not good for the corneal epithelium

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18
Q

other than purevision night and day, name another silicone hydrogel lens that is good to use for therapeutic reasons and why

A
  • acuvue oasys
  • has low modulus/is flexible
  • comfortable
  • high Dk/t = 147
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19
Q

list 5 painful conditions that TCLs are used for

A
  • bullous keratopathy
  • band keratopathy
  • filamentary keratitis
  • thygeson’s disease
  • superior limbic keratitis
20
Q

what happens in bullous keratopathy and how does TCLs help with this

A
  • the cornea is compensating and has chronic, high level of oedema which can get very painful
  • this causes the formation of bully on the epithelium and when they burst, you can get exposure of the nerve endings = acutely painful condition
  • TCL is protecting the surface alleviates but does not eliminate a lot of the associated pain
  • also protecting the surface tends to prevent the bully from forming in the first place
21
Q

what happens in band keratopathy

A

an accumulation of calcium sub-epithelially

22
Q

what are the symptoms and signs in superior limbic keratitis

A
  • a localised inflammatory condition = very painful

- mauve injection at superior limbus, extended onto the bulbar conjunctiva

23
Q

name some conditions where TCLs are required for promotion of epithelial healing
explain how this is treated

A
  • recurrent erosions
  • persistent epithelial defects
  • first tend to use gels and ointments to help
  • but if that doesnt work then use TCLs to protect the epithelium whilst it forms a better attachment to the basement membrane and prevent the recurrence of the erosion
  • for persistent epithelial defects which are indulgent i.e. dont want to heal - protecting the area with a TCL will help
  • when corneal epithelium is absent = high risk of infection, so need some protection of the ocular surface
24
Q

list 3 conditions where a TCL will be used for apposition of wound edges
why are TCLs used for this purpose

A
  • corneal perforation
  • post corneal suture removal
  • corneal graft
  • a lot of perforations are glad rather than stitched nowadays and the TCL is applied on top
  • lose of broken sutures can be shielded with a TCL or also when theres a breakdown of the graft junction
25
Q

why is a TCL used for mechanical protection

A
  • used in a short term

- to allow resolution of a corneal incident

26
Q

how is a TCL used for maintenance of corneal hydration

A

used with ocular lubricants

27
Q

what is dellen and what role does a TCL have

A
  • marked stromal thinning from a corneal graft
  • is at risk of perforation if not treated
  • Hydrogen TCL promotes wetting over that area which will improve and heal
28
Q

list 5 types of rigid lenses used for therapeutic use and the sizes they come as

A 
- corneal:
up to 11.50
- scleral:
20mm or larger 
- limbal:
11.50 to 13.00 
- semi limbal:
12.00 to 15.00mm 
S LIM (J Allen) and
So Clear (No7) 
- mini scleral:
15.00 to 20.00mm
29
Q

give 4 reasons why scleral and corneal RGP lenses are used as TCLs

A
  • Restricted fornices
  • Simpler to fit
  • Concurrent topical medication
  • High Dk/t ~ 80-100
30
Q

what are the 4 indications for using a limbal diameter RGP and a TCL and examples of conditions for each

A
  • Maintenance of epithelial hydration:
    severe dry eye, exposure, neurotrophic k.
  • Mechanical protection of ocular surface:
    eye lashes, keratin, exposure.
  • Promotion of epithelial healing:
    persistent epithelial defect (PED)
  • Pain relief:
    In the presence of a severe dry eye
31
Q

how does a limbal diameter RGP TCL provide maintenance of epithelial hydration and name a condition for which this will be useful

A
  • it provides the cornea with a tear reservoir
  • as with a large lens you are capturing a large volume of tears beneath the lens
  • so rate of tear turnover is slow compared to a small diameter RGP of ~9.50mm
  • useful for steven johnson syndrome or sjogrens syndrome
32
Q

what occurs in steven johnson syndrome whereby a limbal diameter RGP TCL is required to provide maintenance of epithelial hydration

A

it causes chronic drying of the eye and a poor tear film = tend to get a vascularised cornea and irregularities to the lid

33
Q

how does a limbal diameter RGP TCL provide mechanical protection of the ocular surface better than a hydrogel TCL

A

the rigid lens can protect the cornea more effectively

e.g. with a hydrogel lens and interned lashes, the lens can crumple up, but not with rigid lenses

34
Q

how does a limbal diameter RGP TCL provide pain relief and to which lenses does it provide it better than

A
  • in the presence of severe dry eye

- more effective than a hydrogel or Sihydrogel

35
Q

list 4 advantages of scleral and mini scleral TCLs

A
  • No corneal contact
  • Ocular surface protection
  • No tears required
  • Stability: ocular anatomy, CL BVP
36
Q

which 2 materials can a scleral and mini scleral TCL be made out of and which one is less commonly use and why

A
  • PMMA
  • Gas permeable
  • both a impression or pre formed

PMMA rarely used because of hypoxic promoting properties

37
Q

list 4 disadvantages of scleral and mini scleral TCLs

A
  • Tear exchange, can take long time beneath big lens
  • Oxygen permeability, can control when selecting lens material
  • Conjuctival irritation
  • Complex fitting and manufacture
38
Q

what are the 6 indications for using scleral TCLs

A
  • Maintenance of epithelial hydration:
    severe dry eye, exposure, neurotrophic k.
  • Mechanical protection of ocular surface:
    eye lashes, keratin, exposure.
  • Maintenance of fornices:
    scleral ring
  • Ptosis prop
  • Promotion of epithelial healing
  • Pain relief
39
Q

how is a scleral ring used with a scleral TCL for maintenance of fornices

A
  • for people who have had reconstructive surgery
  • do to prevent any adhesion between the palpebral conjunctiva and bulbar conjunctiva
  • the lens is clear in the centre
  • an aperture of 12-15mm is completely open
  • the purpose of the ring is to prevent any adhesions between the conjunctiva and the fornices
40
Q

how is exposure due to lid scarring after irradiation treated with extended wear scleral TCLs

A
  • due to incomplete lid closure

- scleral TCL will avoid dehydration of the epithelium particularly at night

41
Q

list the 5 stages of ocular cosmesis treatments from oldest to most recent

A
  • Corneal tattooing
  • Scleral shells
  • Rigid prosthetic lenses - 11.50 to 3.00mm TD
  • Soft prosthetic lenses
  • Soft stabilised lenses
42
Q

what 3 disadvantages does corneal tattooing have

what is a better alternative

A
  • Pigment migrates laterally (so doesn’t last)
  • Can irritate ocular surface
  • Persistent epithelial defect
  • CL gives better lasting effect
43
Q

how is a scleral shell CCL made
what varieties is it available in
what is the wearing requirement
what maintenance does it require and why

A
  • Acrylic hand painted

varieties:
- Sclera + iris
- Sclera or iris only - for those with huge naevus etc
- Variable thickness
- Offset iris - for disguising squint
should only address the area that is affected

wearing requirement:
- Nightly removal as are PMMA and other similar material so o2 performance is low

maintenance:
- Re-polish if not will get GPC

44
Q

what are the properties of a rigid CL for cosmetic use

A
  • Maximise visual acuity, irreg astigmatism (in addition to cosmesis)
  • Usually limbal diameter 11.50-12.50mm
  • RGP translucent tint
  • PMMA laminar construction
  • Permanent colour
  • Limited wearing time with PMMA
  • Aphakic eyes more tolerant to hypoxia - as has aqueous current in AC, so helps to alleviate hypoxic changes
45
Q 
which type of CCL will you use for a:
26yo soldier
Aphakic
Irreg astigmatism
Partial aniridia
Poor cosmesis
Diag VA 6/5

and why

A
  • rigid CL
  • it will maximise his visual potential and improve his cosmesis and reduce the amount of light that is going into his eye
  • as long as you can get a good match of his iris hue, the small details does not matter
46
Q

what 6 varieties does a soft CCL come as

A
  • Black pupil
  • Translucent tint +/- black pupil
  • “Opaque back”
  • Hand painted +/- bp, +/- opaque
  • Dot matrix printed lenses
  • Iris print +/- black back, OP/CP

Contact lenses year 3 (15 decks)

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