Therapeutic and cosmetic contact lenses Flashcards
list 8 indications for using therapeutic CLs
- 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
why is CLs indicated for apposition of wound edges
if a wound has been broken down.
to avoid resuturing or doing more surgery, use CLs instead to resolve it
how is CLs indicated for the maintenance of fornices
it is incorporated in scleral CLs
name a condition where you will need to use CLs as ptosis props
steven johnson syndrom
a condition where you get some blepharon and adhesions of the conjunctiva fornices
list the 4 advantages to a therapeutic lens mechanism
- Protection from shearing force of eyelid
- Retention of tears
- Reduction in neutrophil infiltrate (from tears)
- Retention of fibrin matrix on surface of injured cornea
list 5 disadvantages to a therapeutic lens mechanism
- Mechanical - CL rigidity and poor CL fit
- Corneal desiccation
- Toxicity, inflammatory
- Corneal hypoxia
- Complications – high risk for ocular infection in this ‘group’
list 8 properties an ideal therapeutic lens should have
- 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…
why would you want minimal movement in a ideal therapeutic CL
if the ocular surface is fragile, to dont want a lens that moves excessively
what is contradicting about a therapeutic lens being able to reduce the risk of ocular infection
a CL can increase the likelihood of that anyways, so must be mindful of that
which 3 materials of therapeutic CLs are used
- Hydrogel (soft):
silicone hydrogel - Rigid:
scleral (haptic) PMMA and RGP
corneal PMMA and RGP - Collagen shield
what are the 6 advantages of using hydrogel lenses for therapeutic use
- Comfort (low modulus and wraps around cornea well)
- Easy fit
- Readily available
- Large range of parameters and materials (also custom made)
- Cost
- Tint possible
what are the 6 disadvantages of using hydrogel lenses for therapeutic use
- 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
why are hydrogel and Sihydrogel lenses used as bandage CLs
- 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
list 4 examples of hydrogel therapeutic CLs
- proclear: drapes well
- bespoke lens
- Igel select
Both drape well, large range of TD and BOZR - Acuvue: Ionic
list 7 advantages to the silicone hydrogel lens: purevision night and day for therapeutic use
- 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
list 5 disadvantages to the silicone hydrogel lens: purevision night and day for therapeutic use
- 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
what implications does reduced tear exchange of the silicone hydrogel lens: purevision night and day for therapeutic use have
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
other than purevision night and day, name another silicone hydrogel lens that is good to use for therapeutic reasons and why
- acuvue oasys
- has low modulus/is flexible
- comfortable
- high Dk/t = 147
list 5 painful conditions that TCLs are used for
- bullous keratopathy
- band keratopathy
- filamentary keratitis
- thygeson’s disease
- superior limbic keratitis
what happens in bullous keratopathy and how does TCLs help with this
- 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
what happens in band keratopathy
an accumulation of calcium sub-epithelially
what are the symptoms and signs in superior limbic keratitis
- a localised inflammatory condition = very painful
- mauve injection at superior limbus, extended onto the bulbar conjunctiva
name some conditions where TCLs are required for promotion of epithelial healing
explain how this is treated
- 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
list 3 conditions where a TCL will be used for apposition of wound edges
why are TCLs used for this purpose
- 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
why is a TCL used for mechanical protection
- used in a short term
- to allow resolution of a corneal incident
how is a TCL used for maintenance of corneal hydration
used with ocular lubricants
what is dellen and what role does a TCL have
- 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
list 5 types of rigid lenses used for therapeutic use and the sizes they come as
- 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
give 4 reasons why scleral and corneal RGP lenses are used as TCLs
- Restricted fornices
- Simpler to fit
- Concurrent topical medication
- High Dk/t ~ 80-100
what are the 4 indications for using a limbal diameter RGP and a TCL and examples of conditions for each
- 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
how does a limbal diameter RGP TCL provide maintenance of epithelial hydration and name a condition for which this will be useful
- 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
what occurs in steven johnson syndrome whereby a limbal diameter RGP TCL is required to provide maintenance of epithelial hydration
it causes chronic drying of the eye and a poor tear film = tend to get a vascularised cornea and irregularities to the lid
how does a limbal diameter RGP TCL provide mechanical protection of the ocular surface better than a hydrogel TCL
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
how does a limbal diameter RGP TCL provide pain relief and to which lenses does it provide it better than
- in the presence of severe dry eye
- more effective than a hydrogel or Sihydrogel
list 4 advantages of scleral and mini scleral TCLs
- No corneal contact
- Ocular surface protection
- No tears required
- Stability: ocular anatomy, CL BVP
which 2 materials can a scleral and mini scleral TCL be made out of and which one is less commonly use and why
- PMMA
- Gas permeable
- both a impression or pre formed
PMMA rarely used because of hypoxic promoting properties
list 4 disadvantages of scleral and mini scleral TCLs
- Tear exchange, can take long time beneath big lens
- Oxygen permeability, can control when selecting lens material
- Conjuctival irritation
- Complex fitting and manufacture
what are the 6 indications for using scleral TCLs
- 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
how is a scleral ring used with a scleral TCL for maintenance of fornices
- 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
how is exposure due to lid scarring after irradiation treated with extended wear scleral TCLs
- due to incomplete lid closure
- scleral TCL will avoid dehydration of the epithelium particularly at night
list the 5 stages of ocular cosmesis treatments from oldest to most recent
- Corneal tattooing
- Scleral shells
- Rigid prosthetic lenses - 11.50 to 3.00mm TD
- Soft prosthetic lenses
- Soft stabilised lenses
what 3 disadvantages does corneal tattooing have
what is a better alternative
- Pigment migrates laterally (so doesn’t last)
- Can irritate ocular surface
- Persistent epithelial defect
- CL gives better lasting effect
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
- 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
what are the properties of a rigid CL for cosmetic use
- 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
which type of CCL will you use for a: 26yo soldier Aphakic Irreg astigmatism Partial aniridia Poor cosmesis Diag VA 6/5
and why
- 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
what 6 varieties does a soft CCL come as
- Black pupil
- Translucent tint +/- black pupil
- “Opaque back”
- Hand painted +/- bp, +/- opaque
- Dot matrix printed lenses
- Iris print +/- black back, OP/CP
