Contact Lens Introduction Flashcards
What are the common misconceptions about contact lenses
- CL are uncomfortable
- They can be bought online so no clinical care is required
- CL are a replacement for spectacles
- CL pose no risk or significant risk to ocular health
State five optical advantages of contact lenses
- Larger FOV
- high rx can minify or magnify view but with CL there is no BVD so you get normalisation of retinal image sizes
- few aberrations /prismatic effects due to lenses moving with the eyes
- hyperopes need to converge less at near due to absence of base out prims
- certain lenses can slor progression of myopia
State cosmetic advantages of CLs
- no reflections
- doesn’t minify or magnify eyes
- doesn’t hide the eyes
- can change iris colour and size and hide unsightly eyes
State five practical advantages of CL
- condensation or fogging avoided
- good stability for certain sports and occupations
- improved BV for sport
- potential for myopia control
- potential for therapeutic uses such as glaucoma
Discuss the disadvantages of lenses
Hassle Factor Cost Optically Health Comfort
What are soft contact lenses ?
made out of soft flexible plastic
designed to cover approx 1.5-2mm over the limbus
mould to shape cornea
no of different types of wearing modalities
what are the two types of hydrogel polymer
conventional hydrogel lenses
silicone hydrogel lenses
What are the advantages of SCL
- good initial comfort
- little or no adaptation
- large optic zone = few problems with flares/halos
- not easily dislodged = good for sports like rugby
- few foreign body problem
What are the disadvantages of SCL
- conventional hydrogel - lx o2 to cornea = causes peripheral vessel growth and hypoxia
- doesn’t correct corneal irregularities
- dryness with lenses if high water content = corneal and conj desiccation
- careful with cleaning - hard to clean , solution reactions common , deposits
- complications common = allergies to deposits , infections
- easily damaged with handling
What are cosmetic soft lenses
small/regular sized
some larger and are used in films or to hide unsightly eyes
What are Rigid Gas permeable lenses
a hard rigid contact lenses made of oxygen permeable polymers
rigid = provides smooth refracting surface
covers approx. 1.5-2mm smaller than the Hz visible iris diameter
wide range of designs available /customised
large no of material options varying in permeability and wettability
state some advantages of RGP lenses
provides a smooth refracting surface
fit is easy to asses with nafl
any lens design avail and easily modified
few problems with hypoxia
contamination and solution problems are rare - few deposits /infections/replacemnt less freq
state some disadvantages of RGP lenses
discomfort initally until cornea and lid margins desensitise easily dislodged 3,9 staining corneal warpage broken and scratched flare and halo probs with large pupils
What are scleral contact lenses
large cl that rests on sclera and over cornea (24mm)
prefit lens or custom made
rage of materials = rgp/pmma
used for ocular conditions requiring support of cornea , hiding unsightly eyes , for certain occupations
fitted in HES or specialist practises
what are the types of cl appts
cl fitting
cl aftercare
cl teach
