Week 1 - History of Cls & Types of Modern Cls Flashcards
What are the 2 types of contact lens designs and the 3 subtypes of one of them?
- Corneal Contact Lenses
- Scleral Contact Lenses
* Corneo-scleral/semi-scleral lens
* Mini-scleral lens
* Full scleral lens
How did Leonardo Da Vinci experiment with the idea of contact lenses in 1508 ?
Immersing the eye in water
How did Rene Descartes experiment with the idea of contact lenses in 1636?
Glass fluid filled tube
How did Thomas Young experiment with the idea contact lenses in 1801?
Fluid filled eyecup covering the orbit using a headband.
How did Sir John Herschel experiment with the idea off contact lenses in 1845? 2 ways
-Using animal jelly in a glass capsule
-Taking a mould of the cornea
In 1888/89, Adolf Gaston Eugen Fick, Eugene Kalt and August Mueller get the credit for the invention of glass scleral lenses. T/F
True
What was the drawback of the first contact lens? General reasons
uncomfortable
What are 2 unique features of RGP’s?
-less risk using RGP’s compared to PMMA due to gas permeability
-life span is 3 years if no change to the fit
What conditions can you wear RGP’s? 2
-keratoconus
-highly astigmatic eyes
What are 2 unique features of hybrid lenses?
-a soft skirt is fused to a gas permeable lens centre
- offer the clarity of a GP lens with adaptation time close to a soft lens
What conditions can you wear Hybrid’s? 2
- irregular corneas
- highly astigmatic eyes
What are 3 unique features of soft contact lenses?
- water content unlike rigid lens material
- planned replacement/disposing to avoid corneal damage
- faster adaption compared to RGPs
What conditions can you wear soft contact lenses? 2
-best peripheral vision for highly hyperopic and aphakic pxs
-low to moderate astigmatism
Polymethyl Methacrylate (PMMA) is a rigid Non-gas permeable material and is a very uncommon material used in modern day. T/F
True
Why is PMMA a bad material?
can cause corneal exhaustion syndrome due to chronic lack
of oxygen and mechanical action of the lens
