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Contact Lens

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by

Shilpa Jacob

on 30 January 2014

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Transcript of Contact Lens

Contact Lenses
The Manufacturing of Contact Lenses
Soft Contact Lenses
Made out of soft, flexible plastic (thermo-set polymer hydrogels) that allows the eyes to receive oxygen while wearing contact lenses
About Contact Lenses
The History of Contact Lenses
1508:
Leonardo da Vinci designs and sketches the first ideas for contact lenses
Spin Casting
1. The liquid monomer is placed in a mold and the mold is rotated, polymerizing the monomer
Injection Molding
1. The soft contact lens material is heated to a melted state and then injected into computer-designed molds under pressure
Hard Contact Lenses
Made out of polymethyl methacrylate (PMMA)
Small, thin, curved plastic or silicone discs placed on the film of tears that cover the surface of the eye
Used to correct the eyesight for refractive errors such as
myopia
(nearsightedness),
hyperopia
(farsightedness),
presbyopia
and
astigmatism
Made according to the shape of the eye and the type of vision problem to help the eye focus light directly to the retina
1887:
German glassblower F.E. Muller produces the first glass contact lens.
1936 :
New York optometrist William Feinbloom produces the first contact lens containing both glass and plastic.
1956:
Czech chemist Otto Wichterle begins making contact lenses with a soft, water-absorbing plastic he helped create.
1979:
The first rigid gas permeable (RGP) hard contact lens is introduced.
1981:
Extended wear soft contact lenses are introduced.
1987:
Disposable soft contact lenses became available for commercial distribution
Hard Contact Lenses
Hard Contact Lenses
Leonardo Da Vinci's Sketches
Glass Contact Lenses
The Chemistry of Contacts
Uncomfortable for wearers as it blocks the air passage to the eyes
Its impermeability restricts RGP lenses from being worn for more than 8 hours at a time
Are custom made to fit the shape of the cornea
More durable and has a high modulus of elasticity than soft contact lenses
Hydrophobic qualities allows it to last many years if taken proper care
Started to make hydrogels from silicone based polymers such as polydimethylsiloxane (PDMS)
- Siloxane lenses have great permeability, comfort, wettability and biofilm resistance
Comes in almost every type of correction, in a variety of colours and in disposable varieties
Highly hydrophilic
More comfortable to wear for longer periods of time
Easily absorbs residue of substances
Soft Contact Lens
Lathe Cutting
Hard Contact Lens
1. The monomer is bulk polymerized into rods
2. The rods are cut into “buttons”, which are non-hydrated disks, and placed in the lathe
3. The lathe is directed by computer controlled precision cutting tools to cut and shape the lens
4. The lens is removed from the lathe and hydrated to soften it
Produces a high yield but moderate quality
Lens optics can be changed by altering the speed of rotation or the shape of the mold
Produces a low yield but high quality soft contact lens
2. The lenses are cooled and removed from the molds
3. The edges of the lenses are polished until smooth and hydrated in water to soften the lenses
4. The finished contact lenses undergo quality assurance testing before being sent to the user
Most commonly used for disposable contact lenses
Contact Lens Solutions
A one-step system that made it much easier for users to quickly apply and remove contacts in a safe, infection-free way
Two types of solutions: Peroxide and multipurpose solutions
Contains cleaners to break down proteins sticking to lenses or surfactants to interfere with the interactions that have no proteins
Contains conditioning or moisturizing agents
Peroxide
Uses peroxide as the disinfecting agent and involves a 3% peroxide solution and a neutralization catalyst
Kills the microbes that cling onto the lens
Not very eye friendly
Oxidizes organisms other than microbes
Multipurpose Solution
Uses a polymeric disinfection agent such as polyhexamethylene biguanide or polyquaternium
Uses polymers instead of monomers to receive effective antimicrobial activity while still being gentle to the eye
Current Research
1. A new way to distribute latanoprost, a drug commonly used to treat glaucoma without eye drops
2. Finding ways to eliminate preservatives from contact lens solutions to prevent unwanted organisms from entering the eye
3. Creating a dual-purpose conditioning agent that will keep contact lenses comfortable and repel microbes
Thank you!
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