Unit 1 Flashcards
beggining Leonardo DaVinci
-Described a method of directly altering corneal power
–By immersing the eyeball in a bowl of water
◦ Controversial topic
beggining Rene Descartes
◦ Fluid filled tube on the eye
◦ While impractical, the principle of directly neutralizing corneal power is consistent with the principles underlying modern contact lens design
* Contact lens name origin
◦ In “contact” with the eye
beginning Thomas Young
◦ Constructed a “fluid-filled eyecup”
◦ Similar system to that used by Descartes
◦ He did not intend the device to be used for correction of refractive errors
1800- * Sir John Herschel
◦ Proposed ‘taking a mould of the cornea and impressing it on some transparent medium’
1800- * F.A. Muller
◦ Manufacturers of prosthetic eyes
◦ Described the fitting of a partially transparent shell of thin clear blown glass to a patient
1800- * Eugene Kalt (French ophthalmologist)
Fit thin glass shells for keratoconus patients and obtained significant improvement in vision
1800- * August Muller
Credit for fitting the first powered contact lens
◦ Described the correction of his own high myopia with a contact lens
-Lens was made by optical engineer, Karl Otto Himmler
-First manufacturer of optically ground contact lenses
early 1900- * Carl Zeiss Company
Applied for a patent proposing the manufacture of contact lenses from ‘cellon, celluloid, or similar organic substance…’
◦ First to cut lenses from moulds
◦ Diagnostic lenses (trial lens set)
early 1900- * Joseph Dallos
◦ Refined fitting and moulding techniques
◦ Went on to develop techniques for taking impressions of the human eye
1930- * PMMA (polymethyl methacrylate)
◦ Moulded or lathe cut
◦ Difficult to break, lighter than glass
◦ NOT oxygen permeable
1930- * William Feinbloom
◦ Combined PMMA with glass (centre)
* Large glass contact lens
- Dallos (1946)
◦ Fenestration (putting little holes, helps w/ oxygen permeability)
1940- * Large plastic contact lenses
Contact Lenses (1948)
- Kevin Tuohy (1948)
-Credited with the first PMMA corneal contact lens
-Error during the lathing of a PMMA scleral lens (haptic and corneal portions separated)
- Tanaka (1950)
◦ PMMA corneal lens in Japan
◦ Developed a machine to make lenses
◦ Precursor to Menicon contact lens company
- Joseph Soper (1950s and 60s)
◦ Smaller diameter corneal lenses
◦ Soper keratoconus lens
1960s and 1970s- * Norman Gaylord
Incorporated silicone into the basic PMMA structure
◦ Patented oxygen permeable lenses (gas permeable lenses)
1960 and 1970- * Otto Wichterle
◦ Unable to attract support…Wichterle conducted experiments in his own home
-Developed the spin-casting technique
◦ Invented soft contact lenses
◦ HEMA material (hydroxyethyl methacrylate)
1960-1970- * Bausch & Lomb
◦ Acquired the patent to develop soft contact lenses commercially in the USA
◦ Introduced soft lenses into the world market in 1972
1980s- * Toric soft contact lenses
correct astigmatism
1980- Silicone lenses
◦ Oxygen permeability
◦ Extended wear
1980 CL
- Bifocal soft contact lenses
- Coloured contact lenses
- Disposable contact lenses (daily)
1980- disposable lenses
◦ In the early days, patients would typically use the same pair of lenses…until they couldn’t
what did Klas Nilsson of Gorthenburd, sweden do??
convinced patients of the benefits of 6-month replacement frequency
Gothenburg study’
proved the benefits of regular lens replacement
◦ ‘Danalens’
low-cost, multiple individual lens packs
-First truly disposable lens
-Purchased by Johnson & Johnson in 1984
-Acuvue lens!
1990- * Daily disposable contact lenses
◦ ‘Premier’ daily disposable launched in the UK in 1994
◦ Johnson & Johnson released the ‘1-Day Acuvue’ around the same time
◦ CIBA Vision entered the daily disposable lens market in 1997 with ‘Dailies’
-More disposable options
- Silicone Hydrogel Lenses (1998)
◦ Focus Night & Day (CIBA Vision)
◦ Purevision (Bausch & Lomb)
* The introduction of these lenses is considered to be the most significant advance in contact lens material technology since the development of HEMA by Wichterle
The future
- Convenience and ocular health benefits of daily disposable lenses are likely to increase in popularity
- Silicone hydrogels are set to continue as the main material from which lenses are fabricated
◦ However, the possibility of a new lens material should not be discounted - Likely to be used increasing for the correction of presbyopia (refractive error for middle-aged & older adults to see things up close)
- Extended wear is unlikely to break through the ‘glass ceiling’
more of the future
- Anti-myopia designs
- Anti-infective and anti-inflammatory lenses (medications released into the eye)
- Glucose monitoring
- Intraocular pressure measurement
- Digital information acquisition and display (e.g. a contact lens version of Google Glass)
Soft Lens Manufacture
- Lathe cutting
- Spin casting
- Cast moulding
Lathe cutting
- More expensive
- Custom lenses
◦ High spherical and/or toric powers, keratoconus - Polymer button
- Diamond tipped tool
◦ Back surface lathed first
◦ Front surface lathed - Inspection -> hydration -> re-inspection
- Inserted into vial
- Autoclaved to effect sterilization
Spin casting
- Stainless steel convex tool produced
- Plastic concave mould formed
- Liquid plastic monomer added to spinning concave mould
- UV radiation to initiate lens polymerization
- Edge polished
- Inspection -> hydration -> inspection
- Inserted into blister pack containing saline
- Autoclaved
Cast Moulding
- Stainless steel concave and convex tools produced
- Plastic concave and convex moulds formed
- Liquid plastic monomer added to concave plastic mould
- Plastic moulds clipped together
- Contact lens forms in between moulds
- UV radiation to initiate lens polymerization
- Inspection -> hydration -> inspection
- Inserted into blister pack containing saline
- Autoclaved
Cast Moulding
- Most common
◦ Very consistent production
◦ Do not need to polish
◦ Lower cost
◦ Efficient - Also called injection moulding
