Wednesday, 22 February 2012

5 things you Should Know about Contact Lenses

If you wear contact lenses you may be interested in knowing at least a couple of facts about the thing that touches your eyes so intimately.  Without surface tension of the eye fluid

1)  Can be credited to Leonardo De Vinci by him wanting understand how to alter the corneal power by submerging the eye in a bowl of water.  I guess altering would be the key word here.  This reference can be found in his 1508 Codex of the eye, Manual D.

2)  Your tears not only are used for when you are crying (which are something entirely different) than the tears that bathe the eye, wash out dust and debris to keep the eye moist.  Tears also contain enzymes like phospholipase A2 (also in snake and bee venom which destroys cell membranes) and lysozyme (also found in egg whites which is used to lyse bacteria).  These neutralize the microorganisms that could colonize the eye. Tears are essential for good eye health.

The tears have a surface tension of 42-46 mN/m composed of water, the enzymes mentioned above, and some lipids.  When you take out the lipids (lipids are surface reactive) you get a surface tension of 53-55-5 mN/m.  The surface tension of the fluid is probably necessary to maintain the proper interaction and eliminate dryness of the contact.

3) Sir John Hershel suggested that one could use glass and animal gelly for the contact lenses to conform to the spherical nature of the eye.  This mathematician knew what he was talking about.  And it wasn't until 140 years later that some Czech chemists made some hydrophobic gels that were approved by the FDA.  CIBA Vision later came out with some silicone gels that had oxygen permeability.  Hydrogels can be studied nicely using langmuir blodgett troughs. 

4) It seems like something out of a science fiction movie but some contacts can fix forms of dyslexia.  Special filters on contact lenses are used help with diseases like dyslexia.  Chromagen offers an solutions for  ' dyslexics who suffer from the perceptual distortion of text that makes reading more difficult.'

Bionic lenses fitted with LEDs and lenses fitted with cameras are also being developed.  

5) surfactants in the contact lens solution systems is useful not only to solubilize the organic tear film components adsorbed on lens surface, but also to disrupt microbial membranes. In order to disrupt the microbial membranes and provide best wetting their critical micelle concentration needs to be optimized.