Hard Contact Lenses

Glass contacts were the first hard contact lens developed. They could not be tolerated for long periods of time and are no longer prescribed. PMMA (polymethyl metacrylate), or Plexiglas, lenses were developed to replace the glass lens. They were lighter but still uncomfortable. Plexiglas lenses caused corneal damage due to decrease oxygen flow. They are still available but rarely prescribed. Rigid Gas Permeable (RGP) lenses are the most prescribed hard contact lens today.
Rigid gas permeable lenses are made of a hard material that allows increased oxygen flow as compared to the PMMA lens. Therefore it avoids the corneal damage caused by its predecessor. RGP lenses offer many other benefits to the contact lens wearer.
ADVANTAGES OF RIGID GAS PERMEABLE LENSES
• Retain shape better than soft contact lenses
• Provide better vision than soft contact lenses
• Increase durability, lasting up to a year
• Less costly due to increase durability
• Can be worn occasionally or regularly when cared for properly
• Increase visual clarity
• Treats astigmatism and karatoconus well as the lens can be formed to correct such problems
• Effectively treats presbyopia
• Used to correct the cornea shape during sleep
• Can slow down the progression of near-sightedness in children
DISADVANTAGES OF RIGID GS PERMEABLE LENSES
• Take longer for the wearer to adjust to and achieve max comfort than soft contact lenses
• “spectacle blur”- a blurring of the vision that occurs when the contacts are removed that may last for a period of time
• Requires greater care during cleaning
Rigid Gas Permeable lenses are equal if not better than soft contact lenses but thye are much less popular because they are usually uncomfortable to wear. Speak with your optometrist to determine what is best for you.

Ronny Smith is the contact lens specialist. He writes many books on history & future of contact lenses. He always focused on contact lenses usages.