What makes some people choose glasses for their eyes over contact lenses, and some others just the opposite? How is one different from the other, other than in appearance?
A contact lens is a corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye. Otto Wichterle and his assistant Drahoslav Lím are credited with manufacturing the first of several modern contact lenses and the gel that is used to manufacture them. Glasses or spectacles are frames bearing lenses worn in front of the eyes, normally for vision correction, eye protection, or for protection from UV rays. Salvino D'Armate is credited for having invented the first pair of wearable corrective eye glasses.
There are various types of contact lenses available in the market.
- Corrective contact lenses are widely used by people suffering from myopia, hypermetropia, astigmatism and presbyopia, who do not wish to opt for corrective eye surgery. X-Chrom is a type of lens that is used to overcome color blindness to a large extent.
- Decorative or Cosmetic contact lenses are used by people to bring in a change in their eye colors. These lenses can be used as corrective lenses too.
- Therapeutic contact lenses are also available in the market and have healing properties. These lenses can help an injured or diseased cornea to recover slowly. They are also used to correct disorders like bullous keratopathy, dry eyes, corneal ulcers and erosion, keratitis, corneal edema, descemetocele, corneal ectasis, Mooren's ulcer, anterior corneal dystrophy, and neurotrophic keratoconjunctivitis.
Lenses are also differentiated on the basis of the material that they are manufactured with. Initially lenses were made from glass and eventually Plexiglas was used as a substitute. These lenses came to be known as hard lenses. Later, polymacon was used in place of Plexiglas and a new breed of lenses was manufactured. These were known as soft lens. The latest materials to be used are silicon and hydrogels.
Spectacles or glasses are used to correct disorders like myopia, hypermetropia, astigmatism and presbyopia.
- Safety glasses are also manufactured, where their primary motive is to protect the eye from flying debris. They are made from a variety of shatter-resistant glasses and need to be 1 mm thick at their thinnest point.
- Sunglasses are also another type of eye glasses that are used to provide protection against harsh visible light and UV light. They can be made with prescription or without it and are darkened to serve their purpose.
- Another popular type of eye glasses are the 3D glasses. These enable the wearer to view images that are specially prepared for 3D viewing. Some people need reading glasses to correct their hyperopia and mild presbyopia conditions.
Progressive and bifocal lenses used in glasses are used to treat both long sightedness and short sightedness. Progressive lenses differ from bifocals as they do not have a line or a visible demarcation differentiating between lenses when the user shifts from one lens to another. Bioptics are those glasses that are used by people with severe eyesight impairment.
Though contact lenses can be worn for up to 14 hours a day, one needs to switch to the traditional spectacles once the 14 hours run out. A new category of contact lenses which are disposable on a daily basis, offer comfort for over 14 hours. Contact lenses should be worn for the shortest period of time since it has a few hazards related to it. Spectacles have no upper limit for their usage.
Contact lenses are manufactured from chemical substances. Though these are suitable to most wearers, problems related to the cornea, eyelid and dryness of the eye have been reported. Wearing spectacles has no known ill effect on the wearer.
Usage & Care
Contact lenses can be used to their optimum capacity if they are well taken care of. One needs to ensure that the contact lens remains submerged in the protective solution at all time when it is not being used. The solution that it should be submerged in, should be changed on a regular basis as well. Spectacles need no external aid for care, except a few wipes to clear off any oil or dust particles that have settles on its lenses.