Hard Contact Lens

Hard Lens And Soft Lens

 
Contact lenses are easy and comfortable enough to get fitted over the eye to replace the traditional spectacles by providing superb peripheral vision without sacrificing on the part of the appearance or outlook. There are various types of contact lenses available in the market. You should select that lens which would suit your requirements like profession, type of vision disorder and alike. Out of the many types, contact lens can be hard or soft.

Soft lenses
Soft lenses are generally manufactured from a plastic hydrogel polymer called hydroxyethylmethacrylate which constitutes of 38 % to 70 % water. They are made of soft plastic and are water absobing in nature which sits on the surface of the cornea. Some soft lenses also provide ultraviolet protection. These lenses are more comfortable to wear than the hard lenses as they are able to hold more water. The main advantage of soft lenses is that, they are usually disposable which means they can be thrown away after sometime, depending upon the type of lens prescribed. This provides an opportunity to the users to have a new pair of fresh lenses thus reducing the chances of infection and giving enough comfort to the user. The size of the soft lenses is somewhere between 13 and 14.50 mm with the center thickness of 100 um. These lenses allow the oxygen to reach the cornea. Apart from the various benefits, it also has some disadvantages as they easily absorb pollutants like soap or lotion from your hands resulting in irritation in your eyes. They can also rip or tear easily as they are more fragile than the hard lenses.

Hard lenses
Hard contact lenses are generally manufactured from a rigid material called polymethylmethacrylate. In order to increase the oxygen permeability, this material can be combined with other plastics. The hard lenses mainly come under the sizes of 8 to 18 mm with the center thickness of 100 um. These lenses are very durable but they don't allow oxygen to reach the cornea, directly. Oxygen dissolved in the tear indirectly reaches the cornea because of eye movement due to blinking of the eye. Inspite of their durability and lower cost, these are the least comfortable lenses and are used by very few people. But, they maintain their shape better as compared to soft lenses. The reason behind its least use is the number of adverse conditions associated with it like risk of corneal ulcers, undesirable reshaping of the cornea, often difficult to wear in case of non-habituality.