Silicone hydrogel or hydrogel—what should it be? That is the question many people needing vision correction face when they buy lens online. To answer this better, we need to compare certain inherent features.
Basic material of the lenses
Hydrogel is a water containing plastic with gel-like consistency. Lenses made from hydrogels are generally very thin and extremely pliable. Thus they conform to the eye surface and adhere to it leaving no gap in-between. They are uniquely bio-compatible to the human eye. Dry and delicate eyes benefit hugely from the use of hydrogel lenses.
Advantages of using hydrogel lenses are:
- Greater wearing comfort,
- Durability and longevity of lenses,
- Human eye biocompatibility and
- Extreme benefit for delicate eyes.
- Lesser permeability of oxygen,
- Not meant for long-duration wear and
- Relatively less elastic.
Silicone hydrogel, as the name suggests, is a combination of hydrogel and silicone and is relatively more porous. This enables oxygen to percolate and reach the cornea. Thus these lenses offer increased oxygen permeability even when the water volume is low. This reduces the chances of eye hypoxia making them suitable for long duration wear.
Advantages of silicone hydrogel Proclear contact lenses are:
- Extremely high oxygen transmissibility,
- Reduction in the risk of eye hypoxia and
- Comfortable long duration wear.
- Not compatible with delicate eyes,
- Results in deposition in the eye and
- People who are silicone intolerant react to it.
Generally contact lenses are divided into 3 types based on the water content wiz:
- The ones that have water content lower than 45% are generally made of silicone hydrogel and meant for continuous wear for long durations. They are also characterised by oxygen permeability of about 100%.
- Ones with water content up to 60% suite most wearers and are made from hydrogel.
- Ones with a very high water content of about 90% are also made of hydrogel but are meant for people with delicate or sensitive eyes.
Other than water content, this is the most important criteria to check when selecting bausch and lomb contact lenses. The rate of oxygen permeability depends on the water content. The higher the water content, the lesser is the oxygen permeability and vice versa. This is due to the fact that water binds oxygen preventing its absorption by the cornea.
It would be prudent to mention here that moist contact lenses are easy to apply, maintain and offer immense eye comfort. But as the water evaporates during the day, the eyes become dry resulting in an uncomfortable burning sensation and itchiness.
Thus both moisture and oxygen permeability are equally important for ensuring a healthy eye for contact lens wearers. While Hydrogel contact lenses provide moisture, Silicone hydrogel lenses ensure greater oxygen permeability. This makes choosing between either of the two difficult.
Both the materials used to make contact lenses have individual pros and cons. Neither of the materials can boast of offering superior comfort. Thus the choice of the material for contact lenses had best be discussed with the eye doctor before taking a decision to buy lens online.