The key difference between hydrogel and silicone hydrogel is that the lenses made of the hydrogel are less porous, whereas the lenses made of silicone hydrogel are a more porous type of soft contact lenses.
Hydrogel is a crosslinked hydrophilic polymer that cannot dissolve in water. Silicone hydrogel, on the other hand, is a combination of silicone rubber and conventional hydrogel monomers. Both these materials are very important in manufacturing contact lenses due to their porous nature.
CONTENTS
1. Overview and Key Difference
2. What is Hydrogel
3. What is Silicone Hydrogel
4. Hydrogel vs Silicone Hydrogel in Tabular Form
5. Summary – Hydrogel vs Silicone Hydrogel
What is Hydrogel?
Hydrogel is a crosslinked hydrophilic polymer that cannot dissolve in water. Although hydrogels are highly absorbent, these materials also tend to maintain a well-defined structure. We can prepare these materials using different polymers, either natural or synthetic. Among them, the natural sources for hydrogel production include hyaluronic acid, chitosan, heparin, alginate, and fibrin, while the synthetic sources include polyvinyl alcohol, polyethylene glycol, sodium polyacrylate, acrylate polymers, and their copolymers.
There are many different uses of hydrogel: manufacture of contact lenses, scaffolds in tissue engineering, cell cultures, drug carriers, biosensors, manufacture of disposable diapers, water gel explosives, breast implants, etc.
Hydrogel is useful in manufacturing contact lenses. Typically, these lenses are thin and fit onto the front part of the eye. This part is known as the cornea. This can fit onto the cornea without causing any excessive discomfort. Moreover, hydrogel lenses can allow more air to pass through to the cornea compared to regular contacts; thus, it reduces the risk of dry and red eyes.
What is Silicone Hydrogel?
Silicone hydrogel is a chemical component that is a combination of silicone rubber and conventional hydrogel monomers. It has important properties, such as increasing the oxygen permeability and clinical performance of contact lenses.
This substance is useful in making silicone hydrogel lenses having a stiffer matrix due to the incorporation of the silicone and having a lower water content that can make them stiffer than other types of lenses, such as CH lenses. These contact lenses can be worn for about 30 nights without removal; however, for some users, poor comfort has made the wear time limited. The comfort becomes less because of the friction between the anterior and the under-surface of the eyelid.
In the late 1990s, the first two silicone hydrogels were launched. These were known as balafilcon A and lotrafilcon A lens. Both these were licensed for 30 days of continuous wear. Silicone hydrogen is useful in manufacturing contact lenses, and eye care professionals usually recommend silicone hydrogel over regular hydrogel because this type of contact lens can deliver more oxygen to the cornea due to its high porosity. Therefore, it is highly beneficial for patients expecting long hours of wear.
What is the Difference Between Hydrogel and Silicone Hydrogel?
Hydrogel and silicone hydrogel are important materials in manufacturing contact lenses. However, they have different chemical and physical properties. The key difference between hydrogel and silicone hydrogel is that the lenses made of the hydrogel are less porous, whereas the lenses made of silicone hydrogel are a more porous type of soft contact lenses.
The below infographic presents the differences between hydrogel and silicone hydrogel in tabular form for side-by-side comparison.
Summary – Hydrogel vs Silicone Hydrogel
Hydrogel is a crosslinked hydrophilic polymer that cannot dissolve in water, while silicone hydrogel is a combination of silicone rubber and conventional hydrogel monomers. The key difference between hydrogel and silicone hydrogel is that the lenses made of the hydrogel are less porous, whereas the lenses made of silicone hydrogel are a more porous type of soft contact lenses.
Reference:
1. “Silicone Hydrogel.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “First Contact Lenses” By Jill Carlson (jillcarlson.org) (CC BY 2.0) via Flickr
2. “CSIRO ScienceImage 3241 O2OPTIXTM contact lens for healthier eyes” By CSIRO (CC BY 3.0) via Commons Wikimedia