Corneal oxygen deficiency, also known as corneal hypoxia, occurs when there is an insufficient supply of oxygen to the cornea. This is the most commonly occurring side effects of contact lenses, especially when you choose extended-wear contacts. This is a concerning problem because the cornea is one part of your body that doesn’t have a blood supply of its own.
The cornea gets its oxygen supply only from direct contact with the atmosphere and from the tears. When you wear a typical contact, it reduces the supply of oxygen to it. When you wear it overnight the supply of oxygen decreases further to the eye.
The Impact - Corneal Neovascularization
When the cornea doesn’t get enough oxygen for a long time, it can increase the chances of in-growth of new blood vessels in the avascular corneal tissue. This affects corneal transparency and reduces the clarity of your vision. This is a highly complicated situation and may require surgical intervention.
This is where modern high-permeability contact lenses have provided an excellent solution. Contacts made of silicone hydrogel help prevent corneal clouding and over-wearing syndrome.
Corneal Oxygen Deficiency – The Challenges
When it comes to choosing your contacts, keeping them clean should not be the only concern on your mind. You should be careful about choosing the right material. There are lens designs that can be more oxygen-friendly. But when you sleep with the contacts on, the situation can become worse. Some of the symptoms of this problem include:
· Burning sensation
· Blurred vision
· Scratchy sensation
· Excessive tears
Even in mild conditions, there can be swelling in the epithelial layer and/or temporary blurring. If you don't seek timely and proper treatment, it can also cause permanent damage to the epithelial cells. So it is extremely important to choose the that are designed keeping in mind this problem.
Technical Challenges
The main challenges with regard to soft contact lens materials, meant for extended wear, included the following:
· Increasing oxygen transmissibility, measured in Dk/t
· Lower modulus
· Surface biocompatibility
Preventing responses like microbial keratitis has also been a challenge. The method employed to increase oxygen transmissibility of hydrogel lenses has been to increase water content and reducing lens thickness. The Holden/Mertz criterion set for minimal oxygen transmissibility, in 1984, was meant to avoid corneal edema. But most of the soft lenses could not meet this criterion.
This forced the industry to make changes and create new material to increase oxygen transmissibility. This requirement was set at 125x10-9 for the prevention of stromal hypoxia. And silicone and hydrogel were found to be the best-possible contact materials for creating extended wear soft lenses.
Both these materials offered various advantages and mostly negated each other’s drawbacks.
· Silicone (or fluorine-containing silicone) offers high oxygen permeability
· Hydrogel part offers wettability that enables lens movement
The Right Contact Lenses
Silicone hydrogel contacts with high Dk were first made available for clinical practice and research 5 to10 years ago. Several studies over the years have shown significant improvement in the material technology in terms of physiological response to the eye. The improvements have specifically been noted with regard to wearing contacts overnight.
Silicone hydrogels currently constitute a very small percentage of contact lens wearers. The advantages offered by them over low-Dk contacts mean that they will soon become the most widely worn lenses. So when it comes to the question of how long can you wear contact lenses in a day, the answer is now easier with these new contact materials.
Thus, the new types of contact lenses, made of silicone hydrogels, have shown significant improvements over the conventional materials used in making contacts. These modern lenses enable optimum oxygen permeability to ensure that the cornea receives enough supply of oxygen for the duration you wear the lenses. Thus, you will not have to worry even when you choose extended-wear contacts.
Out of all contact lenses available in the market, the Miacare Contact lens shows the most promise in terms of quality. Eyeing the opportunity and with the aim to eliminate contact lens-related discomfort and risks Taiwanese electronics giant BenQ Corporationsdecided to enter contact lens industry with its material related arm called“BenQ Materials” and launched their contact lens brand called Miacare™ in the Indian markets.
Miacare Contact lens is made of Silicone Hydrogel material which is the most advance form of Contactlens material available.
Miacare contact lens also has Double Moisturizing Agents: Hyaluronic Acid (HA) & SodiumAlginate (SA). These natural ingredients retain a high degree of moisture and are highly compatible with the human body. HA locks moisture in both inside and outside the lenses and helps inhibit tear evaporation to keep the lenses moist. The excellent moisture retention of SA helps extend the moisturizing effect of HA.
Miacare™ Contact Lens offers the world's highest Dk/t; with water content and modulus similar as Hydrogel contact lenses, which is a breakthrough in material science.
