Did you know that the part of your eye called the cornea actually breathes? It takes in Oxygen when your eyes are open. Yes. It does.
Wondering what the Cornea is?
Like a sheet, the cornea covers the coloured part of your eyes.
It is actually transparent in real terms. So in contact lens fitting, the lens is made to sit on the cornea (for corneal contact lenses). The cornea’s relationship with Oxygen intake is a key determinant of comfort. As a tissue of the body, the Cornea must take in oxygen from the atmosphere for it to stay alive, healthy and function maximally for sight. The contact lens must not interfere with this process.
So let’s go a little further
If a Contact Lens (CL) will need to stay in front of the cornea, how will the cornea get oxygen?
The comfort experienced when wearing CL depends on the type of material used in making the CL. The first concern in selecting a CL material is its Oxygen permeability ( how well can oxygen pass through the material) and this, in turn, translates to comfort for the wearer. This leads us to different types of Contact Lenses.
Soft Contact Lens
– It’s made from hydrogel: a gel-like, water-containing plastic.
– It’s porous, allowing oxygen to pass through easily.
– It’s very thin and pliable
– It conforms to the front surface of the eyes easily.
– It gives immediate comfort, hence it’s popular.
– Advanced type of Soft CL
– It’s more porous than regular hydrogel CL, hence allows more oxygen to pass through.
– It’s the most prescribed in the USA
GAS PERMEABLE CL (RGP)
– It is rigid
– Its porous but not as much as the Soft and Silicone hydrogel CL
– It delivers better clarity of sight than Soft and Silicone hydrogel CL. This is because of the rigid nature of the lens material.
– Combines the comfort of Soft or Silicon hydrogel with the clarity of the Gas Permeable (RGP) CL.
– Rigid Gas Permeable central zone surrounded by the hydrogel or silicone hydrogel area like a skirt.
– It’s difficult to fit
– It is more expensive to replace compared to the Soft or Silicon hydrogel CL
PMMA (Polymethylmethacrylate) CL
– Has excellent clarity for sight
– Poorest Oxygen permeability compared to others.
– Difficult to adapt to
– It’s the old fashion hard CL
– It’s rarely prescribed today.
Okay. Now we know how to achieve comfort. The next question becomes:
How long should I wear my contact lens?
Until 1979, Contact lenses were removed and kept in a solution overnight, before it can be worn the next morning. With advancement, it is now possible to sleep with certain types of contact lenses.
There are 2 types of Contact Lens
1. Daily wear: You remove this type of CL every night.
2. Extended Wear ( EW): You can wear overnight, usually for about 7 nights or less, without removal.
* Continuous Wear: This CL can be worn for up to 30 consecutive nights.
Now someone may ask:
How often will I be replacing my Contact lens?
Replacement of Contact lenses should be frequent to prevent the build-up of lens deposits and contamination that increases eye infection. Hygiene is a top priority for you as a CL user to keep enjoying the best of it.
– Daily disposable lens
– Disposable lens: dispose in 2 weeks or sooner than that.
– Frequent replacement: dispose off monthly
– Traditional (reusable) CL: it is disposed off every six months or longer.
RGP Contact lenses are more resistant to lens deposits and less frequently discarded compared to Soft Contact Lens. But the Soft and Silicon hydrogel are prescribed more for all the good reasons. Hence, frequent replacement and hygiene become your new Culture as a regular user.
Now that we have a landing knowledge on how to get comfort and usage choice, in our next discussion we’ll look at how it actually helps you to see, considering which one will be right for your eye condition; also, how to care for your Contact lens.
Keep making healthy choices.
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