Which Soft Contact Lens Should I Buy?

      With so many soft contact lenses available right now, I'm sure you're confused on which is the best.  I'm not going to be able to answer that either because one lens is not the best for everyone.  That is why I discourage "lay" people from telling me what they want to buy because they saw it online or their friend wears XYZ brand ad they have to have it.  You should let your optometrist or optician determine the best options for you.  That being said, I'll go over some more popular brands and lenses I use on a regular basis.

Hydrogel vs. Silicone Hydrogel 

Hydrogel lenses:

 

        

 have a percentage of water content (between 38% and 70%) to make a softer material.  Examples of hydrogel lenses are Acuvue 2, Soflens 38, Freshlook, Frequency, and all single use or "daily" contacts (except Acuvue 1 Day TruEyes).

Some of the properties of hydrogel lenes are that they are lower *Dk or oxygen value (usually between 15 and 45Dk).   They are less healthy for the eye, increased chances of corneal edema and blood vessel growth to the cornea, due to low oxygen values.  Although this doesn't seem to be a problem with contacts that are replaced daily.  They are less expensive and tend to be drier on the eye.

              

 Silicone hydrogels: 

They have water content like hydrogel lenses.  The percentage of water ranges from 24% to 60%.  Like the name says, it utilizes silicone combined with the hydrogel material to achieve a higher oxygen lens.  The Dk, or oxygen, values range from 78 to 160.  Since silicone is a poor wetting material, manufacturers need to "hide" it.  Moisturizers or surface treatments are typically used to do this.  Examples of silicone hydrogel lenses using moisturizers are Acuvue Advance, Acuvue Oasys products and the single use TruEyes.  Contacts which use surface treatments are Alcon's Air Optix products and  Bausch & Lomb's PureVision and PureVision 2 HD products.  CooperVision's Biofinity line uses a more natural way of using silicone without the need for moisturizers or surface treatments.

 Silicone hydrogel lenses are healthier for the eye (especially for overnight or extended wear) due to the higher oxygen permeability.  And if you do wear a contact lens overnight, make sure that your eye care practitioner has already determined that you are able to do this safely and the lens has FDA approval for overnight wear.  It is also more important to rub the lenses while cleaning after removal and they seem to be more sensitive to certain solutions.

What is Dk and why should it concern me?

The Dk value is the amount of oxygen permeability of a lens material.

A higher Dk lens will decrease the chance of corneal edema (corneal swelling)

and also the growth of blood vessels in the cornea.

So, you can see that there are a number of good contact lenses available to you.  My suggestion would be to get a lens that allows enough oxygen for the type of wearing schedule that you plan to use, unless that choice is a single use lens.  With a daily replacement lens, make sure it is comfortable.  I hope this helps!