Great question! The short answer is because I need to make sure your eyes are still healthy enough to continue to wear contact lenses, and that you are okay to stay with the brand/material/base curve you're in currently. Now, time for my long answer! :) There are several things that can go wrong when wearing contact lenses, with one of the more common being that your eyes could be starving for oxygen with your current contact lenses, and you wouldn't even know it. You see, the cornea is the only tissue in the body that does not contain blood vessels. Well, at least it's not supposed to contain blood vessels. If a person regularly sleeps in his/her contact lenses or always pushes his/her monthly contacts to two months of wear time, the cornea will eventually start starving for oxygen. To cope with this, the body sends blood vessels to the cornea so that oxygen can be pushed that way. If this continues for a long time, scarring and permanent vision loss can result. These blood vessels, in their early stages, can only be viewed with a microscope and there would actually be no symptoms. This can also occur if a contact lens is fitting too tight or if a person is in a very old, non-breathable material. Unfortunately, I see this almost every week. Fortunately, though, with a change in habits or change in contact lens brand, this vessel formation can be reversed. There are other things that need to be checked for every year as well on contact lens patients, including a check for corneal infiltrates and a check for giant papillary conjunctivitis. I won't go into details on these 2 diagnoses in this blog, but let's just say that if these things were to occur, they could lead to potential problems as well, and need to be treated right away. So, please, don't try to save money by letting your 6 month supply of contact lenses last for an entire year! And take them out at night!
