Extended Wear Contact Lenses
Contact lenses are a safe form of vision correction, as long as all of the rules of engagement are followed. Once you start breaking the rules, the risks of irritation, damage, and vision loss begin to climb.
One of the rules that many doctors give to their patients is this:
“DO NOT SLEEP, NAP, OR CLOSE YOUR EYES FOR ANY EXTENDED PERIOD OF TIME WITH YOUR CONTACT LENSES IN YOUR EYE.”
Despite this common sense approach toward ocular health care, “extended wear” contact lenses are designed to minimize the risk of problems if patients choose not to remove their contact lenses when they sleep or nap. “Extended Wear” is the term used to designate a contact lens that is approved to be slept in, though that is not the safest method of wearing contact lenses.
Let’s be very clear about this, the healthiest option to keep contact lenses safe and minimize risk comes from avoiding any extended wear in contact lenses, even though certain contact lens designs have been approved for it. Some contact lenses are approved for up to 7 days and 6 nights of extended wear while others are approved for up to 30 nights of continuous wear.
How Extended Wear Differs from Daily Wear Lenses
Take notice of how different the mode of extended wear is when compared to the typical “daily wear” (only wearing during the day – while you are awake with eyes open) mode of wear.
With daily wear, we recommend that you:
- Clean, rinse, and disinfect your lenses every day to remove buildup and infectious materials from the lens that may have accrued.
- Put your contact lenses in at least an hour after you wake so that your eyes get a chance to get a full breath of oxygen before you limit the oxygen again with contact lens installation, and again an hour before you sleep so that you go to bed with a fully oxygenated cornea as well.
This is different from daily disposable contact lenses, which we recommend as a lower-risk option since they are simply thrown away instead of taken out and cleaned.
Contrary to daily wear, extended wear does not receive these benefits. Buildup (including – but not limited to: virus, bacteria, microorganisms, allergens, lipids, proteins, dust and debris) accrues throughout every day, and not cleaning your lenses and disinfecting them, you rely on your eye to do all of the work for you.
With extended wear, the eye is limited from the full oxygen supply of the air during the day since the contact lens is never removed, and then the eye also receives a limited oxygen supply that is received from the back of the lid during sleep, because the contact lens poses a barrier to full transfer.
Materials Used in Extended Wear Contact Lenses
Extended wear contact lenses are usually made of a silicone hydrogel (SiHy) material. This SiHy material tends to be extremely porous to oxygen flow, so that even though the contact lens will limit full oxygen transfer to the eye, it is at a less risky level than other materials.
A typical extended wear contact lens has a Dk/t value of well over 100. The minimal Dk/t for swelling to the cornea is a Dk/t value around 87. On one hand, these approved extended wear contact lens designs do exceed minimal oxygen transmission levels by a long shot. However, that encourages repeated days of limiting the full potential to full oxygen transmission, and therefore limiting the full health potential of the eye.
Extended wear contact lenses also require extra attributes that limit the amount of buildup that forms on the lens. Daily wear lenses get buildup removed via rubbing and rinsing the lens once when they are removed from the eye, and again before they are reinserted… that’s twice each day. Extended wearers never get manually cleaned.
Buildup will not only bother the eye, but it can disrupt the tear film as well. Therefore, these extended wear lenses have to take into account the maintenance of extreme tear supporting technology into their design that daily wear lenses don’t even have to worry about.
Manufacturing Process & FDA Approval
The manufacturing of daily versus extended wear is similar via either lathe cut or molded into shape, but the protocol for approving each is different.
The FDA considers extended wear contact lenses as Class 3 (high risk) devices as compared to daily wear being considered Class 2 (moderate risk) devices. Though both classes require regular testing and approval before being distributed for use, the class 3 lenses (extended wear) require much more scrutiny and regulation before gaining approval.
Benefits of Extended Wear Lenses
It’s easy to understand why people like the idea of an extended wear lens.
- Less maintenance detail
- Poor insertion-and-removal skills
- Ease of use
- Less cost for contact lens solutions
- The “wake up and you see” factor
These are all appealing to the wearer. Especially for the one month extended wear designs, you may only have to fiddle with your contact lens 12 times per year instead of 365 times a year x 2 (because you have to put it in in the morning, and take it out at night).
For someone who has limited use of their arms or hands, this method is very attractive. For people who just aren’t very good at handling contact lenses, this definitely minimizes their agony. For people who need to cut the added cost of solutions to maintain their budget, this option may seem lucrative.
Risks of Extended Wear Lenses
Though the extended wear contact lens design may seem attractive, there are still better reasons not to sleep in them. First of all, all contact lenses decrease the health of the eye, and increase the risk of infection and injury. That’s why daily wear is considered a Class 2 device and extended wear a Class 3 device… they demonstrate an increased risk. So, even if you don’t sleep in a contact lens, just by being a wearer, your risk already goes up. Sleeping in contact lenses increases the risk significantly, though reported comparisons will vary.
During the day, the cornea (the clear dome part of the eye upon which a contact lens is placed) requires oxygen to breathe. The cornea is one part of the body that does not get its oxygen from the blood. Instead, it receives oxygen directly from the air when our eyes are open. This is necessary because if blood flowed through our cornea, then the cornea would be red and opaque and light could not pass through it- we would all be blind. At night, when our eyes are closed, the cornea receives oxygen from the blood vessels on the back of the lid (that’s why the back of our lid is so pink, it has extra vessels from which the cornea can “steal” oxygen).
When we wear a contact lens during the day, our eye receives a limited amount of oxygen. The only oxygen that gets to the cornea is the oxygen that passes through the contact lens material, or is transferred around the lens from oxygenated tear flow. Obviously, our eye breathes more oxygen without a contact lens in, regardless of its transmissive properties. With extended wear, this less breathing daytime eye also experiences a continuous night where that limited oxygen is compounded. When our eye receives too little oxygen, the pH will change and create an influx of water that may swell the cornea. This swelling can alter the optics of the cornea which can create haze or prescription changes. (Tip: because of this cornea shift, if you want to receive your correct Rx from your doctor at the time of your exam, do not sleep or nap in contact lenses for at least a week prior to be safe).
Beyond swelling, the greater risk of extended wear is the reduced immunity of the eye. Continual wear threatens the disruption of a stable tear film, and tears defend, lubricate, and hydrate the eye. Also, less oxygen creates an overall decrease in ocular health, and therefore an increased risk of infection and injury. With continuous wear also comes a diminished sensitivity to irritation, so by the time the eye realizes there is a problem, more damage will have occurred. Since infections and damage can be painful and sight threatening, extended wear just doesn’t seem like the best choice for anybody.
The Future of Extended Wear Lenses
In a perfect world, a contact lens that could be slept in every day without any increased risk of health damage would be great. The current designs that are currently approved truly are some of the most breathable lenses on the market, which makes them excellent daily wear lenses, but they still have a limitation to their safety as extended wear lenses.
Some people that want a more permanent and hassle-free vision solution than daily wear lenses can offer, choose to look into laser refractive eye surgeries.
Perhaps as the designs continue to improve and risks come down, all wearers will be in extended wear contact lenses. But until then, most doctors do not encourage extended wear, and when they do authorize extended wear, they proceed with caution. Your best bet is to take those contacts out and use them as daily wear lenses to reduce your risk.
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