Dr. Z explains why we do the contact lens evaluation and fitting exam each year.
Are all of these contact lenses the same?
Every single day I have at least one patient ask me some version of this same question. It can be difficult for patients to understand the difference between contact lenses, and it is our job as your eye doctors to help educate you why we choose the contact lenses we do. There are literally hundreds of different contact lens options (not even including hard contact lenses!), and determining which lens will be the best for each patient's vision and health needs can sometimes be difficult. Luckily there are many excellent contact lens options that all provide different benefits in both vision and ocular health. Some of the main things I look for during a contact lens fitting exam in determining the best contact lens for a patient are the oxygen permeability of a lens, the optics of a lens and the overall shape and construction of the lens.
You keep telling me my eyes need to breathe.....what are you talking about?!
The human cornea is an incredible part of your body, but when it comes to contact lenses there is one major drawback. Unlike other parts of your body, your cornea does not have a blood supply. This is one aspect that what allows it to remain crystal clear. Since there is no vascular blood supply to provide oxygen, however, the cornea must get all of its oxygen supply from the air it is in contact with. Without this oxygen, the cornea can become damaged, and a contact lens sitting on a person's cornea acts as a barrier to this oxygen supply. Contact lenses are permeable membranes, however, so oxygen can still be transmitted through the lens to the cornea. It is absolutely not true, however, that all contact lenses provide the same level of oxygen supply. There is a very wide range of contact lens permeability, and this is a very important factor that I think about when deciding on a contact lens. The ultimate choice comes down to how healthy a person's eyes already are, the amount of time a patient wears the lenses per day and how often a patient replaces their contact lenses. Ideally the healthiest option for most patients are very breathable lenses that are replaced every single day. My least favorite lens is then a lens that has poor breathability that is only replaced every few weeks. If I feel that a person is not in an ideal lens for their contact lens wear habits, I will always recommend what I think will work better. I feel like it is my job to always explain the best option for all patients regardless of price, and luckily there are many options that will work for most patients.
I hate driving at night with my contacts......everything is so blurry!
When it comes to contact lenses, they are definitely not all created equal with respect to vision. I will often have patients try several different lens brands with the same prescription to see how their is with each lens. Many newer contact lenses use an optical technique called aspheric optics in order to reduce glare and vision blur. These lenses match the natural cornea shape more accurately in order to focus light more accurately into the eye. These lenses will generally give patients crisper and sharper vision with less glare when compared with standard contact lenses. Even with the exact same lens prescription, aspheric lenses will generally provide better vision. For certain patients, especially those with low amounts or corneal irregularity (astigmatism), an aspheric lens may be just what is needed to provide the best vision. Once a patient is determined to have a significant amount of astigmatism, a specialized lens is needed in order to provide clear vision. These lenses not only have to fit the patient's cornea, but they also have to maintain a certain orientation without rotating on the eye. A small amount of lens rotation on an astigmatic cornea can cause a major reduction in vision. One critical aspect of the contact lens fitting exam is determining this amount of lens rotation, and making sure the correct lens is chosen for each particular case.
Not too tight.....not too loose.....looking or the Goldilocks contact lens
When it comes to contact lens exams, it is our job to ensure that the lens we choose will fit properly on the eye while providing the highest level of comfort possible. The goal of the contact lens fitting is to match the corneal shape to the contact lens shape. When a patient puts a lens on, I will always have them move their eye around while I watch the lens on the eye, and I might even move the lens myself on a patient's eye to see how it moves. It is important for the lens to move a little bit on the eye, but not too much that it is uncomfortable. As part of every eye exam, the shape of the cornea is measured, and these measurements help me to determine what shape lens will likely fit the best. I also take into account how a patient's eyelids interact with the lens. Sometimes a thicker or a thinner lens will provide a better fit for a patient depending on how the lids move over the cornea when blinking. all of these aspects are considered in order to find the best lens option for every patient's unique eyes.
The contact lens fitting exam is a very important part of the eye exam in order to ensure the best vision and health are being provided by the chosen contact lenses. Just because you can tolerate your current contact lenses okay does not mean that there is not a better option available. I always discuss with patients the comfort of their lenses in order to make sure we are providing the best possible option when it comes to contact lenses. If you are ever unhappy with your current lenses, or if you want to see if there may be something you would be happier with, just ask!