If you already wear corrective lenses you probably know all about the basics: diameter, base curve, material, etc. If you never wore lenses before, then you may not be aware that these are very important information to have before buying and wearing your contact lenses.
BASE CURVE (B.C.): The base curve is the radius of the sphere of the back of the contact lenses, and it is an important measurement to determine how the lenses fit on your cornea. Base curves vary from 8.0 to 10.0, and the lower the number, the tighter (or steeper) the lenses will be on your eye (it also follows that the higher the number the flatter the lenses will be on your eye). Typically commercial lenses come in a rage of 8.2 to 9.0, with the medium being 8.6. When the lenses fit too tightly on your eyes, they can cut out the oxygen to your cornea and cause serious eye problems. When they are too flat, they may move around too much and not only look terrible but be very uncomfortable and also damaging to your eyes.
When the lenses are too flat: 1) Usually uncomfortable, but seldom dangerous.
2) Lenses feel "dry", especially after several hours. 3) Rewetting drops are necessary several times a day. 4) Lenses may pop out or be difficult to insert. 5) Lenses ride high and outside, exposing the cornea. 6) Lens edge may lift or buckle.
When the lenses are too steep: 1) Sometimes comfortable, but can be dangerous.
2) Lenses insert easily and are very comfortable at first. 3) A red ring develops around your iris. DANGER! 4) Vision may vary with each blink.
Your eyes sting or burn after removal. 5) A fine "groove" in the soft tissue around the lens does not necessarily mean lenses are too tight. 6) Lenses which are difficult to remove are not necessarily too tight (it may be because of a more slippery material).
DIAMETER (D): The diameter is exactly that: it basically is the size of the contact lenses, the higher the number, the more of your eye the contact lens will cover. Some people have very small eyes, so they would look pretty weird with extremely large lenses (somewhat like a cartoon character) but if the lenses are too small, then your natural eye color will show around the lenses, and that may not look so cool.
MATERIAL: The lens fit is also determined by the material, thickness and edge technology. The material is readily available on the vile and description of the lenses online, but usually the only way to know the thickness is to wear them. When they are too thick they can be uncomfortable, but they also stay put a lot more (unless you get GPC, which I will address later on). When they are too thin, they move around more, can fall out when you blink, and are more likely to tear, so you have to be careful. Daily disposables tend to be thinner than yearly lenses, but that too is changing a bit because thinner lenses allow more oxygen to get to the cornea, so they are seen as healthier to the eye. The edge technology is really how the contact lens is cut, and that can be hard to find out and it is more important that they just fit well and are comfortable than to be tied up with how their edges are finished. The material varies, there are many kinds, and usually the higher the water contact the better the lenses are for the eye. The material is also important if you have an eye allergy to certain materials, which would require you to switch your contacts to the materials that you are comfortable with and your eyes can handle. Some materials include:
Asmofilcon A
Methafilcon A
Polymacon
Hilafilcon A
Hilafilcon B
Balafilcon A
Tetrafilcon A
Galyfilcon A
Senofilcon
Lotrafilcon B
Omafilcon A
Phemfilcon A
Vifilcon A
GETTING FITTED FOR CONTACTS
A contact lens fitting is performed by your eye doctor and usually is not covered by insurance. It can be pretty costly, but that will depend on too many factors, so I will not speculate the prices. During a contact lens fitting the eye doctor will take your eye measurements, and try on a pair of lenses that matches your measurements. It is important to note that most brands have their own specific sizes, and you cannot get a size different than what they have available. That means if you don't fit the sizes they have available, then you cannot wear that brand. That can be really annoying when it comes to color contacts, because each brand has an entirely different effect on the eye.
You probably will have to return several times to the doctor so that he/she can check your eyes with the time of wear of the contacts, see whether there are any bubbles or air pockets, any inflammation or irritation, and whether your vision is being negatively affected. This is true even if your lenses are PLANO (meaning, no corrective prescription) because the fit of the lenses itself are a prescription (B.C. and D).
Most of the time you need a valid doctor's prescription to buy contact lenses, even online, but that is not always the case. There are plenty of places where you can simply buy the contact lenses without ever visiting a doctor's office. The problem is, not only is that sale illegal, but you could damage your eyes. So it is important to at least check with a doctor to make sure whatever lens you bought is not harming your eyes by not being a proper fit.
BASE CURVE (B.C.): The base curve is the radius of the sphere of the back of the contact lenses, and it is an important measurement to determine how the lenses fit on your cornea. Base curves vary from 8.0 to 10.0, and the lower the number, the tighter (or steeper) the lenses will be on your eye (it also follows that the higher the number the flatter the lenses will be on your eye). Typically commercial lenses come in a rage of 8.2 to 9.0, with the medium being 8.6. When the lenses fit too tightly on your eyes, they can cut out the oxygen to your cornea and cause serious eye problems. When they are too flat, they may move around too much and not only look terrible but be very uncomfortable and also damaging to your eyes.
When the lenses are too flat: 1) Usually uncomfortable, but seldom dangerous.
2) Lenses feel "dry", especially after several hours. 3) Rewetting drops are necessary several times a day. 4) Lenses may pop out or be difficult to insert. 5) Lenses ride high and outside, exposing the cornea. 6) Lens edge may lift or buckle.
When the lenses are too steep: 1) Sometimes comfortable, but can be dangerous.
2) Lenses insert easily and are very comfortable at first. 3) A red ring develops around your iris. DANGER! 4) Vision may vary with each blink.
Your eyes sting or burn after removal. 5) A fine "groove" in the soft tissue around the lens does not necessarily mean lenses are too tight. 6) Lenses which are difficult to remove are not necessarily too tight (it may be because of a more slippery material).
DIAMETER (D): The diameter is exactly that: it basically is the size of the contact lenses, the higher the number, the more of your eye the contact lens will cover. Some people have very small eyes, so they would look pretty weird with extremely large lenses (somewhat like a cartoon character) but if the lenses are too small, then your natural eye color will show around the lenses, and that may not look so cool.
MATERIAL: The lens fit is also determined by the material, thickness and edge technology. The material is readily available on the vile and description of the lenses online, but usually the only way to know the thickness is to wear them. When they are too thick they can be uncomfortable, but they also stay put a lot more (unless you get GPC, which I will address later on). When they are too thin, they move around more, can fall out when you blink, and are more likely to tear, so you have to be careful. Daily disposables tend to be thinner than yearly lenses, but that too is changing a bit because thinner lenses allow more oxygen to get to the cornea, so they are seen as healthier to the eye. The edge technology is really how the contact lens is cut, and that can be hard to find out and it is more important that they just fit well and are comfortable than to be tied up with how their edges are finished. The material varies, there are many kinds, and usually the higher the water contact the better the lenses are for the eye. The material is also important if you have an eye allergy to certain materials, which would require you to switch your contacts to the materials that you are comfortable with and your eyes can handle. Some materials include:
Asmofilcon A
Methafilcon A
Polymacon
Hilafilcon A
Hilafilcon B
Balafilcon A
Tetrafilcon A
Galyfilcon A
Senofilcon
Lotrafilcon B
Omafilcon A
Phemfilcon A
Vifilcon A
GETTING FITTED FOR CONTACTS
A contact lens fitting is performed by your eye doctor and usually is not covered by insurance. It can be pretty costly, but that will depend on too many factors, so I will not speculate the prices. During a contact lens fitting the eye doctor will take your eye measurements, and try on a pair of lenses that matches your measurements. It is important to note that most brands have their own specific sizes, and you cannot get a size different than what they have available. That means if you don't fit the sizes they have available, then you cannot wear that brand. That can be really annoying when it comes to color contacts, because each brand has an entirely different effect on the eye.
You probably will have to return several times to the doctor so that he/she can check your eyes with the time of wear of the contacts, see whether there are any bubbles or air pockets, any inflammation or irritation, and whether your vision is being negatively affected. This is true even if your lenses are PLANO (meaning, no corrective prescription) because the fit of the lenses itself are a prescription (B.C. and D).
Most of the time you need a valid doctor's prescription to buy contact lenses, even online, but that is not always the case. There are plenty of places where you can simply buy the contact lenses without ever visiting a doctor's office. The problem is, not only is that sale illegal, but you could damage your eyes. So it is important to at least check with a doctor to make sure whatever lens you bought is not harming your eyes by not being a proper fit.
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