Studies show that a single base curve of 8.4mm managed a “good or better” fit in approximately 90% of individuals,1 and base curves of 8.4mm and 8.6mm together encompassed 98% of individuals.
Besides, What is the normal BC for contact lenses?
Typical base curve values range between 8.0 and 10.0 mm, though it can be flatter (from 7.0mm) if you have a rigid gas-permeable lens. A person with a higher base curve number has a flatter cornea (the clear, front surface of the eye) compared to someone with a lower base curve number, which indicates a steeper cornea.
Keeping this in mind, What happens if you wear the wrong base curve? If your lenses have the wrong diameter or base curve, you’ll likely feel that something is always in your eye. If the lenses are too flat, your eyelids will tend to dislodge them when you blink. The wrong size lenses can even cause an abrasion of your cornea.
Is there a difference between 8.6 and 8.8 base curve?
A base curve of 8.6 mm of radius is more curved, and therefore a tighter fit, compared to the 8.8 mm base curve. People who have steeper corneas require tighter fitting contacts. If a contact is too loose, it may be uncomfortable, fold, or come right out.
Does base curve diameter matter for contacts?
The diameter and base curve are important factors in determining what the optimum fit is for you. A proper fit ensures full coverage of the cornea, optimum edge alignment, and adequate movement of the lens for tear exchange.
What is the average power for contact lenses?
Power is written as a unit of measurement called a diopter.
The average number for both far and nearsighted is 3.00. The additional numbers almost always include the curve and size of a contact lens, but may contain other information as well.
Does the BC of contact lenses matter?
You should never order contact lenses with a base curve that is different from your prescription. This can damage your eyes and cause problems with vision. This is especially important for people who purchase cosmetic coloured contact lenses, which are often of a standardised size.
What is the difference between 8.4 and 8.8 BC?
The 8.4mm base curve is still the likely best fit for the majority of eyes. In instances when the 8.4mm lens is too steep, the 8.8mm lens allows a flatter option. This is more likely needed in smaller eyes, and possibly in some very flat corneas. … Oasys lenses are approved for up to six nights of continuous wear.
Does base curve have to be exact?
The base curve number would be a number between 8.0 and 10.0 millimeters and would be more precise because these lenses need to fit just right. Now that most contact lenses dispensed are soft lenses, this measurement doesn’t need to be quite as precise.
Can I change base curve?
Only a computer can determine the correct base curve on a lens designed using free-form technology. In fact most labs today will not allow you to change or request a base curve at all. … 3) Never attempt to change the lens base curve to match a frame base curve.
What is the difference between 8.4 and 8.8 base curve?
The 8.4mm base curve is still the likely best fit for the majority of eyes. In instances when the 8.4mm lens is too steep, the 8.8mm lens allows a flatter option. This is more likely needed in smaller eyes, and possibly in some very flat corneas.
What base curve should I choose?
The most basic rule is that you always want the base curve to be as close to +6.00 as you can get and still have the Rx work. … The more minus the power (less plus power to minus power) the lower plus the base curve will become. A high minus Rx may even have a base curve of +0.25 or even 0.00.
Does base curve affect vision?
The base curve of a lens may affect certain aspects of vision, such as distortion and magnification, and wearers may notice perceptual differences between lenses with different base curves.
Is diameter important for contact lenses?
It’s very important because it shows in which part of your eye the edges of the contact lens will rest. If the diameter is wrong, too small or too large it wont be stable on your eye and move around too much or it can be too tight and cause eye irritation and corneal abrasions.
What is the difference between 14.1 and 14.2 diameter contacts?
14.0mm and 14.2mm contacts
In fact, there is not much difference between these two. Some manufacturers only make 14.2mm diameter contacts, and some others produce 14.0mm diameter contacts. … In other words, the predominant size for the small contacts is between 14.0mm to 14.2mm.
How do I choose a base curve for soft contact lenses?
Adjusted base curve in
mm + 0.3mm
= soft lens base curve.
…
Still another method is to use the following as a guide for selecting base curves:
- If Low K is >45.00D, then fit the steeper BCR.
- If Low K ranges from 41.00D to 45.00D, then fit the median BCR.
- If Low K is <41.00D, then fit the flatter BCR.
Does 0.00 power contacts mean?
On a glasses prescription, 0.00 (zero focusing power needed) represents good vision. Generally, the further away from zero you go (whether the number is positive or negative), the worse your eyesight and the greater the need for vision correction.
Is minus 7 eyesight bad?
Generally, the further away from zero (+ or -), the worse the eyesight. A number between +/-. 025 to +/-2.00 is considered mild, a number between +/-2.25 to +/- 5.00 is considered moderate, and a number greater than +/- 5.00 is considered severe. Eye prescriptions can change over time.
How do I know the power of my contacts?
Regular Prescription
- Eye – Which eyes the prescription line item is for. …
- SPH – Sphere (this can also be referred to as Power or PWR)
- BC – Base Curve (usually a number between 8 and 10)
- DIA – Diameter (usually a number between 13 and 15)
- Brand – The brand/type of contact lens that your doctor has fitted you for.
What if the BC is wrong in contacts?
Lenses with the wrong base curve feel like they won’t settle right on your eyes. If the lens is too curved for example, it may just slide around in your eye. Every time you blink, it may shift its position. This will make the lens extremely uncomfortable to wear.
What is BC 8.4 on contacts?
Basecurve (BC): This number indicates how curved your contact lens is. Your optician will try and match the curve of your contact lens to the curve of your eye to find the best fitted contact lens for you. E.g. BC 8.4.
What is the difference between 8.6 and 8.8 base curve?
A base curve of 8.6 mm of radius is more curved, and therefore a tighter fit, compared to the 8.8 mm base curve. People who have steeper corneas require tighter fitting contacts. If a contact is too loose, it may be uncomfortable, fold, or come right out.
How do you determine base curve?
Simple Rule for estimating lens base curve on a PLUS POWER lens
- For plus power use the spherical equivalent (SE) and add 4.00 diopters to that. For example, if you have an Rx of + 2.00 sphere, the base curve for the lens will be approximately 6.00.
- Rx +2.00Sph -> [+2.00 +4.00D] = 6.00BC.
How do I choose a contact lens base curve?
Adjusted base curve in mm + 0.3mm = soft lens base curve.
…
Still another method is to use the following as a guide for selecting base curves:
- If Low K is >45.00D, then fit the steeper BCR.
- If Low K ranges from 41.00D to 45.00D, then fit the median BCR.
- If Low K is <41.00D, then fit the flatter BCR.
How is base curve measured?
Generally, your eye doctor will use a keratometer to measure the curve of your cornea, which is the front surface of the eyes – where contacts rest. These numbers help to determine the lens diameter and base curve that appear on your contact lenses prescription.