What is the base curve on contact lenses?
By John Johnson
Typical values for a contact lens are from 8.0 to 10.0 mm. The base curve is the radius of the sphere of the back of the lens that the prescription describes (the lower the number, the steeper the curve of the cornea and the lens, the higher the number, the flatter the curve of the cornea and the lens).
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Then, what is the average base curve for contacts?
Most patients will fall in the range of 8.5 to 8.7 base curve (median) and 14mm would be averages. Typically its better for soft lenses to fit flatter than steeper. Soft lenses cover the entire cornea and actually extends past the limbal area by a few mm. If they are fit too steep, they may restrict tear exchange.
is there a big difference between 8.4 and 8.6 base curve? A BC of 8.4 mm of radius is more curved, and therefore a tighter fit, than 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.
Beside this, does the base curve of contact lenses matter?
Yes they do matter. The BC, or base curve, is measured based on your cornea's curvature. If the base curve is too small, it'll squeeze your eye, and if it is too big, it won't stay on your cornea. These both may cause damage to your eye.
What is the base curve and diameter of contact lenses?
Contact Lenses - Base Curve & Diameter
| Contact Lenses Name | |
|---|---|
| 1-Day Acuvue | |
| Power Range | +6.00 to -10.00 |
| Base Curve(s) | 8.6, 8.8 |
| Diameter(s) | 14.2 |
What does 8.4 mean on contacts?
A BC of 8.4 mm of radius is more curved, and therefore a tighter fit, than 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 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. Consequently, some practitioners may specify "match base curves" on a new prescription.Is there a difference between 8.4 and 8.5 base curve?
The difference between an 8.5 and an 8.6 isn't the curvature , but the fact that it is a different lens. People put way too much importance on the diameter and base curve of contacts without any understanding of what they actually mean or how they affect the fit.What happens if you wear the wrong size contacts?
A wrong sized contact lens will not only cause discomfort but it can cause some serious problems to the surface of your eye. If the size is different, the contacts can either be too steep or too flat. This compromises the fit of your contact lenses. This causes your eyes to swell and makes your vision hazy.How do you know your base curve for contacts?
The base curve is the measurement of the inside curve of your contact lenses. As part of your contact lens exam, your optometrist will do a Keratometer reading. This assessment helps the optometrist measure the shape of your cornea.Can my base curve change?
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.Does contact lens diameter make a difference?
Yes, it is quite important. When you are wearing contact lenses with bigger diameter than you need, the contact lenses are so loose that they move around everywhere and out of its own place. This causes discomfort and visual acuity. What's worse, it may cause corneal damage by tearing or scrape your cornea.How important is base curve?
A base curve measurement represents how curved your contact lens is. This measurement affects how a contact lens sits on the front surface of your eye, and is quite important. They will make sure that it's the right fit for you, even if all the other numbers on your prescription match those of the new lens.Can contacts be too big?
If the base curve of the contact lenses is too big, the contacts won't sit perfectly om the eyes. It will moves around in your eyes and also make you uncomfortable. This is the reason why you need to take an eye examination for prescription before you buy contact lenses.Which contact lenses are best for astigmatism?
The most popular brands for soft long-wear lenses for astigmatism are Air Optix, Biofinity Toric and Acuvue Oasys. The Air Optix lenses for astigmatism can be safely worn for up to 30 days and are designed with comfort in mind.How important is base curve in contacts?
Base Curve (BC) is a measure of the curvature of the contact lens. This helps it fit your cornea more comfortably since some corneas are "steeper" or "flatter" than others. The higher the Base Curve number the "flatter" the curvature of the cornea. How do you determine the diameter for contact lenses?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.
