The base curve of a contact lens is the curvature of the back surface of the 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.
Is there a big difference between 8.4 and 8.6 base curve?
LENSBASE CURVES AVAILABLE (mm)DIAMETERS AVAILABLE (mm)38.614.248.4, 8.613.858.614.068.5, 9.014.2
How do I choose a contact lens base curve?
Base curve : Select the base curve which is 0.4 – 0.6 mm flatter than the flattest ‘K’ for smaller lenses and 0.6 – 1.0 mm flatter for larger lenses. 6. Fit the contact lens to the respected eye and leave the patient to wait for 15-20 minutes to settle the lens well.
Does the base curve on contacts 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.
Is there a difference between 8.6 and 8.8 base curve?
The 8.8 BC is “flatter” than the 8.6 lens, meaning that the 8.6 lens has slightly more curvature or “steeper”. The 8.6 base curve will be a better fit for most people. In general, 8.8 BCs are more likely to fit loose and move excessively on the eye.
How do I choose a base curve?
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. In theory +6.00 should always give you the best possible combination of curves for weight, optics, etc.
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.
What does 8.8 mean on contacts?
The 8.8 BC is “flatter” than the 8.6 lens, meaning that the 8.6 lens has slightly more curvature or “steeper”. The 8.6 base curve will be a better fit for most people. In general, 8.8 BCs are more likely to fit loose and move excessively on the eye.
What if base curve is too big?
A base curve that is too big will cause the contact lens to not sit properly on the cornea. While less medically dangerous than wearing an overly-small base curve, it can still cause annoyance from the contact lens shifting around or poor vision.
What is the difference between 14.0 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. … Many 14.0mm contacts users use 14.5mm or 14.8mm contacts to demonstrate dolly effects on their eyes.
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Is higher base curve flatter or steeper?
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).
What is rule of thumb in contact lens?
A simple rule of thumb exists. For every 0.05mm that the BOZR is steeper than K, the tear lens power increases by +0.25D. Therefore you must counter this by adding -0.25D to the power of the contact lens.
What is the difference between 8.5 and 8.6 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. Different material , different water content , different modulus , a different way of reacting to your eye.
Can I order contacts with a different base curve?
Can I order contact lenses with a different base curve? 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.
What does axis mean for contacts?
The axis indicates the angle (in degrees) between the two meridians of an astigmatic eye. The axis is defined with a number from 1 to 180. The number 90 corresponds to the vertical meridian of the eye, and the number 180 corresponds to the horizontal meridian.
How do you tell if your contacts are not the right size?
Place the contact lens between the tips of your thumb and forefinger, grasping it near the center so the entire edge is free. Gently squeeze the lens, as if you are about to fold it in half. If the edge of the lens points upward (resembling a hard-shell taco), the lens is correctly oriented.
What contacts are best for astigmatism?
Toric contact lenses are often the best choice for contact lens wearers with an astigmatism, because they’re specifically designed to address the problem. The special shape of a toric lens creates different refractive, or focusing, powers that can help correct either a corneal or a lenticular astigmatism.
Does your eye base curve change?
Base curve can also change as you wear a contact lens based on environmental factors like the lens drying out, temperature changes, and exposure to makeup or soaps. As a doctor, selecting a contact lens for best fit is also challenging because the sagittal depth of any contact lens is not notated on the packaging.
How is base curve measured?
The base curve of any lens can be measured with a tool called a radius gauge, also known as a lens clock. A lens clock has three prongs that can measure the curvature of lenses (and other surfaces). When those 3 prongs are place against a flat surface, the gauge should read zero.
Should I get 8.4 or 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. … Oasys lenses are approved for up to six nights of continuous wear.
What does median base curve mean?
Base Curve. … BC median refers to a base curve 8.7 mm. Diameter. Abbreviated “DIA” the diameter of a lens measures the width of a lens in millimeters, from end to end. The average size of a contact lens is between 13.5 and 15 millimeters.
How do I know my eye diameter?
For accuracy and consistency, always measure from the white part of one side of the eye directly across to the white part of the other side of the eye. Reference the example image below; the corneal diameter or visible iris diameter measures 12.01mm.
Is there a difference between 14.2 and 14.3 diameter contacts?
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.
What does BC and DIA mean for contacts?
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 does 8.3 mean for contacts?
The numbers you provided are the base curves of the contact lenses, and they are typical for soft lens products. The 8.3mm curve is steeper than the 8.6 (which is an “average” curvature). That means you are wearing a lens that is flatter than prescribed, and yes, it will move around more than it should.
How does base curve affect glasses?
If you have a high prescription, the flatter base curve will accommodate the stronger correction. However, the lower the base curve, the more light will be let in through the sides of your sunglasses.
Is BOZR the same as base curve?
BACK OPTIC ZONE RADIUS (BOZR): Radius of curvature of the central, optic zone of a hard contact lens; previously known as back central optic radius (BCOR). … BASE CURVE: Term used to specify the back optic radius of a soft contact lens. For hard lenses, see back optic zone radius.
What is corneal warpage?
Corneal warpage is lens-induced irregular astigmatism with a loss of radial symmetry, a reversal of normal flattening of corneal contour, and reduced vision on post-lens-wear refraction (Calossi et al, 1996).
Why do toric lenses rotate?
Soft toric lenses have cylinder power built into the lens to correct astigmatism. Unlike spherical GP lenses, if a soft toric lens rotates on the eye, the astigmatism correction does change. As the lens rotates, the lens’ cylinder axis shifts away from the desired location.
How important is the BC number for contacts?
The ‘BC’ or base curve measurement indicates the back curvature of your contact lens, in millimetres. … It also means your contact lenses will be less likely to fall out. A lower BC number means a steeper curve of your cornea (the clear front surface of your eye). A higher BC number means your cornea is flatter.
Is there a difference between 8.7 and 8.9 base curve?
No, the difference is small. The 8.7 curve is . 1mm flatter, but since these are soft lens curvatures, and soft lenses assume some of the shape of the cornea, the fitting value won’t be changed dramatically.
