FAQs

Another way in which CooperVision differs from competitors is in manufacturing. We're the only company in the world that has all three types of manufacturing for our torics as well as our spheres. That is, we use auto-lathing, moulding, as well as what we call FIPS? [front inside polymerization system] manufacturing: a hybrid part moulding part lathing, which allows us to make a product like Frequency 55 Toric? that has so many different parameters.

Can CooperVision lenses be prescribed for conventional wear?
With proper cleaning and disinfecting by the contact lens patient, all annual replacement CooperVision soft contact lenses will provide patients with superior comfort and visual acuity for periods of up to 12 months.

In which countries are CooperVision contact lenses available?
CooperVision soft contact lenses currently are available from authorized international distributor in 24 countries.

Rotation

How do I determine the amount (degrees) of rotation on a soft toric lens?
Look at the lens on the eye, and visualize the face of a clock over the lens. Frequency® Toric lenses have one laser mark at the base of the prism. In most cases this laser mark will position at what would be 6 o'clock. In this situation the lens has no rotation or "is sitting at 90" indicating no need to change the axis. See clinical case studies for examples of exceptions. If the lens is positioned at either 7 o'clock or 5 o'clock, then the lens is rotating 30 degrees. Each hour on the clock is equal to 30 degrees. A lens rotating half way between the hours on a clock is considered to be rotating half of 30 degrees for a total of 15 degrees.

What is the best way to determine the new axis when a lens rotates on the eye?
There are two methods. One is the Left Add, Right Subtract rule LARS, and the other is Sphero-Cylinder Over-Refraction (SCOR)

SCOR

What is SCOR
Sphero-Cylinder Over-Refraction is a precise method of determining the best possible parameters of a soft toric lens for any given patient. Once an optimal fitting relationship between the lens and cornea has been confirmed and the lens has equilibrated, then perform a sphero-cylinder over-refraction. Retinoscopy may be helpful to start. Once you have the over-refraction, calculate the resultant and reorder the lens. For best results with this method, allow the patient to wear the lenses for at least one week and return for a follow-up visit. Reliability can be confirmed by a good end point acuity and repeatable findings.

How do I calculate the rotation with the over refraction to find the resultant?
Calculate the cross cylinder (SCOR) by using the parameters marked on the contact lens vial and the over-refraction. The over-refraction must have a good end point acuity to provide a valid result. The resultant will give the new axis, along with any sphere or cylinder changes needed, and no further adjustment is needed. If a good end point is not achieved, consider changing the physical fit by selecting a different base curve, material or lens thickness.

How do I get the cross cylinder formula to calculate my sphero-cylinder over-refraction with the lens parameters?
Place the contact lens prescription and the over-refraction into a trial frame and read the resultant at the lensometer. Our Customer Services department (0870 9000 055 or via e-mail) can help to answer your questions.

Since the new lens will rotate like the original lens, should I calculate the true axis of the lens before calculating the sphero-cylinder over-refraction?
We recommend using the axis as marked on the label of the contact lens. The risk for error increases because the calculation must be done twice. We have seen much success with the use of the labeled axis method.

LARS

What is LARS?
LARS (Left Add, Right Subtract) is an alternative method of calculating the needed axis on a soft toric lens when the lens rotates on the eye. If the lens marking is positioned in a clockwise direction, or to the left, then add the amount of rotation (in degrees) to the spectacle axis. This will give the axis for the new lens. If the lens marking is positioned in a counter clockwise direction, or to the right, then subtract the amount of rotation from the spectacle axis.

When a new lens is ordered at a new axis in order to compensate for the rotation, where will the new lens position?
The new lens should position to the same place as the first lens. The axis is changed in order to compensate for the rotation. The laser marking is strictly an orientation tool. It marks the prism base of the lens. When compensating for rotation, the axis is adjusted in the lens. The orientation mark will be at the prism base.

I'm finding cylinder at an oblique axis over a soft toric lens. What does this indicate?
The axis of the lens needs to be altered.

Why will a lens always rotate off of the 6 o'clock position with some patients? Is it due to a poor lens design? What is the best way to get the lens to position at 6 o'clock?
It is common to find that a well designed lens providing an optimal fit rotates on a specific patient. A soft toric lens' final position is due to the corneal topography, lid interaction, aperture and lens design. For example, a lens that rotates 15 degrees temporal is an acceptable fit as long as this rotation is consistent with each lens. Adjust the axis to compensate for the rotation by using the LARS or SCOR formula. Changing the axis will not "make" the lens position to the 6 o'clock position, but will compensate for that rotation.

What should I do if each lens I put on the patient rotates to different positions from time to time?
If the visual acuity is good, do nothing. If the visual acuity is compromised, consider a steeper base curve, change of diameter or a new lens design.

When the over-refraction calls for a new axis that is not consistent with the observed rotation, which axis is best?
Manually rotate the lens to see if vision clears. Manual rotation is especially valuable when you see rotation and the axis of the over refraction is different from the spectacle axis. Rotate the lens to the left at least 30 degrees. Ask the patient to blink normally while looking at the Snellen chart. If they report improved vision at some point while the lens is repositioning, this is confirmation that the axis should be decreased. Then repeat, rotating the lens to the right. If the acuity is briefly cleared then you must add to the axis. If the over refraction also indicates a significant change in the sphere or cylinder power, then this procedure will confirm that the change in the sphere and cylinder are true findings.

You have verified that only an axis change is needed when manual rotation of the lens improves vision. If manual rotation does not improve vision, all parameters of the lens need full evaluation.

A soft toric lens is rotating 15 degrees on a patient who wants to change to a frequent replacement toric. Do I assume that the new lens, which is a similar design, will rotate to the same position?
The only way to predetermine the amount of rotation is with a diagnostic lens of the exact lens design you plan to use. CooperVision's trial lens programs and 100/100 warranty support this philosophy.

Ordering

Can I use the over-refraction findings over a pair of soft toric lenses that have been worn for one year?
No. You should use the new subjective refraction to calculate the replacement lens parameters.

Can I use the over refraction findings over a pair of soft toric lenses, which the patient has been wearing, even if I plan to change the lens type?
No. Use the new refractive findings and follow the recommended fitting formula or perform a sphero-cylinder over-refraction over a diagnostic lens of the new lens type that closely matches the patient's axis.

I must change the base curve of the lens to best fit the patient. Do I use the over-refraction that I found over the poor fitting lenses?
No. The poor lens cornea fitting relationship will give an erroneous finding in the over-refraction.

What should I do when the over-refraction does not provide 6/6 vision?
If the patient is capable of 6/6 vision, you need to change the lens design. If this finding is only in one eye, reverse the lens to determine if the fault is with that specific lens. The first change to consider is to flatten the base curve. A lens that has a steep lens/cornea relationship may appear to fit well with the slit lamp, but the visual acuity will be compromised.

Improving Visual Acuity

Is there anything that can be done to improve visual acuity when the power of the lens appears correct and there is no lens rotation?
Perform a sphero-cylinder over-refraction SCOR. You may find a small amount of plus in the sphere and twice as much cylinder at an oblique axis. If this is the case, and the end point acuity is equivalent to the patient's best visual acuity, then calculate the resultant using the cross cylinder formula for the new axis. An axis deviation of 10 degrees from the spectacle refraction is a common finding.

Why would the visual acuity decline during the first few weeks of wear?
A properly fitted lens will allow you to reach a consistent and sharp endpoint acuity when performing a sphero-cylinder over-refraction SCOR. If the endpoint acuity is poor, the physical fit of the lens is suspect. Consider adjusting the base curve, thickness or lens design. Most often we see this happening when the base curve is steeper than necessary, even when the lens appears to move well on the cornea. Retinoscopy or over-keratometry will help evaluate the base curve/cornea relationship.

Be sure to consider lens reversal. Either reverse the lenses, or perform an over-refraction and calculate the resultant as if lenses were worn in correct eyes.