CLARITY PLUS EXTENDED ADD
Lens Design
Clarity Plus Extended Add is an aspheric multifocal translating lens design that incorporates a concentric zone for near enhancement. It is indicated for presbyopic add powers from +2.50 and greater. Its proprietary dual aspheric design allows for an alignment fit eliminating the need to fit excessively steeper than flat "K". Patients who wear Clarity Plus Extended Add have clear stable vision at all distances no matter what the add power.
Base Curve Selection
On corneas that have two diopters or less of with the rule astigmatism the initial base curve should be fit 1.50 D steeper than the flattest "K". On corneas with more than 2.00 D of cylinder fit the base curve an additional 0.25 D steeper. You are trying to create an alignment fit.
| EXAMPLE |
| OD |
42.00 / 43.00 (42.00 + 1.50 = 43.50 or 7.76 mm base curve) |
| OS |
42.50 / 45.00 (42.50 + 1.75 = 44.25 or 7.63 mm base curve) |
|
Diameter Selection
The most common diameter used is 9.5. mm. However, if the cornea is on the steep side fit a smaller lens and if it is on the flat side fit a larger lens.
| EXAMPLE |
| Flat "K" |
Diameter (mm) |
| 41.00 & Flatter |
9.7 |
| 41.25 - 46.50 |
9.5 |
| 46.75 & Steeper |
9.3 |
|
Power Determinations
- Clarity Plus Extended Add should be fit on patients who have not had a good outcome with Clarity Plus or who have an add power greater than +2.25.
- Use a Clarity Plus trial lens for determining proper fit and distance correction.
- An over-refraction in spheres must be performed.
- The distance over-refraction is done first and the result should be the most plus power that provides a slow 20/20.
Distance and Near Zones
Clarity Plus Extended Add has anterior concentric zones. The design is a center distant zone with a near periphery. The center distance zone is pupil dependent and range in size from 3.0mm to 4.0mm. The distant zone should be the same size of the patient's pupil in normal illumination. The most common distant zone size is 3.4mm. If the distant zone is too large your patient will have problems reading. Thus, try a lens with a small optic zone. Clarity Plus is a non prismatic lens that does translate minimally. This allows for good comfort but makes it critical that the distant optical zone be exact.
Conclusions
Clarity Plus Extended Add is indicated for older patient's with higher add powers. An accurate measurement of your patient's pupil size is very important since the distance zone is pupil dependent. A proper fit lens will have good papillary coverage, center well and be aligned. The lens should have a slight translation on downward gaze.
Important Criteria
- Fit lenses on patients with who do not have excessive high corneal astigmatism.
- The base curve should be fit 1.50 D steeper than the flattest K.
- The lens must center well.
- Maximum plus must be prescribed for distance.
- Distance optic zone is pupil size dependent.
- Measure pupil size in normal illumination.
- Patients who have poor near go to a smaller OZ.
