Welcome to our continuing series of Credit Education Courses for Opticians.
This course has been approved for one hour of credit by the American Board of Opticianry. No fee is required for ABO credit.
Learning Outcomes:
At the conclusion of this credit education course, participants should be able to:
1. Understand PAL distortion and methods of correction, including external and internal methods.
2. Be able to explain the research, development, and design process behind new Succeed Internal Free-Form™ progressive addition lenses.
3. Implement in-depth, in-office training and laboratory interaction using detailed product information.
4. Plan and execute free-form PAL sales and marketing based on lens features and benefits.
Test procedures: Read the article and then click on the button:
This will open a new window with a test consisting of 20 questions. To receive ABO continuing education credit, respondents must correctly answer 16 of 20 test questions. Simply click on the best answer for each question and click the submit button at the end of the test. You are notified immediately on-line if you have failed the test. If you pass the test, CE Certificate will be mailed to your address. Note, normal turn arounf time for CE Certificates if 7 to 10 days, but this can extend to 3 to 4 weeks during busy periods of the year.
Note: Some states do not accept home study courses for continuing education credit. Check with the licensing board in your state to see if this course qualifies.
Understanding Succeed Internal Free-Form
Seiko Succeed Internal Free-Form(TM), the newly introduced general-use internal or backside progressive addition lens (PAL), utilizes unique features that answer in-depth lens performance problems by challenging conventional PAL designs. Succeed Internal Free-Form lenses incorporate a patented, advanced design that moves the progressive surface from the front to the back of the lens. This separates the design from conventional external PAL designs and other backside design PALs.
Internal Free-Form design offers a multitude of visual benefits. But only by understanding why and how distortion occurs in PALs can you grasp the breakthrough benefits offered by a fully back surface design using free-form processing methods.
UN-DISTORTING DISTORTION
Distortion in multifocal lenses exhibits in several ways. Size distortion occurs when the magnification of an object appears different through different areas of a lens (see Fig.1). Lens power, front base curve, thickness, refractive index, vertex distance, and lens vertex power all factor into various levels of distortion. Skew distortion can create peripheral swimming and swaying.
Succeed Internal Free-Form lenses have a spherical surface on the front side and a fused progressive and toric surface on the back surface. Due to the use of the spherical surface on the front side, the distortion is reduced because of the decrease of magnification change in the viewing area. Moving the progressive surface from the front to the back of a lens reduces magnification or size distortion, while also minimizing swaying and swimming. The process allows complex surfaces to be placed on the back of a lens, controlling off-center astigmatism and power error.
Seiko Epson Corporation conducted a study to determine the effect of placing a progressive surface on the concave, or back, surface of a progressive lens along with the toric surface already present. They compared a conventional Seiko Proceed II Short progressive lens to a lens where they placed the pre-molded add power on the back portion of the lens, along with the distance power.
One hundred conventional progressive power lens users were randomly selected to compare external and internal power lenses. The sampling included patients ranging in age from 39 to 73 years old, with add powers from +1.25 to +3.00. The patients' distance prescriptions were from +3.75 to -5.75, with cylinder powers from sphere to -3.00 diopters.
Results published in the Japanese Society of Ophthalmological Optics' Japanese Journal of Visual Science (Vol. 19 No. 3 1998) verified the optical performance resulting from placing a progressive and toric surface on the internal (back) surface of a lens. The results showed an increase in optical performance using the lenses with the progressive power lens power on the concave surface along with the toric power. Lenses were graded on a point scale of 1 to 5, with 1 being "very bad" and 5 being "very good." In all areas distortion showed a marked improvement; results by Rx showed that as addition power increases, distortion decreases (additional data available upon request).
A significant expansion of visual fields and reduction of skew distortion was experienced by all wearers, especially by hyperopic PAL wearers. By moving the add power design to the back surface, the progressive power lens was able to achieve a high level for both of these factors. This allowed the study to conclude, "The optical performance resulting from the placing of a progressive and toric surface on the internal surface of a lens has been verified in conjunction with developing the production technology for it."
Based on these results, Seiko Epson invented and patented the internal progressive lens design. This more advanced design incorporates full aspheric compensation, significantly reducing marginal astigmatism and power error when compared to an external PAL.
TECHNOLOGY OVERVIEW
Old: On a conventional PAL lens, distortion is caused by the shape changes of the front curve as well as by power changes.
New: By moving PAL power from the front to the back of a lens, groundbreaking Internal Free-Form technology reduces the magnification difference between the visual areas of the lens. In the Succeed PAL, the front surface is spherical, which eliminates distortion due to front surface shape changes. This results in a considerable reduction in size and skew distortion. By placing the progressive surface closer to the eye, the manufacturer expands all fields of view: distance, intermediate, and near. The larger fields of vision provide better image stability, exceeding the limitations of conventional PALs.
Old: Conventional PALs offer limited base curves to cover a wide range of powers. This means that each selected base curve is only optimized for a specific spherical Rx at the center of its range. Therefore, good visual acuity is only effective somewhere in the middle of the entire recommended range for each base curve. This affects a PAL's reading area the most; power error and unwanted astigmatism are automatically present by introducing aberrations in all Rx's that fall outside this narrow band. Conventional PALs can have only one optically precise Rx per base curve and add power combination, generally around a total of 65.
New: Internal Free-Form technology fuses toric and progressive surfaces into one complex, three-dimensional curve. Aspheric power compensation is customized for each visual area based on the patient's complete Rx. The compensation in each field of view for each sphere, cylinder, axis, and add power combination is specific and exact rather than random or general. This means the power range of Succeed Internal Free-Form lenses has millions of unique Rx combinations; billions if you include Rx prism up to 3.0 diopters.
Old: When the progressive power is on the front surface of a lens, prism is the only non-Rx tool available for improving near vision. Using prism allows for only a small amount of near vision improvement while causing other trade-offs in the lens.
New: Internal Free-Form technology controls aspheric power along the entire principle corridor. This compensates for both changes in vertex distance and the degree of visual axis (rotation) as the eye focuses from distance to near. Gradient cylinder control within the corridor significantly improves intermediate vision. Using a plano Rx with a +3.00 add as an example, a Succeed Internal Free-Form lens contains 30 percent less distortion with a 20 percent wider visual field than traditionally-produced PALs.
SUCCEEDING WITH SUCCEED
With patients: Being able to present complicated technology to patients simply can mean the difference between a sale or no sale. Define the patient's practical needs and desires and by strictly focusing on lens features and benefits. Patients must understand the value in upgrading to free-form produced PALs before they buy.
In the case of Succeed Internal Free-Form lenses, explain that this is breakthrough lens technology that allows for the most precise correction and visual acuity. Patient accommodation has been documented to be automatic; wearers' success rate is 99 percent.
Each lens is truly prescription-specific down to the finest optical details. Patients with challenging Rx's such as high-cylinder or strong plus-or-minus distance corrections can especially appreciate reduced off-center astigmatism when looking through off-center visual areas.
You can also tell patients that they'll enjoy distortion-free distance vision. Improved image stability means no swimming sensation. These are strong selling points for those considering converting from conventional PALs to free-form PALs. All patients will appreciate an expanded field of view. Their PAL experience in these sophisticated design lenses could be that they are just as easy to use as regular, single-vision lenses.
In practice: Selecting the best frame to fulfill and enhance lens performance is a crucial first step in patient satisfaction. Choose a frame that balances the pupil location vertically. Ideally the pupil should be located in the upper half of the frame between 50 and 75 percent of the total frame height. Avoid a frame that's above or below this range. Follow fitting height recommendations; don't fit lenses below the recommended fitting height.
Pre-adjust the frame before taking measurements. Fit the frame as close to the face as possible without touching skin or eyelashes. Set pantoscopic tilt to approximately 10 degrees. Decrease the tilt if distance PD decreases below 58mm, and increase the tilt if the distance PD exceeds 68mm, since pantoscopic tilt modifies the near/distance PD ratio.
Succeed Internal Free-Form PALs are designed so that the pupil sits right at the beginning of the corridor. With the patient looking straight ahead, place a dot on the sample lens at the center of each pupil, then draw a horizontal line through each dot. Double check to make sure the lines bisect the pupils. Place the frame on the fitting guide scale so that the vertical line labeled "0" divides the bridge in half and the dots and lines on the sample lenses line up on the horizontal line.
Measure fitting height from the lines on the sample lenses to the deepest part of the frame. Be sure to verify the cutout by placing the frame over the cutout circle on the fitting guide. Align the pupil dot and horizontal line on the sample lens with the fitting cross on the diagram. If the frame doesn't fit within the circle, the lens may not cutout correctly and a different frame should be selected.
For the lab: Succeed Internal Free-Form lens blanks are design-specific. This means that they are engineered for accurate design production and front curves are optimized for accurate aspheric compensation. The lenses come engraved and ready to use. Tool elimination and reduction, yield increases, and less non-adapts help labs and ECPs improve efficiencies and be more cost-effective.
From the lab: When Succeed PALs are returned from the lab, they should have verification markings or a verification sticker. If these are absent, you can carefully place the lenses face down on the fitting guide to draw the verification markings. Confirm the fitting height and monocular PD by using the fitting guide.
Succeed Internal Free-Form lenses have been designed for power verification in the same way that you verify a conventional PAL.
The distance area is verified 7mm above the fitting cross and prism reference point, which are both located at the lens' optical center.
The near reference point is offset 2.5mm and is located 16mm below optical center in the design featuring a 13mm corridor and 18mm below optical center in the 15mm design. These values provide the best possible quality at the retina when the lenses are in position of wear.
When dispensing, place the frame on the patient and verify that the fitting cross is at the pupil center. Adjust the frame if necessary.
For the rare case where the patient has visual difficulty, lower the frame slightly (1.0 to 2.0mm) to increase wearing comfort.
Support: Manufacturer and lab ECP support includes merchandising, technical support, and warranties. By taking advantage of wholesale lab and manufacturer programs, ECPs can leverage product technology in training and re-training, P.O.P. materials, demonstration units, and other practice-and-patient focused programs and materials.
