1. Shouldn’t Lens Effective Power Be Equal to Your Prescription
Shouldn’t Lens Effective Power Be Equal to Your Prescription? Mark Mattison-Shupnick, ABOM Barry Santini, ABOM
Welcome to this course about a lens’ effective power in the glasses that we dispense. Shouldn’t that lens’ effective power be equal to the prescription that we are filling?
I’ll be your instructor, I’m Mark Mattison-Shupnick, Director, Education at Jobson Medical Information and 20/20 Magazine. Joining me is Barry Santini, frequent contributor to 20/20 and an owner of Long Island Opticians in Seaford NY.

2. ABO Approved Course e-learning module, 2 parts
Details how a lens’ effective power isn’t necessarily the prescription a patient sees. It’s been changed by the way that glasses were ordered and worn.
Improve your professional ability
2. This is an ABO approved course delivered as an e-learning, self-paced module in 2 parts.
It shows detailed examples of how a lens’ effective power isn’t necessarily the prescription a patient sees. It’s been changed by the way that glasses were ordered and worn.
Use this information to improve your professional ability.

3. Objectives
Making eyewear that delivers the patient’s prescription exactly can be complex. Understand the effects of frame fit and the way it changes lens power.
Learn how position of wear and refracting vertex values can be used to produce better prescriptions on center and especially, off-center.
Know how and when to make the case for a better pair of glasses i.e., Rx correct and how to promote that capability.
3. By the end of this course, you should understand that:
Making eyewear that delivers the patient’s prescription exactly can be complex. Understand the effects of frame fit and the way it changes lens power.
Learn how position of wear and refracting vertex values can be used to produce better prescriptions on-center and, especially, off-center.
Know how and when to make the case for a better pair of glasses i.e., meaning delivering the vision the Rx intended and how to promote that new capability.

4. Navigation
Resources
Notes 1 2 3
4. Navigating these slides is easy. Follow along with me as I describe the parts of the screen that you can use.
1. Are the slide Titles
2. Click on the tab Notes and you can read along with the narration
3. Is the Slide itself
4. Adjusts the Volume
5. Is Pause or Go
6. Shows slide and narration Progress
7. Allows you to Review at the slide again
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9. Move to the Next slide 5 6 7 4 8 9

5. Part 1: Effective power (Positional, not Back vertex power)
5. Part 1 Let’s understand Effective Power and how it affects eyewear. We’re talking about the positional effective power and not the back vertex power that is measured on a lensmeter.
Part 1: Effective power (Positional, not Back vertex power)

6. Why Can't I See Clearly Out of My New Glasses?
Of course there can be many reasons.
6. A customer returns with their new glasses and says, “Why can’t I see clearly out of my new glasses?”
Embarrassing huh. Of course there can be many reasons…

7. Why Can't I See Clearly Out of My New Glasses?
Of course there can be many reasons.
But, if you are confident the Rx you're starting with is good, then more than ever, you should consider the primary suspect behind their visual dissatisfaction…
Might be you…
7. Why can't I see clearly out of my new glasses? There can be many reasons. But, if you are confident that the prescription you're starting with is good, then more than ever, you should consider the primary suspect behind their visual dissatisfaction…
Might be you…
Now, I don’t mean that disparagingly, I’m suggesting that there’s an elevated precision in eyewear that we can access today that we couldn’t before, and using that precision makes for better ‘seeing’ glasses.
Mark: Would you explain this by giving us an example?

8. Example Rx -6.00 sph, PD 61 Frame, Ray-Ban Wayfarer, purchased online
Vision? Just not as clear as previous glasses
Prescription checks correct!
What’s different?
8. For example, this sphere prescription, with a 61 PD in a great vintage Wayfarer comes back into your office and says, “My vision, it’s not as clear as my previous glasses”.
What do we do? We immediately rip the glasses off their face and get right to that Lensmeter to see what could be wrong. Nooooooo…. The prescription checks out correctly, no lens waves or aberrations that I can see and, the previous glasses were the same sphere, though in a small oval frame.
What in the world could be different – they measure the same!!!
But they ONLY perform the same in the lensmeter...not in front of their eyes!

9. Here’s Why Prescription Refraction vertex Glasses
Difference between eyeglass vertex and refractor (phoropter) vertex
9. Here’s a possibility that happens with higher prescriptions. Vertex distance affects the power of the lenses as the eyes see through them.
Look at the illustration from a paper showing that not everyone may have the right position and posture when being behind the refractor or phoropter. In this study, that distance was as little as 14mm and as much as 26mm, yikes.
Turns out that the distance the lens’ back surface is to the eye affects the positional effective lens power, not the power of the lens itself. In fact, that’s true for both the refraction and the way that the lenses in the glasses fit.
That means that a -6.00D sphere prescription is correct in eyeglasses if the lenses are also fit at the same distance the lenses in the refactor were from the eye.
Patients with different vertex distances (Left: 14 mm vs. Right: 26 mm) due to differences in forehead anatomy. Same investigator, refractor, and headrest setting.
From “Clinical Importance of Accurate Refractor Vertex Distance Measurements Prior to Refractive Surgery”, Richard A.Weiss, MD et al, J Refract Surg, 2002;18:

10. Example, Positional Effective Power
-6.00 sph Rx, refracted at 13mm
Glasses fit at 20mm
D2 x mm moved/1000 = power change
(72 x 6)/1000 = 0.29D
Effective power becomes more plus farther away, more minus when closer
Positional power is ~0.25D weak
To be a effectively, the lens should have been a to start
10. Here’s our -6.00D sphere prescription, refracted at 13mm, but the glasses fit at 20mm. Perhaps there’s a flat bridge, recessed eyes and the nose pads have been adjusted so the lenses are far from the eyes.
The glasses place the back of the lenses at 20mm
I use the approximation formula to illustrate the effect on power of moving a lens to the position of the lenses in the frame.
D2 x mm moved/1000 = power change
(72 x 6)/1000 = 0.29D (do this on your calculator)
Remember CAP and FAM (from contact lenses)
Effective power becomes more plus farther away, more minus when closer
Positional power is ~0.25D weak
To be a effectively, the prescription, the lens should have been a sphere to start. That’s because a -6.25D sphere moved 7mm farther from the eye has an effective power of -6.00!

11. Example, -8.00, +2.25 Add -8.00 sph, +2.25 Add
Refracted at 12mm, glasses fit at 17mm
To read clearly patient must hold the reading material farther away!
17mm
11. What happens if the lens is a progressive? Patient has returned and is saying that they need to hold reading farther away. Aha, that suggest the add is not strong enough – right? Why?

12. Example, -8.00, +2.25 Add -8.00 sph, +2.25 Add,
refracted at 12mm, glasses fit at 17mm,
1. D2 x mm moved/1000 = power change
(82 x 5)/1000 = (64x5)/1000 = 0.32D
2. Effective power becomes more plus farther away, more minus when closer
Lens is ~0.32D weak, but so is the add, = ~0.25D weak
17mm
12. Let’s look at what the positional power would be of the -8.00D lens? Again using the formula to estimate the effective power at the wearing position…
1. D2 x mm moved/1000 = power change
(82 x 5)/1000 = (64x5)/1000 = 320/1000 = 0.32D
2. Effective power becomes more plus farther away, more minus when closer
The effective power of the lens is ~0.32D weaker, but so is the add, ~0.25D weak
No wonder the patient is holding their reading material farther away.

13. Example, -8.00, +2.25 Add -8.00 sph, +2.25 Add,
refracted at 12mm, glasses fit at 17mm,
1. D2 x mm moved/1000 = power change
(82 x 5)/1000 = (64x5)/1000 = 0.32D
2. Effective power becomes more plus farther away, more minus when closer
Lens is ~0.32D weak, but so is the add, = ~0.25D weak
3. To be a the lens should have been about an to start
17mm
13. Look at number 3. To be a the lens should have been about an -8.37, if you were ordering standards powers, if free-form was ordered, the lens would have been started as a -8.32, then modified again for the tilt and wrap effects.
Instead of sending the patient back to see the doctor for an add power not strong enough, anticipate when effective power changes the way that the lenses were intended to work.

14. Matching Quiz
lens moved 6mm closer has an effect power of _______?
A sph lens, fit 4mm farther than refracted should have been ordered as a __________ lens?
About -9.37
About
About -9.87D
About -9.12D
About
14. Matching Quiz
Answers: 1. b; 2. c

15. What About Fit? Prescription Refraction vertex Glasses (POW)
PD, height, tilt, wrap, vertex distance and OC vertical position varies, by frame
15. Next, the effective power, both at the pupil position and across the lens, is also affected by the frame's position of wear, which includes the tilt angle, the wrap angle, and the vertical placement of the optical center, or 'OC', in the frame.

16. Example Tilt, Wrap 16. Here’s what I mean.
Using one of the calculators at Opticampus.com, we can calculate what lens to order so that if the patient’s prescription is a sphere, we deliver a sphere, even in a frame that tilts the lens 12 degrees and is wrapped 8 degrees. That means that the patient will actually see as though their lenses were a -6 effective power, even though the actual lens power reads a different value in our lensmeter.
Input for sphere, zero for cylinder, 180 for axis, 12 degrees tilt, 8 degrees wrap, pick a lens material and click Calculate.
So to provide a in this frame, we would need to order a x 056 lens! At 12 degrees of tilt and 8 degrees of wrap this power delivers that wearer in that frame a sphere. Got it?
Keep in mind that if you have to troubleshoot power-related problems in compensated lenses, the Rx you start with may also be amongst the potential suspects.
Go to opticampus.com and try it.
Source: OptiCampus.com

17. Prove It Yourself
A lens changes effective power as its tilt, vertex and wrap angle changes
Lenses in frames change the lens’ effective power A B
17. To prove it to yourself, do what I describe here with a lensmeter.
Simulating a frame, hold a lens against the lens stop of your lensmeter. This is a -6.00D sphere, and watch the change in the lens’ effective power as you begin tilting it. Photo A shows that the lens is a sphere. Photo B shows the same lens tilted, and the target mires have become cylindrical.
That shows what we know: A lens delivers an effective power that is different as its tilt, vertex and wrap angle change or depart from the position of the lenses used in the exam lane.

18. Prove It Yourself
A lens changes effective power as its tilt, vertex and wrap angle changes
Lenses in frames change the lens’ effective power
18. Watch this video:
First I lift the lens a few millimeters above the lens stop and the power changes, when I readjust the power to focus the target, the lens is 0.25D different.
Then tilt the lens, it becomes cylindrical, I can refine the axis and focus the sphere and cylinder lines individually.
In the Opticampus example, if I had a x 056 and tilted it 12 degrees and wrapped it 8 degrees, the target would be a sphere!
Effective Power video

19. If the Rx is Correct…
Make the effective power equal to the prescription
19. Again, if the prescription is correct, the one that was received from the doctor, use all your technical powers now to make the effective power of the lens, in the frame deliver that prescription. It makes the best eyewear.

20. Why More Important Today?
Fashion!
Frame size
Frame angle
Frame depth
Eye placement
Refraction technology
<0.25D
Increased precision
20. Why is this more important today than before?
Fashion! It can significantly affect the resulting delivery of the Dr.'s prescription. Frame size, angle, depth and eye placement all combine to change the way that prescription lenses focus the light and can impact patient acuity and comfort. Today, we are able to make glasses that deliver terrific vision, pretty much regardless of the frame style chosen. Mastering the skills and understanding to accomplish this is essential in defining what makes a great optician.
We are now seeing that the precision of refractions will improve to include prescriptions values in increments less than 0.25D. By starting with finer precision in the initial prescription, we can reduce the likelihood of problems that result when surface calculations and processing tolerances combine unfavorably in a finished pair of lenses.

21. Big, Deep, Hipster Influenced
Trendy, deep frame shapes
Frames fit flatter and farther from the face
Pupil height 6mm-10mm above the mechanical center (MC)
Why is this important?
What are the potential problems?
What happens in progressive lenses?
21. Let’s take a deep dive into what we mean by the big, deep hipster influenced eyewear we sell. Fashion and social trends are influencing everything from eyewear to cosmetics. In eyeglasses, this means we're seeing unusually deep frame shapes that fit flatter and farther from the face. In addition, the pupil heights found are now often 6mm to 10mm above the mechanical center (MC).
Why is this important? What are the potential problems? What happens in progressive lenses? A lot!
L.A.M.B. 005 from Tura

22. Fashion Cycles
Smaller round, oval and rectangle shapes (especially in kids)
The average pupil position is much closer to the frame mechanical center
Less decentration
More like average tilt, vertex and wrap values
22. Fashion cycles all the time. From the smaller round, oval and rectangle shapes of just a few years ago, we're swamped in a style trend favoring very big and deep shapes, and this has resulted in more than a few fitting and fabrication problems.
When frame styles were smaller, the average pupil placement was much closer to the frame’s mechanical center. Therefore, there was less decentration required, and lenses were often thinner and lighter. In fact, overall frame fit was much closer to the averaged values for tilt, vertex and wrap that lens designers use for both their recommended base curves and lens surface calculations.

23. Lenses Used In Refraction
Refractors or phoropter lenses are:
Small in diameter (weight and size)
Flat in profile (for rapid change)
23. Let’s review the optical system used to determine the prescription:
First, during the refraction, trial frame and phoropter lenses are small in diameter. That reduces weight and size so that many lens powers and potential combinations can be available for use by the refractionist.
The lenses are also flat in profile. That allows both a rapid change of dials and permits lenses to be reasonably close when stacked. This reduces additional errors by minimizing lens to lens distances.

24. Lenses Used In Refraction
Refractors or phoropter lenses are:
Flat, Base curve = 0
Aligned perpendicular to floor, Pantoscopic Tilt = 0
Held in a flat plane, Wrap Angle = 0
24. That means that phoropters use flat, plano base curve lenses, with zero tilt or wrap.

25. Lenses In Eyeglasses
Eyeglass lenses, in order to achieve good peripheral optics are not flat, but curved.
This reduces the obliquity of off-axis light rays and improves peripheral vision
The result: wider areas of sharp vision
25. However, lenses in eyeglasses are not flat but curved, in order to achieve good peripheral optics.
This reduces the obliquity of off-axis light rays, makes the line of sight behind the lenses more perpendicular to the lens and therefore improves peripheral vision.
The result: wider areas of sharp vision.

26. Limitations of Corrected Curve Lenses
Even if the proper base curve, corrected curve (CC) lenses suffer compromises in off axis clarity
Their original optimization was for sphere powers only, no astigmatism
A CC lens must be oriented properly to the CR to realize maximum clarity in all gaze angles
26. But that doesn’t mean that all curved eyeglass lenses deliver crisp vision from edge to edge.
Even if the proper base curve, recommended by the designer is used, corrected curve can still suffer compromises in off-axis clarity.
Why? Because the theory of corrected curve lens optimization was designed for sphere powers only, and no astigmatism corrections or cylinder powers were included in the calculations.
Also, in order for a corrected curve (CC) lens to function as the designer intended, and deliver good peripheral optics in all gaze angles, it must be properly oriented and aligned to the eye’s center of rotation (CR). Look at the illustration.
In a typical situation, most optical centers are placed at the mechanical center of the frame. But the eye’s visual axis, or line of sight, is looking straight ahead, above the lens's optical center.
So a typical lens has be intentionally tilted from absolute vertical in order to align the lens's optical axis to intersect the eye's center of rotation. Our rule of thumb here is to ensure the OC is positioned1 millimeter below the pupil for every 2 degrees of tilt.
It should be obvious from this discussion that it is a incorrect to refer to the wearer's pupil position as an"OC' height. The proper terminology to use for vertical eye poistion in the frame is pupil position or pupil height," not 'OC' height. They can be, and often are, two different things.

27. Refractive Lenses vs. Eyeglass Lenses
Flat in form
OC in front of pupil
Zero pantoscopic tilt
Zero wrap angle
Nominal 13mm Vertex
High Abbé/low dispersion lenses
27. To summarize, lenses in an exam room are flat in form, place the OC in front of pupil, have zero pantoscopic tilt, zero wrap angle, and sit at a nominal 13mm vertex distance.
All of these conditions are typically not the way that we make eyeglasses.

28. Refractive Lenses vs. Eyeglass Lenses
Flat in form
OC in front of pupil
Zero pantoscopic tilt
Zero wrap angle
Nominal 13mm Vertex
High Abbé/low dispersion lenses
Eyeglasses
Curved in form
OC always below pupil
degrees panto tilt
degrees wrap
9mm - 20mm Vertex
Lenses may have low abbé/high dispersion
28. Eyeglass lenses on the other hand are curved in form, the OC is almost always below pupil center, and have degrees pantoscopic tilt. They are usually wrapped degrees, can sit anywhere from 9mm - 20mm vertex distance.
So, understanding the affects of lens positioning i.e., tilt, wrap and vertex helps to produce lenses that perform as you would expect, have increased value to the patient and separate your office from your competition.

29. Fitting Eyeglasses
Eyeglasses are tilted in front of the eye to improve cosmetics and visual utility
Increased pantoscopic tilt
Decreased to miss the cheeks
TILT
29. Therefore, understanding the effects of adjustments is critical.
We tilt eyeglasses front of the eye to improve cosmetics and visual utility. For example, it brings the near reading area of a progressive closer to the eye increasing the useful size of the reading area.
For some patients with flat bridges, that tilt is decreased, also called retroscopic tilt so that the lens bottom does not rest against the top of the cheeks or lifts the lens when the patient smiles.

30. TILT
Fitting Eyeglasses
Eyeglasses are tilted in front of the eye to improve cosmetics and visual utility
Wrapped for sports or cosmetics
30. Understanding the effects of adjustments is critical.
In eyeglasses horizontal tilt also can improve cosmetics and visual utility. They can be wrapped for sports or cosmetics.
The bottom illustration shows an extreme amount of tilt or wrap and these angles of 15 to 25 degrees require that the lens be compensated or customized with prism. This neutralizes the prism induced at these angles, which would otherwise cause double vision. In addition, these high angles require better management of the peripheral lens optics to ensure wide, clear fields of vision.

31. Why Adjust for Effective Power?
Traditionally only higher powered Rx's (>6D)
Almost solely concerned with adjustments for significant differences in refractive versus fitted vertex distances
For example, contact lenses
31. Haven’t we typically adjusted for position of wear or for refractive vertex distance? Not usually.
Traditionally only higher-powered Rx's i.e., >6D were considered and that was only when we were concerned with adjusting for significant differences in refractive versus fitted vertex distances that might have been noticed by the doctor.
Contact lenses, for example, are a usual vertex conversion that takes place in every office and even consumers are often aware that their contact lens prescription is different than their eyeglass prescription. Vertex compensation for effective power is one of the reasons.

32. Before Free-Form Lenses
Before digital Free-Form lenses, adjusting lens power for individual values of wrap angle, pantoscopic angle or vertex distance couldn’t be done
We adjusted the glasses to the fitting values in the original lens design, if known
32. Before digital Free-Form lenses, adjusting lens power for individual values of wrap angle, pantoscopic tilt or vertex distance couldn’t be done. Stock lenses are a good example of that.
When using stock lenses, in almost all cases, the lens power used and the prescription ordered match exactly. That means that stock, finished lenses area one size fits all approach from a design and effective power point of view.
We adjusted the glasses to the lens designer’s average fitting values used for the original lens design, if known.
That explains why adjustments to a new pair of glasses often has patients saying, “that’s better…”. That’s because, the lenses were adjusted to the intended average vertex, tilt and wrap for which the lenses were designed.

33. Digital, Free-Form Lenses
Use refraction vertex
Use custom fitting values for tilt, wrap and vertex
Order and receive adjusted power lenses
Changes effective sphere, cylinder and axis values to equal the Rx when worn
Customizes the optics across the entire lens surface
33. Now, digital, free-form lenses can be delivered customized to the way that the frame fits and the way lenses are positioned in that frame.
Here’s a menu that is made possible by the results of a frame reference device and Spectangle Pro, a digital measuring device for fitting eyeglasses. Follow along with me…
1. We consider the refraction vertex, especially in higher-powered prescriptions. We source that from the prescribing doctor.
2. This digital device measures and shows custom fitting values for tilt, wrap and vertex
3. Lenses are ordered using the POW or position of wear values and we receive back from the lab lenses whose power has been
adjusted, the 'prescription' stays the same
4. The changes affect sphere, cylinder and axis values to equal the Rx when worn
5. This also customizes the optics across the entire lens surface

34. Look Out Below!
Oversize plastic styles place the eye's pupil further and further away from the optical center (OC)
OC is normally placed at the mechanical center (MC) or midline of the frame
Induces prism, can degrade vision
Include fitting height, free- form can compensate
34. Last item… Look out below!
Oversize plastic frame styles place the eye's pupil further and further away from the lens’ optical center (OC).
The OC is normally placed at the mechanical center (MC) or midline of the frame and as we said, therefore, that induces prism and can degrade vision at the height that the eye is looking straight ahead through the lenses.
Many free-form lens producers can also make the correct changes to include fitting height, the use of free-form can compensate for this.

35. Verification Compensated power
Card or invoice supplied with lens values
Sph, cyl axis
Add
Right and left lens different
Average vertex, tilt or wrap fitting values or actual POW
35. How do we verify a lens whose measured power is different from the ordered prescription? In the absence of a sophisticated program to calculate what to order, we choose the lab in which we trust.
We receive a compensated power usually on an invoice or patient card.
It includes the new sphere, cylinder and axis values as well as add power for right and left lenses, that when worn, delivers the ordered prescription.
It also shows whether POW or average fitting values were used. This is an effective reference for the patient if they move or change practices.

36. Summary, Part 1
Refraction vertex and eyeglasses vertex distance are different, compensating for it can add precision, explain problems
Include the position of wear measurements, they add precision to the prescription, and the Add power
Free-form can customize the entire lens for the way the patient wears the glasses
Improved lens designs makes precision at every step more important
36. In summary and to close this Part 1
1. Refraction vertex and eyeglasses vertex distance are different, compensating for it can add precision, explain problems.
2. Include the position of wear measurements, they add precision to the prescription, and the Add power.
3. Free-form can customize the entire lens for the way the patient wears the glasses.
4. Improved lens designs makes precision at every step more important.

37. End of Part 1 Congratulations on completing Part 1, Effective Power
Visit the final exam center after completing Parts 1 and 2 and complete the 20 question test
For ABO credit, log into the Opticianry Study Center at 2020mag.com/CE, review the questions and take the exam.
37. Congratulations, this is the end of Part 1, take a break or continue to Part 2.
End of Part 1

38. Part 2, your opportunity Now that you understand the math
 38. Now that you understand the math, what is the opportunity for you and your practice using knowledge about lens effective power?
Part 2, your opportunity

39. Understand The Opportunities
What affects this prescription the most?
Improve the measured power
Use vertex measurements
Make the effective power the prescription
Prescription is not just the lens’ center
Optimize using average fitting characteristics
Customize using actual fitting characteristics (POW)
Personalize for the way that patients use their lenses most
Some guidelines
Change is positive for almost all patients
Strong Rx’s, cyls over 1.00D
Patients that want the best
39. Here’s an outline to use at the next patient opportunity where effective power is at work.
First, determine what affects this prescription the most. Is there an opportunity to improve the measured power by using vertex measurements?
Make the effective power the ordered prescription, not just at the lens’s center, but globally. Optimize by using averaged fitting characteristics, or customize by using actual fitting characteristics , or POW values. In some cases, it makes sense to personalize the lenses for the way that a patients will use them the most. More about that in a minute.
Some general guidelines are: this kind of change is positive for almost all patients. However, strong Rx’s or those with cyls over 1.00D are clear winners. Of course, patients that want the best are the likely candidates.

40. Vertex Measurements When is it important?
Consider prescriptions over ± 4D
Cylinders over 3D
Children’s prescriptions
Often large vertex changes
Consider prescriptions over ± 4D, Cylinders over 3D
Was it trial framed? If so, now what?
Helps confirm power
Compare to the frame’s fit
Measuring Vertex
Digital, gauge, mm rule
40. When is it important to take Vertex measurements?
Consider prescriptions over ± 4D and Cylinders over 3D. Also for children’s prescriptions where powers may be high and there are often large vertex changes.
Was it trial framed? If so, now what?
Using a trial frame helps confirm power since the lens positions are more analogous to a frame. It helps confirm power and relates well to the frame’s fit.
Measuring Vertex? Use a digital measuring device, a Distometer or vertex distance gauge, or develop an efficient and accurate technique with a mm rule.

41. It’s Not Just About The PD
Don’t define yourself by the PD
Consider the whole pair of glasses
The frame changes monocular PDs
How to measure PD?
Combine digital and traditional methods
Pantoscopic angle and pantoscopic tilt
How to measure tilt?
Time to do it digitally
41. Remember, an optician’s expertise is more than the ability to take an excellent PD.
Consider the whole pair of glasses. As we’ve seen, tilt, wrap and vertex affect the effective power of the lenses. Did you know also that the frame changes monocular PDs? Yes, since frames, depending on nose and bridge shape, can alter the position of the lens optical center, it’s more accurate to consider both the digital and traditional PD measurement methods.
Pantoscopic angle the angle between the temple and front is different than the pantoscopic tilt, the angle of the eye to the horizontal eye axis. Measure tilt, not pantoscopic angle.

42. Hyperopic, 80 Years Old, Posture Change
42. What happens to us as we age?
Look at the illustration. Positional effects of lenses, placement of segments and optical centers should be considered for each patient’s posture and the way that they actuall use their glasses.
Free-form techniques allow the management of corridor length, inset, and the extremes of posture changes.
Take new measurements every Rx
Take measurements while seated and also standing since the eyewear is worn with the effects of standing, walking and changes to posture

43. OC Height? Adjust for the OC placement when extreme
Consider thickness changes
Inform the patient
Consider Asian fit when needed
Choose the right frame manufacturer
Measure after adjusting
43. Adjust for the OC placement if there’s an extreme difference. If the Rx is high and the separation between pupil and OC is great, modifying the OC height, or employing free-form lenses, may help to avoid patients saying that if they raise their glasses, they ‘see better’.
Also consider the thickness changes that can result at that top and bottom of the lens if you ,move the OC at a vertical poistion other than the frame’s midline. For example, minus lenses get thicker at the frame bottom, thinner at the top, as the OC is moved upward from the frame's mechanical center.
If you suspect OC changes will be impact perception, be sure to inform the patient that a suitable "get used to" time may be required.
Consider using alternative fit frames when needed i.e., when there is a flat bridge and standard frames would need to be fit with less tilt and wrap that usual.
Choose the right frame manufacturer since there are a number of excellent companies that produce frames for patients with bridge-fit challenges.
Since we are talking about how frames fit affects effective power, you can now appreciate why all fitting measurements must be taken after adjusting the frame for the best fit.
And don't forget the negative impact of low Abbe value. Both the power of the lens and the material's Abbe Value may require some departures from target OC placement.

44. Speaking of Adjusting
Frame adjusting can change effective power and centering
44. Speaking of adjusting, small changes can help get to adjust the PD. But it won’t however help if there’s a big error.
Look at the illustrations – the OC of higher power plus lenses are in front of the lenses in space, behind the lenses in minus.
You can now see why adding or reducing wrap helps fine-tune a PD, as well as adjust the angle closer to the intent of the lens designer.

45. Speaking of Adjusting
Frame adjusting can change lens power and centering
Did the lab’s glazing technique or base curve choice change the POW?
45. And, that also means that one must consider lens bevel position.
Look at the arrows in the photos. The lab’s beveling technique, choice of base curve and bevel selection - either to follow the lens curve or the frame's bevel curve - can alter the final POW values.
If the adjustment is small, no issues. If larger, fine tuning through adjustments may be necessary.

46. Tell Them About Precise Measurements
Social Media
Facebook posts about new digital tools
Advantages of new precision
Investment in this technology
Images and testimonials
e-Newsletter
Collect addresses and communicate multiple times/year
Opt in for messages
Privacy policy
Postcards
Mine the addresses in PM software
Great photo showing measurement
46. Be the Paul Revere of opticianry. Ride through social media letting all know that ‘POW and digital measurements are here…’.
In Facebook posts talk about your new digital tools, take photos and post them. Describe the advantages of this new precision in your office and what your patients have been saying.
Talk about how you have invested in this new technology, add images and patient testimonials
In an e-Newsletter from your office… That means that you need to collect addresses, but then you can, with little expense, talk to your patients multiple times/ between yearly visits. Why not? Lots of other optical offices and online sellers are talking to them all the time.
But be sure that they agree to receive those messages. Teach them that by giving you their address that they Opt in for frequent communications. Have a visible Privacy Policy that teaches them how you will use their address. Questions? Talk to those folks helping you with your website and/or social communications.
Postcards still work and can be personal. Many brands will help you with images and messaging.
For addresses, mine the addresses in your Practice Management software, and just to be different, how about a great photo showing the new measurement equipment in your office and happy patient on a postcard.
Mark: Can you wrap up what we learned in Part 2 for us?

47. Summary, Part 2
Using detailed measurements for new eyewear opens a cache of opportunities
Think how the whole lens can deliver better vision
Make customized and personalized lenses a bigger part of your practice
Consider posture and eye position
Use a great lab that can deliver your intent
Tell every patient an prospective consumer about your new measuring technologies
47. That’s it for Part 2, in summary… (read along with me)
Using detailed measurements for new eyewear opens a cache of opportunities
Think how the whole lens can deliver better vision
Make customized and personalized lenses a bigger part of your practice
Consider posture and eye position
Use a great lab that can deliver your intent
Tell every patient and prospective customer about your new measuring technologies

48. Conclusion
Vertex, tilt and wrap are not new for adjusting the effective power of eyeglasses
It’s a reminder of the precision tools available that make differentiable eyewear
Take position of wear measurements on all patients, use them more frequently when ordering lenses
48. In conclusion, vertex, tilt and wrap are not new for adjusting the effective power of eyeglasses. It’s a reminder of the precision tools available that make differentiable eyewear.
Take position of wear measurements on all patients and use them more frequently when ordering lenses
Remember: It is not important to isolate every potential suspect when troubleshooting vision complaints with finished eyeglasses. You only have to know enough about all the potential suspects to decide to "haul-in" the most suspicious offenders. Perfection in glasses is an elusive goal. But when you get close-enough for most people, they'll be happy, satisfied customers

49. End of Part 2 Congratulations on completing Part 2, Your Opportunity
Visit the final exam center after reviewing Parts 1 and 2. Then complete the 20 question test
For ABO credit, log into the Opticianry Study Center at 2020mag.com/CE, review the questions and take the exam.
49. Congratulations on completing Part 2
Now, visit the final exam center after reviewing Parts 1 and 2. Then complete the 20-question test.
For ABO credit, log into the Opticianry Study Center at 2020mag.com/CE, review the questions and take the exam. Jobson notifies ABO directly of your pass (80 percent or greater) there’s nothing more for you to do.
End of Part 2