ophthalmic despensing

1. Adjusting the frame
Mikael G.
MSc in clinical optometry

2. CAUSES OF COMPLAINT
related to the fit of the frames—a direct result of the frame
selection and spectacles adjustment.
Many wearers seem more likely to tolerate spectacles in which
the prescriptions are slightly awry if the frames fit comfortably.
The comfort and suitability of the fitting seem to be the most
significant criteria for satisfaction.

3. Triangles of Force
The fitting triangle is composed of the three points where the
spectacles contact or put pressure against the head.
The apex of the triangle is the contact point on the crest of the
nose, and the endpoints of the base of the triangle are the two
pressure points just above the roots of the ears, one on each side
of the head. Since pads are often used for frames, there may
actually be two resting points to the apex of the triangle.

4. Achieving the Proper Temple Spread
The temple-spread angle of the frame should be such that the
shafts of the temples exert no pressure, even if touching, on any
area of the face or temple before the point of the head at which
they should exert pressure— just above the root of the ears.

5. Temples Not Spread Enough
If the temples are not spread far enough, there will be too much
pressure on both sides of the head, causing the temples to bow
out.

6. This forces the frame forward until the temples are opposite a
narrower part of the head.
When the frame slides forward, the pressure that tends to bend
them is somewhat relieved.
If the glasses are fitted in this manner and the temple spread is
never corrected, the glasses will not only tend to slide down, but
as they do so, the bent-down portions of the temples will pull
against the backs of the ears.

7. Then not only do the glasses slip down as if they were loose, but
they hurt behind the ears as well.
disadvantages of both loose and tight glasses at the same time.
achieve the temple-spread angle that permits the front to rest easily
on the nose without being forced forward.
This is done by adjusting the end pieces so that the temples do not
exert pressure against the sides of the head at any point in front of
the ears.

8. • The temple shafts may touch the sides of the head, but should
not exert pressure.
• The adjustment should be such that the corner of a sheet of
paper may be slipped between the temple shaft and the side of
the head.
• The only place where pressure is allowable is above the root of
the ears.

9. • If the head is very round or is wider in front of the ears than
above the ears, it may be necessary to bend the temples into an
arc that follows this wider portion of the head, but eventually
presses the head only at the desired point (i.e., immediately
above the root of the ear).

10. Temples Spread Too Far
If the temple angle is too wide for the patient’s head, the glasses
will tend to slide down the nose.
More often this occurs if the frame has been worn for some time.

11. Equality of Lens Vertex Distance
At this point, it is advisable to check the glasses for equality of
vertex distance.
This is done by having the wearer tilt his head forward while the
dispenser views the glasses from above.
If the temple spread is unequal with one temple angling farther
in or out than the other.
A single bowed temple can cause a vertex distance inequality in
the same way as differences in templespread angles.

13. THE FRONT
The adjustment of the frame front takes place afte making certain
the temple spread angles are right. Here is the two step overview:
• First, the proper pantoscopic angle or tilt of the frame front is
set.
• Next the straightness of the frame on the face, when viewed
from the front, is adjusted.
It is clear that proper pantoscopic angle and frame straightness
should precede any bridge adjustments.

14. Reference Points
Although it is helpful to refer to the eyebrows when determining
the level of the frame, facial asymmetry can cause one lens to
appear higher than the other.
The frame front should not be aligned solely on the basis of
eyebrow height or the position of the eyes in the head because
either of these features may be asymmetrical.
Instead, overall appearance of both eyes and brows should be
used.
If due to facial asymmetry the frame conforms better to facial
features when fitted slightly higher on one side, then it should be
fit that way.

15. Other Sources of Error Causing the Frame Front to Appear
Crooked
When the glasses are crooked, the following areas should also be
checked in determining the source of error.
1. Are the unequally angled temples caused by bent end pieces or
just the hinges?
2. Are the temples themselves bent?
3. Is the bridge skewed?
4. Is one ear farther back than the other?

16. THE TEMPLES
When all adjustments having to do with the front of the glasses
have been done—open temple angle, pantoscopic angle, height,
vertex distance, and pad positions on the nose—final attention is
paid to the adjustment of the temples.

17. • Lateral pressure—The pressure of the temples against the
sides of the head just above the ears is increased, if necessary,
by decreasing the temple spread.
• The correct amount of lateral pressure is such that the patient
feels no pressure or, if pressure is felt, no discomfort.
• The glasses should stay firmly in place even if the head is
lowered. This should be true even though the backs of the
temples have not as yet been adjusted.

18. fitting temples is that the best way the glasses are held in place is
with friction, not pressure.
Friction is increased when the contact with the side of the head is
maximized.
Earpiece or curl—When the lateral pressure is satisfactorily
applied, attention is given to that portion of the temple that lies past
the top of the ear.
Adjustment varies depending on the type of temple used and will
be considered according to temple type.

19. If the frame front has been properly adjusted, the lateral temple
pressure correctly applied, and the friction contact of the temple
ends well established, then the spectacles will remain secure
without hurting.

20. Positioning the Temple Bend
The proper position of the bend in the temple lies just past the top
of the ear.
The downward slant of the earpiece should parallel the slope of
the back of the root of the ear.
If it even touches the root of the ear, it should just barely touch it.

21. Above all, the temple must not press into the crease between ear
and head or on the small cord of cartilage that helps in connecting
the ear to the head.
The earpiece portion of the temple should not be just bent down.
It must be positioned against the side of the head, usually
requiring inward angling.

22. Summary of Temple Fitting Criteria
• The shaft of the temple should not exert pressure on the face or
head at any point.
• The bend should be just at the point immediately following the top
of the root of the ear, so that it does not rest on either the top of the
root of the ear or push against the back of the origin of the ear.
• The bent-down portion should be angled so that it approximately
parallels the posterior descending slope of the root of the ear without
either pressing into the crease between the ear and the head or the
cord located there.

23. • The cross section of the shaft, if other than round, should be
parallel to the slope of the head and lie with its widest part
against the head.
• The bent-down portion (earpiece) should slope with its widest
part flat against the side of the head.
The ends of the temples should not gouge the back of the head or
exert greater pressure than the balance of the earpiece.

24. Fitting Adjustable Nose pads
Adjustable nose pads give tremendous versatility when fitting
and adjusting frames.
This section presents step-by-step methods for doing just what is
needed to correctly position the frame.
Where adjustable pads and pad arms are available, the frame can
be altered in height by widening or narrowing the distance
between the pads.

25. • It should be remembered however, that increasing or
decreasing the distance between pads will not only lower or
raise the frame on the face, but also allow the frame to fit
closer to or farther from the eyes.
• There are primarily two types of adjustable pad arms.
• The older type is shaped like a question mark; the more
common like an upside down U or a gooseneck

26. PROPER PAD ANGLES FOR ADJUSTABLE PADS
With any pad adjustment that moves a pad arm, it can be
expected that afterwards the face of the pad may no longer sit flat
on the nose.
The pads must then be realigned to their proper positions so that
frontal, splay, and vertical angles are once again correct.
Remember: Adjust the pantoscopic angle first before adjusting
the three pad angles. Adjusting the pantoscopic angle after
aligning the pads means that the pads will have to be aligned all
over again a second time.

27. Adjustable Bridges
The adjustment of rocking pads is most easily performed using
pad-adjusting pliers.
These special pad pliers come in a variety of configurations.
The pad can readily be adjusted for splay, vertical, and frontal
angles using these pliers.
Snipe-nosed or other fl at-jawed pliers can also be used and are
intended to be used on the pad support arm.

28. For pads to be adjusted to rest correctly on the surface of the nose, they
should fulfill the following criteria:
1. The pads should rest halfway between the crest of the nose and the
inner corner of the eye.
2. The long diameter of the pads should be perpendicular to the floor
when the head is erect.
3. The full surface of the pads should rest uniformly on the nose.

29. To correct these problems, the pad face should be readjusted as listed
below:
1. If the lower edge cuts in, change the frontal angle by moving the
bottom of the pads apart.
2. If the top edge cuts in, change the frontal angle by moving the lower
part of the pads closer to each other.
3. If the front edge cuts in, decrease the splay of the pads.
4. If the back edge cuts, increase the splay of the pads.
5. If the cutting edges seem oblique, the pad is not vertical. Alter the
vertical angle and readjust to correct for one or more of the errors listed
above.
6. If the upper part of the pad surface seems to be parallel to the nose,
but the lower part cuts in, or vice versa, change to a flexible, silicone
pad that will conform more readily to changes in nasal angles.

31. When Pad Angles Are Correct, But Still Slide Down or Hurt
This may occur when the frontal angle of the nose is almost
straight up and down.
When this happens, replace the nose pads with replacement pads
made from silicone material.
Another alternative is to replace the existing pad with a larger
pad. This is especially helpful when the pad is causing an
irritation to the skin, as often happens in older wearers as the skin
loses its elasticity.

32. RECHECKING THE FRAME FIT
1. Are the glasses at the correct height vertically?
2. Is one lens or one multifocal segment higher than the other, or
are progressive lens fitting crosses directly in front of the pupils?
3. Is the pantoscopic tilt correct?
4. Are right and left vertex distances equal?
5. Is the temple pressure along the side of the skull correct?
6. Is the temple bend positioned correctly relative to the tops of
the ears?
7. Does the bent-down portion of the temple angle downward
correctly?
8. Do both right and left bent-down portions of the temples
follow the contour of the side of the head?

33. When nose pads are present, recheck these points:
1. Is the distance between pads correct for the wearer?
2. Are the pads sitting on the correct part of the nose for the
wearer?
3. Do the frontal angles of the pads correspond to the frontal angles
of the wearer’s nose?
4. Do the splay angles of the pads correspond to the splay angles of
the wearer’s nose?
5. Are the longitudinal axes of the pads perpendicular to the floor?
6. Overall, do the pads sit flat on the surface of the nose?

34. Ordering and Verification
ORDERING
When ordering a prescription, use the manufacturer’s or supplier’s
own printed form or enter it online if possible.
This will prevent many errors or omissions in processing. Online
ordering can help prevent errors because the program will often
keep the order from being sent until all necessary information is
present.
With paper forms, it is very important to print the necessary
information. Poor or illegible handwriting usually results in errors.

35. General Procedures for Forms
Use a separate form for each job ordered, since the form itself may
travel with the materials during laboratory processing.
When ordering less than a total frame and both lenses, specify this
clearly on the order form.
For printed forms, write this in fairly large letters or check the
appropriate places on the form.

36. Lens Information
When writing the prescription in paragraph form, such as in a letter,
always write the data referring to the right lens first, followed by the
data for the left lens.
For example, “Mr. Hensley was issued a prescription of OD: −3.00 D
sphere, OS: −2.75, −1.50 × 175.”
When written on a blank prescription pad, such a prescription would
be written with the left lens value directly below that of the right lens.
This would appear as follows:
OD: −3.00 D sph
OS: −2.75 −1.50 × 175

37. • Always use at least three figures for the sphere and cylinder
components.
• If the dioptric unit is less than 1.00 D, use a prefatory zero before
the decimal point, as for example, +0.75 D.
• Carry figures two places after the decimal point, as for example,
+2.00 D (not +2 D) or −1.50 D (not −1.5 D).
• State the axis as x, but do not put a degree sign after the numbers
representing the cylinder axis because it may be mistakenly read as
an extra zero.

38. • For example, 10 degrees may be misread as 100 when written
out with the degree sign in longhand as 10°.
• Many also use 3 numbers for the axis. Therefore it is normal to
see a 5 degree axis written as 005.
• Check the base curve of the wearer’s old lenses, particularly
when only one lens is being replaced

39. Frame Information
Be sure to specify the style of temple desired if more than one
style is available.
Print the name of the frame and include the name of the
manufacturer.
.

40. REORDERING FROM EXISTING SPECTACLES
Sometimes it is necessary to use a person’s existing spectacle
lenses as the basis for ordering another pair of glasses.
This can occur in an emergency situation if the person has
cracked or broken a lens and the lenses are still in the frame.
It may also happen that an individual has a pair of glasses and
wants a second pair, but no longer has the written prescription

41. Obtaining Lens Information for Existing Spectacles
Although it is possible to read the prescription directly from the
current eyeglasses, it is best to contact the prescriber or previous
dispenser to verify what was ordered—not just what was received.
For example, when taking a prescription from an existing pair of
glasses, one may misread a cylinder axis as 170, when the lens is
really axis 168.
Yet the original order could have called for axis

42. VERIFICATION
Always use the original examination or prescription form rather
than the actual order form to verify a prescription received from
the laboratory.
This will reveal any errors made when filling out the order form
as well as any errors made by the laboratory.

43. Verifying Lens Powers and Determining Error
Tolerances
Lens power is verified using the lens meter, and in the United
States tolerances for ophthalmic lens prescriptions are set by the
American National Standards Institute.

44. • The American National Standards Institute, abbreviated ANSI,
is a non governmental agency made up of representative
segments of industry.
• The specific standard for prescription lenses is identified by
the number Z80.1 and is titled “American National Standard
for Ophthalmics— Prescription Ophthalmic Lenses—
Recommendations.”

45. • Each aspect of a spectacle lens prescription has a small range
of tolerance within which that particular variable of the
eyeglass prescription can fall and still be considered
acceptable.
• It must be recognized that it is a difficult task to fabricate a
prescription that meets ANSI standards in all variables.

46. Tolerance for Error in “Sphere” Power and Cylinder
Axis
The technique for using a lensmeter to measure a lens of unknown
power was explained earlier in this chapter.
Verifying a lens of known power with the lensmeter is much the same.
After focusing the eyepiece, the lens with the strongest power in the 90
degree meridian is placed in the lensmeter.
If the lenses have similar powers and there is also prescribed prism in
the prescription, then choose the lens with the most vertical prism and
start with that lens.

47. • The power wheel of the lensmeter is preset for the expected
sphere power, and the axis wheel is preset for the expected
axis.
• If either of these two values is incorrect, the lensmeter’s
illuminated target will blur.
• With the sphere power and axis preset, center the lensmeter
target on the reticle.
• If the mires are unclear, focus the power wheel or axis wheel
and note what the sphere power and cylinder axis reads
compared with what was ordered.

48. The question is, how far away from the expected value can the
sphere power of the prescription be and still be considered
acceptable?
According to older ANSI standards, for most lenses, the
allowable error tolerance was ±0.12 D and for higher powers, the
allowable error tolerance increased.
Now the power standard is not based on the sphere power, but on
the meridian of highest absolute power.
To know if this power is off, we may need to fi nish reading the
full spherocylinder prescription before we can tell if the power is
acceptable.

49. So before deciding on power acceptability, we will write our
sphere fi nding down and go on to the cylinder.
Cylinder axis error tolerances vary, depending on the strength of
the cylinder power.
For small 0.25 D cylinders, the axis can deviate up to 14 degrees
either way.
If the cylinder power is equal to 1.75 D or greater, however, the
tolerance drops to ±2 degrees.
An easy way to visualize axis tolerances is to think of a cross
with the 0.25 D cylinder on the bottom and 1.75 D on the top.

50. Axis tolerance cross

51. Cylinder Power Verification and Error Tolerance
Cylinder power verification is done by finding the difference
between the sphere power reading (where the narrowly spaced
sphere lines focus) and the power wheel reading where the three
broadly spaced cylinder lines focus.
The ANSI standard cylinder power tolerances vary depending on
the strength of the cylinder.

52. For cylinder with a power of 2.00 D or less, this tolerance is
±0.13 D. For cylinders from 2.25 D through 4.50 D, tolerance is
±0.15 D.
Above these powers the tolerance is 4% of the cylinder power.
When using a standard lensmeter, this means the cylinder power
tolerance is close to 1/8th diopter.
These tolerances are slightly greater for progressive addition
lenses.

53. Meridian of Highest Absolute Power Error
Tolerance
As stated earlier, the power standards for prescription eyewear
have changed from looking at sphere power to looking at the
power of the lens in the meridian of highest absolute power.
Basically, power standards are stricter for low powers. Up to
±6.50 D, the tolerance is ±0.13 D.
For powers above 6.50, the standard is ±2% of the power.
So what about power standards for a prescription written in
minus cylinder form that has a power of −6.00 −4.00 × 180? The
sphere power is −6.00 D.

54. This would give the appearance of requiring a standard of ±0.13
D.
But what if this lens were written in plus cylinder form? In this
case, the lens would be written as −10.00 +4.00 × 090.
So is the sphere power for this prescription −6.00 D or −10.00 D?
The answer to this question makes a big difference when
applying standards that are stricter for low powers and less strict
for high powers.

55. • For this reason, the power tolerance is no longer based on
sphere power, but on the meridian of highest absolute power.
• So how can the meridian of highest absolute power be found
and verified? The meridian of highest absolute power can be
found and verified in two ways.

56. The first method is to put the ordered lens powers on a power
cross.
The two meridians show −6.00 D and −10.00 D. The meridian of
highest absolute power is the one with the −10.00 D power.
Next we read the power of the lens. Suppose the lens verifies as
−6.15 −4.00 × 180.

57. • Initially this looks like the lens power fails the standard
because the power standard for a −6.00 D power is ±0.13 D.
• But if we place this on a power cross, we have −6.15 in one
meridian and −10.15 in the other meridian.
• The power standard for a −6.00 D power is ±0.13 D, but for a
−10.00 D power the standard is 2% of the lens power, or ±0.20
D.

58. • So looking at it this way, the lens would pass.
• The second method for finding and verifying the meridian of
highest absolute power is to rewrite the prescription so that the
meridian of highest absolute power is the sphere.
• Then we can verify it as sphere power, cylinder power, and
cylinder axis in the same manner we are accustomed to
reading lenses.

59. • So for our example, we convert the prescription to plus
cylinder form, which is −10.00 +4.00 × 090.
• We read the lens in plus cylinder form and find −10.15 +4.00 ×
090. We see that sphere power, cylinder power, and cylinder
axis are all in tolerance.

60. Thank you!!!