It is the age of state-of-the-art technology: free-form lens designs,
ultra-thin materials, high-quality anti-reflective coatings and light
weight frames, to name but a few. Opticians are in a position to
make patients the finest pair of glasses they have ever had by using
all the resources at
their disposal.
However, without
precisely fitting and
adjusting the finished
product to the patient,
with the very same
attention to detail
given to the choice of
material, design and
treatment, it may com-
promise both your and
your patient’s expecta-
tion. In fact, without
quality dispensing
techniques, the eye-
wear may as well be a
pair of 62-eye aviator,
photogray glass,
executive trifocals. No
offence to those out
there who like these.
The point is fashion-
able, high-quality
eyewear deserves
professional, high-
quality dispensing.
New products and
sophisticated tech-
nology purchases today require precision and comfort to go
along with great vision and looks.
The patient’s long-term satisfaction with their new eyewear
depends on how comfortable the eyewear is and how well the
optician has done their job in the fitting and adjustment process.
The following information is intended to provide an overview of
the fitting and adjustment process and its importance in the
services performed by the optician.
IT STARTS AT FRAME SELECTION
Eyewear adjustments should begin at the time of frame selection.
It is important to pre-fit the frame to the patient prior to measur-
ing segment and optical center (O.C.) heights. Attention should
especially be made to the degree of pantoscopic tilt and the way
the nose pads, if present, sit on the bridge of the nose. These
details can dramatically affect the measurements taken.
First, inspect the touch of the nose pads, or the way the bridge of
the frame rests on the nose: look for good alignment of adjustable
nose pads, or good touch of a zyl saddle or keyhole bridge. For
adjustable pads, each pad should be flat on the side of the nose
without their edges bunching up the skin. The bridge of a zyl
frame should touch a large portion of the side of the nose for good
support and comfort. Be sure that the edges or corners of the
bridge won’t leave red marks or indentations on the nose. This is
especially important on the crest of the nose.
Once the frame is in good alignment, take any measurements
that are required, place the order with the lab and wait for the
lenses, or completed glasses, to be returned.
STANDARD ALIGNMENT
Once the lenses have been fabricated and mounted, the frame
should be put in “Standard Alignment” (also called four-point
touch) as part of the verification process. Standard alignment refers to the process of preparing the frame for
the patient by making sure it is not distorted from
its natural shape.
Check the frame for horizontal and vertical
alignment; temples should be at 90 degrees to the
frame front when extending backwards (Figure
3A) and the frame front should not be propel-
lered, or skewed in one direction or the other,
when viewed from above and sideways sometimes
referred to as “Xing” (Figure 3B). It should also
have a small amount of faceform.
The “Table top test” is a good way to check for
standard alignment: Sit the inverted frame on a
table top with the temples open and there
should be no wobble. (Figure 3C Xing Table
Top Test)
Figure 3A
Figure 3B
Figure 3C
DELIVERY
Dispensing is the optician’s opportunity to shine.
The patient gets to see the eyewear that has been
carefully designed for them. Do not take the plas-
tic lab tray out to the patient when dispensing
new eyewear—this just kills the presentation.
Let the patient know how special their glasses
are by presenting them like a piece of fine jewelry.
Make it known that their purchase has been han-
dled with the utmost care—for example, any
cloths used to clean the lenses should be clean,
not stained and dirty. It is recommended the opti-
cian place the glasses on the patient for the first
time in case substantial additional adjustment is
needed, in which case the eyewear can be
removed immediately to avoid a negative first
impression for the patient.
 Adding the correct amount of pantoscopic tilt brings the
optic axis of the lens in line with the center of rotation
of the eye—improving visual comfort for the patient.
With zero pantoscopic tilt, the lens optical center and optical
axis will pass through the center of rotation of the eye only if
the pupil is at the same height. However, the pupil is rarely
vertically centered within the lens—it is generally positioned
approximately 5mm above the datum line, or frame midline.
If zero pantoscopic tilt is applied to the frame, the wearer
may experience some visual discomfort from
lens aberrations induced by changes in
sphere and cylinder powers due to the
misalignment. In addition, glasses look
better with some degree of tilt, on average
7 to 10 degrees.
 It is important to note that for every 2
degrees of pantoscopic tilt added to the
frame front, the O.C. of the lens should be
lowered 1mm. As mentioned above, most
eyes sit about 5mm above the frame mid-
line, so it is important that the amount of pantoscopic tilt
needed, usually 5 to 15 degrees, is applied to the frame prior
to measurements being taken. The O.C. height ordered must
factor in the degree of tilt applied to the frame—if no O.C.
height is specified, most labs will place it at, or just above,
datum, assuming approximately 7 to 10 degrees of tilt. If the
frame is not pre-fit, the relative (Figure 1: Pantoscopic Tilt)
placement of the segment, or O.C., will be misaligned with the
line of sight of the eye in the finished lens (Figure 2).
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To place the glasses on the patient, carefully
slide the eyewear on, gently spreading the temples
if necessary, guiding the temples over the ears and
down behind the ears.
If the patient prefers to wear the glasses at a spe-
cific place on their nose (vertex distance), this
should have been considered during the initial
selection and measurement process. Changing
the vertex distance can change the effective power
if dealing with high powers, and also affects the
segment and O.C. heights. Increasing the vertex
distance will make a “plus” lens effectively more plus and a “minus”
lens effectively less
minus. Conversely,
decreasing the vertex
distance will make a “plus” lens less plus
and a “minus” lens
more minus. When
dealing with high
powers, above ±6D
the optician must factor in any significant vari-
ations from the refracting vertex distance to
the worn vertex distance when ordering lenses.
If vertex compensation is not applied to the
written Rx, the patient will be unhappy with
the quality of vision using their new eyewear.
With regards to the effect of varying the vertex
distance on segment and O.C. height—de-
creasing the vertex distance generally results in
sliding the frame higher up on the nose effec-
tively raising the relative heights. On the other
hand, increasing the vertex distance will effec-
tively lower the relative heights, generally mov-
ing the frame lower down the nose. This will
become increasingly more important as free-
form lenses become more widely used—many
requiring vertex distance measurements to be
provided when the lenses are ordered. A dis-
tometer (Figure 4) can be used to quickly and
easily measure the vertex distance of the glasses
in the “as worn” position.
Although the frame was pre-fit to the
patient, the process of glazing and insertion
of the lenses can frequently cause some mis-
alignment and create the need for fine-tuning.
If present, the nose pad position should be
fine tuned so the frontal/spread angle, the
splay angle and the vertical angle are all cor-
rect for the patient. Slim pad arm adjusting
pliers (Figure 5) work well for this. The fron-
tal/spread angle is how far apart the pads are.
The splay angle is their angle to the nose,
which should complement the angle of the
nose at the point at which the nose pad is sit-
ting. The vertical angle is controlled by the
size of the loop of the pad arm—the standard
position requires the bottom edges of the
pads be closer to the eye wires than the top
edges of the pads. The objective is to make all
three angles sit flush with the skin to achieve
superior comfort.
Figure 4
Figure 5
Generally, the angles should be such that
the pads are angled slightly toward the face
to follow the natural contour of the side of
the nose (Figure 6). A good test is to raise
and lower the frame and closely observe
the nose pads from the front as they touch
down on the nose. The top and bottom tip
of the pads should touch down at the same
time. If one tip or the other touches first,
that part is going to apply too much pres-
sure on the nose and possibly cause irrita-
tion. Also, looking at the nose pads from a
“head on” position, the cushion side of the
pad should not be visible. In addition, to
maintain the correct vertical angle, the loop
of the pad arm should be small in order to
keep the vertex distance to a minimum
(Figure 7).
Figure 6
  
Figure 7
When fitting patients with very flat bridg-
es, such as those of Asian ethnicity, frames
with nose pads are usually the best option.
However, fitting nose pads to these patients
can be very challenging and takes some
practice. The splay angle has to be changed
so the pads are sitting almost parallel to the
face. Also, the loop of the pad arm may
need to be made larger than standard to
keep the frame off the patient’s lower
cheeks by changing the vertical angle (fig-
ure 8). Bent Snipe pliers are good tools for
this purpose (Figure 8a).
Figure 8
Figure 8A
Once the nose pads are sitting well, check
the alignment of the frame front. It should
be level. If the patient’s face is asymmetric,
this can be challenging. In order
to achieve premium vision, the
horizontal optical centers of the
lenses should be level with the
pupils. However, if the eyes are
vertically uneven, the patient is
not going to be happy with a
crooked frame, regardless of
how detailed an explanation of
the effects of prism may be pre-
sented. In a situation like this, try
to achieve a happy compromise.
Remember, a patient is basing their first
impression of how their new eyewear fits on
several things including how level their eye-
brows are relative to the top of the frame
and how comfortable the frame feels.
There are two schools of thought when dispensing progressives—ink markings or no ink markings. If you are of the ink markers, make sure that the markings are still on the lenses; if not, re-mark the location of the fitting cross. If markings are on the lenses, advise the patient that initially these may obscure their vision and will be removed once alignment has been verified. Let the patient know the fitting marks are there to allow the fine adjustments necessary to customize the fit of their eyewear. Inform them that handling during glazing and insertion of the lenses can occasionally cause misalignment and the need to re-verify alignment.
The no ink marks folks believe if the lenses were measured correctly, there’s no need to check, only if troubleshooting is required. In fact, the lenses should be pristine to show off those great AR lenses the patient ordered. Also, suggesting the markings be left on to verify fitting could suggest to the patient that the optician lacks confidence in his or her abilities to measure accurately.
It’s your choice. |
If the frame front is tilted, always correct
in the direction of the error.
If the right side of the frame front is lower
than the left, increase the pantoscopic tilt
of the right side (angle temple down), or
decrease the pantoscopic tilt of the left
(angle temple up) (Figure 9). Use a pair of
wide jaw angling pliers for this task. It
securely holds the temple and end piece
together so as not to put excessive strain on
the hinge. (Figure 10).
Figure 9
Figure 10
The above information has provided an
overview of many components of the eye-
wear dispensing process. However, there
are many more to come; (part 2 of “Get-
ting Adjusted” with appear in an upcom-
ing issue of 20/20).
Part 2 will cover more on the topic of pan-
toscopic tilt and its importance on quality of
vision; provide instruction on correcting
horizontal misalignment of frames; review
the “fitting triangle” and the three-point
touch; give instruction on how to correctly
fit frames behind the ears with consideration
of the Mastoid Process; give instruction on
temple shortening procedures; and show
results of a survey investigating what patients
expect from their optician. |