Dental
Loupes Buyer's Guide
The synergy of resolution
and field width
What is Resolution?
Resolution is the capability to visualize
small structures, and is set by the quality
of the optical design and the use of precision
lenses. Traditionally, this is accomplished
by enlarging items viewed by the naked eye.
Loupes made with inferior materials cannot
deliver peak visualization across the entire
field.
The TV Example
– “Bigger is not always better!”
Which is better? A 52-inch projection television
or a 36-inch high definition television
(HDTV)? If all you care about is the action
of a baseball game, you may pick the projection
TV – lots of action but with a fuzzy
picture. However, if you want to see fine
detail, like the seams on a major league
curve ball, purchase a sharply detailed
HDTV.
Why Field
Width?
Field width is the size of the operating
site when viewed through loupes. Healthcare
professionals appreciate a wider field of
view because it is easier and quicker to
adjust when shifting from the naked eye
to the loupe. A wider field also promotes
less eye fatigue. Field width is linked
to the diameter of the telescope, the optical
design and the magnifying power –
the higher the power, the smaller the field.
Discover the
Synergy.
When purchasing loupes, healthcare professionals
should focus on the resolution and field
width of a particular model, not just on
the magnifying power. A bigger image does
not necessarily mean better visualization.
The best loupes capitalize on the synergy
of resolution and field width.
Other features that
define quality loupes
Field Depth:
This is the range of
focus delivered by the loupe. Longer field
depths allow you to view the entire operating
field, which means less neck and eye strain.
Field depth is dependent on the available
lighting, the optical design, the magnifying
power and the eye’s ability to focus
(accomodation).
Weight:
This really represents
the comfort of the complete frame and loupe
system. The weight of the system has become
an increasingly important feature among
new magnification users. The weight of the
system will increase for higher power, larger
loupes.
Magnifying Power:
This is the size of the
image (not the clarity of the image). Optical
manufacturers do not agree on the definition
of magnifying power. There is no standard
measurement for magnifying power in the
loupe market. Even though specific labels
have been used, most manufacturers actually
round up to the nearest 0.5x.
"There
is no accepted standard for how magnifying
power is defined for surgical loupes.
Different definitions give results
that differ by as much as 15-percent.
Because of this, the quoted magnifying
power is really only a rough guide
to the actual magnification of a loupe.”
John Rogers,
PhD, University of Arizona Director,
Photonic and Imaging Engineering Services
Optical Research Associates* |
Working Angle:
The correct working angle
(angle of declination) allows the user to
work in a comfortable, ergonomically correct
position, thus helping prevent neck and
back pain. Choose a model that delivers
the right working angle for you. Several
flip-up hinge products and through-the-lens
systems can be set to the required ergonomic
working angles.
What really counts
when choosing a loupe?
Superior Visualization.™:
Professionals demand
superior visualization. The visualization
of a loupe system is truthfully governed
by (in order of importance):
1. Resolution
2. Field Width
3. Field Depth
4. Magnification
CONFIRM THIS BY SAMPLING
AND COMPARING
Unfortunately, some loupe
manufacturers are fixated on an old convention
that erroneously identifies magnifying power
as the most important feature. Do not be
misled by this.
“The
resolution and field size of the operating
site are much more relEvant quality
criteria than the size of the image.
Regardless of the stated magnifying
power, a loupe that resolves smaller
features (and more of them) is superior
to a loupe that provides a large but
blurry image. Similarly, this is also
preferable to a loupe that provides
a sharp image, but only over a narrow
region of space.”
John
Rogers, PhD, University of Arizona* |
After your Evaluation,
choose the loupe system that provides outstanding
resolution across the widest field, while
simultaneously delivering a longer depth-of-field,
because it will truly have superior visualization.
*Optical Research
Associates, a leader in the optics industry,
is the largest independent optical engineering
services organization with experience in
the development of high-performance optical
systems for ground, aerial and space-borne
applications.
How to identify
different types of loupes
Historically, loupe makers
have labeled their products by exact power
levels. As previously explained, this is
very inaccurate.
A more realistic approach is to group products,
much like automobile manufacturers group
products (for example: compact, full and
luxury-sized cars). For this reason, we
have adapted a simple system to promote
the professional’s clear understanding
of the choices available:
Class I
Single lens
loupes (flat plane). Refractive power
is measured in diopters (see definition
below). |
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Class II & Class III -
Between 2.0 & 3.25 power magnification
These loupes
are usually a Galilean design (from
the 17th-century astronomer, Galileo
Galilei). |
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Class III*
- Between 3.0 & 3.9 power magnification
Class IV - Between 4.0 & 4.9 power
magnification
Both of these
classes are usually known as prismatic
loupes and are a Keplerian design(from
the 17th-century astronomer, Johannes
Kepler). |
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*Some Class
III loupes are Galilean with narrow field
widths.
Diopters vs. Magnifying Power
The diopter is
a measurement of refractive power and applies
to single corrective lenses. Loupe systems
used by healthcare professionals contain
multiple lenses, so a reference to diopters
describing magnifying power is not appropriate.
Some manufacturers confuse the rule of thumb
that relates diopter value to magnifying
power. This technical area of optics can
be difficult to understand and can be misleading.
A diopter is an optometric unit of measurement
that is equal to the reciprocal of the focal
length of a single lens, measured in meters.**
The diopter value is equivalent to refractive
power (the ability to bend light) and applies
only to single lenses. Loupe systems used
by healthcare professionals contain multiple,
positive and negative, lenses (compound
loupes). Because corrective prescription
lenses may also be employed, the effective
diopter (or refractive) power of a loupe
is not consistently related to its magnifying
power.
** General
Ophthalmology, Twelfth Edition, 1989. Appleton
& Lange, Publisher
Call today to order
your Orascoptic loupes: 1-800-667-9622
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