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Because machines can’t do everything and because
sometimes machines malfunction, this is a test of your
optical knowledge.
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OCULAR ANATOMY
Why do we need to know this stuff? Because we all
(Opticians, Optometrists and Ophthalmologists) need to speak
and understand the same technical language. Our patients
assume that we already do.
1. The eye is made up of three layers. They are the:
A. Sclera, Choroid and Retina
B. Fibrous tunic, Vascular tunic and Nervous tunic
C. Iris, Choroid and Retina
D. Cornea, Iris and Retina
2. The term for the refractive condition where light
comes to a focus directly on the retina is:
A. Hyperopia
B. Myopia
C. Emmetropia
D. Astigmatism
3. The term for the refractive condition where light
comes to a focus behind the retina is:
A. Hyperopia
B. Myopia
C. Emmetropia
D. Astigmatism
4. The term for the refractive condition where light
comes to a focus in front of the retina is:
A. Hyperopia
B. Myopia
C. Emmetropia
D. Astigmatism
5. The term for the refractive condition where light
comes to a focus on 2 different points is:
A. Hyperopia
B. Myopia
C. Emmetropia
D. Astigmatism
6. When the eye has a tendency to turn from its normal
position, it is called:
A. Tropia
B. Exotropia
C. Phoria
D. Exophoria
7. When the eye has a definite or obvious turning from
its normal position, it is called:
A. Tropia
B. Exotropia
C. Phoria
D. Exophoria
8. Phorias and tropias are further defined by their
direction of movement; outward, inward, downward and upward.
Place them in the proper order:
A. Eso, exo, hypo, hyper
B. Exo, eso, hyper, hypo
C. Hypo, hyper, exo, eso
D. Exo, eso, hypo, hyper
9. The index of refraction of the cornea is:
A. 1.33
B. 1.37
C. 1.49
D. 1.58
10. Accommodation is defined as:
A. Light rays entering the eye
B. The act of the crystalline lens changing its shape to
focus for objects at varying distances
C. The refracting power of the cornea
D. A reduction of visual acuity with no apparent cause
BASIC OPTICAL PRINCIPLES
The title says it all. This is the foundation for
everything we do to create the best lens designs for our
patients. Formulae you should know include:
Focal length Formula: D= 1/F where D=Diopter and F=Focal
length in meters.
Prentice’s Law: P=dD/10 where P=Prism power in diopters,
d=distance from the optical center in millimeters and D=the
dioptric power of the lens.
1. Using Prentice’s Law, a -4.00 lens must be
decentered ____ to induce 1.00 prism diopter.
A. 1.0mm
B. 2.5mm
C. 10mm
D. 2.0mm
2. When the direction of light changes as it passes from
one medium to another, it is called:
A. Reflection
B. Refraction
C. Diffusion
D. Retraction
3. The focal length of a +2.00 diopter lens is:
A. +2 cm
B. +5 cm
C. +50 cm
D. +2 meters
4. A +3.00 diopter lens has the following prismatic
effect 8 mm below the optical center:
A. 2.4 base up
B. 2.4 base down
C. 2.4 base out
D. 2.4 base in
5. A +5.00 diopter lens decentered 2 mm creates ____diopters
of prism.
A. 0.10
B. 0.25
C. 2.50
D. 1.00
LENS MATERIALS
This is the meat and potatoes of good dispensing. As eye
care professionals, we have never had the variety of
materials we now enjoy. Our patients have never had so many
choices to make. Knowing what to advise will make the
difference between “just new glasses” and “look at my
new glasses!" You need to know:
Refractive Index: The refractive index of a lens material
indicates how much the chosen material will bend (refract)
light as it enters the material from air. The higher the
index of refraction, the more light will refract. The
greater the ability to refract light, the less curve is
needed to produce a specific power.
Specific Gravity: It is the density of a lens material in
comparison to the density of water. The higher the specific
gravity, the denser and heavier the lens material.
Abbe Value: Light passing through a prism is bent towards
its base and has a tendency to break into its varying
wavelengths, called chromatic aberration. This separation is
measured by its Abbe value and it is inversely proportional
to the chromatic aberration. So, the higher the Abbe value,
the lower the chromatic aberration, or the higher the
Refractive index of a lens material, the lower the Abbe
value.
Yes, this was only a test and a fairly easy one at that.
However, the principles are the foundation of what we must
know as ECPs. We use them every day, often without thinking
about it. Lens manufacturers throw facts and figures at us
like specific gravity and Abbe value, so it’s critical
that we know what those numbers mean. A little education is
a dangerous thing and can get us into hot water with our
patients. Continuing education is absolutely necessary in
our ever-expanding industry.
ANSWERS: OCULAR ANATOMY: 1-B, 2-C, 3-A, 4-B, 5-D, 6-C,
7-A, 8-D, 9-B, 10-B
BASIC OPTICAL PRINCIPLES: 1-B, 2-B, 3-C, 4-A, 5-D
