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# Intro to Opt Test #3

### Planes, Axes, Angles, Frames, Boxing System, PD

What is Listing's Plane? The plane of the front of the face (as if it were flat) from the browline to the chin.
what is Olsho's Plane? Plane of the front of the bony orbit of the eye.
What size angle does the Olsho's plane form to the Listing's plane? 10 - 15 degrees
The front of the frame should be approximate to the angle of...? Olsho's Plane
What is Olsho's Base Line? A imaginary line through the outer canthi.
What is the canthi? Where the top and bottom eyelids come together
What is the fixation triangle? Triangle formed by Olsho's Base Line and the visual axes of the eyes.
Are the X, Y, and Z axes physical or visual axes? Physical
The X, Y, and Z axes all run through the...? center of rotation of the eye
What is the center of rotation of the eye? Imaginary point in the center of the eye about which the eye rotates.
The X axis is also known as the...? horizontal axis
When the eye rotates on the X axis it looks ____ or ____? up or down
The X axis creates and angle of _________? altitude
The Y axis is also known as the...? vertical axis
When the eye rotates on the Y axis it looks ___ or ___? in or out
The Y axis creates an angle of _______? azimuth
The Z axis is also known as the...? fixation axis
The Z axis is _____________ to the X and Y axes? perpendicular
Is the rotation on the Z axis free or limited? Limited
Rotation on the Z axis is referred to as ...? torsion
Is rotation on the X and Y axes voluntary or involuntary? voluntary
Is rotation on the Z axis voluntary or involuntary? involuntary
What are the two circumstances for rotation on the Z axis? 1) if you tilt your head; 2) eye moves to tertiary position
What is the primary position? Looking straight ahead off into infinity
What is the secondary position? Eye moves to secondary position when it rotates on either the X or Y axis (not both).
A movement to the secondary position is called a ________ movement? Cardinal
What is tertiary position? When the eye rotates on both X and Y axis simultaneously; when the eye moves obliquely from the primary position.
What is the Optic Axis? Straight line through the pole of the cornea, center of the pupil, and posterior pole of the globe.
OP is what axis? Optical axis
What is the optical axis also known as? Principal axis
What is the visual axis known as? Line of sight
What is the visual axis? Axis from the macula through the nodal point to the fixation point.
FM is which axis? Visual axis
Where is the macula located compared to the posterior pole of the globe? 1.25 mm out and down (mostly out)
What is the nodal point? Point on the visual axis approximately 7.08 mm behind the pole of the cornea, on the optic axis.
What is the fixation axis? Line from the center of rotation to the fixation point.
FC is which axis? Fixation
Where is the center of rotation? Approximately 13.25 mm behind the pole of the cornea on the optical axis.
What is a fixation point? Point upon which you fix your vision; point you are looking at
What is angle alpha? Angle between the optic and visual axes
What is angle gamma? Angle between the optic and fixation axes.
Average size of angle alpha is about..? 5 degrees
The difference between angle alpha and angle gamma is so small that we use the terms __________ and ___________ interchangeably? visual axis and fixation axis
What is the frame eyewire? Part of the glasses that holds the lenses in place.
What is the end piece? Where the temple attaches to the frame front.
What is the part of the frame that sits on the patients nose? Nose pad
What part of the frame that goes between the two eyewires across the bridge of your nose? The bridge
What is the part of the temple that butts up against the frame front? Butt end
What is the part of the temple that runs from the butt end to the bend? The shaft or shank
Who invented the boxing system? Tom Lynch in 1962
What organization adopted the boxing system as the standard way to measure frames? Optical Manufacture's Association (OMA)
In the frame size 50-18-140, what does the 50 represent? Eye Size, known as A, which is the horizontal width of the lens at it's widest point.
In the frame size 50-18-140, what does the 18 represent? Bridge size, or the distance between lenses (DBL)
In the frame size 50-18-140, what does the 140 represent? The temple lengthH
What does B represent in the boxing system? The vertical dimension of the lens
What does GC stand for in the boxing system? Geometric center of the frame eyewire
How is the geometric center found? By drawing an X in the box created by the boxing system. The point in the center of the X is the geometric center.
What is the datum line? A horizontal line through the center of the geometric center, an important reference line when measuring frames.
What is the DBC? Distance between geometric centers; also known as the frame PD.
How do you find the DBC? DBC=A + DBL
What is ED? Effective diameter - two times the longest radius of the frame eyewire
How is the ED found? It must be looked up in the frame catalog
What is special about an ED in a perfectly round frame. ED = A
What is the formula for ED? ED = A + EDX, where EDX is the the ED extension
What is the frame difference? The difference between the A and B dimensions.
The greater the frame difference....? the more rectangular the boxing system box is
What is PD? Pupilary Distance; the distance between pupil centers
What are other ways PD is seen? IPD - Interpupilary distance; IOD - Interocular Distance
What is a binocular PD? The PD between two eyes
What is NPD? Near PD; PD when eyes are in a reading position
What is DPD? Distance PD: PD when eyes are in the primary position
What is decentration (noun)? The spacial relationship between the geometric center of the frame eyewire and the optical center of the lens.
Decentration always has two components, what are they? 1)Distance; 2)Direction
Is decentration described for both eyes or per each eye individually? Always per eye
What is decentration (verb)? To move the optical center of the lens away from the geometric center of the eyewire to place it in the middle of the patient's pupil (or on the patient's visual axis).
Created by: griffiskr