6 Axes And Angles

Question 1

What is the axis containing the center of curvature of the eye’s optical surfaces? It’s a straight line along which a ray both enters and leaves the system. It’s required for rotationally symmetric optical systems.

What’s the line that connects the fovea and the fixation point passing through nodal points? Also called “______ achromatic axis” as rays experience transverse chromatic aberration (TCA).

The place of intersection of of visual axis w/cornea is known as ‘_______________ pole’. It’s used to locate exact position of cornea and is not influenced by _____ fluctuations or accommodation.

Answer 1

Optical axis

Visual axis. Foveal.

Ophthalmometric pole. Pupil

Question 2

What’s the line normal to the cornea passing through the center of the pupil? Used for aligning optical instruments to the eye.

It’s used as an objective measure to judge the amount of _________ fixation. What is this fixation?

What’s a ray from fixation point that reaches the foveolar via center of the pupil?
The line of _______ is the path of foveal chief ray from fixation point. It’s also referred to as the ‘__________ pupil ray’.
When it intercepts the cornea it’s called the ‘________ __________ center’

Answer 2

Pupillary axis.

Eccentric. Is an adaptation to heterotropia (squint or turned eye)

Line of sight (LoS)
Sight. Paraxial
Corneal sighting center

Question 3

What is the line connecting the nodal point and the center of the pupil? Also called the foveal _____________ axis.

Light passing through this axis doesn’t suffer from any __________ ________ aberration. DEPENDS ON PUPIL POSITION

What’s the line passing through the fixation point and the center-of-rotation of the eye? Reference for measuring eye movements.

Answer 3

Achromatic axis

Transverse chromatic

Fixation axis

Question 4

What’s the line passing through the fixation point and the center of curvature of anterior cornea? Used for alignment in corneal topography measurements. Where the axis intercepts the cornea is called the ________ normal. Which is the center shown on videokeratographs

On what axis do we find that humans are more sensitive to light passing through the section of the pupil that’s coaxial with the receptor axis?

Answer 4

Keratometric axis. Vertex

Photoreceptor axis

Question 5

What axis is used to sample the eye’s optical image by using receptors and neurons. It peaks at the foveola and declines with increasing eccentricity

Answer 5

Neural axis

Question 6

What’s the angle between the optical and visual axis? It’s formed at the first nodal point of the eye. Is usually +3 to +5 and RARELY negative.

What’s the angle between the pupillary axis and LoS? Formed at the first nodal point by optical and visual axis of eye. Is temporal in object space and has a ________ angle. Important for diagnosis of ________ fixation and heterotropia.

What’s the angle between the pupillary axis and visual axis? Practically the same as angle?

Answer 6

Angle alpha

Angle lambda. Positive. Eccentric. Used for mono and binocular testing.

Angle kappa. Basically same as angle Lambda for practical purposes

Question 7

What’s the angle between the visual axis and achromatic axis? Both of the angles pass through nodal points. A _______ sign indicates that visual axis is inclined nasally the the achromatic axis in ______ space

What’s the angle between the optical axis and the fixation axis? It’s within 1 percent of angle alpha for object distances greater than __cm.

Answer 7

Angle Psi. Positive. Object

Angle gamma
50