CPOA Study Set Exam 2025
Questions and Answers
Levator Palpebrae Superioris - ANSWER✔✔-Action: Retracts/Elevates Eyelid
Origin: Sphenoid Bone
Nerve: Oculomotor Nerve (Cranial Nerve III)
Superior Rectus - ANSWER✔✔-Main Action: Elevation
Contributes To: Adduction, Medial Rotation (Intorsion)
Origin: Annulus of Zinn
Nerve: Oculomotor Nerve (Cranial Nerve III)
Inferior Rectus - ANSWER✔✔-Main Action: Depression
Contributes To: Adduction, Lateral Rotation (Extorsion)
Origin: Annulus of Zinn
Nerve: Oculomotor Nerve (Cranial Nerve III)
,Medial Rectus - ANSWER✔✔-Action: Adduction
Origin: Annulus of Zinn
Nerve: Oculomotor Nerve (Cranial Nerve III)
Lateral Rectus - ANSWER✔✔-Action: Abduction
Origin: Annulus of Zinn
Nerve: Abducens Nerve (Cranial Nerve VI)
Superior Oblique - ANSWER✔✔-Action: Depression, Abduction, Medial Rotation
(Intorsion)
Origin: Sphenoid Bone at the Orbital Apex
Nerve: Trochlear Nerve (Cranial Nerve IV)
Inferior Oblique - ANSWER✔✔-Action: Elevation, Abduction, Lateral Rotation
(Extorsion)
Origin: Orbital Surface of Maxilla
Nerve: Oculomotor Nerve (Cranial Nerve III)
Vertex Distance & Effective Power - ANSWER✔✔-Vertex Distance- Distance Between
Spectacle Lens and the Patient's Cornea.
, Effective Power- Change in Rx when the Distance Varies from the Normally Refracted
13.5mm Distance to where the Patient Wears the Rx.
Gain Minus/Lose Plus --> Closer to the Eye
Lose Minus/Gain Plus <-- Away from the Eye
Decentration - ANSWER✔✔-Frame PD - Patient PD / 2
Eye Size + Distance Between Lenses - Patient PD / 2
Induced Prism - ANSWER✔✔-__________ ________ is seen when a patient looks
through any portion of a lens other than the optical center.
Prism Deviation Formula - ANSWER✔✔-Prism△= Deviation in cm / Light source
distance from the prism — i.e. 1△ deviates parallel rays of light 1cm at a distance of 1m
from the prism; 0.5△ deviates parallel rays of light 1cm at a distance of 2m; 2△ deviates
parallel rays of light 1cm at a distance of 0.5m from the prism.
Focal Length - ANSWER✔✔-Distance Between the Lens and Focal Point
Refractive Index - ANSWER✔✔-Speed of Light in a Vacuum / Speed of Light in a
Specific Substance
Transposition - ANSWER✔✔-1. Combine Sphere and Cylinder Powers
2. Invert Cylinder Sign
Questions and Answers
Levator Palpebrae Superioris - ANSWER✔✔-Action: Retracts/Elevates Eyelid
Origin: Sphenoid Bone
Nerve: Oculomotor Nerve (Cranial Nerve III)
Superior Rectus - ANSWER✔✔-Main Action: Elevation
Contributes To: Adduction, Medial Rotation (Intorsion)
Origin: Annulus of Zinn
Nerve: Oculomotor Nerve (Cranial Nerve III)
Inferior Rectus - ANSWER✔✔-Main Action: Depression
Contributes To: Adduction, Lateral Rotation (Extorsion)
Origin: Annulus of Zinn
Nerve: Oculomotor Nerve (Cranial Nerve III)
,Medial Rectus - ANSWER✔✔-Action: Adduction
Origin: Annulus of Zinn
Nerve: Oculomotor Nerve (Cranial Nerve III)
Lateral Rectus - ANSWER✔✔-Action: Abduction
Origin: Annulus of Zinn
Nerve: Abducens Nerve (Cranial Nerve VI)
Superior Oblique - ANSWER✔✔-Action: Depression, Abduction, Medial Rotation
(Intorsion)
Origin: Sphenoid Bone at the Orbital Apex
Nerve: Trochlear Nerve (Cranial Nerve IV)
Inferior Oblique - ANSWER✔✔-Action: Elevation, Abduction, Lateral Rotation
(Extorsion)
Origin: Orbital Surface of Maxilla
Nerve: Oculomotor Nerve (Cranial Nerve III)
Vertex Distance & Effective Power - ANSWER✔✔-Vertex Distance- Distance Between
Spectacle Lens and the Patient's Cornea.
, Effective Power- Change in Rx when the Distance Varies from the Normally Refracted
13.5mm Distance to where the Patient Wears the Rx.
Gain Minus/Lose Plus --> Closer to the Eye
Lose Minus/Gain Plus <-- Away from the Eye
Decentration - ANSWER✔✔-Frame PD - Patient PD / 2
Eye Size + Distance Between Lenses - Patient PD / 2
Induced Prism - ANSWER✔✔-__________ ________ is seen when a patient looks
through any portion of a lens other than the optical center.
Prism Deviation Formula - ANSWER✔✔-Prism△= Deviation in cm / Light source
distance from the prism — i.e. 1△ deviates parallel rays of light 1cm at a distance of 1m
from the prism; 0.5△ deviates parallel rays of light 1cm at a distance of 2m; 2△ deviates
parallel rays of light 1cm at a distance of 0.5m from the prism.
Focal Length - ANSWER✔✔-Distance Between the Lens and Focal Point
Refractive Index - ANSWER✔✔-Speed of Light in a Vacuum / Speed of Light in a
Specific Substance
Transposition - ANSWER✔✔-1. Combine Sphere and Cylinder Powers
2. Invert Cylinder Sign
