Optics Notes Flashcards
Real Object, definition
- emits diverging light
- object distance is negative
- object vergence is negative
Real Image, definition
- When converging light leaves a refracting surface.
- image distance is positive
- image vergence is positive
Virtual object; definition
- when converging light is incident on a surface
- object distance is positive
- object vergence is positive
Virtual Image; definition
- when diverging light leaves a refracting surface
- image distance is negative
- image distance is negative
Lens Clock
Describe what the red and black scale indicate.
The pointer shows your focal power
Red scale: concave surface = minus power
Black scale: convex surface = plus power
Chief rays pass through the ______ _______
Optical center
What are the rules for light rays in refraction?
- A focal ray becomes ________
- A parallel ray becomes ________
- A chief ray is ______ _________.
Focal ray becomes a parallel ray.
Parallel ray becomes a focal ray.
A chief ray is not deviated.
Positive power lens; definition
- secondary focal length is positive
- primary focal length is negative
Negative power lens; definition
- secondary focal length is negative
- primary focal length is positive
Where do oligodendrocytes provide myelination to the axons?
Posterior to the laminar cribrosa
Which cells are found in the PNS, providing myelination?
Schwann cells are found in the PNS, not in the optic nerve.
What is the circle of zinn formed by?
Formed by anastomoses of the SPCAs
Define intraocular optic nerve
Pre-laminar and laminar layers; supplied by the circle of zinn and other branches of the SPCAs
Define intraorbital optic nerve
Post laminar area; supplied by branches from the central retinal artery and the pial mater arterial plexus
Intra-cranial optic nerve
Supplied by branches of the ophthalmic, anterior cerebral, anterior communicating, and internal carotid arteries.
Which glial tissues separates the pre-laminar optic nerve fibers from the choroid?
The border tissue of Jacoby. A continuation of the glial tissue known as the intermediary tissue of Khunt.
Tight junctions within the glial tissue help protect the optic nerve fibers from fluid that leaks from the fenestrated choroidal vessels.
Superior colliculus
Aid in saccadic eye movement.
Pretectal nucleus
Aids in pupil movement.
Define anterior knees of Wilbrand
Inferior nasal fibers that cross through the optic chiasm and then loop anteriorly into the contralateral optic nerve before entering the optic tract.
Posterior knees of wilbrand
Superior nasal fibers that loop posteriorly into the ipsilateral optic tract before crossing through the optic chiasm.
Optic chiasm location
Located within the circle of Willis. The internal carotid artery and posterior communicating arteries travel along the lateral edges of the optic chiasm. The pituitary gland is located to the optic chiasm.
Where do macular fibers travel?
The middle of the optic tract.
LGN: magnocellular layers
Layers 1 & 2. Located inferiorly. Contains large magno cells.
LGN: parvocellular layer
Layers 3 to 6. Extended superiorly that contain medium parvo cells.
Koniocellular layers
Contain small cells located between each layer.
Where do crossed fibers of the optic tract synapse?
LGN layers 1, 4, 6
Where do uncrossed fibers of the optic tract synapse?
LGN layers 2, 3, 5
Define optic radiations
Fibers that leave the LGN and travel to the primary visual cortex. V1
Inferior radiations go to the temporal lobe. Superior radiations go to the parietal lobe.
What are other names for the primary visual cortex and where is it located?
Aka V1, brodmann’s area 17, striate cortex.
On the medial surface of the occipital lobe.
Define calcarine fissure
Divides the internal posterior position of the occipital lobe into anterior and posterior sections.
Define cuneus gyrus
The superior portion of the visual cortex in the occipital lobe. Superior fibers terminate here. Also superior macular fibers.
Lingual gyrus. Define.
The inferior portion of V1 in the occipital lobe. Inferior retinal fibers terminate here. Inferior macular fibers as well.
Optic chiasm, blood supply
Supplied by Circle of Willis and branches of the internal carotid artery.
Optic tracts, blood supply.
Supplied by the anterior choroidal branch of the middle cerebral artery.
LGN, blood supply
Supplied by the anterior choroidal and posterior cerebral arteries.
Optic radiations, blood supply.
Supplied by the anterior choroidal, middle cerebral, and posterior cerebral arteries.
Primary visual cortex, blood supply.
Supplied by the posterior cerebral artery and the middle cerebral artery. This gives a dual blood supply.
Post-chiasmal lesion.
Produces homonymous visual field defects (same side). The more posterior a post chiasmal lesion is located, the more congruous the visual field defects are between the eyes.
Example: right lesion = left visual field defect of both eyes.
Temporal lobe lesion.
Temporal lesions cause superior visual field defects. “Pie in the sky.” This is because lesions in the temporal lobe damages the inferior retinal fibers forming Meyers Loop.
Parietal lobe lesions.
Cause inferior visual field defects. “Pie on the floor.” Lesion in the parietal lobe damages the superior retinal fibers (and associated with the asymmetric OKN response).
