Podcast
Questions and Answers
In what order does light pass through these structures to reach the retina?
In what order does light pass through these structures to reach the retina?
- Aqueous humor → Cornea → Pupil → Lens → Retina
- Pupil → Cornea → Aqueous humor → Lens → Retina
- Cornea → Aqueous humor → Pupil → Lens → Retina (correct)
- Cornea → Lens → Aqueous humor → Pupil → Retina
The lens of the eye has the highest refractive power.
The lens of the eye has the highest refractive power.
False (B)
In an emmetropic eye, parallel rays from a distant object focus directly on the _______.
In an emmetropic eye, parallel rays from a distant object focus directly on the _______.
retina
Which type of lens is used to correct hyperopia (farsightedness)?
Which type of lens is used to correct hyperopia (farsightedness)?
What type of lens corrects myopia, and where does light focus in relation to the retina in myopic individuals?
What type of lens corrects myopia, and where does light focus in relation to the retina in myopic individuals?
Which of the following describes what happens during accommodation to focus on near objects?
Which of the following describes what happens during accommodation to focus on near objects?
Which part of the nervous system primarily controls accommodation?
Which part of the nervous system primarily controls accommodation?
Match the following pupil constrictions with their corresponding stimuli:
Match the following pupil constrictions with their corresponding stimuli:
Which of the following describes the function of ON-center ganglion cells?
Which of the following describes the function of ON-center ganglion cells?
What visual field defect results from a lesion of the optic chiasm?
What visual field defect results from a lesion of the optic chiasm?
Which of the following sequences correctly describes the path light takes as it enters the eye and travels to the retina?
Which of the following sequences correctly describes the path light takes as it enters the eye and travels to the retina?
The lens of the eye has the highest refractive power compared to other parts of the eye's optical system.
The lens of the eye has the highest refractive power compared to other parts of the eye's optical system.
In an emmetropic eye, where do parallel rays from a distant object converge?
In an emmetropic eye, where do parallel rays from a distant object converge?
Hyperopia, or farsightedness, occurs when parallel rays from a distant object focus ______ the retina and is corrected with converging lenses.
Hyperopia, or farsightedness, occurs when parallel rays from a distant object focus ______ the retina and is corrected with converging lenses.
Which type of lens is used to correct myopia?
Which type of lens is used to correct myopia?
Match the type of pupillary reflex with its cause:
Match the type of pupillary reflex with its cause:
Contraction of the ciliary muscles leads to which of the following?
Contraction of the ciliary muscles leads to which of the following?
Pupil constriction is primarily controlled by the sympathetic nervous system.
Pupil constriction is primarily controlled by the sympathetic nervous system.
What kind of chart is typically used to assess a subject's visual acuity?
What kind of chart is typically used to assess a subject's visual acuity?
What happens to neurotransmitter release from photoreceptors when light strikes them?
What happens to neurotransmitter release from photoreceptors when light strikes them?
What is the correct order of structures that light passes through before reaching the retina?
What is the correct order of structures that light passes through before reaching the retina?
In an emmetropic (normal) eye, where do parallel rays from a distant object focus?
In an emmetropic (normal) eye, where do parallel rays from a distant object focus?
In a hyperopic eye, parallel rays from a distant object focus ______ the retina, and this error is corrected with ______ lenses.
In a hyperopic eye, parallel rays from a distant object focus ______ the retina, and this error is corrected with ______ lenses.
Match the condition with the type of lens used for correction:
Match the condition with the type of lens used for correction:
What is accommodation in the context of the eye's function?
What is accommodation in the context of the eye's function?
The sympathetic nervous system controls accommodation.
The sympathetic nervous system controls accommodation.
Name two types of pupil constriction reflex:
Name two types of pupil constriction reflex:
Pupil constriction is primarily controlled by the ______ nervous system, while pupil dilation is controlled by the ______ nervous system.
Pupil constriction is primarily controlled by the ______ nervous system, while pupil dilation is controlled by the ______ nervous system.
Which layer of the retina do light photons pass through first?
Which layer of the retina do light photons pass through first?
Flashcards
Light path to the retina
Light path to the retina
Cornea → Aqueous humor → Pupil → Lens → Vitreous humor → Retina
Eye's Highest Refractive Power?
Eye's Highest Refractive Power?
The cornea has the highest refractive power.
Focal point in normal eye
Focal point in normal eye
They focus directly on the retina.
Hyperopic eye focus & correction
Hyperopic eye focus & correction
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Myopic eye focus & correction
Myopic eye focus & correction
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Accommodation (eye)
Accommodation (eye)
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Accommodation control
Accommodation control
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Light's path to photoreceptors
Light's path to photoreceptors
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Best visual acuity area
Best visual acuity area
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Retinal nerve impulse path
Retinal nerve impulse path
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Light reflex
Light reflex
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Accommodation reflex
Accommodation reflex
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Psychosensory reflex
Psychosensory reflex
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Rods
Rods
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Cones
Cones
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Magnocellular Pathway (M)
Magnocellular Pathway (M)
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Parvocellular Pathway (P)
Parvocellular Pathway (P)
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Koniocellular Pathway (K)
Koniocellular Pathway (K)
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Center-surround receptive field
Center-surround receptive field
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Glutamate in bipolar cells
Glutamate in bipolar cells
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Rod vs. Cone function
Rod vs. Cone function
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Visual acuity assessment
Visual acuity assessment
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Photons impact on Photoreceptors
Photons impact on Photoreceptors
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ON-center ganglion cells
ON-center ganglion cells
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OFF-center ganglion cells
OFF-center ganglion cells
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Number of visual pigments
Number of visual pigments
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Visual Field Projections
Visual Field Projections
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Bitemporal hemianopia
Bitemporal hemianopia
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Receptive fields in cortex
Receptive fields in cortex
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Study Notes
- Light travels through the cornea, aqueous humor, pupil, lens, and vitreous humor to reach the retina.
- The cornea has the highest refractive power in the eye's optic system.
- In a normal (emmetropic) eye, parallel rays from a distant object focus directly on the retina.
- In a hyperopic eye, parallel rays focus behind the retina.
- This is corrected with convex (converging) lenses.
- In a myopic eye, parallel rays focus in front of the retina.
- This is corrected with concave (diverging) lenses.
- Accommodation is the adjustment of the lens shape to focus on near or distant objects.
- Ciliary muscles contract, thickening the lens to focus on near objects.
- Ciliary muscles relax, flattening the lens to focus on distant objects.
- The parasympathetic nervous system controls accommodation via the oculomotor nerve (CN III).
- Types of pupil constriction include light reflex, accommodation reflex, and psychosensory reflex.
- Light reflex: Pupil constricts in response to bright light.
- Accommodation reflex: Pupil constricts when focusing on near objects.
- Psychosensory reflex: Emotional or cognitive stimuli can cause constriction.
- The parasympathetic nervous system controls pupil constriction (via the oculomotor nerve).
- The sympathetic nervous system controls pupil dilation.
- Light passes through the ganglion cell layer, inner plexiform layer, bipolar cell layer, and outer plexiform layer to reach the photoreceptors.
- The fovea centralis is the area of best visual acuity in the retina.
- It contains only cones (high-density).
- It has no blood vessels to obstruct light, and minimal convergence for sharp and detailed vision.
Characteristics of Photoreceptors
- Rods
- Number: ~120 million
- Light Sensitivity: High (night vision)
- Distribution: Peripheral retina
- Color Sensitivity: None (monochromatic)
- Function: Dim light & motion detection
- Cones
- Number: ~6 million
- Light Sensitivity: Low (day vision)
- Distribution: Concentrated in fovea
- Color Sensitivity: Yes (trichromatic: RGB)
- Function: Color & fine detail vision
- Visual acuity is assessed using a Snellen chart.
- Visual Acuity (VA) = d/D
- d: Distance from the chart
- D: Distance at which normal vision reads the same line
- Light hyperpolarizes the photoreceptor, making the membrane potential more negative.
- Neurotransmitter (glutamate) is released in the dark and reduced upon light stimulation.
- ON bipolar cells are inhibited by glutamate, activated when light reduces glutamate.
- OFF bipolar cells are excited by glutamate, inhibited when glutamate decreases in light.
- Bipolar cells synapse with ganglion cells, generating action potentials.
- ON-center ganglion cells are excited by light in the center, inhibited by light in the surround.
- OFF-center ganglion cells are inhibited by light in the center, excited by light in the surround.
- Contrast and edge detection are enhanced by center-surround arrangement of the receptive field.
- There are four visual pigments in photoreceptors: rhodopsin (rods) and three cone opsins (red, green, and blue light).
- Rods adapt slowly but reach high sensitivity in darkness.
- Cones adapt quickly but have lower sensitivity to low light.
- Ganglion cells transmit impulses via the optic nerve, optic chiasm, optic tract, to the visual cortex.
- The left visual field projects to the right visual cortex and the right visual field projects to the left visual cortex.
- Nasal retinal fibers cross at the optic chiasm; temporal fibers do not.
- A lesion of the optic chiasm results in bitemporal hemianopia (loss of peripheral vision in both eyes).
- Pathways distinguished in the lateral geniculate body include:
- Magnocellular pathway (M): Motion and coarse features.
- Parvocellular pathway (P): Color and fine details.
- Koniocellular pathway (K): Blue-yellow color processing.
Properties Transmitted by M and P Pathways
- M pathway: Motion, luminance, coarse shapes.
- P pathway: Color, fine detail, texture.
- Nerve cells in the visual cortex are arranged in orientation columns and ocular dominance columns.
- Cells respond to edges, lines, and bars of specific orientations.
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Description
This lesson covers the basics of eye anatomy and function, including the path of light, refractive errors like myopia and hyperopia, accommodation and pupillary reflexes. It explains the mechanism of focusing on objects at varying distances.
