Optics and Vision Science Quiz

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Questions and Answers

What is the wavelength range of visible light?

300-400nm

400-700nm (correct)

700-800nm

800-900nm

What refractive index (RI) value indicates the highest light reflection within the eye?

1.40 (correct)

1.34

1.38

1.33

Which type of lens is required for correcting hyperopia?

Cylindrical lens

Concave lens

Convex lens (correct)

Bifocal lens

In the case of astigmatism, what causes the different focal distances in one plane?

Uneven curvature of the cornea Signup and view all the answers

What is the power of the eye if it is considered a single lens?

+59D Signup and view all the answers

What is not a common cause of myopia?

Short eyeball Signup and view all the answers

What happens to the image when accommodation fails?

The image appears blurred Signup and view all the answers

What correction is typically recommended for keratoconus?

Contact lenses Signup and view all the answers

What protein is associated with rhodopsin in the process of phototransduction?

Scotopsin Signup and view all the answers

During which stage of phototransduction does metarhodopsin II stimulate phosphodiesterase?

Stage II Signup and view all the answers

What happens to sodium channels during the light phase of phototransduction?

They close Signup and view all the answers

Which of the following statements is true about rod cells compared to cone cells?

Rods are more sensitive to light than cones. Signup and view all the answers

What characterizes the ability of cones in terms of adaptation to darkness?

Cones adapt rapidly to darkness. Signup and view all the answers

Which type of pigment is responsible for the red color in human vision?

Photopsin Signup and view all the answers

What is primarily responsible for the perception of movement in light?

Amacrine cells Signup and view all the answers

In the dark, what is the state of the photoreceptor's permeability to sodium?

Highly permeable Signup and view all the answers

What is the primary function of the aqueous humor?

To maintain intra-ocular pressure Signup and view all the answers

Which of the following cells is NOT a type of cell found in the retina?

Mueller cells Signup and view all the answers

What is the typical mean intra-ocular pressure (IOP) value in mmHg?

15 mmHg Signup and view all the answers

What is the pathway for aqueous humor drainage after leaving the anterior chamber?

Anterior chamber -> Pupil -> Schlemm canal Signup and view all the answers

What change occurs in the lens when the ciliary muscles contract during accommodation?

The lens becomes more convex and spherical. Signup and view all the answers

Which of the following structures provides blood supply to the outer third of the retina?

Choroid layer Signup and view all the answers

Which anatomical structure is responsible for initiating the accommodation reflex?

Edinger-Westphal nucleus Signup and view all the answers

What is the role of horizontal cells in the retina?

To inhibit signals from photoreceptors Signup and view all the answers

What is the effect of aging on the power of accommodation in the eye?

It decreases due to lens hardening and decreased elasticity. Signup and view all the answers

What contributes to the high visual acuity of the fovea?

Higher density of cones and absence of blood vessels Signup and view all the answers

What is the maximum amount of light that can enter the eye when the pupil is fully dilated?

64 Signup and view all the answers

Increased intra-ocular pressure can lead to which common eye condition?

Glaucoma Signup and view all the answers

Which nerve fibers are responsible for pupil constriction?

Parasympathetic nervous system fibers Signup and view all the answers

What is the relationship between pupil diameter and the amount of light entering the eye?

The amount of light is proportional to the square of the diameter. Signup and view all the answers

What is true about the refractive power of the lens when there is no accommodation?

The lens is flat and has a refractive power of +20 diopters. Signup and view all the answers

What causes the release of tension in the suspensory ligaments during accommodation?

Contraction of the ciliary muscles. Signup and view all the answers

What is the initial change that occurs to rhodopsin when exposed to light?

It activates and decomposes into protein and all-trans-retinal. Signup and view all the answers

How long does it take for the cones to fully adapt to darkness?

10 minutes Signup and view all the answers

Which vitamin is essential for the recycling of 11-cis-retinal in the photoreceptor cells?

Vitamin A Signup and view all the answers

What is the consequence of vitamin A deficiency in relation to vision?

Night blindness and degeneration of retinal layers Signup and view all the answers

What mechanism occurs when the retina adapts to light?

Decrease in vitamin A concentration Signup and view all the answers

How are rods affected compared to cones in dark adaptation?

Rods adapt for a longer time than cones. Signup and view all the answers

Which type of ganglion cells constitutes the majority in the retina?

W ganglion cells Signup and view all the answers

What is the primary substance produced by converting all-trans-retinol in the photoreceptors?

11-cis-retinal Signup and view all the answers

Study Notes

Physiology of Vision

Light: Electromagnetic radiation, wavelengths range from 400-700nm (visible light), ultraviolet (<400nm) and infrared (>700nm)
Light travels at 300,000km/sec in a vacuum. Speed changes when passing through different mediums.
Refractive Index (RI): RI = speed of light in air / speed of light in medium.
- Cornea RI = 1.38
- Aqueous humor RI = 1.33
- Vitreous humor RI = 1.34
- Lens RI = 1.4
Most refraction in the eye occurs at the cornea-air interface.
Convex lenses converge light rays, focusing at a single point.
Concave lenses diverge light rays.
Power of a lens is measured in diopters (1/focal length in meters). Convex lenses have positive diopters, concave lenses have negative.
A single-lens eye has a refractive power of +59D.

Refractive Errors of the Eye

Myopia (Nearsightedness): Image of distant objects focuses in front of the retina, caused by a long eyeball or a strong lens. Corrected with concave lenses.
Hyperopia (Farsightedness): Image of near objects focuses behind the retina, caused by a short eyeball or a weak lens. Corrected with convex lenses.
Astigmatism: Uneven curvature of the cornea causes the image to be focused at different distances in different planes. Corrected using cylindrical lenses.
Keratoconus: Bulging of the cornea causes the image not to focus correctly on the retina, corrected with contact lenses.

Accommodation

Process by which the eye changes its refractive power to focus on objects at different distances.
Ciliary muscles contract, relaxing suspensory ligaments, allowing lens to thicken (more convex) and increasing refractive power.
Maximum refractive power is +34D in young individuals and +20D in relaxed state.
Accommodation process is a reflex action: The process is triggered by blurred images on the retina. Stimulation of PSNS fibers contraction of ciliary muscles & change in the lens shape. Edinger-Westphal nucleus plays a critical role in triggering this response.
The stimulus is a blurred image of near objects on the retina. Sensory information travels through the optic nerve (CN II) and motor response is sent through the oculomotor nerve (CN III) by activating the Edinger-Westphal nucleus to stimulate ciliary muscles.

Presbyopia

Reduction in the ability to accommodate (focus on near objects) with aging due to decreased lens elasticity.

Pupil

Opening in the iris that controls the amount of light entering the eye.
Size ranges from 1.5mm (constricted) to 8mm (dilated).
Pupil diameter is proportional to light intensity. Large pupils allow more light; small pupils reduce light.
Pupil constriction (miosis): Occurs in bright light, stimulated by parasympathetic (PSNS) fibers.
Pupil dilation (mydriasis): Occurs in dim light, stimulated by sympathetic (SNS) fibers.

Aqueous Humor

Fluid in the anterior and posterior chambers of the eye.
Produced by ciliary processes.
Maintains intraocular pressure (IOP).
Drains into Schlemm's canal, then general circulation.

Retina

Neural tissue lining the back of the eye.
Contains photoreceptors (rods and cones) for light detection, and other neurons for processing signals.
Inner two thirds of the retina is supplied by the central retinal artery; outer one third by choroid layer (diffusion).
Fovea: Area of highest visual acuity, Contains only cones.

Phototransduction

Process of converting light energy into neural signals in the retina.
Stage 1: Light activates rhodopsin (11-cis-retinal and protein).
Stage 2: Activated rhodopsin activates phosphodiesterase, decreasing cGMP levels.
Stage 3: Sodium channels close, resulting in hyperpolarization leading to inhibition of neurotransmitter release.
Dark: Sodium permeable; constantly depolarized, high release of inhibitory neurotransmitters.
Light: Low permeability to sodium; hyperpolarized; low/absent release of neurotransmitters.

Vitamin A

Essential: Part of rhodopsin; converted into 11-cis-retinal, which is recycled, enabling rod function and preventing vitamin A deficiency (night blindness and retinal degeneration).
Lipid-soluble: cannot be produced in the body and must be obtained through the diet or supplements; Stored in the liver.

Visual Pathway

Visual fields: Temporal and nasal visual fields.
Optic nerve: Carries visual signals from retina to the brain.
Optic chiasm: Point where nasal fibers decussate; temporal fibers do not.
Optic tract: carries signals to the lateral geniculate body (LGN).
Optic radiation: Carries signals from the LGN to the visual cortex.
Visual cortex: Processes visual information, located in the occipital lobe.

Visual Field Defects

Bitemporal hemianopia: Damage to the optic chiasm.
Homonymous hemianopia: Damage to the optic tract or optic radiation.

Visual Pathway (Optic Nerve, LGB, Optic Tract, Optic Radiation)

Primary visual pathway: nerve transmits signals from retina to Lateral Geniculate Body (LGN) through the optic chiasm; then to optic radiations to the Visual Cortex.
LGN: relays information from retina to the visual cortex of the brain, contains 6 layers of cells, magnocellular (1, 2); parvocellular (3-6) layers.
The primary visual cortex (PVC) located on the calcarine fissure of the occipital lobe receives signals from both eyes.
Colored visual information and acute visual information are processed by parvocellular and magnocellular layers of the LGB

Visual Streams

Dorsal stream ("Where" stream): Processes information about motion, depth, and spatial location.
Ventral stream ("What" stream): Processes information about object recognition, color, etc.

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Description

Test your understanding of optics and the human visual system with this quiz. Explore topics including wavelength of visible light, refractive indices, lens types, and phototransduction processes. Ideal for students in the field of vision science or medical optics.