C9- Vision
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Questions and Answers

The density of rods increases sharply in the fovea.

False (B)

The foveola, a region in the retina, is completely devoid of cone photoreceptors.

False (B)

The one-to-one relationship with bipolar cells and retinal ganglion cells in the fovea decreases the capacity for visual acuity.

False (B)

Acuity is increased by 75% at 6 degrees eccentric to the line of sight.

<p>False (B)</p> Signup and view all the answers

Humans move their eyes and heads to direct the peripheral retina to objects of interest.

<p>False (B)</p> Signup and view all the answers

The threshold for detecting light at a lower stimulus is lower in the region of central vision due to high number of rods.

<p>False (B)</p> Signup and view all the answers

In the peripheral portion of the monocular system, it is easy to perceive colours.

<p>False (B)</p> Signup and view all the answers

The ability to perceive a shape and details is based on the ability to perceive contrast of light diffraction.

<p>False (B)</p> Signup and view all the answers

When viewing a distant object, the eyes must converge.

<p>False (B)</p> Signup and view all the answers

The parasympathetic nervous system is responsible for muscle relaxation.

<p>False (B)</p> Signup and view all the answers

Light refracts only once before reaching the retina.

<p>False (B)</p> Signup and view all the answers

Emmetropia is the condition where light focuses behind the retina.

<p>False (B)</p> Signup and view all the answers

Myopia is corrected with a convex lens.

<p>False (B)</p> Signup and view all the answers

Hyperopia causes objects to appear blurry when focusing on near objects.

<p>True (A)</p> Signup and view all the answers

The Snellen eye chart measures curvature of the cornea.

<p>False (B)</p> Signup and view all the answers

Astigmatism affects the entire cornea.

<p>False (B)</p> Signup and view all the answers

A biconcave lens is usually transparent and elastic

<p>False (B)</p> Signup and view all the answers

Cataracts cause incoming light to focus correctly on the retina.

<p>False (B)</p> Signup and view all the answers

The movement of a light wave in a specific direction is referred to as a light ray.

<p>True (A)</p> Signup and view all the answers

The curvature of the cornea is flexible and can be altered by muscles.

<p>False (B)</p> Signup and view all the answers

The aqueous humour is responsible for modulating the curvature of the eye's lens.

<p>False (B)</p> Signup and view all the answers

The bending power of the cornea can be adjusted by the muscles around the eye for near and far vision.

<p>False (B)</p> Signup and view all the answers

During close vision, the amount of light entering the eye increases.

<p>False (B)</p> Signup and view all the answers

Light rays are bent 4 times as they travel through the eye before reaching the photoreceptors.

<p>False (B)</p> Signup and view all the answers

The lens of the eye is responsible for most of the light bending when focusing.

<p>False (B)</p> Signup and view all the answers

The cornea has an accommodation strength of about $73$ dioptres.

<p>False (B)</p> Signup and view all the answers

The main function of the vitreous humour is to bend the light rays as they pass through the eye.

<p>False (B)</p> Signup and view all the answers

The light rays must converge to a precise spot on the retina to create a clear image.

<p>True (A)</p> Signup and view all the answers

Mixing equal intensities of blue, green, and red light results in a white light.

<p>True (A)</p> Signup and view all the answers

Combining different pigments gives a reflective effect with minimal overall absorption of wavelengths.

<p>False (B)</p> Signup and view all the answers

Refraction occurs when light passes from one medium to another of the same density.

<p>False (B)</p> Signup and view all the answers

Distant objects, more than 6 meters away, emit light rays that will arrive at our eyes as divergent.

<p>False (B)</p> Signup and view all the answers

Converging light rays from a close object behind the lens will create focal point farther than parallel rays.

<p>True (A)</p> Signup and view all the answers

In order to focus on objects at close range, the focal point must fall farther from the lens to the retina.

<p>False (B)</p> Signup and view all the answers

The aqueous and vitreous humors contribute significantly to the overall refraction of light in the eye.

<p>False (B)</p> Signup and view all the answers

The lens of the eye is concave shaped.

<p>False (B)</p> Signup and view all the answers

Concave lenses increase convergence, thus shortening the focal distance.

<p>False (B)</p> Signup and view all the answers

Light waves radiate outwards in all directions from every point of a light source.

<p>True (A)</p> Signup and view all the answers

Presbyopia is caused by the stiffness of the lens leading to the inability to focus on far objects.

<p>False (B)</p> Signup and view all the answers

The visual field for a monocular view is wider than that of a binocular view.

<p>False (B)</p> Signup and view all the answers

Diverging rays require a lens that is less curved to focus them onto the retina.

<p>False (B)</p> Signup and view all the answers

The outer layer of the retina acts as a phagocyte and is responsible for storing vitamin C.

<p>False (B)</p> Signup and view all the answers

In response to light, photoreceptor cells in the retina depolarize to activate.

<p>False (B)</p> Signup and view all the answers

Flashcards

Foveola

The central 300µm of the fovea that is completely devoid of rods, responsible for the highest visual acuity.

Fovea

A small, highly specialized region in the center of the macula, measuring about 1.2mm in diameter. It's densely packed with cones and virtually rod-free, responsible for detailed central vision.

Rods

Light-sensitive receptor cells found primarily in the peripheral retina, responsible for vision in low-light conditions.

Cones

Light-sensitive receptor cells mainly located in the fovea, playing a crucial role in color vision and detail perception.

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Saccade

A rapid, involuntary movement of the eyes that helps to direct the fovea towards objects of interest.

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Visual Acuity

The ability to distinguish fine details, typically measured by how closely two points can be spaced and still be perceived as separate.

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Contrast Perception

The ability to perceive differences in brightness or luminance.

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Eccentricity Effect

The decrease in visual acuity as the distance between the fovea and the object of focus increases.

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Path of light through the eye

The path light takes through the eye, bending at different points to focus on the retina.

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Refraction

The bending of light as it passes from one medium to another, like air to the cornea.

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Aqueous Humor

The fluid that fills the space between the cornea and the lens.

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Lens

The transparent, flexible structure behind the cornea that focuses light on the retina.

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Vitreous Humor

The clear gel behind the lens that helps maintain the shape of the eye.

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Accommodation

The process of adjusting the lens to focus on objects at different distances.

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Focal Point

The point where light rays converge after passing through the lens.

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Retina

The innermost layer of the eye, containing photoreceptor cells that convert light into electrical signals.

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Diopters

The measurement of how much a lens bends light.

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Convergence of the eyeballs

The process of the eyes moving inwards to focus on a nearby object.

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Emmetropia

A state where light rays from an object are focused properly on the retina, resulting in clear vision.

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Myopia

Nearsightedness; a condition where light rays from distant objects are focused in front of the retina, resulting in blurry vision for faraway objects.

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Myopia Correction

Corrected with a concave lens, which diverges light rays further to compensate for the eye's inability to focus them correctly.

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Hyperopia

Farsightedness; a condition where light rays from distant objects are focused behind the retina, resulting in blurry vision for close-up objects.

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Hyperopia Correction

Corrected with a convex lens, which converges light rays further to compensate for the eye's inability to focus them correctly.

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Astigmatism

An eye condition characterized by an uneven curvature of the cornea, leading to blurred vision at all distances.

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Astigmatism Correction

Corrected with cylindrical lenses that have different curvatures in different directions to compensate for the unevenness of the cornea.

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Cataract

A clouding of the natural lens of the eye, causing blurry, dimmed vision.

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Cataract Removal

A procedure to remove a cloudy lens and replace it with a clear artificial lens, restoring vision.

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Convex Lens

A converging lens that is thicker in the middle, causing light rays to converge at a focal point.

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Concave Lens

A diverging lens that is thicker at the edges, causing light rays to spread out.

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Focal Length

The distance between a lens and its focal point.

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Eye Lens

The internal, adjustable lens of the eye that focuses light onto the retina.

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Presbyopia

A vision defect where near objects appear blurry due to the loss of elasticity in the eye's lens.

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Diplopia

Double vision caused by misalignment or malfunction in the eye muscles, not refraction problems. Images fail to focus on corresponding points on both retinas.

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Visual Field

The area that the eye can see without moving. The field of view is wider when using both eyes (binocular) compared to one eye (monocular).

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Phototransduction

The process by which light energy is converted into an electrical signal that the brain can understand, allowing us to see. It happens in the photoreceptor cells of the retina.

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Study Notes

Visual System - The Eye

  • The eye is composed of a posterior and anterior cavity, separated by the lens.
  • The anterior cavity is further divided into the anterior chamber, between the cornea and iris, and the posterior chamber, between the iris and the lens. The vitreous chamber is the posterior cavity.
  • Aqueous humor, a fluid, fills the anterior chambers.
  • Vitreous fluid, a gel-like substance, fills the vitreous chamber (posterior cavity).
  • The aqueous humor is produced by capillary networks in the ciliary body.
  • Aqueous humor is crucial to maintain the curvature of the cornea and the anterior chamber.
  • The lens plays a critical role in directing light rays to the retina. The lens is in the posterior cavity.
  • Drainage of the aqueous humor occurs through the scleral venous sinus (canal of Schlemm).

Light Path

  • Light must enter the eye before being detected by receptors.
  • Light passes through the cornea, aqueous humor, lens, vitreous humor, and then hits the retina, which contains the photoreceptor cells.
  • The iris controls the amount of light entering the eye.
  • The shape of the lens changes to adjust to the distance of the object being viewed.
  • Concave and convex lenses are used for correction.
  • The lens has to adjust the focal point to maintain the image on the retina.

Pupillary Light Reflex

  • The pupillary light reflex is the automatic adjustment of pupil size in response to changes in light levels.
  • It's a consensual reflex, meaning a change in light to one eye will result in a change to the other eye.
  • The reflex involves the iris dilating or constricting pupil size based on the light exposure.

Lens Accommodation

  • The lens changes shape to focus light on the retina, depending on if the object viewed is close or far away.
  • The ability to change the lens' shape, a process called accommodation, is critical for allowing the eye to focus on objects at various distances.

Light Refraction

  • Light changes direction (refracts) when it passes from one medium to another with a different density.
  • The cornea and the lens are crucial for refracting light to focus correctly on the retina.

Visible Light

  • Visible light is a narrow range of electromagnetic radiation that humans can see.
  • Visible light has a spectrum of wavelengths, ranging from about 400 to 700 nm.
  • The different wavelengths correspond to different colors.

Homeostatic Imbalances of Refraction

  • Myopia (nearsightedness): light is focused in front of the retina.
  • Hyperopia (farsightedness): light is focused behind the retina.
  • Astigmatism: unequal curvature in the cornea or lens, causing blurred vision.
  • Cataracts: clouding of the lens, reducing transparency.

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PHYSIO C9 – Visual System PDF

Description

Test your knowledge on the intricacies of human vision, focusing on the roles of rods and cones in the retina, visual acuity, and light perception. This quiz explores key concepts such as fovea structure, light refraction, and common visual conditions like myopia. Perfect for students in biology or health sciences.

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