2 Eye and the Retina Flashcards
Q: What is light in terms of physical properties?
A: Light is a form of electromagnetic energy characterized by wavelength (distance from peak to peak) and intensity/amplitude (distance from peak to trough).
Q: What are the psychological aspects of light?
A: The psychological aspects of light are color and brightness.
Q: How is light involved in vision?
A: Light is reflected from objects and enters the eye.
Q: What is the main function of the eye in the process of vision?
A: The main function of the eye is to focus the image on the retina.
Q: What are the roles of the iris and pupil in the eye?
A: The iris and pupil form an adjustable aperture that limits the amount of light passing through, allowing us to handle a wide range of light levels.
Q: How does the pupil adjust to different light levels?
A: The pupil can adjust its diameter between 2mm and 9mm to regulate the amount of light entering the eye.
Q: What is the role of the cornea in vision?
A: The cornea provides 80% of the eye’s focusing power by focusing light on the retina.
Q: How does the lens contribute to focusing light?
A: The lens contributes 20% of the eye’s focusing power and can change shape due to the action of ciliary muscles, becoming fatter to focus on close objects and thinner to focus on distant objects.
Q: What is myopia and how is it corrected?
A: Myopia, or nearsightedness, occurs when light is focused in front of the retina. It is corrected with concave lenses.
Q: What is hyperopia and how is it corrected?
A: Hyperopia, or farsightedness, occurs when light is focused behind the retina. It is corrected with convex lenses.
Q: What is the retina?
A: The retina is the light-sensitive layer at the back of the eye.
Q: What are photoreceptors?
A: Photoreceptors are light-sensitive cells in the retina that carry out transduction by reacting to light with visual photopigments, triggering electrical signals.
Q: What are the two types of photoreceptors?
A: The two types of photoreceptors are rods and cones.
Q: How do rods and cones differ in number?
A: There are more rods than cones in the retina.
Q: How do rods and cones differ in sensitivity?
A: Rods are very sensitive and respond well in dim light, making them most useful at night. Cones are less sensitive and work best in daylight.
Q: How are rods and cones involved in color perception?
A: Rods do not contribute to color perception, while cones are responsible for detecting color.
Q: What is the retinal distribution of rods and cones?
A: Rods are more numerous and are distributed mostly around the periphery of the retina, while cones are concentrated in the fovea, the central part of the retina.
Q: How do rods and cones differ in neural convergence and acuity?
A: Rods exhibit high neural convergence, leading to lower acuity, whereas cones have low neural convergence, resulting in higher acuity.
Q: What are the three types of vision based on photoreceptor activity?
A: Scotopic (only rods active), photopic (only cones active), and mesopic (both rods and cones active).
Q: What happens to photopigments in bright light?
A: Bright light bleaches photopigments, causing photoreceptors to stop responding temporarily.
Q: What is dark adaptation?
A: Dark adaptation is the process by which the eyes increase sensitivity in the dark, with sensitivity increasing up to 100,000 times after about 20 minutes.
Q: What happens to photoreceptors when moving from bright to dark environments?
A: Photoreceptors must recover and regain their sensitivity when moving from bright to dark environments.
Q: Which photoreceptors are responsible for color vision?
A: Cones are responsible for color vision.
Q: What types of cones are there and what wavelengths do they respond to?
A: There are red, green, and blue-sensitive cones that respond to different wavelengths of light.
Q: What type of vision do rods provide?
A: Rods provide monochromatic (black and white) vision.
Q: To which wavelengths are rods most sensitive?
A: Rods are most sensitive to medium wavelengths.
Q: What is the Purkinje shift?
A: The Purkinje shift is the phenomenon where, at night, red objects appear darker than green objects.
Q: How are cones and rods distributed in the retina?
A: Cones are concentrated in the fovea, the small central area of the retina, while rods are more numerous and distributed around the periphery.
Q: What is the fovea?
A: The fovea is a small central area of the retina that contains only cones and is responsible for sharp central vision.
Q: What happens to the image of an object when looking directly at it?
A: The image falls on the fovea when looking directly at an object.
Q: What is the blind spot in the retina?
A: The blind spot is an area with no photoreceptors where the optic nerve exits the eye.
Q: Why don’t we perceive a blind spot in our vision?
A: There is no perceived blind spot because it is located in different places in each eye, and the brain fills in the missing information.
Q: What is neural convergence?
A: Neural convergence is when one neuron receives signals from many other neurons.
Q: What is the ratio of rods to ganglion cells?
A: There are 120 rods for every 1 ganglion cell.
Q: What is the ratio of cones to ganglion cells?
A: There are 6 cones for every 1 ganglion cell.
Q: How does neural convergence affect visual acuity?
A: Higher neural convergence (as in rods) leads to lower acuity because the ganglion cell averages information from a larger area. Lower neural convergence (as in cones) results in higher acuity.
Q: What is visual acuity?
A: Visual acuity is the ability to detect fine details of a stimulus.
Q: Where is visual acuity the highest?
A: Visual acuity is highest at the fovea.
Q: How do eye movements contribute to acuity?
A: Eye movements ensure that objects of interest are imaged on the fovea, where acuity is highest.
Q: How does lighting affect acuity?
A: Acuity decreases in low lighting conditions.
