EXERCISE NO. 5 (C and D) Flashcards
The minimum distance that an object can be comfortably held in focus
Near Point
The capability of the eye to focus is due to the elasticity of the lens and the pliability of the lens decreases with _____-.
age
Average Near Point accommodation:
- 20 yrs
- 30 yrs
- 40 yrs
- 50 yrs
- 60 yrs
- 20 yrs - 3.5 in
- 30 yrs - 4.5 in
- 40 yrs - 6.75 in
- 50 yrs - 20.5 in
- 60 yrs - 33 in
refers to the clarity or sharpness of vision, specifically the ability to discern details of objects at a given distance
visual acuity
a widely used tool to assess visual acuity. It consists of rows of letters, and as you move down the chart, the letters become smaller.
Snellen Chart
normal vision in Snellen Test
20/20
at 20 feet, you can see the same details with what most people can see at the same distance
The ability to read these letter indicates that there are no aberrations of the ________ to interfere with the angle of light reaching the retina of the eye.
lens or cornea
interpret the vision 20/15
you can see at 20 feet what most people can see at 15 feet
what level of vision is the fighter pilot minimum and is required to read the stock quotes in the newspaper or numbers in the telephone book
20/20
what level of vision allows you to be able to pass Driver’s License Test in all 50 states. Most printed material is at this level.
20/40
what level of vision is when you are able to read alarm clock at 10 feet and the news headlines are this size
20/80
what level of vision is the legal blindness where you are able to see STOP sign letters
20/200
refer to the automatic, involuntary responses of
the pupils to changes in light and focusing distances
Pupillary reflexes
A reflex that involves the constriction of the pupils when the eyes shift focus from a distant object to a near object.
- When you look at something up close, the pupils constrict to increase the depth of field and enhance the clarity of close-up vision.
Pupillary Near Reflex (PNR)
A reflex that involves the constriction or dilation of the pupils in response to changes in light intensity.
- In bright light, the pupils constrict to limit the amount of light entering the eyes and protect the sensitive cells of the retina. In dim light, the pupils dilate to allow more light to enter and improve visibility in low-light conditions.
Pupillary Light Reflex (PLR)
To adapt to different distances and varying light conditions, the lens changes its shape through a process called _________. In bright light, the lens tends to flatten, and in dim light, it thickens.
accommodation
When the eyes change their focus from a distant object to a nearer one: (3)
- The eye muscles react to achieve convergence of the eyes.
- The lens becomes more convex.
- A change occurs on the size of the pupil.
Do the pupils remain the same size when looking at the printed page?
No.
ciliary muscles contract to change the shape of the lens, making it more convex (accommodation)
In summary, during a shift from a distant to a near object, the size of the pupils can decrease (constrict) as part of the near response, but the main adjustment for focus comes from the accommodation of the lens.
The pupil _____ to approximately 1.5mm when the eye is exposed to intense light, and it _______to almost 10mm in compete darkness.
contracts
enlarges
When a penlight is shone into the right eye (which is dilated in complete darkness), the pupillary light reflex occurs not only in the stimulated eye (right eye) but also in the non-stimulated eye (left eye). This is referred to as the __________, where a stimulus applied to one eye causes a simultaneous and corresponding response in the other eye.
consensual light reflex
In the light intensity and pupil size experiment, did the pupil of the unexposed eye become smaller when the right eye was exposed to light?
This is due to the connection of nerves known as the optic nerves and __________, where fibers from each eye cross to the opposite side of the brain.
there is a consensual response where the pupil in the unexposed eye also constricts*.
the optic chiasm
a photosensitive pigment of the eye, composed of _________ and the protein ______.
Rhodopsin
light-sensitive retinal and opsin
When light strikes the retina, the purple-colored rhodopsin splits into its two component parts and becomes pale. This process is known as __________
bleaching
refer to the visual perception of an image that persists or appears after the actual visual stimulus has been removed. These are often seen as a result of the continued stimulation of the retina.
Afterimages
Visual perceptions that occur when you stare at a bright stimulus for an extended period, and when you look away, you see a ghostly, complementary image. same color as original
Positive Afterimages
Visual perceptions that occur when you stare at a brightly lit stimulus for an extended period, and when you look away, you see an inverted or complementary version of the original image.
Negative Afterimages
___________ afterimage reflects the bleaching effects of the rhodopsin.
Negative afterimage
- a region where the retinal nerve fibers exit from the back of the eye and form the optic nerve.
- due to the lack of photoreceptor cells, this region is insensitive to light.
Optic Disc (Blind Spot)
test used to get distance that ears can perceive sound
watch tick test
are important for maintaining the upright position of the body. These reflexes are __________ feedback mechanisms.
example: if you lean slightly to the left, your left foot abducts to regain the center balance
postural reflexes
negative feedback mechanism
3 types of balance
- Steady-state balance
- Reactive balance control
- Proactive/Anticipatory Balance
twitching of the eyes
nystagmus
It examines the visual responses to changes in dynamic equilibrium. As the head turns, one of the reflexes that occurs is movement of the eyes in the opposite direction of the rotation so that there is enough time for a visual image to be fixed. This ensures that the eyes remain focused on a target despite the head’s motion, preventing blurring of vision and maintaining visual acuity.
Barany’s test
is responsible for the body’s equilibrium. It maintains balance and provides awareness of the body’s spatial orientation.
vestibular system
phase of nystagmus that is driven by a reflex such as the vestibular reflex that causes the eyes to drift in a certain direction, and often reflects a difficulty in maintaining a stable gaze. It is typically followed by a fast corrective phase to bring the eyes back to a central position
slow phase of nystagmus
phase of nystagmus that quickly resets the position of the eye. This corrective action helps to maintain visual acuity and prevents blurring of vision during the nystagmic movement. The specific function of the slow and fast phases depends on the individual’s condition.
fast phase
