12-vision
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Lab. no.12:
Vision Acuity of vision (visual acuity): Color vision: Visual reflexes: -Pupillary light reflex. -Consensual light reflex. -Accommodation reflex.
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Acuity of vision (visual acuity): This is the appreciation of fine details in a visual image. The acuity of vision is determined by the smallest retinal image, which can be appreciated, and it is measured by the smallest object, which can be clearly seen at a certain distance. Distant vision is tested on Snellen’s Chart. Determine the visual acuity of each eye separately.
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(cones are responsible for color vision): Color vision is tested by Ishihara’s charts. These consist of numerals constituted by dots of different colors. A normal person can read the numerals, whereas a color blind cannot. The subject should be asked to read each plate from a distance of 75 cm, within 30 sec. [email protected]
Abnormalities of color vision, known as color-blindness, are common in men (about 8%) but much less common in women (about 0.4% ). The common abnormalities are inherited as X-linked recessive characters and result from absence of appropriate color genes in the X-chromosome.
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Therefore 2% of all men are red color blind (protanomaly) and 6% are green color blind (deuteranomaly). Blindness to blue color (tritanomaly) is very rare. Use Ishihara’s charts to test for color vision.
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Visual reflexes: Pupillary (direct) light reflex: Throw tourch light into an eye and observe constriction of pupil in the same eye. [email protected]
Consensual light reflex: Keep one hand between the 2 eyes of the subject, and throw tourch light into one eye and observe constriction of the pupil in the other eye. The consensual light reflex is due to decussation of the optic nerve fibers in the optic chiasma so that the impulses reach oculomotor nuclei of the two sides.. [email protected]
Accommodation reflex: This is the ability of the eye to focus on objects at varying distances. Hold one finger at a distance of 25cm from the subject. Ask him to first look at a distant object and then look at the finger.
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Accommodation consists of three associated events: 1- Eyes converge toward the near object.
2- Pupils constrict. 3-The optical power of the lens is increased.
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The mechanism of increased optical power of the lens includes: The ciliary muscles on both sides contract, due to increased parasympathetic stimulation.
The suspensory ligament of the lens is relaxed.
The anterior surface of the lens becomes more convex, which increases its focusing power. [email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
[email protected]
Lab. no.12:
Vision Acuity of vision (visual acuity): Color vision: Visual reflexes: -Pupillary light reflex. -Consensual light reflex. -Accommodation reflex.
[email protected]
Acuity of vision (visual acuity): This is the appreciation of fine details in a visual image. The acuity of vision is determined by the smallest retinal image, which can be appreciated, and it is measured by the smallest object, which can be clearly seen at a certain distance. Distant vision is tested on Snellen’s Chart. Determine the visual acuity of each eye separately.
[email protected]
(cones are responsible for color vision): Color vision is tested by Ishihara’s charts. These consist of numerals constituted by dots of different colors. A normal person can read the numerals, whereas a color blind cannot. The subject should be asked to read each plate from a distance of 75 cm, within 30 sec. [email protected]
Abnormalities of color vision, known as color-blindness, are common in men (about 8%) but much less common in women (about 0.4% ). The common abnormalities are inherited as X-linked recessive characters and result from absence of appropriate color genes in the X-chromosome.
[email protected]
Therefore 2% of all men are red color blind (protanomaly) and 6% are green color blind (deuteranomaly). Blindness to blue color (tritanomaly) is very rare. Use Ishihara’s charts to test for color vision.
[email protected]
Visual reflexes: Pupillary (direct) light reflex: Throw tourch light into an eye and observe constriction of pupil in the same eye. [email protected]
Consensual light reflex: Keep one hand between the 2 eyes of the subject, and throw tourch light into one eye and observe constriction of the pupil in the other eye. The consensual light reflex is due to decussation of the optic nerve fibers in the optic chiasma so that the impulses reach oculomotor nuclei of the two sides.. [email protected]
Accommodation reflex: This is the ability of the eye to focus on objects at varying distances. Hold one finger at a distance of 25cm from the subject. Ask him to first look at a distant object and then look at the finger.
[email protected]
Accommodation consists of three associated events: 1- Eyes converge toward the near object.
2- Pupils constrict. 3-The optical power of the lens is increased.
[email protected]
The mechanism of increased optical power of the lens includes: The ciliary muscles on both sides contract, due to increased parasympathetic stimulation.
The suspensory ligament of the lens is relaxed.
The anterior surface of the lens becomes more convex, which increases its focusing power. [email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
What number do you see revealed in ?the pattern of dots below
[email protected]
[email protected]
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