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In farsightedness, the light is focused ____ the retina.
BEHIND
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The lens required to treat myopia
convex lens
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The "near point" increases with age because the ____ of the lens decreases as we get older.
ELASTICITY
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Real Image
an image produced by a convex lens that is upside down and reversed from left to right
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Distance Vision:
- ciliary muscle: relaxed
- suspensory ligament: taut
- convexity of the lens: decreased
- light refraction: decreased
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Close Vision:
- ciliary muscle: contracted
- suspensory ligament: relaxed
- convexity of the lens: increased
- light refraction: increased
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Why is vision lost when light hits the blind spot?
Vision is lost when light hits the blind spot because the blind spot lacks photoreceptors, so light focused on it cannot be seen.
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Astigmatism:
A defect in the eye or in a lens caused by a deviation from spherical curvature, which results in distorted images, as light rays are prevented from meeting at a common focus
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Presbyopia:
Farsightedness caused by lack of elasticity of the lens of the eye, occuring typically in middle and old age
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Which wavelengths of lght do the three cone types of the retina respond maximally?
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How can you explain the fact that we see a great range of colors even though only three cone types exist?
the three colors blend, letting you see different colors
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Binocular Vision:
the ability to maintain visual focus on an object with both eyes creating a single visual image. Lack of binocular vision is normal in infants; adults experience distortions in depth perception and visual measurements of distance.
Advantage: provides 3D vision
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Panoramic Vision:
an unobstructred and wide view of an extensive area in all directions
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convergence reflex:
- both eyes move medially
- medial rectus: controls the eye movement
- value: tracks very close objects
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photopupillary reflex:
- constriction of the pupil of the eye as light was exposed
- constriction of the cone of the eye as light was not exposed
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Why is the ophthalmoscopic examination an important diagnostic tool?
- used to examine the fundus or interior eyeball; determine the condition of the retina, optic disc, and internal blood vessels
- Diabetes mellitus and arteriosclerosis can be detected by this examination
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Why is it more of a strain on the extrinsic and instrinsic eye muscles to look at close objects than at far objects?
The nearer the objects, the greater degree of convergence is needed to maintain binocular vision
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accommodation
ability to focus for close (less than 20 ft) vision
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hyperopia
inability to focus well on close objects
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convergence
medial movement of the eyes during focusing on close objects
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conduction deafness
- occurs when there is a problem conducting sound waves anywhere along the route through the outer ear, tympanic membrane (ear drum), or middle ear.
- can result from the fusion of ossicles
- can result from otitis media
- can result from impacted cerumen or a perforated eardrum
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sensorineural deafness
- type of hearing loss in which the root cause lies in the vestibularcochlear nerve, the inner ear, or the central processing centers of the brain.
- can result from a lesion of the cochlear nerve
- sound heard in one ear but not in the other during bone and air conduction
- can result from blood clot in the auditory cortex
- often improved by hearing aid
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nystagmus
rapid involuntary movements of the eye
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vertigo
a sensation of whirling and loss of balance, associated particularly with looking down from a great height, or caused by disease affecting the inner ear or the vestibular nerve
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