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50 Cards in this Set

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cataract
opacification of the crystalline lens in the eye
types of cataract surgerys
extra-capsular: nucleus and cortex removed from capsule, leaving posterior capsule, peripheral part of the anterior capsule and the zonules intact

intra-capsular: whole lens removal
Phakia
Aphakia
Pseudophakia
Phakia: with natural crystalline lens
Aphakia: w/o natural crystalline lens
Pseudophakia: IOL implant following surgery
what schematic eye model is used for a aphakic eye
Gullstrand's Simplified Schematic Eye
how do you treat aphakia with spectacles
high plus lens
contact lens
what is ring scotoma? what does it treat?
edge of plus lens act as a prism
object located in the shadowed areas are not seen

used to treat aphakia with spectacles
what is the jack in the box phenomenon
associated with the ring scotoma

1. a patient turns head to see an object
2. object disappears in the peripheral of the ring scotoma
3. object then reappears once the image is in the visual area
spherical aberration effect of high plus lens
mag. of image is more at the peripheral than in the center of the lens due to prismatic effect

object appears stretched out at the corners like a pin-cushion
presbyopia
a decline in accommodative ability that occurs normally with age and necessitates a plus lens addition to perform near task
what to the 4 classification of presbyopia
incipient
functional
absolute
premature
how does the lens change throughout lifetime
1. axial thickness of the lens increase with age
2. radius of curvature of the central anterior surface decreases with age
in clinic how much accommodation should the patient sustain on their own
up to half
what are four ways to treat presbyopia
spectacle lens
contact lens
special IOL
surgery
what are some classical reasoning for presbyopia
crystalline lens hardening reducing the efficiency of the ciliary muscles

crystalline lens gets larger throughout lifetime
Isometropia
equal refractive errors between the two eyes
Anisometropia
unequal refractive errors between the two eyes
Antimetropia
one eye is myopic and one eye is hyperopic
when does Anisometropia occurs
developmental
ocular surgeries (monocular cataract surgery)
what is Aniseikonia
1. a difference in image sizes and/or shape seen by the two eyes
2. cause distortions of binocular space perception
what is Asymmetric regression
if the patient is far-sighted to begin with, one eye may achieve the appropriate correction (or become myopic in that eye) while the other eye may regress back to hyperopia
what percent difference can a human fuse an image
1-6%

above 6% suppression of eye or diplopia
how do you calculate RELATIVE SPECTACLE MAGNIFICATION (RSM) for a distant object
RSM =
corrected image size (ametropic eye)/image size of the emmetropic eye
Knapps Law
A spectacle lens placed at the anterior focal point of any axial ametrope (myope or hyperope) will produce retinal images of the same size.
Clinical Corollaries of Knapp’s Law: To reduce interocular differences in retinal image size
1) If a patient has an axial anisometropia, correct the patient with spectacle lenses. (AS)

2) If a patient has a refractive anisometropia, correct the patient with contact lenses. (RK)
AXIAL ametropia correction with SPECTACLES, what is the relationship between SM and RSM for myopes and hyperopes
Hyperope
SM > 1.0; RSM = 1.0

Myope
SM <1.0; RSM =1.0
AXIAL ametropia correction with CONTACT LENSES, what is the relationship between SM and RSM for myopes and hyperopes
Hyperope
SM = 1.0; RSM < 1.0

Myope
SM =1.0; RSM >1.0
REFRACTIVE ametropia correction with CONTACT LENSES, what is the relationship between SM and RSM for myopes and hyperopes
Hyperope
SM = RSM = 1.0

Myope
SM = RSM = 1.0
REFRACTIVE ametropia correction with SPECTACLES, what is the relationship between SM and RSM for myopes and hyperopes
Hyperope
SM = RSM > 1.0

Myope
SM = RSM < 1.0
what is Accommodation
the ability of the eye to change its refractive power by altering the shape of its crystalline lens to bring objects of interest at different distances into focus.
what happens anatomically in the UNACCOMMODATED eye
the ciliary muscle is relaxed, the suspensory zonules of Zinn is at its greatest tension, and the lens takes its flattest curves
what happens anatomically in the ACCOMMODATED eye
a contraction of the ciliary muscle causes a release of resting zonular tension and a decrease in the lens equatorial diameter allowing the young lens to take a more convex form
what is Spectacle Accommodation
Accommodative amplitude or demand is measured with respect to the spectacle plane (phoropter)
what is Ocular Accommodation
Accommodative amplitude or demand is measured with respect to the eye’s principal plane
what is Range of Accommodation
It is the linear distance between the far point and the near point of accommodation.
what is Amplitude of Accommodation
the amount of accommodation exerted in diopter power to move the focus from the far point to the near point
what FOUR things happen to the lens during accommodation
1. Decrease radius of curvature, anterior surface decrease more than the posterior surface
2. Increase anterior-posterior thickness -- effective forward displacement of the whole lens; Decrease in equatorial diameter
3. May sink in direction of gravity
4. Increase in lens power causes a decrease in the eye’s focal lengths
how do you calculate accommodative amplitude
accommodative amplitude= (far point vergence) - (near point vergence)
what is Accommodation
the ability of the eye to change its refractive power by altering the shape of its crystalline lens to bring objects of interest at different distances into focus.
what happens anatomically in the UNACCOMMODATED eye
the ciliary muscle is relaxed, the suspensory zonules of Zinn is at its greatest tension, and the lens takes its flattest curves
what happens anatomically in the ACCOMMODATED eye
a contraction of the ciliary muscle causes a release of resting zonular tension and a decrease in the lens equatorial diameter allowing the young lens to take a more convex form
what is Spectacle Accommodation
Accommodative amplitude or demand is measured with respect to the spectacle plane (phoropter)
what is Ocular Accommodation
Accommodative amplitude or demand is measured with respect to the eye’s principal plane
what is Range of Accommodation
It is the linear distance between the far point and the near point of accommodation.
what is Amplitude of Accommodation
the amount of accommodation exerted in diopter power to move the focus from the far point to the near point
what FOUR things happen to the lens during accommodation
1. Decrease radius of curvature, anterior surface decrease more than the posterior surface
2. Increase anterior-posterior thickness -- effective forward displacement of the whole lens; Decrease in equatorial diameter
3. May sink in direction of gravity
4. Increase in lens power causes a decrease in the eye’s focal lengths
how do you calculate accommodative amplitude
accommodative amplitude= (far point vergence) - (near point vergence)
Incipient Presbyopia
earliest stage at which symptoms or clinical findings document the near vision effects of the condition
Functional Presbyopia
When faced with gradually declining accommodative amplitude and continued near task demands, adult patients eventually report visual difficulties
Absolute Presbyopia
the condition in which virtually no accommodative ability remains
Premature Presbyopia
Accommodative ability becomes insufficient for the patient's usual near vision tasks at an earlier age than expected due to environmental, nutritional, disease- related, or drug-induced causes