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Visual Ana FINALS > Accommodation > Flashcards

Accommodation Flashcards

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1
Q

is the ability of the optical system of the eye to increase its dioptric power so that parallel rays of light will be focus upon the retina.

A

Accommodation

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2
Q

The adjustment of the eye for seeing at different distances accomplished by changing the shape of the
___________ through action of the __________, thus focusing a clear image on the _________.

A

crystalline lens
ciliary muscles
retina

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3
Q

2 kinds of accommodation

A

physical accommodation
physiological accommodation

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4
Q

actual deformation or contraction of lens
unit of measure i diopters

A

physical acc

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5
Q
  • the contraction of the CM, cannot be measured clinically.
  • unit: Myodiopters
A

physiological acc

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6
Q

LENTICULAR CHANGES DURING ACCOMMODATION

A
  1. Radius of curvature is increased.
  2. Crystalline lens move forward towards the cornea
  3. This cause the anterior chamber to be shallow
  4. Equatorial diameter of the lens increase
  5. Thickness of the lens increased
  6. MORE BICONVEX
  7. Increase power of the lens
  8. In case of aniridia (absence of iris), it has been observed that the equatorial diameter is decreased.
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7
Q

Radius of curvature
1. relaxed
2. accommodates

A
  1. 10mm
  2. 5.3mm
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8
Q

As radius of curvature increases, the diameter of the lens _________

A

decreases

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9
Q

when the ROC of the lens increases, the front portion of the lens becomes closer to the cornea with about ___________

A

0.30 mm movement forward

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10
Q

Thickness of lens
1. Without accommodation
2. W/ acc

A
  1. 3.6 mm
  2. 4 mm
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11
Q

Power of lens
1. Without acc
2. With acc

A
  1. 19D
  2. 33 d
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12
Q

In every 1mm increase in axial length there is an equivalent of ____D in power

A

-3.00

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13
Q

In every 1mm decrease in axial length there is an equivalent of ____D in power

A

+3.00

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14
Q

Hofstetter’s Computation

A

Minimum AOA = 15 - (0.25 x patient’s age)
Average AOA = 18.5 - (0.30 x patient’s age)
Maximum AOA = 25 - 0.40 x patient’s age

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15
Q

Anomalies of accommodation

A
  1. Presbyopia
  2. Acc excess
  3. Acc spasm
  4. Acc insuff
  5. Ill-sustained
  6. Acc infa
  7. Accom paralysis
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16
Q

physiological insufficiency of accommodation leading to progressive fail in near vision due to increasing age, decrease elasticity of lens capsule & sclerosis of lens substance

A

presbyopia

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17
Q

physiological insufficiency of accommodation leading to progressive fail in near vision due to
1.
2.
3.

A
  1. increasing age
  2. decrease elasticity of lens capsule
  3. sclerosis of lens substance
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18
Q

ciliary muscles _________, and the contraction of zonules, and sclerosis of the lens all lead to decrease of accommodation in presbyopic patient

A

decreases

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19
Q

Decreased accommodation → decreased_____

A

PRA

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20
Q

Etiology of presbyopia

A
  1. decrease elasticity of the lens
  2. hardening of the lens, stiffer and more plastic & sclerotic-like
  3. lens size/volume increases which makes the lens capsule function less
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21
Q

refractive error first to become presby

A

hyperope

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22
Q

ref error that can or cannot have near reading add

A

emmetropia

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23
Q

ref error last to be a presby

A

myope

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24
Q

symptoms of presby

A

vision at the customary near-work is blur or can be sustained only with excessive accommodative effort
drowsiness after a short period of reading or near work
reading materials must be held farther away or receding near point

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25
occasionally, for early or incipient presbyopia, ________ related to attempt at excessive accommodative effort is reported. It may even lead to an _____________ and __________
asthenopia, accommodative spasm, pseudomyopia
26
____________- and ____________ may be experienced by presby as a result of the increased accommodative effort
transient diplopia, variable esophoria
27
accommodation that is persistently higher than the normal expected due to excessive action of the ciliary muscles & flexibility of the lens
Acc excess EXCESSIVE ACTION
28
the result of AOA is 2D greater than the maximum AOA
acc excess
29
causes of acc excess
- large amount of near work - deficient illumination - wearing of improper or ill fitted spectacle - physical or mental ill-hyper active - young hyperopes - young myopes performing excessive near work uses excessive accommodation in association with excessive convergence
30
CHARACTERISTICS OF EXCESSIVE ACCOMMODATION
- low 17A - Fails + in flipper test - Low NRA - Lead MEM (towards minus) & fused crossed cylinder - AOA - Normal or high
31
tx for acc excess
- Correction of refractive error using wet refraction - Near work should be forbidden for a period (limited/controlled near) - Atleast half of wet refraction is given but the cylinder is fully corrected
32
Excessive accommodation may lead to ___________-
pseudomyopia
33
accommodation is higher than normal average expected due to involuntary control of the ciliary muscles & its amount may reach to 10.00D
spasm of acc
34
causes of spasm acc
- Drug induced spasm of accommodation like strong miotic drugs when too much - Uncorrected hyperopes, astigmatic & mopes in children - excessive near work in unfavorable conditions like poor illumination, bad reading position, high energy (hyperactive), neurosis such as mental stress - Iridocyclitis - Lesion of brainstem such as encephalitis and meningitis - Toxic reaction exogenous such as arsenic poisoning and smoking
35
tx for acc spasm
- complete paralysis of ciliary muscles with atropine for 4 weeks or more - correcting spectacle should be worn immediately when eyes are used again after period of cycloplegia - near work should be forbidden or not closer than 16"
36
accommodation is constantly below the lower limit of what may be expected for px's age
INSUFFICIENT ACCOMMODATION
37
the result of AOA is 2D less than the minimum AOA
acc Insuff
38
Constant low results
acc insuff
39
Characteristics of acc insuff
- low 16A (BO) - Fails minus (-) binocular & monocularly accommodative facility - Low PRA - High MEM (lag of accommodation) & fused cross cylinder - Low AOA - Esophoria at near
40
CAUSES of acc insuff
- Premature sclerosis of the lens - Weak ciliary muscles due to muscular fatigue, anemia, stress, pregnancy & malnutrition
41
Treatment for acc insuff
- spectacle correction & reading addition-absolute hyperopia - If px has convergence excess, full spherical correction is given - Treatment of systemic cause
42
Also called as accommodative fatigue
ILL-SUSTAINED ACCOMMODATION
43
decreasing results per trial of AOA
ILL-SUSTAINED ACCOMMODATION
44
Causes of ILL-SUSTAINED ACCOMMODATION
- Convalescence from illness recovery from sickness, body is still weak → accommodative fatigue - Stage of general tiredness
45
CHARACTERISTICS OF ILL-SUSTAINED ACCOMMODATION
- BO blur at near may be low - fails minus (-) binocular & monocular accommodative facility - Low PRA High MEM & fused cross cylinder - Normal AOA if administered just once, then decreases if repeated. Low AOA after some period of time - Can also be tested using RAF Rule for VT19, where the results decrease every trial
46
tx for ILL-SUSTAINED ACCOMMODATION
- Avoiding the near work during situation described in etiology - Improve visual hygiene such as sufficient illumination & proper posture during study
47
Also calles as accommodative infacility
INERTIA OF ACCOMMODATION
48
This is a condition in which patients report difficulties in changing focus from a distant object to a near object and vice versa. Px changes from one state of accommodation to another with difficulty or sluggish
ACCOM INFA
49
Patient has difficulty both at far and at near
ACCOM INFA
50
the ability of a px to rapidly change accommodation without changing vergence.
ACC FACILITY
51
ACC infa can be tested by two methods
- Near-fart Test - Flipper lens
52
T/F Near-far test is done under monocular & binocular conditions
TRUE
53
Near-far test is appropriate for absolute presbyopia
false Near-far test is NOT appropriate for absolute presbyopia
54
PROCEDURE OF NEAR-FAR TEST 1. Place a series of ________ high contrast letters on wall 6M/20ft away 2. Patient holds _________ at distance corresponding with 3. Appropriate __________ is worn 4. ________ one eye 5. Tell px to switch focus back & fort between letters on the wall and near chart after making letters clear (this is done for____ seconds) 6. Procedure repeated for left eye for___ seconds 7. OD, OS, OU for_____ each test 8. Count the number of cycle per_____ 9. Record number of_____ per minute 10. 1cycle = _______
1. 20/25 to 20/30 2. near VA chart 3. distance correction 4. Occlude 5. 60 6. 60 7. minute 8. minute 9. cycle 10. 2 flips (far to near)
55
Expected results FOR NEAR FAR TESTS: Monocular: 1. MINIMUM 2. AVERAGE Binocular 3. MINIMUM 4. AVERAGE
1. 15cycles per minute 2. 20 cycles per minute 3. 12cycles per minute 4. 16 cycles per minute
56
Two plus and 2 minus lenses mounted in same holder
FLIPPER LENS TEST
57
+/- 2.00 is the best choice because it's the ______________
max available lag
58
FLIPPER LENS IS USED To determine the ability of accommodative system to respond to lens created______ with a monocular stimulus presentation
blur
59
TT for flipper
20/25 at 40cm
60
LIP for flipper
distance cx
61
normal expected result for flipper with polaroid glasses YOUNG ADULTS 1. MONO 2. BINO CHILDREN 8-12 Y.O 1. MONO 2. BINO
1. MONO - 11cycles/minute 2. BINO - 8 cycles/min CHILDREN 8-12 Y.O 1. MONO - 7 cycles/min 2. BINO - 5 cycles/min
62
normal expected result for flipper withOUT polaroid glasses MONO 1. MINIMUM 2. AVE BINO 3. MINIMUM 4. AVE
MONO 1. MINIMUM - 12 2. AVE - 17 BINO 3. MINIMUM - 10 4. AVE - 13
63
CHARACTERISTICS OF INFACILITY
BO & BI blur at near maybe low Fails binocular & monocular +/-accommodative facility (flipper) Low NRA & PRA do flipper already MEM is normal
63
PARALYSIS OF ACCOMMODATION ALSO KNOWN AS
PARESIS
63
mark reduced AOA due to drugs, head trauma, and other factors, TBI (traumatic brain injury)
PARALYSIS OF ACC
64
temporary, once the patient removes the cause, accommodation will also return to normal
PARALYSIS
65
CAUSES OF PARESIS
- excessive drugs & alcohol - head trauma - cerebral syphilis - infectious diseases like mumps, tonsillitis, herpes zoster & pneumonia - Once the systemic disease is treated - AOA will be normal - All characteristics or results are LOW
66
no accommodation like the case of Aphakia and Pseudophakia No contraction of crystalline lens is happening
ABSENCE OF ACC
67
3 GRADES OF BINO VISION
- simultaneous perception - fusion - stereopsis
68
if all 3 GRADES OF BINO VISION are lost, it can lead to
amblyopia
69
When stereopsis becomes _____ seconds of an arc, anti suppression tests and therapy are recommended before amblyopia occurs.
700

Visual Ana FINALS (4 decks)

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