Accommodation & presbyopia expected amplitude of accommodation
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Transcript of Accommodation & presbyopia expected amplitude of accommodation
DOCTOR OF OPTOMETRY
LECTURE
PREPARED BY
Kausar Ali .OD student .
2nd year
Lecture Topics ...
ACCOMMODATION
&PRESBYOPIA .
Amplitude of accommodation. The Minimum potential of an eye to
increase optical power while seeing the near object . Clearly is know as amplitude of accommodation .
Note to be important . If a person need 4 D power to accommodate . He fulfill it except it he have 3 D power in reserve.
Total amplitude of accommodation will be (3+4= 7)
Procedure for measurement amplitude of accommodation. There are many methods but the most
common is pen – push up method . It is used for convergence insufficiency .
This procedure measures in diopters . The ability of a person to change the
focus of crystalline lens in response to near stimulus .
EQUIPMENTS. Near V.A card. Tape measure in cm . Occlude which is necessary or not.
PIN-PUSH UP METHOD.
Set up . The patient is tested while he/she is
wearing habitual distance correction . This test may also be performed behind
the chiropter. Either the patient or examiner may hold
the near point card or chart . The near point card should be well
illuminated .
Step by step procedure . Instruct the patient to occlude the left eye to
test the right eye . Direct the patient attention to the row of
letters on or two lines better than the best near V.A line .
Instruct the patient to keep the letters clear . Slowly move the chart closer to the patient
and ask him to report when the letters become and remain blurry .
Measure the distance from the chart to the patient spectacles . Plane in cm . The linear measurement is referred to as near point of accommodation .
Convert the linear distance into diopters by dividing the near point of accommodation of taking reciprocal of it .
The resultant dioptric represent the patient amplitude of accommodation .1/10 = 10 D ( 1 = 100cm )
Occlude the right eye and test the left and repeat the same procedure .
Recording . Record the testing procedure . Record the amplitude of accommodation
in round figure . Separately record the result of right and
left eye . E.G
AMP OD 7.0 D OS 7.0 / OD (right eye ) OS (left eye ) .
Expected Amplitude of Accommodation. The expected amplitude of accommodation decrease with age . The two most commonly used system for obtaining the excepted
amplitude of accommodation are . 1) Hofstetters formula . 2) Donders table
Hofstetters Formula Menimum expected amplitude .
15 – 0.25 (age) Average expected amplitude 18.5 – 0.3 (age ) Maximum expected amplitude 25 – 0.4 (age )
Minimum excepted amplitude for 1 year age . = 15 – 0.25 (age) 15 – 0.25 ( 1 ) 15 - 0.25 = ( 14.75 D )
Minimum excepted amplitude For 10 year = 15 – 0.25 (age) 15 – 0.25 ( 10 ) 15 - 2.5 = ( 12.5 D )
Minimum excepted amplitude For 30 year . = 15 – 0.25 (age) 15 – 0.25 ( 30 ) 15 - 7.5 = ( 7.5 D ) .
Minimum excepted amplitude For 40 year . = 15 – 0.25 (age) 15 – 0.25 ( 40 ) 15 - 10 = ( 5 D )
Minimum excepted amplitude For 50 year = 15 – 0.25 (age) 15 – 0.25 ( 50 ) 15 - 12.5 = ( 2.5 D )
Minimum excepted amplitude For 60 year . = 15 – 0.25 (age) 15 – 0.25 ( 60 ) 15 - 15 = ( 0 D )
Average expected amplitude . For 1 year = 18.5 - 0.3 (age ) 18.5 – 0.3 ( 1 ) 18.5 – O.3 = 18.2 D
Average expected amplitude . For 10 year = 18.5 - 0.3 (age ) 18.5 – 0.3 ( 10 ) 18.5 – 3 = 15.5 D Average expected amplitude . For 30 year = 18.5 - 0.3 (age ) 18.5 – 0.3 ( 30 ) 18.5 – 9 = 9.5 D
Average expected amplitude . For 40 year = 18.5 - 0.3 (age ) 18.5 – 0.3 ( 40 ) 18.5 – 12 = 6.6 D Average expected amplitude . For 50 year = 18.5 - 0.3 (age ) 18.5 – 0.3 ( 50 ) 18.5 – 15 = 3.5 D
Average expected amplitude . For 60 year = 18.5 - 0.3 (age ) 18.5 – 0.3 ( 60 ) 18.5 – 18 = .5 D Maximum expected amplitude . For 1 year = 25 – 0.4 (age ) 25 – 0.4 (1) 25 – 0.4 = 24.6
Maximum expected amplitude . For 10 year = 25 – 0.4 (age ) 25 – 0.4 (10) 25 – 4 = 21 Maximum expected amplitude . For 30 year = 25 – 0.4 (age ) 25 – 0.4 (30) 25 – 12 = 13
Maximum expected amplitude . For 40 year = 25 – 0.4 (age ) 25 – 0.4 (40) 25 – 16 = 9 Maximum expected amplitude . For 50 year = 25 – 0.4 (age ) 25 – 0.4 (50) 25 – 20 = 5
Maximum expected amplitude . For 60 year = 25 – 0.4 (age ) 25 – 0.4 (60) 25 – 24 = 1
Donders table . Donders table for age referenced amplitude of
accommodation .Age Amplitude of
accommodation
10 y 14 D
15 y 12 D
20 y 10 D
25 y 8.5 D
30 y 7 D
35 y 5.5 D
40 y 4.5 D
45 y 3.5 D
50 y 2.5 D
55 y 1.75 D
60 y 1 D
65 y .5 D
70 y .25 D
75 y 0 D
QUESTION PLZ IF SOME ONE HAVE