Monday, February 7, 2011

Prismatic Effect Calculation

Assalamualaikum and Very Afternoon to all readers,

For 2nd year students, do you still remember the rule how to determine Prismatic Effect (base up, down, in out) that I've been taught in class last week. InsyaAllah, I'll share it the rule using video post with all of the readers in next time.

How to calculate the prismatic effect amount induced by decentration??? The formula is very simple.

P (prism power)=c (decentration, in cm, not in mm) x F (focal power, D)

Simple, right...most of us have difficulty to determine which base will be induced by the decentration (c- in, out, up, down) and focal power (F- plus, minus)...by using my rule, InsyaAllah it will be easier to determine it. As I said before, the video is under construction but I've explain it in 2nd year class..Thus, in this post I would to give a tutorial to all 2nd year regarding this topic.

Question: Calculate prismatic effect if the decentration and focal power as follow; 


  1. c=2mm in F=-3.00D
  2. c=2mm in F=+3.00D
  3. c=2cm out F=-13.00D
  4. c=4mm up F=-3.00D
  5. c=7mm out F=-12.00D
  6. c=2mm in  F=+12.50D
  7. c=3cm in F=-0.250D
  8. c=2mm down F=-2.00D
  9. c=2mm down F=-31.00D
  10. c=8mm up F=+3.75D
  11. c=4mm downF=-3.00D /-2.00x 180
  12. c=6mm in F=-3.00D/-1.00x 90
  13. c=21mm out F=+3.00D/+2.00X180
  14. c=8mm up  F=-3.00D /+4.00@90
  15. c=8mm out F=-3.00D/+4.00X90
  16. c=9mm in F=-3.00D/-9.00@90
  17. c=1mm down F=-13.00D/+2.000X90
  18. c=1.5mm in F=+23.00D/-2.75X180
  19. c=9mm up F=-7.00D
  20. c=8mm up F=-8.00D
  21. c=3mm  out F=-9.00D
  22. c=1.2mm up F=+5.00D/+5.00x90 
Please choose 1 question to answer..please state your question no.

Deadline is this Sunday 13/ February/2011

30 comments:

  1. SITI NUR LIYANA MUSTAFARFebruary 7, 2011 at 5:09 PM

    no 3
    c: 2cm out
    F: -13D

    P=cF
    P=2cm x -13D
    P= 26 Prism Diopter Base In

    ReplyDelete
  2. no 1
    c=2mm in F=-3.00D

    P = cF
    P = (0.2cm) x (-3D)
    = 0.6 Prism Diopter Base out

    ReplyDelete
  3. no 2
    c=2mm in F=+3.00D

    P=cF
    P= (0.2cm) x (+3.00D)
    = 0.6 Prism Diopter Base In

    ReplyDelete
  4. 19)

    c:9mm (0.9cm)
    base-up
    F:-7.00D

    P=cF
    =(0.9cm)(-7.00D)
    =6.3 Prism Diopter Base-Down

    ReplyDelete
  5. raja nor shahila raja mohamadFebruary 7, 2011 at 5:33 PM

    no.6
    c= 2mm in
    F= +12.50D

    P=cF
    = 0.2cm X +12.50D
    = 2.5D base in

    ReplyDelete
  6. raja nor shahila raja mohamadFebruary 7, 2011 at 5:36 PM

    @raja nor shahila raja mohamad
    correction:
    P= cF
    = 0.2cm X +12.50D
    =2.5 Prism Diopter Base In

    ReplyDelete
  7. salam..
    question 21:

    P = cF
    P = (0.3cm)x (-9D)
    P = 2.7 prism diopter base in

    ReplyDelete
  8. no. 9

    c=2mm down F=-31.00D

    P = cF
    P = (0.2cm)x (-31.00D)
    P = 6.2 Prism Diopter base up

    ReplyDelete
  9. norsyazwani mohamad daudFebruary 7, 2011 at 5:56 PM

    q20
    c= 8 mm (0.8cm)
    F= -8.00 DS
    P=cF
    = (0.8) (-8.00)
    = 6.4 base down

    ReplyDelete
  10. Question #7

    c= 3cm
    F= -0.25DS

    Answer;

    P = cF
    P = 3cm x -0.25DS
    P = 0.75 base out

    ReplyDelete
  11. nur amalina zulkefliFebruary 7, 2011 at 6:27 PM

    P=cF
    P= (4mm/10) x 3
    P= 1.2pd base down

    ReplyDelete
  12. no 5
    c= 7mm out (0.7cm)
    F= -12.00 D

    P=cF
    P= (0.7 cm)(-12.00 D)
    = 8.4 prism diopter base in

    ReplyDelete
  13. Question #8

    c= 2mm
    F= -2.00DS

    Answer;

    P = cF
    P = 0.2cm x -2.00DS
    P = 0.40 base up

    ReplyDelete
  14. @Kisah Seorang Penchenta

    Question #8

    c= 2mm
    F= -2.00DS

    Answer;

    P = cF
    P = 0.2cm x -2.00DS
    P = 0.40 prism diopter base up

    ReplyDelete
  15. @Mimie Halil

    Question #7

    c= 3cm
    F= -0.25DS

    Answer;

    P = cF
    P = 3cm x -0.25DS
    P = 0.75 prism diopter base out

    ReplyDelete
  16. Q10.
    c= 0.8cm
    F= +3.75 D

    P= cF
    = (0.8) x (+3.75)
    = 3 prism diopter base up

    ReplyDelete
  17. Q 15:
    c =8mm out
    F=-3.00D/+4.00X90

    @ vertical : -3.00 DS
    @ horizontal: + 1.00 DS

    c = 0.8 cm

    1) @ vertical meridian:
    P = cF
    P = 0.8 cm x -3.00 DS
    = 2.4 prism diopter base in

    2) @ horizontal meridian:
    P = cF
    P = 0.8 cm x +1.00 DS
    = 0.8 prism diopter base out

    ReplyDelete
  18. Q 11:
    c =4mm down
    F=-3.00DS/-2.00 DCX 180

    @ vertical : -5.00 DS
    @ horizontal: -3.00 DS

    c = 0.4 cm

    1) @ vertical meridian:
    P = cF
    P = 0.4 cm x -5.00 DS
    = 2.0 prism diopter base up

    2) @ horizontal meridian:
    P = cF
    P = 0.4 cm x -3.00 DS
    = 1.2 prism diopter base up

    ReplyDelete
  19. Soalan 13

    c=21mm out F=+3.00D/+2.00X180
    Transpose...F=+5.00D/-2.00X90

    +5.00D @90
    +3.00D @180

    c= 2.1cm

    P=cF

    At vertical meridian:
    P=(2.1)(+5.00)
    =10.5prism diopter base out

    At Horizontal meridian:
    P=(2.1)(+3.00)
    =6.3prism diopter base out

    ReplyDelete
  20. Question 17
    c= 1 mm down
    F= -13.00DS/ +2.00DC x 90

    transpose = -11.00DS/ -2.00DC x 180
    c= 0.1 cm

    @ vertical= -13.00DS
    @horizontal = -11.00 DS

    a) @ vertical:
    P= cF
    =(0.1 cm )(-13.00DS)
    = 1.3 prism diopter base up

    b) @ horizontal :
    P=cF
    = (0.1 cm ) ( -11.00DS)
    = 1.1 prism diopter base up

    ReplyDelete
  21. salam..
    my answer for question no.22

    C=1.2mm up
    F= +5.00D/ +5.00X90

    transpose: +10.00D/-5.00X180
    c=0.12cm

    @vertical=+5.00DS
    @horizontal=+10.00DS

    a) @vertical

    P=cF
    P=(0.12cm)(+5.00DS)
    P=0.6 prism diopter base UP

    b) @horizontal

    P=cF
    P=(0.12cm)(+10.00DS)
    P=1.2 prism diopter base UP

    ReplyDelete
  22. Q 12:
    c =6mm in
    F=-3.00DS/-1.00 DC X 90

    @ vertical : -3.00 DS
    @ horizontal: -4.00 DS

    c = 0.6 cm

    1) @ vertical meridian:
    P = cF
    P = 0.6 cm x -3.00 DS
    = 1.8 prism diopter base out

    2) @ horizontal meridian:
    P = cF
    P = 0.6 cm x -4.00 DS
    = 2.4 prism diopter base out

    ReplyDelete
  23. Q16:

    c = 9mm(0.9cm) in
    F = -3.00DS/-9.00DC @ 90
    P = cF

    @ horizontal meridian
    F = -3.00D
    c = 0.9cm in
    P = cF
    P = (0.9) x 3.00
    P = 2.70 Prism Diopter BO

    @ vertical meridian
    F = -12.00D
    c= 0.9cm in
    P = cF
    P = (0.9) x 12.00
    P = 10.80 Prism Diopter BO

    ReplyDelete
  24. norsyazwani mohamad daudFebruary 13, 2011 at 11:43 PM

    correction:
    q20
    c= 8 mm (0.8cm)
    F= -8.00 DS
    P=cF
    = (0.8) (-8.00)
    = 6.4 prism diopter base down

    ReplyDelete
  25. q14 :c=8mm up F=-3.00D /+4.00@90


    @ horizontal meridian
    F = -3.00D
    c = 0.8cm
    P = cF
    P = (0.8) x 3.00
    P = 2.40 Prism Diopter BD

    @ vertical meridian
    F = +1.00D
    c= 0.8cm in
    P = cF
    P = (0.8) x 1.00
    P = 0.80 Prism Diopter BU

    ReplyDelete
  26. sbgai salh seorang budk optometri...nampk macm menarik jer blog nie,,,bole join????huhuuu...

    ReplyDelete
  27. can some plz help me need some help with dencentaion and PE

    ReplyDelete
  28. GUYS PLS HELP, HAVE TO SUBMIT MY COURSWORKBY TOMORROW.

    BASICALLY MY DECENTRATION VALUE IS 70MM BUT HOW DO YOU DETERMINE ITS DIRECTION?( IN , OUT, UP, DOWN)
    PLS REPLY TO junaidk595@gmail.com

    ReplyDelete
  29. Guys plz help me calculate pe of apoint 6mm below and 4mm inwards from optical center of alens +3.00/-3.00x120

    ReplyDelete

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