Transposition is very usefull for optometry cousres . transposition is 2 type 1- simple transposition 2- toric transposition

1. Shubhangi shukla

2. Transposition-
It means making equivalent
forms of prescription. It is required
● For manufacturing of glasses.
● Something refractive error of a patient
needs plus cylinder at 900 in one eye and
minus cylinder 900 in other eye. In such
cases we make the power Of cylinder plus
or minus in both the eyes to avoid
eyestrain. This is possible by
transposition only.

3. Type of transposition-
Two type of transposition.
1. Simple transposition
2. Toric transposition
Simple transposition-
it's 3 form of simple transposition.
1. Spherocylinder forms
2. optical cross forms
3. two cylinder forms or cross forms

4. 1. Spherocylinder to new spherocylinder
● We are making new spherical power, to add
the power of spherical and cylindrical and
given prescription.
● To make the new cylinder power, change the
sign in cylindrical power and given
prescription.
● To make the new axes ,if axis is 900 below 900
add the 900 ,if above the 900 then subtract 900
and given prescription

5. ● Ex- 1.00DS/-0.25DC*105
1. New spher = spherical power+ cylindrical power
= 1.00+(-0.25)
=+0.75 DS
2- new cylindrical = change the sign power of cylindrical
lens
= + 0.25 DC
3- new axis = above the 900 then subtract the 900 and
below the 900 , equal the 900 then add the 900
=105 0 -900
= 150
Final prescription = +0.75DS/+0.25DC*150

6. 2- Spherocylinder to optical cross.
● We making the optical cross.
● The spherical value write in both
meridian.
● The cylindrical value added in
perpendicular meridian and do the
calculation.

7. Ex -0.75DS/+050DC*800
900
800
-0.75 -0.75+0.50= - 0.25
0.
1800

8. 3- spherocylinder to two cylinder
● We make spherocylinder to new spherocylinder.
● We are making the first cylindrical, spherical
value in old prescription and axis of new
prescription.
● We are making second cylindrical, Power
spherical value of new prescription and axis of
old prescription.
Ex - 1.75DS/+0.50DC*90
New sphere power =sphere+ cylinder power
= 1.75+0.50
=2.25 DS

10. New cylinder power= change the sign of cylinder power
= - 0.50 Dc
Next axis = equal 900 below the 900 tthen add the 900 and
above the 900 then subtract the 900
=900+900 = 1800
New spherocylinder prescription
= 2.25DS/-0.50DC*1800
First cylinder power
= Old sphere power and new axis
= +1.75 DC*1800
Second cylinder
=New sphere power and old axis
= + 2.25Dc*900

11. 4- optical cross to spherocylinder
● We are making of 1 meridian power is
spherical power mostly small degree power is
made spherical power.
● To find out cylinder power the spherical
power is subtract in other meridian.
● The axis is write in spherical power.

12. Ex- +0.50
+1.00
= +0.50Ds/+1.00-(+0.50)DC*900
=+0.50DS / +0.50DC *900

13. 5- optical cross to two cylinder
Write the power and axis write in
perpendicular. Ex- +0.50
+0.75
1st cylinder= +0.50*1800
2nd cylinder = + 0.75* 900

14. 6- two cylinder to spherocylinder
● We are make first cylinder is sphere power.
● The cylinder power is found the sphere power
is subtract in second cylinder power.
● Axis is write in second cylinder power.
Ex- +5DC *900
+7DC*1800
=+5.00DS/+7-(+5.00)DC*1800
=+5.00DS/+2.00Dc*1800

15. 7-two cylinder to optical cross
● We are making the optical cross.
● Power is write in perpendicular meridian.
Ex- +5 DC*900
+7Dc*1800
+7.00
+5 .00

16. Toric transposition - for toric transposition a base curve is
required. The following rule should be observed for toric
transposition.
● Sign of cylinder should be same as sign of base curve.
If not change the sign of cylinder by doing simple
transposition.
● Power of new sphere= power of given sphere minus
power of base curve
● Power of cylinder No 1 = power of base curve with same
sign and axis rotated 900
● Power of cylinder No 2 = power of sign given cylinder+
power of base curve with same axis as of given cylinder

17. Ex -2.00Ds/-0.50Dc*900 BC= +5
1- Sign of cylinder should be same as sign of base
curve,sign of cylinder needs to be changed by simple
transposition. = -2.50Ds/+0.50DC*1800
2- power of new sphere= -2.50-(+5.00)
= -7.50DS
3- Power of cylinder No 1= +5.00*900
4- Power of cylinder No 2 =
+0.50+(+5.00) =+5.50Dc*1800
Final prescription
=-7.50DS/(+5.00Dc*900 )(+5.50DC*1800)

18. Ex 2 = -2.00Ds/-1.00Dc*1450 BC= -6
1- power of new sphere= -2.00-(-6.00)
= -2.00+6.00
=+4.00DS
2- Power of cylinder No 1= -6.00*350
3- Power of cylinder No 2 = -1.00+(-6.00)
=-7.00Dc*1450
Final prescription
=+4.00DS/(-6.00Dc*350 )(-7.00DC*1450)

19. Thank you