TRANSPOSITION

Question 1

Optometrists use

ophthalmologists use what

Answer 1

Optometrists use minus cylinder and ophthalmologists

typically use plus cylinder. IN THIS PROGRAM, YOU WILL BE LEARNING EVERYTHING IN PLUS CYLINDER FORM.

Question 2

IN CLINIC

Answer 2

In clinic though, you may encounter prescriptions in either form. But It doesn’t matter what form a prescription is written in, because we can easily transpose a prescription from one format to another. You will see that It is just like doing the optical cross!

Question 3

FOR EXAMPLE

Answer 3

FOR EXAMPLE, CONTACT LENS PRESCRIPTIONS ARE ALWAYS IN MINUS CYLINDER. YOU MAY BE FAMILIAR WITH PLUS CYLINDER AND USE PLUS CYLINDER IN YOUR CLINIC. SO YOU MUST BE ABLE TO TRANPOSE A PRESCRIPTION FROM ONE CYLINDER FORM TO THE OTHER.

Question 4

Transposition means what?

without doing what?

Answer 4

refers to the process of changing the prescription from a plus cylinder form to a minus cylinder form, or from a minus cylinder to a plus, without changing its refractive value.

Question 5

1

Answer 5

At first glance, these prescriptions appear to be different. But they are in fact equal in refractive power. They are just written differently. One is in minus cylinder and one is in plus cylinder

OD: -2.50 -0.50 X 180
OS: -1.00 -1.00 X 175

OD: -3.00 +0.50 X 090
OS: -2.00 +1.00 X 085

Question 6

BECAUSE

Answer 6

BECAUSE THEY LOOK DIFFERENT, PATIENTS WILL SOMETIMES THINK AN ERROR HAS BEEN MADE IN THEIR PRESCRIPTION OR THINK THEIR PRESCRIPTION HAS CHANGED DRAMATICALLY BECAUSE THEY ARE COMPARING A MINUS CYLINDER PRESCRIPTION TO A PLUS CYLINDER PRESCRIPTION. ONCE TRANsPOSED, THE PRESCRIPTIONS CAN THEN BE COMPARED. Otherwise, it is like comparing apples to oranges!

Question 7

THERE ARE A FEW SIMPLE STEPS TO COMPLETE IN ORDER TO TRANsPOSE A PRESCRIPTION. THEY DO NOT NECESSARILY HAVE TO BE COMPLETED IN A PARTICULAR ORDER!

Answer 7

THERE ARE A FEW SIMPLE STEPS TO COMPLETE IN ORDER TO TRANsPOSE A PRESCRIPTION. THEY DO NOT NECESSARILY HAVE TO BE COMPLETED IN A PARTICULAR ORDER!

Add the cylinder power to the sphere power algebraically.
Change the sign of the cylinder
Change the axis by 090 degrees

Question 8

GOING FROM PLUS CYLINDER TO MINUS…

Answer 8

OD: -2.00 +1.00 X 085


IN THIS EXAMPLE, THE SPHERE IS 
-2.00 AND THE CYLINDER IS +1.00. WE WILL ADD THEM TOGETHER.

 -2.00 
+ (+1.00) 
 -1.00

So our sphere power in our transposed prescription is now -1.00.

Question 9

1.

Answer 9

OD: -1.00 +1.00 X 085

THE NEXT STEP IS TO CHANGE THE SIGN OF THE CYLINDER POWER. IN THIS CASE, WE WILL CHANGE IT FROM +1.00 TO -1.00. THE NUMBER DOES NOT CHANGE, just THE SIGN! OUR PRESCRIPTION IS NOW…

	OD -1.00 -1.00 X 085

Question 10

1.

Answer 10

OD -1.00 -1.00 X 085

THE LAST STEP IS TO CHANGE THE AXIS BY 090 DEGREES.
	     085
            \+ 090 
	     175
OD -1.00 -1.00 X 175
THIS IS OUR NEW, TRANPOSED PRESCRIPTION.

Question 11

GOING FROM MINUS CYLINDER TO PLUS…

Answer 11


OD: -2.50 -0.50 X 180

IN THIS EXAMPLE, THE SPHERE IS 
-2.50 AND THE CYLINDER IS -0.50. WE WILL ADD THEM TOGETHER.

 -2.50 remember, when adding a -
+ (-0.50) it is really like subtracting!
 -3.00

So our sphere power in our transposed prescription is now -3.00.

Question 12

1,

Answer 12

OD: -3.00 -0.50 X 180

THE NEXT STEP IS TO CHANGE THE SIGN OF THE CYLINDER POWER. IN THIS CASE, WE WILL CHANGE IT FROM -0.50 TO +0.50. THE NUMBER DOES NOT CHANGE, JUST THE SIGN! OUR PRESCRIPTION IS NOW…

	OD -3.00 +0.50 X 180

Question 13

1.

Answer 13

OD -3.00 +0.50 X 180

THE LAST STEP IS TO CHANGE THE AXIS BY 090 DEGREES.
	    180
            - 090 
	     090
OD -3.00 +0.50 X 090
THIS IS OUR NEW, TRANPOSED PRESCRIPTION.

Question 14

1,

Answer 14

OD: -2.50 -0.50 X 180 (MINUS CYLINDER)

OD: -3.00 +0.50 X 090 (PLUS CYLINDER)

THESE PRESCRIPTIONS APPEAR DIFFERENT BUT THEY ARE REALLY JUST 2 DIFFERENT WAYS OF SAYING THE SAME THING!