what is Duochrome Test, Why do we take Red and Green color only, What is the Principal of Duochrome Test, Why Hyperopic Pt sees green better than red and vice versa

1. DUOCHROME TEST
KHULESH SAHU
(Consultant Optometrist)
Sai Baba Eye Hospital Raipur

2. INTRODUCTION
 Duo+ Chrome
 Also known as Bichrome test
 Used to refine final Spherical power

3. WHY DO WE TAKE RED AND GREEN COLOR ONLY ?

4.  Both colors is same distance from yellow color
 Complementary color
Means Red and Green are opposite to each other on the color wheel .when
complementary color viewed together ,they enhance to each other with brightness
and clarity

5. PRINCIPAL
 Chromatic Aberration
Means the shorter wavelength of light
(green) is refracted more by the eye optics
Than the longer wavelength of light (red)

6. CAN THE DUOCHROM TEST BE USED PRIOR TO
CORRECTING THE REFRACTIVE COMPONENT ?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4361575/#:~:t
ext=The%20Duochrome%20Test%20is%20based,light%20(i.e.%2C
%20red).

7. PROCEDURE
 ARRANGEMENT
History taking , Vision, Objective refraction, Fogging, JCC
 INSTRUCTION
Sir I will show you letters on two background please tell me letters in which
background more clearer darker and sharper
 RESPONSES

8. EMMETROPIA (R=G)
HYPEROPIA (G>R)
MYOPIA (R>G)

9. WHY HYPEROPIC PATIENT’S SEES G>R AND VICE
VERSA ?

10. NOTE- BLACK RAY=YELLOW RAY

11.  EMMETROPIA
As we know that in Emmetropic Pt the green color light focus infront of retina, the
yellow light on the retina and the red color light away from the retina
 HYPERMETROPIA
In HMT Pt the plus power is deficient and we know that the property
of plus power is converging the light rays and converging power is less in the HTM
pt. So all the rays diverge
So the green light diverge near the retina ,the yellow light away from the retina and
red light is away to away from the retina that’s the reason green color is dominant

12.  MYOPIA
In the myopia the minus power is deficient and we know that the property
of minus power is diverging the light rays and diverging power is less in the myopic
Pt. So all the rays converge
So the red light converge on the retina ,the yellow light infront of the retina and
greenlight is infront of yellow light the retina that’s the reason green color is
dominant

13. THUMB RULE FOR DUOCHROM
 RED ADD MINUS (RAM)
• Either over corrected hyperopia or under corrected myopia
• Need Minus lens
• Increased minus in 0.25 Ds steps until both are clear
 GREEN ADD PLUS (GAP)
• Either under corrected HTM or over corrected myopia
• Need Plus lens
• Increased Plus in 0.25 Ds steps until both clear

14. Q/A SESSION
1) If pt has -2.00Ds and saying that R>G So ______ lens we will add
and the find correction will be _____ Ds
2) If pt has +4.75Ds and saying that G>R So _______lens we will add
,after that he is saying R>G ,what is the interpretation and final
correction of the pt _______

15. Q. Can we perform Duochrome test in pt who has color blind ?
Q. In the Duochrome test which eye should be tested first ?
Q. Can we perform Duochrome test for near ?
Q. Can a Duochrome test be used to diagnose specific eye condition
such as Glaucoma or ARMD ?