subjective refraction

1. Refraction

2. What is Refraction? R
Determination of the refractive status
(prescription) of the eye.
OBJECTIVE Retinoscopy
SUBJECTIVE
Subjective Refraction

3. Subjective Refraction R
To determine by
subjective means
the
combination of
spherical and cylindrical
lenses
necessary to to provide
best visual
acuity
. (with
accommodation relaxed
)

4. Principles of Refraction 1.
Accommodation
-relaxed state
2.
Maximum
PLUS
, minimum minus
3.
Always trial frame before prescribing
4.
Take into account vertex distance
especially for high prescription
individuals

5. How to ensure accommodation is relaxed? R
Use PLUS lens to FOG
R
Ensure image is located infrontof retina
R
This causes image / VA to become worse if
eye attempts to accommodate (Image point
becomes further away from the fovea)

6. STEPS IN SUBJECTIVE REFRACTION
Start from Auto-Ref Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU

7. STEPS IN SUBJECTIVE REFRACTION
Start from Ret Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU
Start from Auto-Ref Results (OD)

8. How to achieve BVS? R
Strongest positive spherical lens to give
best VA
FOGGING
DUOCHROME

9. FOGGING
TO ACHIEVE BVS
R
Place enough PLUS lenses to FOG vision
to ~6/12 line
R
ROT: every line= ~0.25 DS
R
Slowly reduce the plus power until best VA
is obtained
R
Remember:
“Maximum plus power for best visual acuity”

10. USING 
DUOCHROME TEST
TO 
ACHIEVE BVS
R
Based on chromatic aberration
R
Patient asked: “Are LETTERS in the red darker or
LETTERS in the green darker?” R
Green letters clearer = Add ‘+ 0.25DS’
R
Red letters clearer = Add ‘-0.25DS’
R
End-point is obtained when the letters on the Red-
Green chart appears equally dark or when a reversal
occurs.
PT TP

11. STEPS IN SUBJECTIVE REFRACTION
Start from Ret Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU
Start from Auto-Ref Results (OD)

12. STEP 2: 
JACKSON CROSS CYLINDER 
(JCC)
R
JCC used to find used to determine the
cylindrical axis
and the cylindrical power
for
the patient.

13. Determining Cylinder Axis
R
Patient directed to observe a round target
R
Align dots
with trial lens axis ie: 180
OR

14. Determining Cylinder Axis
R
JCC is flipped such that two views are shown
R
Patient asked: “Is view one rounder, sharper, clear er
or view two?”
FLIP
VIEW 1
VIEW 2

15. Refining the axis
R
If view one is clearer
e
turn trial lens’axis
TOWARDS red lines (~5-10 degrees)
VIEW 1
Turn 10 degrees

16. Refining the axis
R
JCC is flipped again such that two views are shown
R
Patient asked: “Is view one rounder, sharper, clear er or view
two?”
FLIP
VIEW 1
VIEW 2
R
Patient directed to observe a round
target
R
Align dots with trial lens axis ie: 170

17. Refining the axis
R
If view two is clearer
e
turn trial lens’axis TOWARDS
red lines (~5 degrees)
VIEW 2
Turn 5
degrees

18. Determining Cylinder Power
R
Patient directed to observe a round target
R
Align red lines OR white lines to trial lens axis
OR

19. Determining Cylinder Power
R
JCC is flipped such that two views are shown
R
Patient asked: “Is view one rounder, sharper, clear er
or view two?”
FLIP
VIEW 1
VIEW 2

20. Determining Cylinder Power
R
If view one is clearer, ADD -0.25 DC
To maintain the circle of least confusion on
the retina,
a +0.25DS is added for every -0.50DC

21. Determining Cylinder Power
R
If view one is clearer, ADD +0.25 DC
To maintain the circle of least confusion on
the retina,
a -0.25DS is added for every +0.50DC

22. STEPS IN SUBJECTIVE REFRACTION
Start from Ret Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU
Start from Auto-Ref Results (OD)

23. How to achieve BVS? R
Strongest positive spherical lens to give
best VA
FOGGING
DUOCHROME

24. STEPS IN SUBJECTIVE REFRACTION
Start from Ret Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU
Start from Auto-Ref Results (OD)

25. STEPS IN SUBJECTIVE REFRACTION
Start from Ret Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU
Start from Auto-Ref Results (OD)

26. STEP 4 BINOCULAR BALANCING R
The technique is also known as "equalising".
R
During the monocular refraction, a different state of
relaxation of accommodation may occur because one
eye was under test while the other was not.
R
Thus, binocular balancing is performed to
balance
accommodation between eyes
.
ALTERNATE
OCCLUSION
HUMPHRISS
IMMEDIATE CONTRAST

27. BB: Alternate Occlusion R
Used only when VA is EQUAL in both eyes
1.
Fog both eyes with + 0.75DS
2.
Direct patient to view 3 lines above best VA
3.
Alternately occlude each eye for ~0.5 secseach whil e
asking patient: “Which eye sees clearer/sharper?”
4.
Add +0.25DS to the better eye
5.
Repeat step 3 and 4 until both eye’s vision is
equalised
6.
Slowly reduce fog until best VA is reached

28. BB: Humphrissimmediate contrast R
Used when VA is EQUAL or UNEQUAL between both
eyes
1.
Fog OS with +0.75DS
2.
Direct patient to view OD’s best VA line
3.
(Perform BVS in OD)
4.
Add +0.25DS in OD
e
VA same or better Add
+0.25DS, VA worse remove +0.25, until you achieve
max plus min minus
5.
Repeat Step 1-3 to test OS

29. STEPS IN SUBJECTIVE REFRACTION
Start from Ret Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU
Start from Auto-Ref Results (OD)

30. BINOCULAR BEST VISION SPHERE R
After binocular balancing, spherical lenses are add ed
in front of the 2 eyes at the same time to determin e
the Binocular Best Sphere. The most plus/ least min us
lens that would not reduce VA would be the end-poin t.
R
Strongest positive spherical lens to give best VA
1.
Direct patient to view best OU VA
2.
ADD +0.25DS
e
VA same= Add +0.25DS (Repeat
with additional +0.25DS), VA worse= Remove
+0.25DS

31. STEPS IN SUBJECTIVE REFRACTION
Start from Ret Results (OD)
1. Best Vision Sphere
2. Jackson Cross Cylinder
3. Best Vision Sphere
M
O
V
E
T
O
O
S
Repeat 1-3
4. Binocular Balancing
5. Binocular Best Sphere
OU
Start from Auto-Ref Results (OD)

32. What about for reading?
“I can see clearly at distance, but I can’t read my
newspapers!”

33. Near Addition R
Presbyopic
patients would
require a near
addition for
their reading.

34. Finding the Near Addition R
Step 1: Estimation from patient’s age
+ 2.50 and Above 70 +
+ 2.50 to + 2.75 66 -70
+ 2.50 to + 2.75 61 -65
+ 2.50 to + 2.75 56 -60
+ 2.00 to + 2.50 51 -55
+ 1.25 to + 1.75 46 -50
+ 0.50 to + 1.00 40 -45
Estimated Add (in D)
Age (in Years)

35. Finding the Near Addition R
Step 2: Place the estimated near addition on
top of the distance prescription
R
Step 3: Patients holds the near vision chart at
habitual distance. The amount of near add is
then adjusted to position the patient’s habitual
reading distance in the middle of the range of
clear vision.

36. Range of clear vision
20CM
60CM
40CM
R
Patient’s
habitual
reading
distance in
the middle of
the range of
clear vision.

37. Range of clear vision
10CM
50CM
40CM
R
If range is
too close to
patient: Add
-0.25DS in
steps

38. Range of clear vision
30CM
70CM
40CM
R
If range is
too far to
patient: Add
+0.25DS in
steps

40. Instruments for
Refraction
Trial lens set and frame
Phoropter

41. Two sets of commonly used
instruments

42. Clinical notes for trial lens and trial
frame

Spherical lenses
are usually
placed first
in the
trial frame, while
cylindrical lenses
are then
placed
in the front
of the spherical lenses.

When there are
2 or more spherical lenses
,
the one with the
strongest power
should be
placed in the
cell closest to the eye
.

43. Adjusting Sphere Powers

44. Adjusting Cylinder Powers and Axis

45. Cross Cylinder