~

National Programme
for
Control of Blindness

A Practical Guide
on
Refraction

Ophthalmology/ Blindness Control Section

Directorate General of Health Services
Ministry of Health & Family Welfare
Government of India, New Delhi - 11 O 011.
Printed and Distributed under : Danish Assistance to the
National Programme for Control of Blindness (DANPCB),
A1/148 Safdarjung Enclave, New Delhi-110029, India.
 Contents
1. Visual Acuity
2. Amplitude of Accommodation : Pushup Method 3
3. Finger Counting Fields (Confrontation Fields) 4
4. Colour Vision 6
5. Cover Test 7
6. Worth4Dot 10
7. Stereopsis 11
8. Near Points of Convergence (NPC) 12
9. Hirschberg (Corneal Reflex) 14
10. Extraocular Muscles 15
11. Interpupillary Distance (IPD) 17
12. Tangent Screen (Bjerrum's Screen) 19
13. Amsler Grid 21
14. Lensometry 23
I 5. Keratometry 25
16. Static Retinoscopy with Trial Case 27
17. Subjective Refraction with Trial Case 29
18. Binocular Balance with Trial Case 31
19. Static Retinoscopy with Phoropter 32
20. Subjective Refraction with Phoropter 33
21. Binocular Balance with Phoropter 35
22. Measuring Phorias & Vergences with Phoropter 36
23. Maddox Rod Phoria 44
 Visual Acuity

A. Equipment

1.Wall chart
2. Near-point VA card
3. Occluder
4. Lamp

B. Set-up

1. Patient wears habitual Rx for the distance being tested (when the clinician wants
to measure the patient's VA both with and without Rx. VA should be measured
without.Rx first)
2. Patient holds occluder (or uses his/her hand)
3. Patient views full chart

C. Step-by-step procedure

1. Always observe the patient not the chart.

2. Patient covers OS, always check OD first.
3. Instruct patient to read the smallest line of letters he can. If patient is unable to
read 6/60, then start counting fingers .5 meter up to 6 M.
4. Patient covers OD. Repeat steps 1-3.
5. Illuminate near point card and hold it at proper distance: (40cm) for Jaeger card
6. Repeat steps 1- 4 for near testing.

D. Recording

1. Write C, Vee, or VAcc, cc means 'with correction' . If VA is taken without

correction, use sc instead of cc: (e.g, If patient habitually wears no Rx).
2. For each eye record Snellen fraction and/or print size separately for smallest
(lowest) line in which more than half the letters were correctly identified. If off-
the -chart. See #8.
3. If additional letters were read on the next line, follow fraction or print size with a
'+' sign and the number ofletters read.
4. If letters were missed, follow fraction or print size with '-' sign and number
missed.
5. Steps 3 and 4 can be used simultaneously.
6. For near, also record the test distance.
7. Record quality of responses if abnormal.
8. If vision is so poor that Snellen fraction is inappropriate, measure and record the
acuity that applies:
 CF (counting fingers)@ .... ... ........... (distance)
HM (hand motion) @ ...
PR (light projection)
PL (light perception)
NPL (no light perception)

E. Example

VAcc OD 6/12 +l.J2@40 cm

OS 6/9-2, Jl-2 @40 cm

Pinhole VA

A. Equipment

1. Same as for distance VA

2. Pin-hole disc (PH)

B. Set-up

1. Patient wears habitual distance Rx while looking at distance VA chart. PH done

only at distance.
2. PH is done when VA less than 6/12 at distance and near through the habitual Rx.

Note: When called for, PH is done in conjunction with VA.

C. Step-by-step procedure

1. Patient occludes eye not being tested. If both eyes are to be tested, occlude OS
first.
2. Instruct patient to read the smallest line of letters he/she can through the PH.
3. Urge patient to read the next smallest line, even ifhe has to guess.

D. Recording

1. Write 'PH' followed by the numbers as for VA

E. Example

1. OD VAcc. 6/12, PH: 6/9

OS VAsc. 6/60, PH: 6/12

2
 Amplitude of Accommodation: Pushup Method
A. Equipment

I. Near point card

2. Tape measure in cm

B. Set-up

1. Patient wears his habitual distance correction

2. Patient or examiner can hold near point card

C. Step-by-step procedure

I. Occlude OS.
2. Direct patient's attention to a row of letters one or two lines larger than his best
near VA.
3. Slowly move the chart closer to the patient and instruct the patient to report when
the letters first appear blurry.
4. Measure the distance from the chart to the patient' s spectacle plane in centimeters
and convert to diopters.
5. Repeat with the OD occluded
6. Repeat OU.

D. Recording

1. Record amplitude of accommodation in diopters

2. Record each eye separately
3. Record the method of testing used

E. Example

1. Amp OD 7D
OS 7 D (pushup)
2.Amp OD6D
OS6D
OU 7 D (pushup)

3
 Finger Counting Fields (Confrontation Fields)

A. Equipment

1. Occluder
2. Lamp

B. Set-up

1. Patient wears habitual Rx

2. Patient holds occluder
3. Examiner faces patient at eye level, 50 cm away
4. Lamp illuminates space between patient and examiner without shining in either's
eyes
5. Rest of room is dimly lighted

C. Step-by-step procedure

1. Instruct patient: 'I will hold up one, two, or five fingers' (demonstrate) in your.
side vision. 'You keep looking right her (point) at my eye'. ' Without looking at
my fingers tell me how you see' .
2. Patient occludes OS/examiner closes OD.
3. Examiners looks at pt's open eye.
4. Examiner places closed fist in side vision equidistant between patient and
examiner, in each of the 8 positions and then exposes 1,2,or 5 fingers. See below.
5. If patient reports number of fingers correctly, move to new position and repeat #3.
If patient fails to count fingers correctly, move hand closer to center of field and
repeat.
6. When FCF for OD has been 'mapped' in 8 positions, patient occludes
OD/Examiner closes OS and then repeats steps 3 through 5.
7. Throughout, Examiner compares his/her presumably normal field to the patient's
field.

D. Recording

1. Record for each eye separately

2. If field appears normal, write 'full'
3. If field is abnormal, write ' restricted' and location of problem.

4
E. Example

1. FCF: full OD and OS

2. FCF: full OD, restricted temporally OS
3. FCF: restricted upper high quadrant OD and OS

X X

X
X
X
X

X X

5
 Colour Vision

A. Equipment

1. Occluder
2. Lamp
3. Color vision test book or other material

B. Set-up

1. Patient wears habitual Rx for near

2. Patient holds occluder
3. Examiner holds test book at 50cm, pages illuminated by lamp.

C. Step-by-step procedure

1. Patient occludes OS.

2. Observe patient to make sure only one eye can see test plates.
3. Flip pages one at a time and note pt' s response: correct or wrong.
4. Patient occludes OD.
5. Repeat steps 2 & 3.

D. Recording

1. Write number of correctly identified plates, a slash mark, and then the number of
plates tested, for each eye separately, ie., a fraction.
2. Record the type of test used.

Notes

1. It is considered normal to make as many as 3 mistakes in 14 plates.

2. Always compare the two eyes.

6
 Cover Test

A. Equipment
....
1. VA chart
2. Near cover test target
3. Occluder
4. Overhead lamp
5. Horizontal and vertical prism bars

B. Set-up

1. Patient wears habitual Rx for the distance being tested

2. Target
a. Distance - fixate at isolated letter, one line above VA in patient's poorer eye
(with correction)
b. Near - accommodative target - reduced Snellen letters or picture,
approximately on line above VA in the patient's poorer eye; patient holds
target.
3. Examiner holds occluder
4. Examiner or patient holds prism bar(s)
5. Room illumination must be sufficient to allow examiner to easily observe
patient's eye movements
6. Examiner must be positioned to be able to see the patient's eyes easHy but
examiner must not interfere with the patient's view of the target.

C. Step-by-step procedure

1. Instruct patient to look at the target and to keep it clear.

2. Cover- uncover test (to differentiate phorias from tropias).
3. Flip pages one at a time and note pt's response: correct or wrong.

7
Cover right eye observe left eye

Left eye moves

I Left eye does not move

I Cover left eye, observe right eJe

Right eye moves Right eye does not move

I I
Tropia Tropia No Tropia

UncoJer right eye Uncover left eye Alternatively cover right eye,
Observe both eyes Observe both eyes then left eye, observe
uncovered eye
·I I I I
Both eyes move No movement Both eyes move No movement Movement No movement

Alternating Left monocular Alternating Right monocular Phoria No Phoria

Tropia tropia tropia tropia (Orthophoric)

Diagnosis of phorias and tropias by using cover-uncover test

The occluder is held in front of the patient's eye for one second and eyes are observed as
indicated in the above chart. Before the occluder is placed in front of the other eye, a few
seconds should be allowed to elapse so the eye can return to their normal relationship.
Repeat the cover-uncover test several times to be sure an alternating tropia or intermittent
tropia is not missed.

3. Alternate cover test (to determine size and direction of deviation)

a. Cover the patient's right eye, holding the occluder in front of the eye for
approximately one second, then quickly place it in front of the left eye.
b. Alternate the occluder back and forth between the two eyes several times,
maintaining coverage of each eye for one second.
c. Observe the movement of the right eye as the occluder is moved from the right to the
left eye; observe the movement of the left eye as the occluder is moved from the left
to right eye.
d. Always observe the eye that is being uncovered for movement.
e. Responses
1. No movement - ORTHO
2. Eye moves toward the nose as it is uncovered- EXO
3. Eye moves temporally as it is uncovered - ESO
4. Eye moves downward as it is uncovered - HYPER deviation of that eye.
f. Neutralize movement with prism. Alternate cover test is repeated as described in
steps a-d with prism in front of one eye. (The prism bar(s) may be held by the patient
or the examiner). Increase the amount of prisms until no movement is observed as
the eye is uncovered (or until the motion reverses to the opposite directjon).

8
Prism should be added as follows:
Observed motion Prism orientation
EXO Base in
ESO Base out
HYPER Base down
HYPO Base up

4. Patient holds near point target at 40 cm on the same plane as his eyes with overhead
lamp on the target.
5. Repeat step 1-3 at near.

D. Recording

1. Write 'Cover Test' or ' CT'

2. Write sc (for without Rx) or cc (for with Rx)
3. Record the amount of prism needed to neutralize the deviation
4. Record the direction of deviation
E (eso)
X (exo)
RH (hyper)
LH (left hyper)

cp ORTHO

-0-
+
ISO

ORTHO,ISO

5. Record P if patient has a phoria

6. Record T if patient has a tropia
Record R or L or alt. for right, left or alternating tropia
7. Record D for distance and N for near

Note
Lateral phorias reflect the relationship between the two eyes. Therefore they should not
be identified as R, L, or alt. However, R, L, or alt. Must be recorded for all vertical
phorias and all tropias.

E. Examples

CT cc--$-DandN

+
CT sc 20° RXT; 10 XP at N

CT c~ at D; 25° alt ET at N

CT sc 25° RET with IO RH at D and N

cc 4° RET with 5 RHT at D and N

9
 Worth 4 Dot
A. Equipment

I. Red-green glasses
2. Worth 4-dot flashlight for near and/or box for distance.

B. Set-up

1. Patient wears Rx for D or N

2. Red-green glasses over the Rx. Red over the OD

C. Step-by-step procedure

1. Turn on the Worth 4-dot stimulus for distance or near (40 cm)
2. Ask patient 'How many spots of light do you see: two, three, four, or five?'
3. If patient reports 2,3 or 4, the test is over.
4. If patient sees 5 spots, ask patient ' Where are the green ones (seen by OS), to the
right, left, above, or below the red ones (seen by OD)?'

D. Recording

1. Patient sees 2 dots : Suppression OS

2. Patient sees 3 dots : Suppression OD
3. Patient sees 4 dots : Fusion
4. Patient sees 5 dots : Fusion
a. Green ones to left of red : Eso
b. Green ones to right : Exo
c. Green ones above : OD hyper
d. Green ones below : OS hyper
e. Combinations of vertical and horizontal are possible

E. Examples

1. Worth 4 Dot - fusion

2. Worth 4 Dot - suppression OS
3. Worth 4 Dot - diplopia RE hyper eso

10
 Stereo psis
A. Equipment

1. Polaroid glasses
2. Stereo target
3. Overhead lamp

B. Set-up

1. Patient wears polaroid glasses over his habitual Rx

2. Patient holds stereo target at 40 cm
3. Overhead lamp is directed toward the target

C. Step-by-step procedure

1. Direct pt's attention to the first set of circles. Ask patient 'In target number one,
which of these circles appear closest to you? Which circle appears to be floating
above the· plane of the page?'
2. Continue tes_ting until patient gives two consecutive incorrect answers.
3. If the patient is unable to identify any of the circles correctly, repeat steps 1 and 2
using the animal targets and then repeat using the circle target.
4. If the patient is unable to identify any of the animals correctly, show the patient
the large targets and ask him or her to identify the geometric figures (s) he sees, or
show the patient the fly and ask him or her to pinch the wings of the fly.

D. Recording

1. Write 'Stereo at N' (Near).

2. If done without correction, record sc; if done with correction, record cc.
3. Record the amount of stereopsis in seconds of arc (taken from the instructions that
come with the stereo test) for the last correct response the patient gave before two
incorrect responses.
4. Record the name of the test used.

E. Examples

Stereo at N sc 40 sec Titmus

Stereo at N sc 20 sec Randot
Stereo at N sc 3000 sec (stereo fly)

11
 Near Points of Convergence (NPC)
A. Equipment

1. Penlight
2. Red glass
3. Near accommodative target
4. Overhead lamp

B. Set-up

1. Patient wears habitual near Rx

2. Overhead lamp shining on target
3. Penlight (or other target) is held by examiner at 40 cm.

C. Step-by-step procedure

1. Patient is instructed to look at light (or other target) and report as soon as he sees
the target double.
2. Examiner moves target towards the patient, observing pt' s eyes until he sees one
eye lose fixation on the target. Note distance from patient's eye.
3. Move the target away from patient's eyes and note the distance at which the
patient's deviated eye regains fixation (patient will report single vision at this
distance if he reported diplopia as described below).
4. Patient should report double vision when the examiner sees one of his eyes lose
fixation. If patient reports diplopia, ask the patient to report when the target
becomes single.
If break and recovery are less than 15 cm, record the results. If either is greater
than 15 cm, do step C.5.
5. Repeat steps 1-4 with an accommodative target and a penlight as a target with a
red glass placed over one of the patient's eyes.

D. Recording

1. Write NPC and sc or cc

2. Recor.d target used:
Aecom for accommodative target
Lite for penlight
RG for penlight with red glass
3. Record the distance in cm. at which the eye deviated (or at which the patient
reported diplopia) (break)
4. Record the distance in cm at which the eye regained fixation (or at which the
patient reported seeing two targets)

12
 5. Record which eye deviated and in which direction
6. Record diplopia if patient reported seeing two targets
7. Record suppression if patient did not report seeing two targets
8. If examiner was able to move target to the bridge of the patient' s nose without the
patient losing fixation, record 'TTN' (for 'to the nose')
9. Repeat steps 2-8 for each target used

E. Examples

NPC sc accom. 5 cm/10cm OS in suppression

Lite 5 cm/10cm OS in suppression
RG 5 cm/10cm OS in suppression

13
 Hirschberg (Corneal Reflex)
A. Equipment

1. Penlight

B. Set-up

1. Patient removes Rx
2. Examiner faces patient with 50-70 cm between them
3. Examiner holds penlight

C. Step-by-step procedure

1. Turn on penlight/hold directly in front of patient 40 cm

2. Instruct patient to look at the light with both eyes
3. Observe location of the corneal reflex of the penlight relative to the pupil for each
eye
4. Compare locations of reflex in the two eyes

D. Recording

1. Record symmetry of asymmetry of reflexes

2. Record location of reflex:
'positive angle'
'central'
'negative angle'
3. If a deviation is manifest (ie., the reflexes are asymmetrical), identify the
deviating eye.
4. Estimate size of deviation in prism diopters (Imm- 15-20)

E. Examples

1. Hirsch: Sym, post. angle

2. Hir: 15 OS-exo, OD central

14
 Extraocular Muscles
A. Equipment and set up

Same as Hirschberg, (similar to NPC, but sc)

B. Step-by-step procedure

1. Like Hirschberg:
a. Tum on light/hold directly in front of patient
b. Instruct patient to tell you if,
- He ever sees the light double or become two:
- He feels any pain or discomfort
Move the light
- Move the light to other side, up, down, completing a big H pattern
- Throughout, point light at the patient's eyes, looking for asymmetries of
corneal reflex as the eyes follow the penlight, as in the Hirschberg
- Note: Do not move the penlight too far. Travel of 30-40cm from primary
position is sufficient to discover wake EOM's
- Throughout, observe:
a. Smoothness of movement
b. Accuracy of following the penlight
c. Extent of movement

C. Recording

1. If normal, write 'SAFE' or ' FESA'. You must know what these letters stand for:
S Smooth
A Accurate
F Full
E Extensive

2. If abnormal, record only the letters that apply and describe the abnormality,
whatever applies:
Jerky, unsteady, nystagmoid
failure to follow into (location).
restricted, lagging, non-commitment
3. Identify direction (s) of gaze that result in diplopia (double vision) and /or
discomfort.
4. If only one eye is the abnormal one, be sure to identify it.
5. Identify the possible paretic muscles.

15
D. Examples
1. EOMs: Safe
2. EOMs: Smooth, OS restricted left gaze and diplopia on left gaze.
3. EOM Diplopia on up-right gaze, OD lagging
4. EOM: Fesa, OD pain on left gaze

16
 lnterpupillary Distance (IPD)

A. Equipment

Easy to hold ruler marked in mm

B. Set-up

Examiner sits directly in front of patient within easy arm' s reach.

C. Step-by-step procedure

I. Distance P.D.
1. To tell patient to look at your open OS. Close OD.
2. Align zero-point of ruler on a landmark (e.g. nasal pupillary edge or limbus)
of pt's OD. Stabilize ruler by resting hand on patient.
3. Close your OS. Tell the patient to look at your new open OD.
4. Measure the corresponding landmark on patient's OS (e.g. temporal pupillary
edge or limbus).
5. Recheck the entire procedure.

@) OD
OS Examiner

OS- Pt.

OD~
Examiner

OD Pt. OS

OD
OS Examiner.

17
Net result

Although patient never looks at distance, you measure the P.D. with both eyes pointing
straight ahead, as if patient had been looking at distance.

II. Near P.D.

l . Close your OD and tell patient to look at your open OS, tip of nose, or other
near
target, Align zero - point of ruler on a landmark of patient's OD (nasal
limbus)
2. Still using your OS, measure the corresponding landmark on patient's OS
(temporal limbus)

D. Recording

1. Write distance, a slash, then near P.D. in mm

2. Sometimes the eyes are not centered with respect to the nose, and separate,
' monocular' P.D.'s are recorded for each eye relative to the centre of the bridge of
the patient' s nose.

E. Examples

1. 64/61
2. 62/58
3. OD 30/28
4. OS 32/30

F. Other facial measurement

1. Bridge
11. Intra Temporal Distance(I.T.D.)
iii. Temple or side

G. i. Measurement of gross bifocal height

ii. Measurement of gross trifocal height

18
 Tangen~Screen (Bjerrum's· Screen)
A. Equipment

1. Tangent screen
2. 3 mm white object attached to black, non-glossy stick (wand)
3. Eye patch
4. Bright illumination

B. Set-up
1. Patient wears distance Rx if it is over -4.00 or+1.00 (spherical equivalent)
2. Patch on OS
3. Patient seated 1 meter from screen, eyes level with fixation target.
4. Examiner stands to right of screen to begin
5. Brightly illuminate screen from behind patient

Note

Stand on side of vertical meridian you are plotting

C. Step-by step procedure

1. Show object to patient near fixation point

2. Tell patient you are doing a test of his side vision. Instruct patient to tell you
when he sees the object in his side vision and always to maintain fixation ori the
central fixation target (point to it).
3. Explain to patient that disappearance of the object is normal, that he should not be
alarmed, but to say 'gone' when he no longer sees it, and to say ' I see it' when it
comes into view.
4. Always observe the patient not the screen, make sure OS is occluded. Patient
fixating properly.
5. Plot the blind spot.
a. Move objective away from fixation, into the temporal field along or slightly
below the horizontal meridian.
b. When patient says 'gone' move object back toward centre until patient reports
seeing it and mark this location with a black pin. Plot seven more points,
approximately equally spaced, along the edge of the blind spot.

Note: In perimetry, always plot from unseen to seen.

6. Plot the isopter

a. Find the limits of the field of your object-size/ test -distance combination with
special emphasis on the V looking for meridional steps. Again plot from
unseen to seen.
b. If patient sees object at edge of the tangent screen, put black pin at the edge
and move to next location.

19
 c. Move object all the way around the blind spot instructing the patient to report
if the object disappears.

7. Zig-zag the object through Bjerrum's areas, superior and inferior.

8. Switch sides to plot Bjerrum's area and limits of the field for the nasal field.
9. Cover OD and repeat for the OS, starting in temporal field (patients left) an'd
switching as appropriate.

D. Recording

1. Mark locations of your black pins by putting small x' s on a standard VF recording
diagram and connect with straight lines.
2. Cross-hatch areas of non-seeing, incl. blind spot.

E. Example: Central Fields

10 mm object ~
120
Absolute~

15

195 345

210

315
300
255 270 285

Name : Dinesh
Test Object : 3 mm white
Remarks : Good fixation
Field done with +2. ODS O.U.

20
 Amsler Grid
A. Equipment

I. Amsler Grid book

2. Occluder
3. Illumination source

B. Set up

1. Patient wears best near Rx and holds occluder.

2. Examiner holds chart# 1 30 cm from patient under bright illumination.

C. Step-by-step procedure

1. Patient occludes the OS.

2.- Instruct patient: Look at the center white dot. Can you see it*? Throughout this
test you must continue to look at the white dot, while I ask you some questions
about this drawing.
*If patients cannot see white dot, use chart # 2. Most patients will be able to see
the dot, however.
3. Say to the patient:
a. While continuing to look at the white dot and without moving your eyes:
b. Can you see the four comers?
c. Repeat 'a' and notice the lines. Are any of them missing pieces? Do any
have holes in them? If so, where?
d. Are all the lines straight? Are any wavy and if so, where?"
e. Repeat ' a' and are all the little squares the same size? If some are larger or
smaller, which ones?
4. Throughout the test watch the patient. Make sure non-tested eye is occulded and
patient maintains fixation on the white dot.
5. Have patient occlude OD and repeat steps 2-4
Note: If one eye sees much better than the other, start with the better eye as this
will enhance patient's understanding of the tests and the reliability of his
responses of the tests.

D. Recording

1. If there are no problems, record 'Amsler' the eye tested followed by 'WNL'
(within normal limits).
2. If there is a problem record the eye, the nature of the problem, and its location on
the grid.
3. It is understood that plate # 1 was used unless otherwise noted.
4. If there are problems, you may also draw what the patient sees on an Amsler
black-on-white recording chart (see below).

21
E. Examples

1. Amsler OD WNL/OS WNL

2. Amsler OD WNL
OS up left corner not screen
3. Amsler OD lines wavy centrally
OS scotoma 2-5 degree to left 3 degree above and below fixation

Note

The Amsler Grid book contains a detailed account of the theory of the test and lists the
questions you should ask. It also explains when and how to use each of the 6 plates
(included in the book).

This procedure sheet is a quick reference to refresh your memory about the Amsler Grid
test. It is not a substitute for Amsler' s book, which should be read in its entirety before
performing an Amsler Grid test on a patient.

22
 Lensometry
A. Equipment

1. Lensometer

B. Set up

I. Lensometer ON
2. Glasses held in machine and level, ocular surface away from you
3. Center of mires in center of eyepiece reticle
4. Eyepiece focused for you
5. Always do OD lens first

C. Step-by-step procedure

I. Single vision lens

1. Focus each set of lines once. If they are both in focus at once, the lens is
spherical. Record the power. Go on to other lens. If lens has cyl. go to
next step.
2. Focus on the lines requiring the less minus (or more plus).
3. Orient the axis of the lensometer so that the single line mires are in-focus
with the less minus and are perfectly straight and aligned. Record the
power reading.
4. Now focus the triple mires with the power knob. This should involve shift
to more minus. Record the difference between the powers in step 3 and 4.
This is the amount of minus-cyl power in the lens.
5. Record an 'X' and the axis reading from the lensometer.

II. Multifocal lenses

1. Perform I on the carrier (distance part).
2. Turn glasses around so ocular surface faces you.
Y. Recheck one meridian in the carrier and compare this power to power in the
same meridian through the segment. The difference between these powers is
the ADD.
4. The ADD should be determined for each different seg. power.

III. Prism
1. Locate the center of the mires at the center of the eyepiece reticle.
2. Dot this location on the lens (this is the optical center of the lens).
3. Subsequently dot the location of the pt' s line of sight on the lens.
4. Prism is computed by the relationship
P in prism diopters = Dell 0.

23
 Where D is the power of the lens in diopters and c is the liner distance
between the patient's line of sight and the optical center of the lens in mm. It
is customary to calculate vertical, and horizontal prism separately.
5. If prism is 'ground' into the lens, it may be impossible to center the mires in
the reticle. In this case, dot the lens with the patient's line of sight & centre
this part of the lens in the reticle.-
6. Measure the amount of prism using the prism scale of the reticle
Note: With high amounts of prism, it is difficult or impossible to locate the
center of the mires. In this case, hand-held prisms must be inserted along with
the lens until the mires can be located. The value of these prisms is added to
the final result.
7. Record'=' anct amount and direction of prism in the glasses.
Note: Prism induced by spectacles is the Net Discrepancy between the prism
induced in the two eyes, not the prism induced by any one lens.

D. Recording
1. Record the Rx for each lens in stand Rx form

E. Examples
I. OD - 2.75DS
OS-2.25DS / -1.0DC x 10

2. OD+ 2.75DS / +0.50 DC x 90 I +2.0D add

OS+ 3.25DS I +l.25 DC x 110 / +2.0D add

3. OD-2.0DS /-1.0DC x180 / +1.5 add

OS+ 2.75DS / l.SDC x 160 / +20D add

4. OD+ 2.0DS I -1.0DC x 165 / 2Af3I/ +1.0D add

OS+ 2.0DS / -1.0DC xlO / 2Af3I / +I.OD add

24
 Keratometry
A. Equipment

1. Keratometer or ophthalmometer

B. Set-up

1. Patient removes Rx
2. Focus the eyepiece
a. Set the adjustable eyepiece so that it extends as far out as possible
b. Place a white paper in front of the instrument objective to retroilluminate the
reticle
c. Adjust the eyepiece until the reticle is first seen in sharp focus
3. Adjust height of chair and instrument to a comfortable position of both patient
and examiner
4. Unlock instrument controls (B & L keratometer)
5. Instruct patient to place his chin in the chin rest and forehead against the forehead
rest
6. Raise or lower the chin rest until the patient's outer canthus is aligned with the
hash mark on upright support or the pointer on the side of the instrument.

C. Step-by-step procedure (See figure I - IV)

1. From outside the instrument, roughly align the telescope with the patient's eye
2. Instruct the patient to look at the image of his eye in the keratometer
3. Look into the keratometer and align it by moving it P-om side to side or up and
down until you can see the image of the mires(# circulus) on the patient's cornea
(Fig. I)
4. Focus the mires and align them with the reticle in the lower right and hand circle
(Fig II)
5. Lock the instrument (B & L keratometer only)
6. Adjust horizontal and vertical power wheels until mires are in close apposition.
7. Rotate the telescope to align the spurs on the mires to 2 major meridians of the
patient's cornea (Fig III)
8. Adjust the horizontal power wheel until the horizontal mires are co-incident
9. Adjust the vertical power wheel until the vertical mires are co-incident
I 0. Readjust focus and/or re-center reticle as needed.

D. Recording

1. Record for each eye separately

2. Record the power and meridian for horizontal meridian first (the pnmary
meridian)
3. Write a slash mark after the primary meridian and record the power and meridian
for the vertical meridian (the secondary meridian)
4. Record the amount of corneal astigmatism in diopters

25
 5. Record the type of astigmatism:
WR - with the rule
AR - against the rule
OBL - oblique
6. Record the conditions of the mires e.g. MCAR- mires clear and regular
MIAD - mires irregular and distorted

E. Examples

OD 42.50 at 180/43.50 at 90; 1:00 D WR, MCAR

OS 47.35 at 180/41.37 at 90; 6:00 DAR, mires distorted

OD 41.75 a 180/43.75 at 70; 2.00 D irregular astig; mires distorted

OS 43.12 a 135/41.87 a 45; 1.25 D OBL; MCAR

OD 42.00/43.00 at 90; 1.00 D WR MCAR

OS 42.00/42.00 at 90; sphere MCAR

(Meridians are expected to be 90 degree apart : therefore if only the secondary

meridian is recording the position of the primary meridian can be assumed to be 90
degrees away)

Keratometry

Figures for part C; step-by-step procedure

I. steps C 1-3 III. Steps C 6-7

0
X

+
II. step C 4 IV. Steps C 8-9

0
()+G)
26
 Static Retinoscopy with Trial Case
A. Equipment

1. Retinoscope (Plane Mirror)

2. Trial Frame
3. Trial Lenses
4. Retinoscopy Lamp
5. Fixation chart

B. Set-up

1. Patient wears trial frame. It should sit straight and comfortably on the pt's
face
2. Examiner is at same level as the patient, checks pt's OD with his/her OD and
the pt's OS with his/her OS.
3. Examiner holds retinoscope 1 meter or 67 cm from pt's eye. This is the
retinoscopy working distance and is converted to diopters

C. Step-by-step procedure

1. Instruct patient to fix at distance target with both eyes open.

2. Observe the reflex of pt' s OD. If the movement is AGAINST neutralise with
minus lenses, if the movement is WITH neutralise with plus lenses. If the
patient is accommodating at distance then over plus or unde minus the patient
by 1.5-2.0 D (this is called fogging the patient).
3. Locate the 2 principle meridians for the OD. If there is astigmatism,
neutralise the less myopic (or the less hypermetropic) meridian with sphere
first. Then neutralise the more myopic (or the more hypermetropic) meridian
with cylinder. Use minus cylinder for myopia and plus cylinder for
hypermetropia and aphakia. Remember to align the axis of the cylinder 90°
away from the meridian of power.
4. Recheck the first (spherical) meridian, it should still be neutral.
5. Keep gross static finding in front of the patient. Patient' s OD and neutralise
the pt's OS using your left eye & left hand Repeat steps# 1-4 for OS.
6. Check patient's VA without any lenses OD+OS (if necessary).
7. Convert the gross retiniscopy to net retiniscopy by adding the working
distance (in Diopters) to the gross.
Example: If the retinoscopy working distance is 67cm, the dioptral value is
100/- 67=1.5D. This value will always be minus. If gross is - 2. OD, net will
be -3.5 D. Only add to the sphere: if gross is +4.0+2.0*90, net is +2.0*90. '
8. Measure the patient's acuity OD and OS through the net retinoscopy.

27
D. Recording

1. Record net static for each eye and the patient's VA through the net static.
Example: Net static
OD - 1.5 sph 6/9
OS - 1.75 sph 6/9

28
 Subjective Refraction with Trial Case
A. Refining the Sphere

I. Take VA with net static retinoscopy OD and OS

2. Think of Egger's chart
3. First Step: Add .25 or .50 DS of plus. This is to recheck that the patient is not
accommodating and is not overcorrected. Keep adding plus until VA is 6/9. Then
start to add .25 DS of minus. (reduce plus), checking VA each time.
4. End point:
a. VA is 6/6 or better
b. No improvement with +/-spheres

B. Refining the cylinder

Jackson crossed cylinder (JCC). Only do this test if the patient does not see 6/6 with the
spherical correction or if patient has symptoms of astigmatism or if there is a large
amount of cylinder (> 1.5 D) and a change of axis. Remember that with hand held JCC,
the white slash marks represent -.50 cylinder and the red slash marks represent +.50
cylinder.

1. Instruct patient to look at 6/12 line or one line above best VA

2. Axis Check

a. Place the JCC in front of the trial frame with the red and white marks each at 45°
to the trial lens cylinder axis, so that the handle of the JCC lies along the same
line as the axis of the trial lens cylinder.
b. Instruct the patient 'I will show you 2 views of the line of letters, both may be
blurry. You tell me which view is sharper or less blurry'.
c. The JCC is now twirled so that the white marks (-) and the red marks (+) change
positions.
d. The patient chooses a position, the axis of the cylinder will now be turned 10°
towards the white marks. Plus cylinder 10° to the red marks.
e. Repeat steps a-d. If patient reverses direction, then tum back the axis only 5°, or
select the mean.
f. End point: Both views equally blurry or same.

3. Power check

a. Place the JCC so that the red marks(+) lie along the trial lens cylinder axis.
b. Instruct the patient as above.
c. Twirl the JCC over so now the white marks (-) lie over the trial lens axis.

29
 d. The patient chooses which side is clearer. If patient prefers red marks(+) add+
.50 to the cylinder; if patient prefers white marks (-) ass -.50 to the cylinder or
+0.25 DS with-0.50 cylinder. The spherical equivalent /JCC rule).
e. End point: Both views equally blurred or the same.
f. Finish by adding maximum plus spherical lenses for best VA, or do + 1.00 DS
blur check test.
Note: JCC can be confusing to some patients. Do not do this technique if the
patient does not understand/ cooperate.

+1.00 DS blur check test

At the end of the distance refraction you need to check if the patient's accommodation is
relaxed.
1. Tell patient that you will now put a lens in the trail frame which will make his vision
worse. Place a+ 1.00 DS in the frame and ask him to read down the chart.
2. With a pupil size of 4 mm (approx) they will only be able to read down to 6/18 if
their accommodation was relaxed.
- If he can read 6/12 or better this usually indicated that the accommodation
was still active.
- If he can read 6/18 or worse their accommodation must be relaxed so there
is no read to confirm the results with a cycloplegic refraction.
Note

If the pupils are small, 2 mm or less, this test is unreliable. This may happen with elderly
patient's and with patient's using pilocarpine drops for glaucoma. In both these groups
the accommodation is rarely active.
For patients with a best VA of 6/12 or worse, this technique is unreliable. Record the
results in brackets.

30
 Binocular Balance with Trial Case

Perform this technique only if the two eyes achieve the same VA separately under
monocular conditions. The purpose of binocular balance is to match and relax
accommodation in the 2 eyes. If you occlude one of the patient's eyes, both eyes will
accommodate up to 1.00 or 2.00 dioptres. By using a technique which encourages both
eyes to relax their accommodation, the full refractive error can be determined.

1. After refracting OD and OS separately, place +0.S0 DS over both eyes. {add
+.50 to the subjective refraction OU).
2. Instruct patient to look at line of letters 3 lines above best VA. If patient is not
6/9 or worse, add more plus to fog patient.
3. Make sure both eyes are able to see target.
4. Alternately occlude OD and then OS asking patient to compare the two eyes
and report which eye is less blurry.
5. Add +0.25 DS to the better eye.
6. Repeat steps 4 + 5 until both eyes equally blurry or same check VA OU
7. Begin to remove plus, +0.25 DS at a time, to both eyes together. Reduce plus
until patient sees 6/6 OU.
Note: It may be difficult to achieve a perfect match between the two eyes. In
this case, leave the slighting dominant eye with the slightly sharper vision.

31
 Static Retinoscopy with Phoropter
A. Equipment

I. Retinoscope (streak)
2. Phoropter
3. Fixation target: 6/60 with red/green filter

B. Set-up

1. Patient removes Rx.

2. Patient looks through the phoropter with both eyes open and no lenses in
place. Adjust the chair and phoropter height, the PD the level, etc., so that
both patient and examiner are comfortable.
3. Examiner holds retinoscopy 50 cm or 67 cm from patient's eye.
4. Room is darkened.

C. Step-by-step procedure

1. Instruct patient to look at fixation target with both eyes open.

2. If patient is a young hypertrope or is accommodating, then fog the patient
(add+ 1.5D over refraction).
3. Neutralise the patient's OD first. If the reflex movement is against use
minus lenses, if WITH use plus lenses.
4. Locate the principle meridians for OD. If there is astigmatism neutralise
the less myopia or more hyperopic meridian first with sphere, then the
second meridian should show against motion.
5. Align the streak with the cylinder axis indicator on the phoropter and
neutralise against motion with minus cylinder.
6. Recheck the first meridian after adding cylinder to be certain it is still
neutral.
7. Leave the gross static finding in front of the patient's OD and neutralise
the patient's OS by using your OS and holding the retinoscope in your left
hand. Follow steps 1-6 for OS.
8. Convert the gross retinoscopy to net retinoscopy by adding your working
distance (in dioptres) from the gross retinoscopy.
9. Measure the patient's acuity OD and OS through the net retinoscopy.

D. Recording

1. Record net static for each eye and the patient's VA through the net static
Example: QD + 2.75 sph 6/18
OS+ 1.5-0.50 * 175 6/6
Note

Ask the patient to inform you if your head blocks his view of the fixation target. It may
be necessary to rotate the phoropter slightly to allow patient to see the target and to allow
you to maintain alignment along the visual axis.

32
 Subjective Refraction with Phoropter
A. Refining the sphere

1. Take VA with retinoscopy OD and OS

2. Think of Eggers chart
3. Add+ 0.50 DS to recheck accommodation. Keep adding plus until VA us 6/12
4. Then reduce plus (add minus) .25D at a time checking VA each time. For each
click, encourage patient to read the next smaller line.
5. End-points:
a. VA is 6/6 or better
b. Next click makes letters smaller or darker but not clearer or sharper
c. Duochrome (optional)
- Expose the duochrome chart.
- Put red-green filter over chart of letters.
- Ask patient to look from green side to red side and back to green side.
Tell patient to report which side has sharper, clearer letters, or if they
are the same.
- If red is better, give another click of minus (0.25 DS); if green is
better; add one click of plus.
- End point: Red - green balance, or one (not more) clicks into the
green.
- Recheck VA without red-green filter.

6. Think:
a. Do the numbers follow Egger' s chart?
b. Remember MPMVA (Maximum plus for Maximum VA).
c. Patient may not see 6/5 or sharp vision with this procedure since you have
only worked with the sphere, and not yet refined the cyl. You may have to
over-minus the patient (0.25DS) before doing JCC to assure that the circle of
least confusion will be on the retina.

B. Refining the cylinder

Jackson crossed Cylinder (JCC) Do this after refining the sphere.

Only do this test if the patient does not see 6/6 with the spherical correction or if the
patient has symptoms of astigmatism or there is a large amount of cylinder (> 1.5 D) and
a change of axis. Remember that in the phoropter, the red marks represent -0.25 cylinder
and the white marks represent +0.25 cylinder. Instruct patient to look at 6/12 line; or one
line above best VA.

I. Axis Check

a. Place JCC before the eye so that the red marks (-0.25 cylinder) and the white marks
(+0.25 cylinder) are at 45° to the axis of the cylinder in the phoropter. It wti.1 click
into place.
b. Instruct the patient: I will show you 2 views of the line ofletters. Both may be blurry.
Tell me which view is sharper or less blurry.
33
c. The JCC is now twirled so that the red marks (-) and white marks (+) change
positions.
d. Move the axis toward the RED marks of the preferred view, about 10°. Report steps
a-c until both views look same or there is a reversal of direction. In this case move
the axis in 5° steps.
e. End point:
- Both views same
- Patient moves back and forth within a narrow range. Select the mean

II. Power Check

a. Place JCC so that white marks(+) lies over the cylinder axis in the phoropter,
and red marks(-) are perpendicular to the cylinder axis.
b. Instructions same as above
c. Twirl the JCC so that red marks(-) and white marks(+) change positions.
d. If patient prefers view with red marks(-) aligned with cylinder axis, increase
the power of the cylinder by 0.25 D. If patient prefers view with white marks
(+) aligned with cylinder axis, decrease the power of the cylinder by 0.25 D.
e. To maintain the spherical equivalent, remember that for each increase in
minus(-) cylinder of-0.50 D, add +0.25 to the sphere. For each decrease in
minus - cylinder of -0.50 D, add - 0.25 to the sphere.
f. End points:
1. Both views same
2. If patient response is varying, use the smaller power of cylinder.

Remember that the JCC in the phoropter is opposite to the hand held JCC; the red marks
represent-0.25 cylinder and the white marks represent +0.25 cylinder.

34
 Binocular Balance with Phoropter

Perform this technique only if the two eyes achieve the same VA separately under
monocular conditions. The purpose of binocular balance is to match and relax
accommodation in the 2 eyes. If you occlude one of the patient's eyes, both eyes will
accommodate up to 1.00 or 2.00 dioptres. By using a technique which encourages both
eyes to relax their accommodation, the full refractive error can be determined.

Methods:
1. Alternate occlusion
2. Prism dissociation

1. Alternate occlusion

a. Isolate a line of letters 2-3 lines above best VA.

b. Fog each eye by +0.50 DS relative to the monocular MPMVA/JCC
refraction. Measure patient's VA OU, if not 6/9 or worse add more plus to
fog patient. Make sure both eyes are looking at the target.
c. Instruct patient to compare the two eyes while you are alternately occluding
OD and OS. Patient should report which eye is less blurry.
d. Add +0.25 DS to the better eye.
e. Repeat steps a-d until both eyes are equally blurry. Check VA OU.
f. Slowly reduce the plus binocularly until the patient sees 6/6 with both eyes.

2. Prism dissociation

a. Isolate a line ofletters 2-3 lines above best VA.

b. Fog each eye by +0.50 DS relative to the monocular MPMVA/JCC refraction.
Measure patient's VA OU, if not 6/9 or worse add more plus.
c. Place 3-4 BU prism over the OD and 3-4 BD prism over the OS, using the
Phoropter's Risley prisms.
d. Make sure both eyes are unoccluded and can see the screen.
e. Inform patient that he/she should see 2 lines ofletters which may be blurry.
f. Tell patient to compare the 2 lines and report which line is less blurry, upper
or lower. Remember, the image is opposite the base of the prism, so BU
prism image is down.
g. Add +0.25 (remove - 0.25) to the better eye.
h. Repeat steps f+g until both lines are same or patient is switching back and
forth between the 2 eyes.
1. Remove prism from both eyes and do MPMVA refraction for the sphere with
both eyes open, adjusting the sphere simultaneously until VA 6/6 OU.

Note

It may be difficult to achieve a perfect match between the two eyes. In this case, leave
the dominant eye slightly sharper vision.

35
 Measuring Phorias and Vergences with Phoropter
A. Equipment

I. Phoropter
2. Projector with VA slide/screen
3. Near-point rod
4. Near point card
5. Lamp

B. Set-up

1. For distance testing:

a. Patient's distance subjective refraction in phoropter
b. Isolate a single letter from the 6/9 line or 1 line above best VA. Whichever
is larger.
2. For near testing:
a. Patient must be able to see near target clearly. If patient is young, leave
dist. subj. in phoropter, but in presbyopes it is necessary to introduce an
add (plus) until patient can see the target.
b. Use a near-patient target with small letters, one line above best near VA.
Letters must occupy a small area to form a discrete target.
c. Card at 40 cm.
d. Card illuminated enough to insure vision, but not brightly.

C. The above apply to horizontal and vertical Von Graefe phorias and to horizontal
and vertical vergences

Note

I. Phorias and vergences may be done with:

a. Habitual Rx-test results obtained through the lens prescription the patient
usually wears.
b. Induced Rx-test results obtained through the lens prescription the clinician
proposes to give the patient
2. It is inappropriate to perform these tests on monocular patients and pts. with
strabismus.

D. Von Graefe (Phoropter) Phorias Distance Lateral

1. Set up for distance testing.

2. Using risley prisms, place 6° BU before the OS and 12° BI before the OD. Have
patient close eyes while doing this.
3. Have patient open both eyes. Ask patient how many targets he sees and where
they are in relation to one another. If patient sees one target for two in the
incorrect relationship to one another, make necessary adjustments. Tell patient to
look at tlie lower image, and to keep it clear.

36
 4. Instruct patient: "Look at the lower target. But think about the other or upper one.
I will make the upper target move. You tell me when the two images for targets
are vertically lined up like the buttons on a shirt, one directly above the other.
You should always see double, keep the images clear, and continue to look at the
lower target."
5. At about 2 per second, reduce the BI-OD prism until the patient reports vertical
alignment.
6. Continue changing prism in the same direction. i.e. overshoot endpoint until
patient sees two targets, one up and to the left, one down and to the right.
7. Then bringing prism back in the other direction until patient again reports
alignment.
8. Result = average of values in steps 5 and 7, if they are within 3° of each other.
Otherwise take another measurement, emphasizing the instructions to the patient,
and average the 2 closer values.
Note: the endpoint is often variable as the images often move around. Use the
first at which patient reports alignment.

Recording
Recording size (in prism diopters) and type of deviation observed.

Example
DLP: 2 BI or 2 exo
DLP: 4 BO or 4 eso

E. Von Graefe (Phoropter) Phorias Distance Vertical

1. Set up for distance testing.

2. Using risley prisms, place 6° BU before the OS and 12° BI before the OD. Have
patient close eyes while doing this.
3. Have patient open both eyes. Ask patient how many targets he sees and where
they are in relation to one another. It patient sees one target or two in the
incorrect relationship to one another, make necessary adjustments. Tell patient to
look at the image to the right and to keep it clear.
4. Instruct patient: "Look at the target to the right. But think about the other, or left
one. I will make the left target move. You tell me when the two images or targets
are lined up like the headlights of a car, one directly beside the other. You should
always see double, keep the images clear, and continue to look at the target to the
right."
5. At about 2 per second, reduce the BU-OS prism until the patient reports
alignment.
6. Continue changing prism in the same direction. i.e. overshoot the endpoint until
patient sees two targets, one up and to the left, one down and to the right.
7. Then bring prism back in the other direction until patient again reports alignment.
8. Result = average of values in steps 5 and 7, if they are within 2 of each other.
Otherwise take another measurement, emphasizing the instrnctions to the patient,
and average the 2 closer values.
Note: With 12° BI some patients will see only one image. Alternately occlude
each eye and be sure each eye can see its image. It may be necessary for some
pts. to start with a different amount of prism before the OD.

37
Recording

Record size (in prism diopters) and type of deviation observed. For vertical phorias, you
must also record the eye (as per these instructions) before which at the vertical prism was
placed.

Example

DVP: 2 BD on OS or 2 L hyper
DVP: 1 BU on OS or 1 R hyper (1 L hypo)

F. Von Graefe (Phoropter) Phorias Near Lateral

1. Set up for near testing.

2. Using Risley prisms, place 6° BU before the OS and 12° BI before the OD. Have
patient close eyes while doing this.
3. Have patient open both eyes. Ask patient how many targets he sees and where
they are in relation to one another. If the patient sees one target or two in the
incorrect relationship to one another, make necessary adjustments. Tell patient to
look at the lower image, and to keep it clear.
4. Instruct patient: "Look at the lower target. But think about the other or upper
one. I will make the upper target move. You tell me when the two images or
targets are vertically lined up like the buttons on a shirt, one directly above the
other. You should always see double, keep the images clear, and continue to look
at the lower target."
5. At about 2 per second, reduce the BI-OD prism until the patient reports vertical
alignment.
6. Continue changing prism in the same direction, i.e.: overshoot the endpoint until
the patient sees two targets, one up and to the left, one down and to the right.
7. Then bring prism back in the other direction until patient again reports alignment.
8. Result = average of values in steps 5 and 7, if they are within 3 of each other.
Otherwise take another measurement, emphasizing the instructions to the patient
and average the 2 closer values.
Note: The endpoint is often variable, as the images often move around. Use the
first value at which patient reports alignment.

Recording

Record size (in prism diopters) and type of deviation observed.

Example
NLP: 6 exo or 6 BI
NLP: 6 BO or 6 eso

G. Von Graft (Phoropter) Phorias Near Vertical

1. Set up for near testing

2. Using Risley prisms, place 6 BU before the OS and 12 BI before the OD. Have
patient close eyes while doing this ..
38
 3. Have patient open both eyes. Ask patient how many targets he sees and where
they are in relation one another. If patient sees one target or two in the incorrect
relationship to one another, make necessary adjustments. Tell patient to look at
the image to the right, and to keep it clear.
4. Instruct patient: "Look at the target to the right. But think about the other, or left
one. I will make the left target move. You tell me when the two images or
targets are lined up like the headlights of a car, one directly beside the other.
You should always see double, keep the images clear, and continue to look at the
target to the right."
5. At about 2 per second, reduce the BU-OS prism until the patient reports
horizontal alignment.
6. Continue changing prism in same direction, i.e.: overshoot the endpoint until the
patient sees two targets, one up and to the left, one down and to the right.
7. Then bring prism back in the other direction until patient again reports alignment.
8. Result= average of values in steps 5 and 7, if they are within 2 of each other.
Otherwise take another measurement, emphasizing the instructions to the patient
and average the 2 closer values.
Note: With 12 BI some patients will see only one image. Alternately occlude
each eye and be sure each eye can see its image, It may be necessary for some
patients to start with a different (more) amount of prism before the OD.

Recording

Record size (in prism diopters) and type of deviation observed. For vertical phorias, you
must also record the eye as per these instructions) before which the vertical prism was
placed.

Example

NVP: 2 BD on OS or 2 L hyper
NVP: 3 BU on OS or 3 R hyper (3 L hypo)

H. Vergcnces (Phoroptcr) Distance Horizontal

1. Set up for distance testing

2. Place Risley prisms, set to zero, before both eyes. The prism-zero marker should
be set so that variable amounts of Horizontal prisms can be introduced
3. Have patient open both eyes. Tell him he should see one image, and to keep it
clear
4. Instruct patient: "Look at the target". (Assure yourself that patient sees one
image only). "Tell me when the target blurs and when you see two targets."
5. At about 2 per second introduce BI prism before both eyes. (Total of 4 per
second)
6. Note total prism before the two eyes for first blur, if observed (=Blur point) and
for break (=Break point)
7. Add a little more prism in same direction, i.e., overshoot the break point slightly.
Instruct patient: "Tell me when the target is single or becomes one again"
8. Then reduce prism until patient again reports single target (=Recovery point) and
note total prism before both eyes
9. Repeat steps 6 - 8 with BO prism before both eyes.
39
~ecording

Record the two sets of three values (blur, break, recovery for BI and for BO) in
prism diopters. If no blur point is ·observed, a dash (-) is entered.

Note: If values are in the direction opposite to what your expect, record value as
minus diopters. e.g.: Ifrecovery on BO vergences occurs only with the use of BI
prism before the patient record minus the amount of BI prism. If patient reports
that the target is moving to one side, the patient is suppressing one eye.
Determine which eye is suppressing, and record appropriately.

Example

1. @D BI: -/10/4 BO: 12/18/8

2 @D BI: 22/24/18 BO: 4/6/-8

I. Vergence (Phoropter) Distance Vertical

1. Set up for distance testing

2. Place Risley prisms, set to zero, before both eyes. The prism-zero marker should
be set so that variable amounts of vertical prism can be introduced.
3. Have patient open both eyes. Tell him he should see one image and to keep it
clear
4. Instruct patient: "Look at the Target." (Assure yourself that patient sees one
image only). "Tell me when the target doubles or when you see two targets."
5. At about 2 per second introduce BU prism over OS
6. Note the amount and the direction of prism before the OS for break(=Break point)
7. Add a little more prism in same direction, i.e. overshoot the break point slightly
Instruct the patient: "Tell me when the target is single or becomes one again."
8. Then reduce prism until patient again reports single target(=recovery point) and
move amount and direction of prism before the OS.
9. Repeat steps 6 - 8 starting with BD prism over the OS

Recording

Record the type of vergence and two sets of values (Break and Recovery for BU
and for BD) and prism diopters
Note: If values are in the direction opposite to what you expect, record value as
minus diopters. If patient reports that the target moving, he is suppressing one
eye. Determine which eye is suppressing and record appropriately.

Example
1. L - infra 4/2, supra 2/-1
2. L - infra 6/4, Supra 3/1

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J. Vergences (Phoropter) Near Horizontal

1. Set up for near testing.

2. Place Risley prisms, set to zero, before both eyes. The prism-zero marker should
be set so that variable amounts of horizontal prism can be introduced.
3. Have patient open both eyes. Tell him he should see one image, and to keep it
clear.
4. Instruct patient, "Look at the target"(Assure yourself that patient sees one image
only). "Tell me when the target blurs and when you see two targets."
5. At about 2° per second introduce BI prism before both eyes. (Total of 4° per
second).
6. Note total prism before the two eyes for first-blur, if observed (=Blur point) and
for break (=Break roint).
7. Add a little more prism in same direction, i.e., overshoot the break point slightly.
Instruct patient "Tell me when the target is single or becomes one again."
8. Then reduce prism until patient again reports single target (=Recovery point) and
note total prism before both eyes.
9. Repeat steps 6-8 starting with BO prism before both eyes.

Recording

Record the two sets of three values (Blur, Break, Recovery for BI and for BO) in prism
diopters. If no blur point is observed, a dash (-) is entered.

Note

If values are in the direction opposite to what you expect, record value as minus diopters.
e.g.: If recovery on BO vergence occurs only with the use of BI prism before the patient
record minus the amount of BI prism. If patient reports that the target is moving to one
side, the patient is suppressing one eye. Determine which eye is suppressing and record
appropriately.

Examples
1. @N BI: 14/18/10 BO: 18/24/16
2. @N BI: 12/20/14 BO: 4/10/-4

K. Vergences (Phoropter) Near Vertical

l . Set up for near testing.

2. Place Risley prisms, set to zero, before both eyes. The prism-zero marker
.should be set so that variable amounts of vertical prism can be introduced.
3. Have patient open both eyes. Tell him he should see one image, and to keep it
clear.
4. Instruct patient: "Look at the target" (Assure yourself that patient sees one
image only). "Tell me when the target doubles or when you see two targets."
5. At about 2° per second introduce BU prism over OS.
6. Note amount and direction of prism before the OS for break (=Break point).
7. Add a little more prism in same direction, i.e., overshoot the break point
slightly. Instruct the patient: "Tell me when t~e target is single or becomes one
again."
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 8. Then reduce prism patient again reports single target (=Recovery point) and
note amount and direction of prism before the OS.
9. Repeat steps 6-8 starting with BO prism over the OS.

Recording

Record the type of vergence and the two sets of values (break and recovery for BU and
BD) in prism diopters.

Note

If values are in the direction opposite to what you expect, record value as minus diopters.
If patient reports that the target is moving, he is suppressing one eye. Determine which
eye is suppressing and record appropriately.

Example

1. L-Infra 6/4, Supra 4/1

2. L-lnfra 6/1, Supra 6/3

L. Flow of Near Refraction Determining the add for a presbyope

Prerequisite 1. First begin with a correct distance Rx

Starting points 2. Patient's age and refractive status: see chart below
3. Current net near Rx and near VA: Think "one click per
line"
4. Amp: leave half the amp in reserve
a. Push-up amps
b. Donder' s table
c. Hofsetter's formula for average

Refinement 5. NRA/PRA: balance

6. Rx matches predictions from starting data
7. Trial-frame the induced near Rx
a. Near VA(OD, OS and OU) should be maximum
attainable
b. Linear range of clear vision should be equally
spaced around the CNWD (Customary Near
Working Distance)
8. Think
a. Add should make sense for patient see starting data
b. Keep changes as small as possible
c. Change should be responsive to patient problem

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 Tentative add as a function of Age and Refractive Status

Age Refractive Status

Myope/Emmetrope Low Hyperope High Hyperope

33-37 0 0 +0.75
38-43 0 +0.75 +1.25
44-49 +0.75 +l.25 +2.00
50-57 +l.25 +2.00 +2.25
58-63 +2.00 +2.25 +2.50
64 and Over +2.25 +2.50 +2.50

Negative Relative Accommodation/Positive Relative Accommodation NRA/PRA

A. Equipment

1. Phoropter
2. Near point card
3. Near point rod

B. Setup

1. Patient wears best distance prescription or tentative near prescription

2. Near point card on near point rod at 40 cm with good illumination
3. Phoropter set for near PD

C. Procedure

1. Direct patient's attention to the letters.

2. For NRA, add plus lenses binocularly +0.25D at a time until the patient
reports the first sustained blur. Note the total amount of plus added to be
recorded later.
3. Return the lenses in the phoropter to the distance prescriptions or proposed
near prescription.
4. For PRA, add minus lenses binocularly, -0.25D at a time until the patient
reports the first sustained blur. Note the total amount of minus added to be
recorded later.

D. Recording

1. Record the amount of plus added for the NRA and the amount of minus added
for the PRA

E. Example
NRA/PRA: +2.25/-2.50

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 Maddox Rod Phoria

A. Equipment

1. Penlight and/ or muscle-light

2. Maddox rod (red or white)
3. Prism (bars or hand-held or Risley prisms)

B. Set up

1. Patient wears best Rx or habitual Rx for distance or near

2. Patient holds Maddox rod over OD
a. For lateral phorias, grooves on Maddox rod are held horizontally,
forming a vertical streak.
b. For vertical phorias, grooves on Maddox rod are held vertically
forming a horizontal streak.
c. Test may be done in space with hand held Maddox rod and prism bar
or in the phoropter with the Maddox rod and Risley prisms.

C. Step-by-step procedure

1. Tum light-source on
2. Have patient look at the light
3. Refine position of the Maddox rod so that the streak is perfectly vertical (for
OLP and NLP) or horizontal (for DVP and NVP)
4. Have patient tell you where the line is located relative to the light.

D. Recording

1. Qualitatively, record the direction of the deviation. Remember, this is a

diplopia test: Deviation of the eye is opposite to the perceived direction of the
target (Exophoria=crossed diplopia, esophoria-uncrossed, the hyperphoric eye
sees the lower target).
2. Quantitatively, use prism over the OD to move the streak to the light.
Remember BI corrects exophoria, etc., Record amt. and direction of
neutralising prism, and the eye for vertical phorias.
3. Remember, zero phoria is recorded ortho or iso.
Note: A cyclophoria (tendency of the eye to intort or extort when fusion is
broken) will cause the streak to appear tilted when the Maddox Rod is in the
exactly correct position. If you suspect a cyclophoria, set the rod as best as the
streak. Be certain to check that pt, is holding his head straight.

E. Example
1. DLP c red MR ortho NLP c red MR 6 exo
2. DVP c red MR iso NVP c red MR O iso

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 Binocular and Accommodative Expecteds

Donder's Table Hofstetter's Formulae Donder's Table Hofstetter's Formulae

AGE AMPLITUDE (DIOPTERS) AGE AMPLITUDE
(DIOPTERS)
10 14.0 45 3.5
15 12.0 50 2.5
20 10.0 55 1.75
25 8.5 60 1.00
30 7.0 65 0.50
35 5.5 70 0.25
40 4.5 75 0.0

Average amp = 18.5 -(.3 x age)

Maximum amp =25 -(.4xage)
Maximum amp = 15 - (.25 x age)

Vergences (Morgan's expecteds)

Distance BI x/7/4
BO 9/19/10
Near BI 13/21/13
BO 17/21/11

NRA +2.00 to +2.50

PRA -2.25

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