Examination protocol for binocular vision

BINOCULAR VISION
Shreya Ghosh
Pritam Dutta

BIOGRAPHY
 SHREYA GHOSH
M.OPTOM ( AMITY UNIVERSITY, GURGAON)
Fellow Binocular Vision and Vision Therapy (SANKARA NETHRALAYA EYE HOSPITAL, CHENNAI)
Clinical Intern ( SANKAR NETHRALAYA EYE HOSPITAL, CHENNAI)
B.OPTOM ( VCOVS, KOLKATA)
 PRITAM DUTTA
M.OPTOM I-YEAR (THE SANKARA NETHRALAYA ACADEMY UNIT OF MEDICAL RESEARCH
FOUNDATION,SANKARA NETHRALAYA,CHENNAI)
B.OPTOM(RIDLEY COLLEGE OF OPTOMETRY,JORHAT,ASSAM)

Title and Content Layout with List
 HISTORY TAKING
 REFRACTION
 SENSORY AND MOTOR EVALUATION
 VERGENCE TESTS
 ACCOMMODATION TESTS

Learning Objectives
Normal and efficient binocular vision is based on the presence of sensory and motor fusion
 To understand binocular vision assessment at a primary eye care set-up

WHY ORTHOPTICS EVALUATION?
 To evaluate the status of binocular vision and management of accommodative, oculomotor and
binocular vision problems

Whom you will refer for ORTHOPTICS
evaluation?
Headache
Eyestrain/ eye
pain
Intermittent
double vision
Sleepiness
while near
work
Difficulty with
near vision
Loss of
comprehension
Difficulty in focusing
or intermittent
blurring of vision
Blurred vision for
distance and near
after prolonged
near work

Examination protocol for binocular vision

 Demographic history
 Nature of presenting problem and associated symptoms
I. Eyestrain associated with near work
II. Poor concentration
III. Skipping lines
IV. Blurred vision for distance on excess near work
V. Diplopia and headache

 Headache history includes-
a. Onset
b. Quality
c. Associated symptoms with near work
d. Relief and precipitating factors
e. Region of headache
f. Ruling out other reasons like sinusitis,
migraine
 Relevant history
a. Time of computer use and distance of work
b. Lightning environment
c. Visual hygiene
d. Sitting posture and head posture
e. Use of any protective glass

 Past ocular and health history
 Developmental and family history
 Medication use and allergic
history
History of any orthoptic treatment
I. Time and condition diagnosed
II. Duration of treatment
III. Type of therapy given
IV. Compliance of treatment
V. Frequency of associated symptoms after treatment
VI. Specific name of the home based or in office therapy given

 Subjective refraction
 Objective refraction
 Borish delayed method

BORISH DELAYED TEST
 Perform the regular monocular subjective acceptance to provide the best monocular
 visual acuity using MPMVA/ MMMVA rule
 The subjective correction is put in the trial frame
 The patient views the best corrected near visual acuity target at a testing distance of 40 cm
 Perform NRA (Negative Relative Accommodation) measurement by adding plus lenses
binocularly in 0.25 DS steps until the patient reports “first sustained blur”
 Direct the patient‟s attention to the previously read best corrected distant visual acuity line
 Defog binocularly in 0.25 DS steps until the patient is able to read the line
 A Compromise of 1 line of monocular distance visual acuity can be done to achieve the goal of
pushing plus or reducing minus. After adequate adaptation binocularly, depending on the
patient‟s comfort the final prescription can be decided

 Extra ocular motility test
 Cover test
 Maddox rod test
 AC/A Ration

i. PHORIA MEASUREMENTS:
MODIFIED THORINGTON PHORIA
This is similar to Maddox testing except for the addition of prisms. The Maddox rod is oriented according to the
nature of the deviation that has to assessed. The modified Thorington card otherwise known as the Bernell Muscle
Imbalance Measure (MIM) card has a central fixation light and grooves on either side which represent the angle
of deviation. The number on which the red streak is coincident directly reads the angle. A diagrammatic
representation of the Modified Thorington card is shown in the Figure.

ii. VERGENCE AMPLITUDES MEASUREMENTS
a. NEAR POINT OF CONVERGENCE (NPC):
PURPOSE: To determine the patient‟s ability to converge the eyes while maintaining fusion
EQUIPMENT: a. Accommodative target comprising of vertically aligned letters b. Penlight with red filter c. RAF Rule

Accommodative Target:
• The patient wears his habitual distance/near correction.
• The accommodative target which is a linear target of 6/9 reduced Snellen size is held by the examiner at
50 cm
• The patient is instructed to look at the accommodative target and to report whether the target appears
single.
• If it appears double, move the target further, farther than 50 cm from the patient until it appears single.
• The target is moved towards the patient, observing the patient‟s eyes until the patient reports that the
target appears double (subjective) or until the examiner observes loss of fixation in one eye (objective).
• The distance from the patient‟s eyes at which the patient reports that the target doubles or at which the
evaluator notes that the patient loses bifixation, is termed as the break point.
• The target is moved away from the patient‟s eyes and the distance at which the patient regains fusion and
reports the target to be single or at which the patient‟s deviated eye regains fixation is noted. This is the
recovery point.

ii. Penlight / Red filters:
NPC is also documented using penlight and Red filters. This is a more sensitive test to pick up convergence insufficiency in
symptomatic patients. While the patient wears the red filter in one eye, the penlight is brought closer till the patient appreciates
two light sources. The recovery point is also noted when the patient reports fusion again as the penlight is taken farther away
from the patient‟s eyes
NPC testing should be repeated thrice to check whether it recedes with fatigue. Average of the three readings should be
documented as the NPC value. Generally a remote NPC of more than 8 cm is suggestive of deficient convergence

b. FUSIONAL VERGENCE RANGE
Fusional vergence ranges can be measured using a variety of equipments in free space using a prism bar, in a phoropter using Risley prisms
and through a Synoptophore.
Convergence is tested using base-out prisms and divergence is tested using base-in prisms. Supra vergence is tested using base-down
prisms in front of the same eye or base-up in front of the other eye and viceversa for Infra vergence.
Fusional vergence range is also referred to as fusional reserves. Jump vergence refers to the vergence facility which tests for the dynamics
of vergence using alternate base-out and base-in prisms similar to plus and minus lenses in accommodative facility testing.
PURPOSE: To measure the patient‟s amplitudes of fusional vergence (Horizontal and Vertical) for distance and near
EQUIPMENT: a. Risley prisms / Synoptophore – Smooth vergence assessment b. Prism bars – Step vergence assessment c. 12 prism base
out / 3 prism base in vergence flippers - Jump vergence assessment d. Timer with seconds hand e. Distance and near linear (vertical) targets of
size one line better than the BCVA, preferably 6/9 reduced Snellen letters
PROCEDURE:
The test is done with the patient‟s habitual correction. The near target is held at 40 cm by the patient or the
examiner. The standard magnitude of flippers used are 12 prisms Base out with a 3 prisms Base in
combination. The patient is instructed to hold the vergence flipper close to the eyes (base in prism first) and
flip the prisms when the print becomes single and clear. The numbers of flips made per minute are noted. A
full cycle consists of both base-in and base-out prisms. Any difficulty to clear base-in or base-out prisms is
noted. The former indicates difficulty with divergence and the latter represents convergence difficulty.
Normal value: 14 ±4 cpm

STEP VERGENCE – PRISM BAR NEGATIVE FUSIONAL
VERGENCE AND POSITIVE FUSIONAL VERGENCE
(NFV/PFV)
PURPOSE: To measure fusional vergence by step vergence method
EQUIPMENT: Prism bars Distance and near linear targets of size one line better than the BCVA, preferably 6/9 reduced
Snellen letters
PROCEDURE:
a. Vertical target is shown at a distance of 6 m b. Prism bar is placed in front of one eye , usually Base in first and the
following responses are expected - 1. Blur- when the target is not clear 2. Break- when the target becomes double 3. Recovery-
when the target becomes single c. Test repeated for near and values are recorded in prism Diopters.

ACCOMMODATIVE CONVERGENCE/ACCOMMODATION RATIO (AC/A RATIO)
The AC/A ratio is a measure of the convergence induced by accommodation per unit of accommodation. The normal AC/A ratio is 4:1. Both
high and low AC/A ratios have been implicated in binocular vision problems. The two most popular methods of calculating the AC/A ratio
are the calculated distance-near deviation method and the gradient method.
PURPOSE:
To determine the change in accommodative convergence that occurs when the patient accommodates or relaxes
accommodation
PROCEDURE:
Calculated AC/A ratio formula:
 Heterophoria method
AC/A = Distance IPD (cm) + 0.4(Near Phoria – Distance Phoria)
 Gradient method
Difference between near ocular deviation with and without added lens / lens power used

Testing of accommodation in a patient should include testing for :
Dynamics of
accommodation.
Accommodative
response
Accommodative
amplitudes

NEAR POINT OF ACCOMMODATION (NPA) Slide Title - 2
The closest point at near or the Punctum Proximum which shows the limit of accommodation at near
PURPOSE
• To determine the
maximum amount of
accommodation that the
eyes can exert
monocularly and
binocularly and thereby
to measure the amplitude
of accommodation in
Diopters
EQUIPMENT
• Near point visual acuity
chart / Minus spherical
lenses / RAF Rule
• Ruler
• Occlude
PROCEDURE
• Push Up Test
• Minus Lens Test

a. The test is done both monocularly and binocularly with the habitual correction with RAF ruler
b. The near point visual acuity chart should be optimally illuminated so that it is clearly visible
c. The patient is directed to keep their attention in a row of letters corresponding to or one line larger than the best corrected
near visual acuity
d. The patient is instructed to „keep the letters clear‟
e. The chart is moved closer to the patient and the patient is asked to report when the letters become and remain blurry (first
sustained blur)
f. The distance from the chart to the patient‟s spectacle plane in cm is measured. The linear measurement is referred to as the
near point of accommodation
g. The linear distance is converted into Diopters. The resulting dioptric value
represents the patient‟s amplitude of accommodation (AA)
PUSH UP TEST

MINUS LENS TEST
a. This procedure is done monocularly
b. The patient‟s attention is directed towards the best corrected near visual acuity target at 40 cm testing distance
c. The patient is asked to report the first sustained blur as minus lenses are added in front of the eye in 0.25 DS steps over
the subjective correction
d. Since the test is done at 40 cm distance, the stimulus to accommodation for that distance amounting to 2.50 DS should be
numerically added to the resulting minus lens power to obtain the accommodative amplitude
e. For example at 40 cm, if the minus lenses added to report blur is -4.00 DS, the amplitude of accommodation would
be 4 +2.50 = 6 D
f. The procedure is repeated for the fellow eye and the findings are recorded

a) Assessment of accommodative response becomes important to know the accommodative status of the person during
near visual activities
b) It also indirectly helps to modify the distant prescription and to determine the near addition. At a distance of 40 cm,
the expected accommodative demand is 2.50 D. But due to the depth of focus, the eye would accommodate lesser than
the demand. This is seen as the lag of accommodation at near
c) An accommodative response that exceeds that of the stimulus would be seen as a lead of accommodation. A lag of
greater than +1.00 D is often found in individuals with accommodative insufficiency or infacility, suggesting the using
of plus lenses at near
d) A lead of -0.25 D or more usually indicates accommodative excess
e) The normal expected accommodative response is lag of accommodation at near of about +0.25 DS to +0.75 DS.
f) Two commonly used dynamic retinoscopy techniques are described below.
ACCOMMODATIVE RESPONSE ASSESSMENT
MEM NOTT

MONOCULAR ESTIMATION METHOD (MEM)
EQUIPMENT
a. Near point visual acuity
chart
b. Retinoscope
PURPOSE
To measure
objectively the
accommodative
response to the near
working distance
PROCEDURE
a. The test is performed under binocular viewing conditions
b. The test is done under normal room illumination with the
patient‟s subjective acceptance values
c. The near target is held at the patient‟s near working
distance
d. The patient‟s concentration is directed to the smallest row
of letters read easily by the patient
e. While the patient is reading, the streak is guided across
either of the eyes along the horizontal meridian and the
reflex is neutralized
f. Lenses are quickly interposed according to the reflex
observed (plus lenses for “with” movement and minus lenses
for “against” movement). It is important that the lenses
should not be left in the trial frame for long, to avoid the
influence on accommodative response
g. The lens power required to attain neutrality is recorded

a) The requirements are the same as for MEM retinoscopy
b) Here the near target is kept at 40 cm fixed distance or at the patient‟s working distance. The retinoscope is moved along the
axis of the near target till neutrality is obtained
c) For “with” movements, the retinoscope is moved away from the target and for “against” movements the retinoscope is
moved towards the subject
d) The accommodative response is obtained by subtracting the demand from the dioptric value of the distance at which
neutrality is observed
e) For example if the near target is held at 40 cm (equivalent to a dioptric demand of 2.50 D) and neutrality is obtained at 50
cm (equivalent to a dioptric demand of 2.00 D), the accommodative response would be a lag of +0.50 D.
NOTT RETINOSCOPY METHOD

i. NEGATIVE RELATIVE ACCOMMODATION (NRA) AND POSITIVE RELATIVE ACCOMMODATION (PRA)
The relative accommodation measurements give an estimate of the range of accommodation from stimulation to relaxation at a fixed distance.
The distance ensures that the vergence demand is maintained constant. The relative accommodation values can be used to determine the near
add and to modify the distance prescription.
• PURPOSE: To determine the range of accommodation at near relative to the constant maintained vergence at a fixed distance
• EQUIPMENT: a. Near point card, b. Positive and negative spherical lenses
• PROCEDURE:
The patient wears his habitual correction. The near vision target is held at 40cms in front of the patient. The patient fixates at the N6 target or
the last line of the near vision chart easily read by the patient. Plus lenses are slowly added binocularly in 0.25 Diopter steps until the patient
reports the first sustained blur. This gives the negative relative accommodation.
The same procedure is repeated with negative lenses, giving the subject adequate time to clear the lenses. The first persistent blur is noted as
the positive relative accommodation. Addition of plus lenses relaxes accommodation and stimulates divergence due to AC/A link. In order to
maintain clear single binocular vision (CSBV) the eyes converge or use fusional convergence. Inadequate fusional convergence therefore can
reduce the end point of NRA. Similarly addition of minus lenses in PRA testing induces accommodation and increases accommodative
convergence due to the AC/A link. In order to maintain CSBV, the eyes must neutralize the accommodative convergence by fusional
divergence response. Inadequate fusional divergence can therefore limit the endpoint of PRA measurements.
• Expected NRA findings: +1.75 to +2.50 DS Expected PRA findings: - 1.50 to -2.50 DS
RELATIVE ACCOMMODATION MEASUREMENTS

ii. ACCOMMODATIVE FACILITY
The purpose of accommodative facility testing is to assess the dynamics of accommodation. Plus and minus lenses are used
alternately to induce changes in accommodation. Binocular testing of accommodative facility indirectly assesses the vergence
response.
PURPOSE: To measure the patient‟s ability to make rapid accommodative changes under monocular and binocular
conditions
EQUIPMENT: a. Accommodative flippers of +2.00 DS/-2.00DS, b. Near vision test chart, c. Eye patch, d. Timer with
seconds hand
PROCEDURE:
Patient wears the habitual correction. Standard testing consists of using +/-2.00 DS accommodative flippers at 40 cm. In this
method, based on the patient‟s accommodative amplitude (AA), the testing distance and the magnitude of the flipper lenses are
determined. Testing distance = 45% of AA (rounded to nearest 0.5 cm).Lens power range = 30% of AA (rounded to nearest
0.25D). Flipper lens power = Lens power range dividedby 2.
Patient is instructed to hold the flipper close to the eye (plus lens first) and flip the lens to the minus
side on clearing the target. The numbers of flips made per minute are noted. A full cycle consists of clearing
both plus and minus lenses. Any difficulty to clear plus or minus lenses is noted. Difficulty with plus lenses
are seen in patients with accommodative excess who cannot relax accommodation and difficulty with minus
lenses are seen in presbyopes, pre-presbyopes and in accommodative insufficiency.

REFERENCES
 Maqsud, M. A. (2013). Orthoptic exercises : a forgotten art ?
 Noorden, G. K. Von. (n.d.). Binocular Vision and Ocular Motility.
 Of, C. M. (n.d.). B inoc ula r Vision

Examination protocol for binocular vision

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