BASIC EXAMINATION OF STRABISMUS -mail

ability. Combined testing such as the Worth 4-dot test at distance
and near and tests for stereopsis may be used. Among commonly
used measures of stereopsis are the Randot and Preschool Randot
stereo tests. More detailed sensory testing (e.g., the Bagolini striated
lenses, Hering-Bielschowsky afterimage, and synoptophore) can be
used to evaluate retinal correspondence in older children and adults.
All sensory testing should be performed while the patient is wearing
his/her optimum refractive correction. In addition, performing
sensory testing while the patient wears prisms to compensate for
any nonaccommodative component of the strabismus can also help
determine sensory fusion potential. Once normal sensory fusion has
been established, motor fusion can be quantified using a prism bar
or rotary prisms for the patient with intermittent strabismus or a
stereoscope for the patient with constant strabismus.

6. ANCILLARY TESTS

Haploscopic tests: These tests are based on the principle that two
different objects are placed on two different foveas.

6.1 Diplopia Charting

In this test one determines the subjective localization of images
of the two eyes. A single object point is imaged on the fovea of
the fixating eye and an extrafoveal retinal area in the other eye in
cases of diplopia. In esotropia, the image of the fixation point in
the deviated eye falls on a retinal area nasal to the fovea, leading to
uncrossed diplopia. In exotropia, the image of the fixation point in
the deviated eye falls on a retinal area temporal to the fovea, leading
to crossed diplopia. If retinal correspondence is normal, double
images not only should be properly oriented but also should have a
distance equal to the angle of strabismus. The distance of the double
images is then a measure of the deviation. It can be very difficult
for a patient to describe the nature of diplopia. The two visual fields
must be differentiated and for this purpose a red glass is placed in
front of one eye (hence, red-glass test)

The test can be used with a red glass over right eye or red green

Basic Examination of Strabismus | 47

glasses with red again in front of the right eye. It is generally done at
50 cm or 1 m. A light source is shown to the patient and the patient is
asked to draw or explain the separation of images and the orientation
of the two colour images perceived in 9 gazes. The test is facilitated
if it is begun by alternately covering the eyes of the patient to show
that a green light is seen with one eye and a red light with the other
eye. Subjective deviation is recorded by red and green glasses. From
the chart, as per patient’s response, we can find out paralyzed muscle/
muscles. According to following rules –
1) Diplopia increases in direction of action of paralyzed muscle.
2) Peripheral image belongs to deviated eye.
3) Separation of image maximum in direction of action of paralyzed

muscle
When both eyes are uncovered, the patient is more likely to become
aware of the double image of the light Interpretation is done as
follows (Figure 16):

Figure 16 Diplopia charting in right superior oblique palsy with diplopia
maximum in laevodepression

48 | Basic Examination of Strabismus

1. What is the nature of diplopia(crossed/uncrossed)?
2. Whether the diplopia is horizontal/ vertical or torsional?
3. Which gaze is the separation of images maximum?

When diplopia is binocular, a red filter held before one eye will
determine whether it is uncrossed (or homonymous), in which case
an esotropia is present; crossed (or heteronymous), in which case
the patient has exotropia; or vertical, in which case hypertropia or
hypotropia is present; or torsional in the case of cyclotropia. The
source of light can be kept vertical in case of a horizontal diplopia
and vice versa to better delineate separation of images.

6.2 Hess Screen

Hess screen is based on foveal projection and dissociation of eyes.
A lot of modifications in Hess screen are available which include
illuminated screens, Weiss screen etc.

Lees screen uses mirror dissociation instead of complimentary
colors. It is a subjective test using red-green glasses as described
for the original test. It charts the field of both eyes relative to each
other. This test is best for documentation and follow up in paralytic
strabismus. During follow up, we can find muscle changes in the
following sequence:

1) Contracture of Ipsilateral antagonist
2) Overaction of contralateral synergist
3) Inhibitory paresis of antagonist to contralateral synergist

2. Overaction 1. Primary paresis
medial rectus leteral rectus

4. Secondary palsy 3. Contracture
lateral rectus medial rectus

Pathological sequelae of right lateral recetus muscle palsy

Figure 17: Order of sequalae that develop after a muscle palsy.

Basic Examination of Strabismus | 49

The patient wears red-green goggles and is seated 50 cm from the
screen. The patient now sees the red dots with one eye and the green
cords with the other and is instructed to place the knot joining the
three green cords over each of the red dots in turn. The points found
by the patient are connected by straight lines to find the under or
overacting muscles. Lees chart: (Based on dissociation by mirror)
The lees screen has two opalescent glass screens at right angles
to each other bisected by a two-sided plane mirror. The screens have
a tangent grid on their back surface which can be illuminated. Two
pointers are used, one by the examiner to indicate each dot and other
by patient who places the ring at the end of his pointer around the
marked dot.

Figure 18 depicting the procedure of lees chart

The patient fixates with one eye and the examiner points at various
points on the projected chart. The visual field of the other eye is
charted when patient marks the corresponding points by a stick
(Figure 11).

50 | Basic Examination of Strabismus

Certain examples of the test are given below

Figure 19 Above: Lees chart with left lateral rectus underaction seen on the smaller
and shifted left eye field. This could occur in cases of left lateral rectus paresis or

duanes retraction syndrome
Below: Right eye superior oblique underaction with both eye inferior rectus

overaction most likely due to right superior oblique palsy.

Interpretations:
Higher field belongs to the higher eye, the smaller usually being
the affected eye. The position of central dot indicates deviation in
primary position. Outer fields can tell us small underactions and
overactions. Equal sized fields denote symmetrical limitation or
non-paralytic strabismus. Each small square on the grid subtends 5
degree at a working distance of 50 cm.

Basic Examination of Strabismus | 51

Precautions:
1. Mirror must exactly bisect the two screens
2. Patients head should remain straight throughout the procedure
3. Presence of normal retinal correspondence should be established

first in the setting of Diplopia. Marked suppression prevents the
use of the screen.
4. The test should be performed if possible, without spectacles to
reduce the prismatic effect.

6.3 Forced Duction Testing(FDT)

Forced duction test (FDT) is done if a patient has limited ductions. In
other words, it tests the passive movement of the globe in cases where
movement is restricted. FDT can be performed on most cooperative
adults in the outpatient department. If we demonstrate a limitation
in passive movement by this test, it indicates a mechanical factor is
involved in causing the limitation.
Technique: It requires topical anesthesia. Two pairs of fine fixation
forceps are used to grab diametrically opposite limbus. For rectus

Figure 18 depicting the procedure of FDT

52 | Basic Examination of Strabismus

muscles one must grasp the eye at the limbus and slightly proptose
the eye, then rotate the eye into the field of limited ductions. If the
eye is pushed posteriorly during testing, the rectus muscles will
relax, which may lead to false negative testing. The patient is asked
to look in the direction of the limited ductions to relax the muscle
that is being tested. The limbus is grasped, and the globe rotated
in direction of limited duction. Inability to rotate the globe fully
indicates a restriction of the antagonist muscle. The examiner notes
the limitation of movement, nature of limitation, and resistance to
rotation. It is ideally described with two pairs of forceps because
using one pair causes retropulsion of the globe. Interpretation
under local anesthesia is often inaccurate. Unfortunately, there is
no standard method of quantifying the result, much depends on
judgement and experience of the surgeon.

6.4 Forced Generation Test(FGT)

Active forced-generation testing assesses if the rectus muscle has
some strength to enable eye movement. The force is generated from
an increase in healthy muscle fibers when activated. The aim is to
calculate isometric contraction force in an apparently palsied muscle
to indicate muscles potential function. The eye is anesthetized with a
topical anesthetic, and the eye is grasped with forceps at the limbus
as in forced-duction testing. The patient is asked to look into the field
of limitation while the eye is held in primary position. The examiner
senses any muscle contraction felt as a tug on the forceps; it implies
some force in the muscle being tested. It again is only a qualitative
assessment test. For example in a complete loss of abduction, a
positive result in the test indicates some potential in the lateral rectus
and surgery is performed accordingly.

6.5 Accomodation

An evaluation of accommodative function, including tests of
monocular accommodative amplitude (push-up or minus lens
method), accommodative facility (plus/minus flipper method),
and accommodative response (dynamic retinoscopy), should be
performed whenever feasible.

Basic Examination of Strabismus | 53

6.7 Fundus Examination

It is customary to do a detailed fundus examination in every case of
strabismus. We should be aware of serious organic ocular disease in
children that may present as strabismus. Detailed fundus examination
is also needed to look for any sensory cause of strabismus. Some of
these conditions include

• RD

• PHPV

• Retinoblastoma

• Toxoplasmosis

• Albinism

Any torsion should also be ruled out as discussed above.

ORDER OF EXAMINATION

Although studies have shown no difference in the binocular status
(particularly stereopsis) at the beginning or the end of the strabismus
exam; traditionally, binocular sensory testing is performed before
tests that require occluding one eye. Covering one eye dissociates
the eyes and may disrupt fusion in a patient with latent strabismus
(large phoria or intermittent tropia). However, the general pattern
followed is amblyopia assessment/visual acuity assessment followed
by sensory testing and then motor examination. Special muscle
tests like FDT and FGT should be performed next; then cycloplegic
refraction and fundus examination.

In summary, cycloplegic refraction is a must for children and can be
scheduled at the time of convenience to the patient as well as parent.
Visual acuity assessment in children is an art more than a science.
53-60 There is a lot of literature on strabismus exercises and how to
carry out various tests61-75 but practice and repetitiveness is the key
to a successful examination. The table below outlines most tests in a
strabismus examination.

54 | Basic Examination of Strabismus

History
Observe: Head Posture, Facial Asymmetry, Anisocoria, Lid
Changes, Systemic
Visual acuity and refraction and rule out amblyopia
Ocular alignment and movements
Binocular status testing
Torsion/ Diplopia/Lees/FDT/GFT
Supplementary tests: AC/A Ratio, Vergences

In 2001 February a two day workshop on the Classification of Eye
Movement Abnormalities and Strabismus (CEMAS) was held at the
National Eye Institute, National Institutes of Health Campus which
gave us the following classification.

BROAD CATEGORIES OF EYE MOVEMENT
ABNORMALITIES

I. Ocular Motor Aspects of Vision
II. Sensory Aspects of Binocular Vision
III. Horizontal Heterotropias
IV. Horizontal Heterophorias
V. Cyclovertical Heterotropias and Special Forms of Strabismus
VI. Cyclovertical Heterophorias
VII. Accommodative Disorders
VIII. Nystagmus and Other Ocular Motor Oscillations

A. Concomitant Esodeviations
1. Infantile Esotropia Syndrome
2. Accommodative Esotropia

a. Pure Refractive
b. Non-Refractive
c. Mixed
3. Monofixation Esotropia Syndrome
4. Basic Non-Accommodative Esotropia
5. Esotropia And Visual or Neurologic Abnormality (e.g., sensory
esotropia)
6. Intermittent Esotropia

Basic Examination of Strabismus | 55

7. Divergence Insufficiency Esotropia (paresis, paralysis)
8. Mixed (Partially Accommodative) Esotropia.

B. Non-Concomitant Esodeviations
1. Cranial Nerve Disease (palsy/paresis, congenital/developmental

anomaly, tumor, vascular, inflammatory, trauma, immune, etc.)
a. Nuclear Location
b. Fasicular Location
c. Subarachnoid Location
d. Cavernous Sinus Location
e. Orbital Location
2. Neuromuscular Junction (Myasthenia, etc)
3. Muscular Disease (congenital/developmental anomaly, tumor,
vascular, inflammatory, trauma, immune, etc.)
4. Oribital Disease (pulley, congenital/developmental, tumor,
vascular, inflammatory, trauma, immune, etc.)

C. Concomitant Exodeviations
1. Infantile Exotropia Syndrome
2. Intermittent Exotropia

a. Low Accommodative Convergence
b. Normal Accommodative Convergence
c. High Accommodative Convergence
3. Monofixation Exotropia Syndrome
4. Basic Exotropia
5. Exotropia Associated with Visual or Neurologic Abnormality
(.g., sensory exotropia)
6. Convergence Insufficiency Exotropia

D. Non-Concomitant Exodeviations
1. Cranial Nerve (palsy/paresis, congenital/developmental

anomaly, tumor, vascular, inflammatory, trauma, immune, etc.)
a. Nuclear Location
b. Fasicular Location
c. Subarachnoid Location
d. Cavernous Sinus Location
e. Orbital Location

56 | Basic Examination of Strabismus

2. Neuromuscular Junction Disease (Myasthenia, etc)
3. Muscular Disease (congenital/developmental anomaly, tumor,

vascular, inflammatory, trauma, immune, etc.)
4. Oribital Disease (pulley, congenital/developmental, tumor,

vascular, inflammatory, trauma, immune, etc.)

IV. HORIZONTAL HETEROPHORIAS

1. Esophoria
a. Divergence Insufficiency
b. Convergence Excess
c. Basic

2. Exophoria
a. Divergence Excess
b. Convergence Insufficiency
c. Basic

3. Fusional vergence dysfunction

V. CYCLOVERTICAL HETEROTROPIAS AND SPECIAL
FORMS OF STRABISMUS

A. Apparent Oblique Muscle Dysfunction

1. Over-Elevation in Adduction (OEA) [Old, Inferior Oblique
Overaction]
a. Primary
b. Secondary

2. Under-Elevation in Adduction (UEA) [Old, Inferior Oblique
Underaction]
a. Primary
b. Secondary

3. Over-Depression in Adduction (ODA) [Old, Superior Oblique
Overaction]
a. Primary
b. Secondary

4. Under-Depression in Adduction (UDA) [ O l d ,
Superior Oblique Underaction]
a. Primary
b. Secondary

Basic Examination of Strabismus | 57

B. Cyclovertical Deviations of Paretic Origin
1. UnilateralSuperiorObliqueParesis(Congenital/Decompensated)
2. Superior Oblique Paresis (Non-Congenital [old “acquired’])
3. Bilateral Superior Oblique Paresis
4. Monocular elevation deficiency [old “double elevator palsy”]
5. Monocular depression deficiency [old “double depressor palsy”]

C. Dissociated Strabismus, Cyclovertical Deviation
1. Dissociated Cyclovertical Deviation

D. Restrictive/Mechanical Strabismus
1. Cyclovertical Deviations Secondary to Muscular Disease
2. Cyclovertical Deviations Associated with Orbital Bony Disease
3. Iatrogenic Cyclovertical Deviations, (“Induced Adhesive

Syndromes”)

E. Neuro-Myogenic Strabismus
1. Myasthenia Gravis
2. Chronic Progressive External Ophthalmoplegia
3. Internuclear Ophthalmoplegia
4. Skew Deviation

F. Special Forms
1. Co-Contractive Retraction Syndrome (CCRS, Types 1-3) [Old

Duane]
2. Co-Contractive Retraction with Lower Cranial Neuropathy

(CCRS, Type 4) [Old, Moebius]
3. Co-Contractive Retraction with Jaw-Eyelid Synkinesis

Syndrome (CCRS,Type“Y”
5) [Old, Marcus Gunn]
4. Co-Contractive Retraction with Exotropia [Old Synergistic

Divergence and Exotropia] (CCRS Type 6)
5. Restrictive Hypotropia in Adduction (RHA) [Old, Brown

Syndrome]
6. Congenital Fibrosis of the Extraocular Muscles (CFEOM)

58 | Basic Examination of Strabismus

VI. CYCLOVERTICAL HETEROPHORIAS

1. Hyperphoria
2. Vertical fixation disparity
3. Latent hyperphoria
4. Pure Cyclophoria

VII. ACCOMMODATIVE DISORDERS

1. Paralysis
2. Infacility
3. Insufficiency
4. Excess

VIII. NYSTAGMUS AND OTHER OCULAR MOTOR
OSCILLATIONS

A. Physiological Fixational Movements
1. Microtremor
2. Slow Drifts
3. Microsaccades

B. Physiological Nystagmus
1. Vestibular Nystagmus
2. Optokinetic Nystagmus
3. Eccentric Gaze Nystagmus

C. Pathologic Nystagmus
1. Infantile Nystagmus Syndrome (INS)
2. Fusion Maldevelopment Nystagmus Syndrome (FMNS)
3. Spasmus Nutans Syndrome (SNS)
4. Vestibular Nystagmus

a. Peripheral Vestibular Imbalance
b. Central Vestibular Imbalance
c. Central Vestibular Instability
5. Gaze-Holding Deficiency Nystagmus
a. Eccentric Gaze Nystagmus
b. Rebound Nystagmus
c. Gaze-Instability Nystagmus (“Run-Away”)

Basic Examination of Strabismus | 59

6. Vision Loss Nystagmus
a. Pre-chiasmal
b. Chiasmal
c. Post-chiasmal

7. Other Pendular Nystagmus and Nystagmus Associated with
Disease of Central Myelin
a. Multiple Sclerosis, Peliazaeus-Merzbacher, Cockayne’s
Perioxisomal disorders, Toluene abuse.
b. Pendular Nystagmus Associated with Tremor of the Palate.
c. Pendular Vergence Nystagmus Associated with Whipple’s
Disease.

8. Ocular Bobbing (Typical and Atypical)
9. Lid Nystagmus

D. Saccadic Intrusions and Oscillations
1. Square-Wave Jerks and Oscillations
2. Square-Wave Pulses
3. Saccadic Pulses (Single and Double)
4. Induced Convergence-Retraction
5. Dissociated Ocular Oscillations
6. Hypermetric Saccades
7. Macrosaccadic Oscillations
8. Ocular Flutter
9. Flutter Dysmetria
10. Opsoclonus
11. Psychogenic (Voluntary) Flutter
12. Superior Oblique Myokymia
E. Generalized Disturbance of Saccades
F. Generalized Disturbance of Smooth Pursuit
G. Generalized Disturbance of Vestibular Eye Movements
H. Generalized Disturbance of Optokinetic Eye Movements

60 | Basic Examination of Strabismus

REFERENCES

1. Thomas R, Braganza A, George T. Practical approach to diagnosis of
strabismus. Indian J Ophthalmol. 1996;44:103-112.

2. Suttle CM. Visual acuity assessment in infants and young children. Clin Exp
Optom. 2001;84:337-345.

3. Anstice NS, Thompson B. The measurement of visual acuity in children: an
evidence-based update. Clin Exp Optom. 2014;97:3-11

4. Sener EC, Mocan MC, Gedik S, Ergin A, Sanaç AS. The reliability of grading
the fixation preference test for the assessment of interocular visual acuity
differences in patients with strabismus. J AAPOS. 2002;6:191-194.

5. Kothari M, Bhaskare A, Mete D, Toshniwal S, Doshi P, Kaul S. Evaluation
of central, steady, maintained fixation grading for predicting inter-eye visual
acuity difference to diagnose and treat amblyopia in strabismic patients. Indian
J Ophthalmol. 2009;57:281-284

6. Prager TC, Zou YL, Jensen CL, Fraley JK, Anderson RE, Heird WC. Evaluation
of methods for assessing visual function of infants. J AAPOS. 1999;3:275-282.

7. de Zárate BR, Tejedor J. Current concepts in the management of amblyopia.
Clin Ophthalmol. 2007;1:403-414.

8. Saxena R, Sharma P; Pediatric Ophthalmology Expert Group. National
consensus statement regarding pediatric eye examination, refraction, and
amblyopia management. Indian J Ophthalmol. 2020;68:325-332.

9. Care of the Patient with Strabismus: Esotropia and Exotropia. https://www.
aoa.org/documents/optometrists/CPG-12.pdf. Accessed on 19 July 2020.

10. Sani RY, Hassan S, Habib SG, Ifeanyichukwu EP. Cycloplegic effect of atropine
compared with cyclopentolate-tropicamide combination in children with
hypermetropia. Niger Med J. 2016;57:173-177.

11. Yazdani N, Sadeghi R, Momeni-Moghaddam H, Zarifmahmoudi L, Ehsaei A.
Comparison of cyclopentolate versus tropicamide cycloplegia: A systematic
review and meta-analysis. J Optom. 2018;11:135-143.

12. Twelker JD, Mutti DO. Retinoscopy in infants using a near noncycloplegic
technique, cycloplegia with tropicamide 1%, and cycloplegia with
cyclopentolate 1%. Optom Vis Sci. 2001;78:215-222.

13. Basmak H, Sahin A, Yildirim N, Saricicek T, Yurdakul S. The angle kappa in
strabismic individuals. Strabismus. 2007;15:193-196.

Basic Examination of Strabismus | 61

14. Choi RY, Kushner BJ. The accuracy of experienced strabismologists using
the Hirschberg and Krimsky tests. Ophthalmology. 1998;105:1301-1306
15.Wallace DK, Christiansen SP, Sprunger DT, et al. Esotropia and Exotropia
Preferred Practice Pattern®. Ophthalmology. 2018;125:P143-P183.

16. Irsch K. Optical Issues in Measuring Strabismus. Middle East Afr J Ophthalmol.
2015;22:265-270.

17. Kaye SB, Ansons AM, Green JR, Wylie J. The prism bar--Prentice and frontal
positions. Eye (Lond). 1989;3:404-408.

18. Barry JC, Backes A. Messungen zum Einfluss von Brillengläsern auf
die Bestimmung des Schielwinkels mit Purkinje-Reflexen und mit dem
Prismenabdecktest [Measuring the effect of eyeglasses on determination of
squint angle with Purkinje reflexes and the prism cover test]. Klin Monbl
Augenheilkd. 1998;212:234-239.

19. Flüeler UR, Elhatton KM, Guyton DL. Eine Kombination einer horizontalen/
vertikalen Prismenleiste [A combination of horizontal/vertical prism bar].
Klin Monbl Augenheilkd. 1996;208:343-347.

20. Flüeler UR, Elhatton KM, Guyton DL. Original papers: A combination
horizontal/vertical prism bar A precisely calibrated tool for use in front of one
eye. Strabismus. 1995;3:27-32

21. Thompson JT, Guyton DL. Ophthalmic prisms. Measurement errors and how to
minimize them. Ophthalmology. 1983;90:204-210

22. Thompson JT, Guyton DL. Ophthalmic prisms. Deviant behavior at near.
Ophthalmology. 1985;92:684-690.

23. Freedman K, Ray C, Kirk D. Reevaluation of Current Prism Standards With
Recommendations to Increase Accuracy in the Measurement of Strabismus. Am
J Ophthalmol. 2019;198:130-135.

24. Helveston EM. Prism placement. Measurements of horizontal and vertical
deviations with the head tilted. Arch Ophthalmol. 1975;93:483-486.

25. Kommerell G, Kromeier M. Prismenkorrektion bei Heterophorie [Prism
correction in heterophoria]. Ophthalmologe. 2002;99:3-9

26. Effert R. Ein alternatives Messverfahren zum Simultan-Prismen-Covertest [An
alternative measuring procedure to the simultaneous prism cover test]. Klin
Monbl Augenheilkd. 1989;194:462-466

27. Effert R. A new method for determining squint angle in primary and all

62 | Basic Examination of Strabismus

secondary positions using the first and fourth Purkinje images. Ophthalmology.
1986;93:436-441.

28. Effert R, Pflibsen K. A new method to perform the cover test. Ophthalmology.
1986;93:433-435.

29. Kupersmith MJ, Fazzone HE. Comparing ocular muscle limitation tests for
clinical trial use. Arch Ophthalmol. 2004;122:347-348.

30. Guibor GP: Squint and Allied Conditions. New York, Grune & Stratton, 1959
31.Kushner BJ. The usefulness of the cervical range of motion device in the
ocular motility examination. Arch Ophthalmol. 2000;118:946-950.

32. Kestenbaum A: Clinical Methods of Neuro-Ophthalmologic Examination, ed 2.
New York, Grune & Stratton, 1961, p 237.

33. Lancaster WB: Detecting, measuring, plotting and interpreting ocular
deviations. Trans Section Ophthalmol AMA 90th session, 1939, p 78.

34. Sharma K, Abdul-Rahim AS: Vertical fusion amplitude in normal adults. Am J
Ophthalmol 114:636, 1992.

35. Lança CC, Rowe FJ. Measurement of fusional vergence: a systematic review.
Strabismus. 2019;27(2):88-113.

36. Anderson H, Stuebing KK, Fern KD, Manny RE. Ten-year changes in fusional
vergence, phoria, and nearpoint of convergence in myopic children. Optom Vis
Sci. 2011;88:1060-1065

37. Jiménez R, Pérez MA, García JA, González MD. Statistical normal values of
visual parameters that characterize binocular function in children. Ophthalmic
Physiol Opt. 2004;24(6):528-542.

38. Hung GK. Quantitative analysis of the accommodative convergence to
accommodation ratio: linear and nonlinear static models. IEEE Trans Biomed
Eng. 1997;44:306-316.

39. Horwood AM, Riddell PM. The clinical near gradient stimulus AC/A ratio
correlates better with the response CA/C ratio than with the response AC/A
ratio. Strabismus. 2013;21:140-144.

40. Schor CM. The Glenn A. Fry award lecture: adaptive regulation of
accommodative vergence and vergence accommodation [published correction
appears in Am J Optom Physiol Opt 1986 Nov;63(11):921]. Am J Optom
Physiol Opt. 1986;63:587-609.

41. Horwood AM, Riddell PM. Disparity-driven vs blur-driven models of
accommodation and convergence in binocular vision and intermittent
strabismus. J AAPOS. 2014;18:576-583.

Basic Examination of Strabismus | 63

42. Havertape SA, Cruz OA, Miyazaki EA. Comparison of methods for determining
the AC/A ratio in accommodative esotropia. J Pediatr Ophthalmol Strabismus.
1999;36:178-183. Ruttum M, Noorden GK von: The Bagolini striated lens test
for cyclotropia. Doc Ophthalmol 58:131, 1984.

43. Khanna RK, Pasco J, Santallier M, Pisella PJ, Arsene S. Reliability of objective
ocular torsion assessment using fundus photography in infantile esotropia. J
Fr Ophtalmol. 2019;42:16-21.

44. Le Jeune C, Chebli F, Leon L, et al. Reliability and reproducibility of disc-
foveal angle measurements by non-mydriatic fundus photography. PLoS One.
2018;13:e0191007. Published 2018 Jan 25.

45. Jethani J, Dave P. The subjectivity of objective evaluation of torsion on
fundus photographs by practicing strabismologists. Indian J Ophthalmol.
2018;66:1301-1303.

46. Khawam E, Abdulaal M, Massoud V, Jaroudi M. Principles and general
strabismus surgical rules in cyclovertical eye muscle palsies. Binocul Vis
Strabolog Q Simms Romano. 2012;27(4):249-263.

47. Zhao L, Wu H. The effect of dot size in random-dot stereograms on the results
of stereoacuity measurements. BMC Ophthalmol. 2020;20(1):253. Published
2020 Jun 24.

48. Chung CS, Berbaum K. Form and depth in global stereopsis. J Exp Psychol
Hum Percept Perform. 1984;10:258-275.

49. Zhao L, Wu H. The difference in stereoacuity testing: contour-based and random
dot-based graphs at far and near distances. Ann Transl Med. 2019;7:193.

50. Romano PE, Von Noorden GK, Awaya S. Symposium: Sensory Adaptations in
Strabismus. A reevaluation of diagnostic methods for retinal correspondence.
Am Orthopt J. 1970;20:13-21.

51. Travers TA. SUPPRESSION OF VISION IN SQUINT AND ITS ASSOCIATION
WITH RETINAL CORRESPONDENCE AND AMBLYOPIA. Br J Ophthalmol.
1938;22:577-604.

52. Verma A. Anomalous adaptive conditions associated with strabismus. Ann
Ophthalmol (Skokie). 2007;39:95-106

53. American Academy of Ophthalmology Pediatric Ophthalmology/Strabismus
Panel. Preferred Practice Pattern® Guidelines. Paediatric eye evaluations.
San Francisco, CA: American Academy of Ophthalmology; 2007.

64 | Basic Examination of Strabismus

54. Simons K. Preschool vision screening: rationale, methodology, and outcome.
Surv Opthalmol.1996; 41 :3 –30

55. Banks MS, Salapatek P. Acuity and contrast sensitivity in 1-, 2-, and 3-month-
old human infants. Invest Ophthalmol Vis Sci. 1978 Apr;17(4):361–365

56. Woodruff ME. Observations on the visual acuity of children during the first five
years of life. Am J Optom. 1972;49:205–215

57. Youngson RM. Anomaly in visual acuity testing in children. Br J Ophthalmol.
1975;59:168–170

58. American Academy of Pediatrics, Section on Ophthalmology, American
Association for Pediatric Ophthalmology And Strabismus, et al. Red reflex
examination in neonates, infants, and children. Pediatrics 2008; 122:1401.

59. Atkinson J, Braddick O, Pimm-Smith E. ‘Preferential looking’ for monocular
and binocular acuity testing of infants. Br J Ophthalmol. 1982;66:264–268
60.Quinn GE, Berlin JA, James M. The Teller acuity card procedure. Three
testers in a clinical setting. Ophthalmology 1993; 100:488.

61. Romano PE, Romano JA, Puklin JE. Stereoacuity development in children with
normal binocular single vision. Am J Ophthalmol. 1975;79:966–971

62. Simons K. Stereoacuity norms in young children. Arch Ophthalmol.
1981;99:439–445

63. Simons K. A comparison of the Frisby, Random-Dot E, TNO, and Randot Circles
stereotests in screening and office use. Arch Ophthalmol. 1981;99:446–452

64. Saunders KJ, Woodhouse JM, Westall CA. The Modified Frisby Stereotest.J
Pediatr Ophthalmol Strabismus 1996; 33:323-7.

65. Manny RE, Martinez AT, Fern KD. Testing stereopsis in the preschool child:
is it clinically useful? J Pediatr Ophthalmol Strabismus 1991 Ju1; 28(4):223-
231.

66. Broadbent H, Westall C. An evaluation of techniques for measuring stereopsis
in infants and young children. Ophthalmic Physiol Opt 1990 Jan; 10(1):3-7

67. Gole, G. (1989), Visual acuity assessment in children. Australian and New
Zealand Journal of Ophthalmology, 17: 1–2.

68. Simons K. Visual acuity norms in young children. Surv Ophthalmol. 1983 Sep-
Oct;28(2):84-92.

69. Arthur BW, Cake S: Bagolini lenses vs the polarized four-dot test. J Pediatr
Ophthalmol Strabismus 33:98, 1996.

Basic Examination of Strabismus | 65

70. Awaya S, Noorden GK von, Romano PE: Anomalous retinal correspondence in
different positions of gaze.

71. Am Orthopt J 20:28, 1970 Jampolsky A: The prism test for strabismus
screening. J Pediatr Ophthalmol 1:30, 1964. Walls GL: The problem of visual
direction. Am J Optom 28:55, 115, 173, 1951.

72. Walraven F, cited by Kramer ME: Clinical Orthoptics: Diagnosis and
Treatment. St Louis, Mosby–Year Book, 1949, p 349.

73. Wright KW, Fox BE, Eriksen KJ: PVEP evidence of true suppression in adult
onset strabismus. J Pediatr Ophthalmol Strabismus 27:196, 1990.

74. Brown HW: The cover test. In Allen JH, ed: Strabismus Ophthalmic Symposium,
II. St Louis, Mosby–Year Book, 1958, p 225.

75. Burian HM: Fusional movements: The role of peripheral retinal stimuli. Arch
Ophthalmol 21:486, 1939.

66 | Basic Examination of Strabismus



About Authors

Dr. (Prof). Subhash Dadeya did his MBBS from Medical College Rohtak.
He did his M.D. (Ophthalmology) from Dr. R. P. Center A.I.I.M.S. He
did his Senior Residency from Guru Nanak Eye Center, Maulana Azad
Medical College Delhi & after a brief period as pool officer at Safdarjung
hospital , subsequently he joined as Assistant Professor at GNEC,
MAMC & is currently working as Director - Professor of Ophthalmology.

He is active Member of Delhi Oph Society . He has been Executive
Member, Library officer , Secretary and Vice President of Delhi Oph
Dr. (Prof). Subhash Dadeya Society. Currently he is President of Delhi Ophthalmology Society.

He has been Executive Member, Joint Secretary and Secretary of Strabismological Society
of India. He has been Secretary , Vice President and President of Strabismus and Pediatric
Ophthalmology Society of India. He has been Chief Editor of Indian Journal of Strabismology and
pediatric ophthalmology.

He is a member of Asia Pacific society of strabismus and Pediatric Ophthalmology. He is also a
Member of the International Strabismus Association.

He is active member of AIOS & has written CME series on amblyopia.

He has around 100 publications to his credit in various regional, national and international journals.
He has been invited as a guest speaker at various regional, national and international conferences
in various capacities.

Dr Savleen Kaur did her MBBS from LHMC Delhi.

She did her MS from Guru Nanak Eye Centre Maulana azad medical
college Delhi in 2011. She is currently working as Assistant Professor
in Department of Ophthalmology (Advanced eye centre) PGIMER,
Chandigarh.

Dr. Savleen Kaur She is fellow of ICO,Visiting fellow Jules Stain Eye Institute California,
fellow all India collegiium of Ophthalmology in pediatric ophthalmology
and strabismus.

She has more than 70 indexed publications and over 30 invited speaker sessions.

She has many awards to her credit namely Woman Scientists award by Department of Science
and technology, Ministry of Health, Govt of India. Best Publication, paper and poster award by
Strabismus and Paediatric Ophthalmology Society of India. Best paper award by North Zone Oph
Society and Chandigarh Oph Society.

DELHI OPHTHALMOLOGICAL SOCIETY

Prof. (Dr.) Namrata Sharma

Secretary, Delhi Ophthalmological Society
DOS Secretariat

Room No. 479, 4th Floor, Dr. Rajendra Prasad Centre for Ophthalmic Sciences,

68 | BAlal Isndicia EInsxtaitumte ionfaMteiodincaloSfcSientrcaesb, iNsemw uDeslhi-110029, India Tel: +91-11-2086371

Email: [email protected] / [email protected] · Website: www.dosonline.org