Accomodation is mechanism by which eye changes refractive power by alternating shape of lens in order to focus objects at variable distances

1. Dr. Sameeksha Agrawal

2. ACCOMMODATION

3. DEFINITION
Accommodation is the mechanism by which the eye
changes refractive power by altering the shape of lens
in order to focus objects at variable distances
Our eyes have been provided with a unique
mechanism by which we can even focus the diverging
rays coming from a near object on the retina. This
special mechanism is called ACCOMMODATION.

4. MECHANISM OF ACCOMMODATION
• Normally the crystalline lens is held under tension by the
suspensory ligament (zonules) which attaches it to the
ring of ciliary muscle and keep the lens flat.
• Ciliary muscle contraction reduces the tension on the
suspensory ligament and lens, allowing the lens to assume
a more globular shape.

5. MECHANISM OF ACCOMMODATION
• The curvature of the lens surfaces (mainly the anterior
surface of the lens) increases.
• Axial thickness of the lens increases.
• Anterior pole of the lens moves slightly forwards carrying
the iris with it, thus making the anterior chamber shallow.
• All these changes lead to increase in the diopteric power of
the lens.

6. OTHER CHANGES
• Pupils constrict and the eyes converge in a bid to achieve
clear vision for near objects.
• Choroid is stretched forwards by the ciliary muscle
contraction.
• The ora serrata moves forward about 0.05mm with each
dioptre of accommodation.

7. • Far point: Position of an object when its image clearly falls on
retina with no accommodation. Also called as punctum remotum
• Near point: Nearest point clearly seen with maximum
accommodation. Also called as punctum proximum.
• Range of accommodation: Distance between far point and near
point.

8. VARIATION WITH STATIC REFRACTION OF
EYE
Hypermetropic eyes: far point is virtual and lies behind the eyes
Myopic eyes: far point is real and lies in front of the eyes
Emmetropic eye: far point is at infinity and near point varies with
age.
07cm at 10 years
25 cm at 40 years
33 cm at 45 years
Thus, amount the eye can alter its refraction is greatest at
childhood and slowly decreases until its lost in middle age

9. • Depth of field: The range of
distance from the eye in which
an object appears clear without
change of accommodation. It is
inversely proportional to pupil
size.
• Depth of focus: The range in
retina in which an optical image
may move without impairment
of clarity. It is directly
proportional to pupil size

10. STIMULUS FOR ACCOMMODATION
• Image blur
• Apparent size and distance of object
• Chromatic aberrations
• Oscillation of accommodation
• Scanning movements of the eye

11. ASSESSMENT OF ACCOMMODATION
• This includes:
1. Assessment of NPA and amplitude of accommodation
2. Assessment of accommodative response
3. Assessment of dynamics of accommodation

12. ASSESSMENT OF NPA AND AMPLITUDE OF
ACCOMMODATION
• It is the difference in dioptric power needed to focus at near
point and far point
• Can be done by measuring NPA or using minus lenses.
TO MEASURE NPA a) RAF rule or Prince’s rule
• Patient wears full refractive correction
• Sliding target with 6/9 letters is moved towards or from the
eye till the closest point is found at which it is still seen
clearly.
• Done for each eye separately and the for both eyes
• Measured in centimeters marked on one side and the side of
the bar marked in dioptres will indicate amplitude.

13. RAF RULE:

14. • Amplitude of accommodation is low: near point lies
beyond the length of instrument
• Plus lenses added to refractive correction to bring near
point within range and the dioptric power of these lenses
is deducted from the measured value of accommodation.
• Amplitude of accommodation is high: young patients
• minus lenses added to distance correction to move near
point away from eyes and the dioptric power of these
lenses is added to the measured value of accommodation.

15. b) Using minus lenses
• Performed for each eye separately.
• Patient wears full refractive correction.
• Patient is asked to fixate the best corrected near vision target at 40 cm.
• Minus lenses of progressively increasing power are added till patient reports
the first sustained blur.
• Power of the minus lens plus +2.5D(for 40 cm) gives amplitude.
c) Pushup test
• Can be done both monocularly or binocularly.
• Patient wears full refractive correction.
• Near vision target is fixed at a point where it is seen clearly.
• Moved closer till the patient reports first sustained blur
• Linear distance measured between the target and the patient’s spectacle
plane gives NPA.

16. ASSESSMENT OF ACCOMMODATIVE RESPONSE
• Assessed with dynamic retinoscopy
• Monocular Estimation Method (MEM)
Patient is asked to fixate the near target at a distance of 40
cm. Retinoscopy is performed using streak retinoscope and
the lens power required to attain neutrality is noted.
• Nott Retinoscopy
Dynamic retinoscopy is performed as in MEM except that
the retinoscopic reflex is neutralized by moving the
retinoscope.
‘With’ movements: retinoscope moved away from patient
‘Against’ movements: retinoscope moved towards patient

17. MEM:

18. • Lag of accommodation: Accommodative response is less
than accommodative demand. Lag of > +1.00D is seen in
accommodative insufficiency or infacility
• Lead of accommodation: Accommodative response is
more than accommodative demand. Lead of > +0.50D is
seen in accommodative excess

19. ASSESSMENT OF DYNAMIC
ACCOMMODATION
• Assessed by testing accommodative facility.
• An accommodative flipper of +2.00 DS with -2.00 DS is used
by rapidly flipping the lenses
Difficulty with + lenses: Accommodative excess
Difficulty with - lenses: Presbyopes

20. TYPES OF ACCOMMODATION
• Tonic accommodation
– It is due to tonus of ciliary muscle and is active in
absence of a stimulus. The resting state of
accommodation is not at infinity but rather at an
intermediate distance.
• Proximal accommodation
– Is induced by the awareness of the nearness of a target.
This is independent of the actual dioptric stimulus.

21. • Reflex accommodation
– Is an automatic adjustment response to blur which
is made to maintain a clear and sharp retinal image.
• Convergence-accommodation
– Amount of accommodation stimulated or relaxed
associated with convergence.
– The link between accommodation and convergence
is known as accommodative convergence and is
expressed clinically as AC/A ratio.

22. ACCOMMODATION REFLEX

23. • The afferent
– Retina (with the retinal ganglion axons in the
optic nerve, chiasm and tract),
– Lateral geniculate body (with axons in the optic
radiations)
– Visual cortex.
• Ocular motor control neurons are interposed
between the afferent and efferent limbs of
this circuit and include the visual association
cortex

24. • It determines the image is "out-of-focus” &
sends corrective signals
|
internal capsule and crus cerebri
|
supraoculomotor nuclei (generates motor
control signals)
|
oculomotor complex.

25. • The efferent
– Edinger-Westphal nucleus -
oculomotor nerve - ciliary
ganglion - short ciliary nerve - iris
sphincter and the ciliary
muscle/zonules/lens of the eye
– oculomotor neurons - oculomotor
nerve - medial rectus, converge
the two eyes.

26. ANOMALIES OF ACCOMMODATION
• Classification (by Duane with some modification):
– Accommodative insufficiency
• Ill-sustained accommodation-
• Paralysis (or paresis) of accommodation
• Unequal accommodation
– Accommodative excess.
– Inertia of accommodation

27. • Diminished or deficient accommodation
– Physiological : Presbyopia
– Pharmacological : Cycloplegia
– Pathological
» Insufficiency of accommodation
» Ill sustained accommodation
» Inertia of accommodation
» Paralysis of accommodation
• Increased accommodation

28. PRESBYOPIA
Presbyopia is a condition of physiological
insufficiency of accommodation leading to a
progressive fall in near vision.

29. PATHOPHYSIOLOGY
• In emmetropic eye far point is infinity and near point
varies with age (being about 7 cm at 10 years, 25 cm at 40
years and 33 cm at 45 years).
• We read from 25 cm. After 40 years, the near point recedes
beyond normal reading or working range.
• Failing near vision due to age-related decrease in
amplitude of accommodation is called presbyopia.

31. CAUSES
• Decrease in accommodative power of lens with
increasing age, leads to presbyopia, occurs due to:
–Age-related changes in lens:
oDecrease in elasticity of lens capsule, and
oProgressive, increase in size and hardness (sclerosis) of lens
substance which is not easily moulded.
–Age related decline in ciliary muscle power.

32. PREMATURE PRESBYOPIA
• Uncorrected hypermetropia.
• Premature sclerosis of the crystalline lens.
• General debility causing pre-senile weakness of
ciliary muscle.
• Chronic simple glaucoma.

33. SYMPTOMS
• Difficulty in near vision.
• Patients complaint of difficulty in reading small prints
• Asthenopic symptoms due to fatigue of the ciliary muscle
are also complained after reading or doing any near work.
• Intermittent diplopia at near may develop because of
interrelation between accommodation and convergence.
• All symptoms of presbyopia are aggravated by fatigue,
illness, fever etc

34. PRESBYOPIA TREATMENT

35. OPTICAL TREATMENT
• Prescription of appropriate convex glasses for near work.
• A rough guide for providing presbyopic glasses in an
emmetrope can be made from patient’s age.
– About +1 DS is required at the age of 40-45 years,
– +1.5 DS at 45-50 years,
– + 2 DS at 50-55 years,
– +2.5 DS at 55-60 years.
What we follow:
+1.00: 40 years.
+1.25: 41-44 years.
+1.50: 45 years.
+1.75: 46-49 years.
+2.00: 50 years.
+2.25: 51-54 years.
+2.50: 55 years.
+2.75: 56-59 years.
+3.00: 60 years and beyond.

36. BASIC PRINCIPLES OF PRESBYOPIC
CORRECTION
• Refractive error for distance is corrected first.
• Correction needed in each eye should be tested separately
and then add it to distant correction.
• Near point should be fixed according to the profession of
patient.
• Weakest convex lens with which one can see clearly at near
point should be prescribed, overcorrection will also result in
asthenopic symptoms.
• Presbyopic spectacles may be unifocal, bifocal or varifocal.

37. SURGICAL TREATMENT
• Corneal procedures
– Non ablative corneal procedure
• Monovision CK
– Laser based corneal procedure
• Laser thermal keratoplasty (LTK)
• Monovision LASIK.
• Presbyopic bifocal LASIK
• Presbyopic multifocal LASIK

38. • Intraocular refractive procedure
– Refractive lens exchange
– Phakic refractive lens
– Monovision with IOLs
• Scleral based procedures
– Anterior sclerotomy with tissue barriers
– Scleral spacing procedure
– Scleral ablation with erbium : yag laser

40. INSUFFICIENCY OF ACCOMMODATION
• Condition in which accommodative power is constantly
less than lower limit of normal range according to
patient’s age.

41. ETIOLOGY
• Premature sclerosis of lens
• Weakness of ciliary muscle due to systemic causes:
Debilitating illness, anemia, toxemia, malnutrition,
diabetes mellitus, pregnancy, stress etc.
• Weakness of ciliary muscle due to local causes: PAOG,
mild cyclitis as during onset of sympathetic ophthalmia.

42. CLINICAL FEATURES
• Features of eye strain and asthenopia.
• Headache, fatigue & irritability of the
eyes, while attempting near work.
• Near work is blurred & becomes difficult
or impossible.
• Disturbance of convergence : intermittent
diplopia.
• It is stable condition, if due to sclerosis of
lens.
• But is not stable in association with ciliary
muscle weakness.

43. TREATMENT
• Identification & treatment of any systemic cause.
• Any refractive error should be corrected & if vision for near work is
seriously blurred then additional near correction has to be prescribed
same as presbyopia.
• If associated with convergence excess then full spherical correction is
prescribed.
• Convergence insufficiency is there, then base in prisms can be added.
• Prismatic correction added should bring near point of convergence to
same distance as near point of accommodation.
• Weakest convex lenses should be prescribed, so as to exercise and
stimulate accommodation.
• After recovery additional correction should be made weaker from time to
time.

44. • Accommodative exercises.
– While doing exercises patient should wear correction
for distance.
– Should be done simultaneously in both eyes, even if
associated with convergence insufficiency.
– If associated with convergence excess then the exercise
should done with one eye alternately.
– Accommodation test card exercise.
– Useless in generalized debility and sclerosis of lens.

45. ILL-SUSTAINED ACCOMMODATION
• Accommodation fatigue.
• It is a situation in which though range of
accommodation is in normal range it cannot be
sustained for a sufficient period of time.
• Initial stage of insufficiency of accommodation.
• It occurs due to
– Stage of convalescence from debilitating illness
– Stage of generalized tiredness
– When the patient is relaxed in the bed

46. CLINICAL FEATURES
• These symptoms are most commonly reported
at the end of the day
• Blurred vision after prolonged near work.
• Headaches
• Eyestrain
• Fatigue, sleepiness and a loss of
comprehension with continued reading
• A dull 'pulling' sensation around the eye.

47. TREATMENT
• Near work should be curtailed during debilitating
illness.
• General tonic measures should be taken.
• The condition of illumination and posture while
doing near work, should be improved.

48. INERTIA OF ACCOMMODATION
• It is a condition in which patient faces difficulty in
altering the range of accommodation.
• Amplitude of accommodation is normal.
• Ability to make use of this amplitude quickly and
for long periods of time is inadequate.

49. CLINICAL FEATURES
• Difficulty changing focus from one distance to
another
• Headaches
• Eyestrain
• Fatigue
• Difficulty sustaining near tasks
• Blurred vision
TREATMENT: correcting any refractive error and
accommodative exercises.

50. PARALYSIS OF ACCOMMODATION
• Cycloplegia, refers to complete absence of
accommodation.
• Causes
–Atropine, homatropine or other
parasympatholytic drugs.
–Internal ophthalmoplegia (paralysis of ciliary
muscle and sphincter pupillae)due to neuritis
associated with diphtheria, syphilis, diabetes,
alcoholism, cerebral or meningeal diseases.

51. –Complete third nerve paralysis due to
intracranial or orbital causes.
–Systemic medications such as anti-hypertensive,
antidepressants.

52. CLINICAL FEATURES
• Blurred near vision
• Photophobia or a 'dazzling' effect
• Diplopia
• Micropsia: objects may appear smaller than
they are due to a false sense of distance
• Dilated pupil.

53. TREATMENT
• An effort should be made to find out the cause
and try to eliminate it.
• Self-recovery occurs in drug-induced paralysis and
in diphtheric cases (once systemic disease is
treated).
• Dark-glasses effective in reducing glare.
• Convex lenses for near vision, if the paralysis is
permanent.

55. EXCESSIVE ACCOMMODATION
• Accommodative response is greater than the
accommodative stimulus.
• There is functional increase in tone of ciliary
muscle, results in a constant accommodative
effect.

56. CAUSES
• Young hypermetropes frequently uses excessive
accommodation as a physiological adaptation
• Young myopes performing excessive near work,
associated with excessive convergence.
• Astigmatic error in young patients
• Presbyopes in the beginning
• Use of improper and ill fitting spectacles

57. PRECIPITATING FACTORS
• Excessive near work done, especially in dim or
excessive illumination.
• General debility, physical or mental ill health

58. SYMPTOMS
• Blurred vision at near is uncommon and is due to
induced pseudomyopia
• Blurred vision at distance
• Headaches
• Eyestrain
• Photophobia
• Difficulty changing focus from distance to near
• Diplopia

59. TREATMENT
• It has a good prognosis.
• Refractive error should be corrected after carefully
performed cycloplegic refraction.
• Near work should be stopped for some time, after
that it should be done with proper illumination
conditions.

60. SPASM OF ACCOMMODATION
• Spasm of accommodation refers to exertion of
abnormally excessive accommodation which is
out of the voluntary control of the individual

61. CAUSES
• Drug induced spasm of accommodation is
known to occur after use of strong miotics.
• Spontaneous spasm of accommodation:
attempt to compensate for a refractive
anomaly.
• Occurs when excessive near work is done with
bad illumination, bad reading position, state of
neurosis, mental stress or anxiety.
• Iridocyclitis: ciliary spasm.
• Lesions of brainstem in their irritative phase.
• Toxic reactions of exogenous poisons:
sulphonamides, arsenic, smoking.

62. CLINICAL FEATURES
• Defective vision: due to induced
myopia.
• Asthenopic symptoms typically
headache and brow ache
• Near point is abnormally close.
• Macropsia occurs due to optical
illusion
• Precipitating factors like marked
degree of muscular imbalance,
trigeminal neuralgia, a dental lesion,
general intoxication.

63. TREATMENT
• Relaxation of ciliary muscle by atropine for 4
weeks or more
• Prohibition of near work allow prompt recovery
from spasm of accommodation.
• Elimination of the associated causative factors to
prevent the recurrence.

64. CONVERGENCE

65. CONVERGENCE
• It a disjugate movement in which both the eyes rotate
inwards so that the line of sight intersects in front of the
eyes.
• Allows bifocal single vision to be maintained at any
fixation distance.
• Remains constant throughout life.

66. TYPES OF CONVERGENCE
A. VOLUNTARY CONVERGENCE
It is the convergence of visual axis which can be produced at
will.
Not a part of normal convergence movement.
B. REFLEX CONVERGENCE
It is the convergence of visual axis which is not under
voluntary control.
Has 4 components:
1. Tonic convergence
2. Fusional convergence
3. Accommodative convergence
4. Proximal convergence

67. A. TONIC CONVERGENCE:
• Due to inherent innervational tone of the EOM when the patient is awake
• Sum of excitatory and inhibitory influences from cortical subcortical
centres and vestibular organs
• Independent of fusion or object proximity
• Strongest in childhood and decreases with age
B. FUSIONAL CONVERGENCE:
• It is the convergence produced to ensure that similar retinal images are
projected on to corresponding retinal areas.
• Occurs without change in refractive state of the eye.
• It is a response to disparate stimuli lying outside the pannum’s fusional
area
• Important mechanism for achievement of bifoveal single vision

68. • Fusional convergence helps control exophoria.
• Decreases in fatigue or illness converting a phoria into a tropia.
C. ACCOMMODATIVE CONVERGENCE:
• Occurs when eyes accommodate or when a nerve impulse to
accommodate is discharged to the eyes.
• Its stimulus is blurred retinal images.
• Forms a part of the synkinetic near reflex complex (miosis+
accommodation+ convergence)
• The quantitative relationship between accommodative convergence
and accommodation is measured as the AC/C ratio. (AC is measured in
prism dioptres and accommodation in lens dioptres)
• It is a linear relationship and stays relatively stable throughout life.
• Myopes: high AC/A ratio
• Hypermetropes: Low AC/A ratio

69. • IPD is also considered while calculating the AC/A ratio as
greater convergence is required in patients with wide IPD
compared to patients with narrow IPD.
• Abnormalities of AC/A ratio
D. PROXIMAL CONVERGENCE
• Induced by proximity of the object or the awareness of the
proximity of the near object.
• Initiation is by psychological factors.
STABISMUS
High AC/A ratio Low AC/A ratio
Convergence excess
Causes convergent squint
On accommodating on near
object
Causes divergent
squint
On accommodating
at near object

70. ANGLE OF CONVERGENCE
• Angle that is formed between the primary lines of sight during
convergence
• Its size depends on fixation distance (inversely) and IPD
(directly; but has negligible effect on the angle)
• Can be measured in metre angle or prism dioptres
Fixation point
Fixation point Fixation point
FIXATION
DISTANCE
IPD

71. METRE ANGLE:
• 1 metre angle convergence is exerted by each eye when the
eyes are directed to an object at a distance of 1 m from the
meridian line between the two eyes.
• The convergence in metre angle is inversely proportional to
the distance of the object in front of the eyes in metres.
• Emmetropic eye: number of dioptres of accommodation
required is equal to number of metre angles the eye must
converge to see object clearly

72. • PRISM DIOPTRES
• The convergence required to see an object placed at 1 m
distance from the eyes singly, when a prism of 1 prism
dioptre is placed in front of one eye.
• Base out prism (converging) is placed in front of the eye.
• Deviates rays of light entering the eye outwards.
• To overcome the diplopia produced the eye will turn
inwards.
• 1 METRE ANGLE CONVERGENCE = 3 PRISM
DIOPTRES CONVERGENCE

73. CONVERGENCE
• Near point: closest point at which an object can be seen
singly during bifoveal vision i.e. the point at which the 2
foveal lines of sight intersect when maximum convergence is
exerted.
• Measurement of NPC: Measures all type of convergences as
the object actually approaches the eye during testing.
• Instruments: RAF ruler
Livingstone Binocular gauge
Prince rule

74. CONVERGENCE
• Far point: relative position of eyes when they are completely at rest.
• Range of convergence: Distance between the near point of
convergence and far point of convergence
Part of range of convergence between the eye and infinity:
positive convergence
Part of range of convergence beyond infinity (behind eye)
when eyes are in divergence: negative convergence or divergence
• Amplitude of convergence: It is the difference in the converging
power needed to maintain the eye in a position of rest and a position
of maximum convergence.
• Measure of the amplitude of convergence can be done by:
1. Prism bar method
2. Synoptophore method

75. AC /A RATIO
• It is a relationship between accommodative convergence
expressed in prism dioptres and accommodation expressed in
lens dioptres.
• Normal ratio: 3 to 5 prism dioptres for 1 D of accommodation.
• Defined by Fry and named by Haines
• Measurement methods:
Hetrophoria method
Gradient method
Fixation disparity method
Haploscopic method

76. HETROPHORIA METHOD
• Full optical correction is given and deviation is measured at 6
m distance and at 33 cm distance in prism dioptres and IPD is
measured in centimeters
• Ratio is calculated as: AC= IPD +∆n-∆d/d
• IPD= interpupillary distance
• ∆n = deviation at 33 cm in prism dioptres
• ∆d= deviation at 6 m distance in prism dioptres
• D = distance of fixation for near in dioptres
• Esodeviations are denoted by positive and exodeviations by
negative

77. GRADIENT METHOD
• For a given distance of fixation, minus lenses placed in
front of the eye increase accommodation and plus lenses
decrease accommodation.
• Calculated as ∆L - ∆O/D
• ∆L is deviation with additional lenses
• ∆O is original deviation without the lenses
• D is the Diopteric power of the additional lens
• Inaccurate as does not take the patient’s IPD into account.

78. ANOMALIES OF CONVERGENCE

79. CONVERGENCE INSUFFICIENCY
• Inability to obtain and/or maintain adequate binocular
convergence for any length of time without undue effort
• Most common cause of ocular asthenopic symptoms.
• ETIOLOGY:
Primary/ idiopathic: mechanism not known
Associated with wide IPD, over work, stress
Refractive errors: seen with uncorrected high
hypermetropia > 5 D make no effort to accommodate and
hence lack accommodative convergence as well
myopia do not need accommodation and hence lack
accommodative convergence.
Presbyopia: less use of convergence as near point of eye
recedes

80. Muscular imbalances: EOM muscles imbalance
In form of exophoria, intermittent XT and vertical muscle
imbalance if neglected for long
Consecutive convergence insufficiency: due to
recession of MR or resection of LR

81. CLINICAL FEATURES
A. Symptoms of muscular fatigue: due to continuous use of
neuromuscular power and marked with near work.
Eyestrain and a sensation of tension in and around globes
Headache and eye ache after prolong near work
Difficulty in changing focus from distant to near
Itching/burning/soreness
B. Symptoms of failure to maintain binocular vision
Blurred near vision + crowding of words while reading
Intermittent crossed diplopia for near vision
Closure of one eye while reading to obtain relief from visual
fatigue

82. DIAGNOSIS
• Remote NPC: When NPC > 10cm from base line CI is said to
exist.
• Decreased fusional convergence for near: measured using
synoptophore. CI is said to exist if its difficult to attain 30⁰ of
convergence.
• Prism convergence: low prism convergence with normal
prism divergence.
• Normal NPA.

83. CONVERGENCE INSUFFICIENCY CONVERGENCE PARALYSIS
Some amount of convergence amplitude can
be demonstrated
Total lack of ability to overcome any amount of
BO prism
On receiving a converging impulse pupillary
constriction occurs while converging on the
approaching target which is followed by
dilation of the pupil when convergence can not
be maintained
On receiving a converging impulse pupillary
constriction occurs while the ability to converge
is lost
CONVERGENCE INSUFFICIENCY ACCOMMODATIVE EFFORT SYNDROME
Exophoria at near Esophoria
Helped by -3 D test by compensating for the
lack of good fusional convergence
Patient goes into tropia with this test
Plus lenses worsen CI due to relaxation of
accommodative convergence
Plus lenses improve symptoms due to
relaxation of accommodative convergence

84. TREATMENT
• Good prognosis
• Children are treated when fusional vergences are poor and
patient shows signs of becoming exotropic.
• Adults are treated when they show symptoms.
• TREATMENT
Optical treatment
Orthoptic excersises
Prismotherapy
Surgery

85. A. OPTICAL TREATMENT
Myopes: full correction
Hypermetropes: undercorrection
Stimulate accommodation which simultaneously stimulate
convergence
B. ORTHOPTIC TREATMENT
Aim: to improve binocular convergence and to increase
amplitude of fusional convergence
Includes:
Exercises to improve NPC
Exercises to increase amplitude of fusional
convergence
Training of voluntary convergence
Relaxation exercises

86. • Exercise to increase NPC
Advancement exercise
Jump convergence exercise:
More elaborate and effective
Trains patient to achieve bifoveal single vision following a sudden change
in convergence requirements
Done only after fourth week of convergence training when convergence
has been improved using other exercises
• Exercises to improve amplitude of fusional convergence
Using prisms: base out prisms placed in front of the eyes
Using synoptophore: The arms are slowly converged starting from the
point where the patient can fuse the picture.
• Exercises using convergence card
• Physiologic diplopia exercise using stereogram in the uncrossed
position.
• Convergence exercise using diploscope.

88. • Training of voluntary convergence
• Relaxation exercises
Physiologic diplopia exercises using stereogram in crossed
position
Divergence exercises on synoptophore
Divergence exercises with prisms
C. Prism therapy:
Useful when orthoptic measures fail.
Base-in prism (relieving prisms) reading glasses are used.
It should be avoided in young age.
D. Surgery:
Last resort, used when all other measures fail.
Medial rectus resection is done in one or both eyes.

89. CONVERGENCE INSUFFICIENCY ASSOCIATED WITH
ACCOMMODATIVE INSUFFICIENCY
• Where convergence insufficiency is secondary to
accommodative insufficiency.
Etiology:
- Early Adie’s syndrome.
- Sequel to head injury viz posterior occipital or whiplash
injury.
- Subclinical viral encephalopathies.
- Infectious mononucleosis.
- Diphtheria.
- Conversion reaction

90. • Clinical features:
- NPC reduced
- NPA reduced drastically
- AC/A ratio is low or even absent.
• Management:
- Orthoptic exercises (alone are usually not much effective
and are hence combined with reading glasses)
- Plus lenses for reading along with base in prisms are the
treatment of choice.
- Resection of medial rectus followed by prescription of
bifocal adds may be helpful in untreatable cases.

91. CONVERGENCE PARALYSIS
• Clinical features:
- Complete absence of convergence.
- Exotropia and crossed diplopia on attempted near fixation
only.
- Normal adduction and normal accommodation.
• Diagnosis: Bielschowsky’s criteria that includes:
1. Evidence of intracranial disease
2. History of sudden onset crossed horizontal diplopia at
near fixation
3. Reproducible findings on subsequent examinations.
4. Preservation of accommodation and pupillary reaction
on attempts to converge.

92. • Management:
1) Base- in prisms for near (for diplopia)
2) Plus lenses with base in prisms for weakness of
accommodation.
3) Occlusion of one eye at near in patients where it is not
possible to restore comfortable single binocular vision.
4) Eye muscle surgery is contraindicated.

93. CONVERGENCE SPASM
• Intermittent episodes of maximal convergence usually
associated with spasm of accommodation.
• Etiology
- Functional (Hysterical & Neurotic patients)
- Organic (after head trauma, encephalitis, tabes dorsalis,
pituitary adenomas, posterior fossa neurofibroma &
Arnold-Chiari malformation)

94. • Clinical features: in most of the cases condition is
episodic. In between the attacks patients are normal.
- Eyes may be fixed in extreme convergence (like bilateral
abducens palsy)
- Homonymous diplopia (patient may give a history of
intermittent diplopia)
- Blurred vision (for near due to associated spasm of
accommodation)
- Miosis (due to near reflex)
- Induced myopia (of 6D due to associated spasm of
accommodation, resulting in decreased VA for distance)

95. • Management:
a. Psychiatric & neurological assessment.
b. Prolonged atropinization with plus lenses.
c. Alternate monocular occlusion may be an alternative to
atropinization.
d. Psychiatric therapy.