2. Convergence
Disjugate simultaneous and synchronous inward
rotation of both eye which results from co-
contraction of the two medial rectus muscles
Allows bifoveal single vision maintained at near
fixation distance
Does not deteriorate with age
Can be improved by exercises

3. Unit of measurement
Clinical measurement – Prism Diopter
The amount of convergence is calculated by using
the formula: 1/d × IPD where
d is the distance and IPD is interpupillary distance.
Thus, a 6-cm IPD requires 6 dioptres of
convergence for a fixation distance of 1 m.

5. Types
Voluntary convergence
Tonic convergence
Accommodative Convergence
Fusional convergence
Proximal convergence

6. Contd..
1.Tonic
due to the tone of the extraocular muscles
initiating movement from the anatomical position
of rest
2. Accommodative
which is initiated by the stimulus of
accommodation.

7. Contd..
3. Fusional
which is initiated by a fusional stimulus.
an involuntary vergence movement to maintain
BSV
4. Proximal
induced by the awareness of a near object

8. One-third of convergence relates to tonic, fusional
and proximal convergence.
Two-thirds is accommodative
NPC value is greater than 10 cm

9. Convergence insufficiency
Inability of eyes to obtain or maintain adequate
binocular convergence
Most common cause of ocular asthenopic
symptoms.

10. First described by von Graefe in 1855 and later
elaborated by Duane
one of the most common causes of ocular
discomfort
most common cause of muscular asthenopia

11. Clinical signs of CI
1) Exophoria greater at near than at distance(N>D)
2) A receded near point of convergence
3) Reduced positive fusional vergence at near
4) Low AC/A ratio
5) Little or no lag of accommodation

12. Symptoms due to muscular fatigue
Eye strain and sensation of tension around globe.
Headache and eye ache after intense near work and
relieved when eyes are closed
Difficulty in changing focus from distance to near
objects
Itching, burning and soreness of eyes and even
hyperemia of nasal half of the conjunctiva

13. Symptoms due to failure to
maintain BSV
Blurred vision and crowding of words while reading
Intermittent crossed diplopia for near under the
condition of fatigue
If untreated, in some cases, convergence insufficiency can
lead to an outward eye turn that comes and goes
intermittent exotropia

14. Less common complaints
Nausea
motion sickness
Dizziness
panoramic headaches
gritty sensation in the eyes
general fatigue

15. Aetiology of CI
Primary or idiopathic:
In many cases, exact etiology is not known.
May be associate with:
Wide IPD
Delayed or inadequate functional development
General debility
Psychological instability
Over work or worry

16. Refractive
Associated with uncorrected high hyperopia
and myopia
High hyperopes (>5D) usually make no effort to
accommodate and there is deficient
accommodative convergence.
Myopes may not need accommodation and
thus lack accommodative convergence.

17. Muscular imbalances
Exophoria
IXT
Vertical muscle imbalances
Consecutive convergence insufficiency :
May occur following either recession of medial
recti or resection of lateral rectus

18. General physical causes
diseases of endocrine gland (e.g. Mobius’ sign in thyroid
ophthalmopathy).
Psychological causes.
include anxiety and neurosis

19. Clinical features
Clinical problem in patient who does intense near
work.
Children with increased school work.
Desk workers
Computer users
Discomfort usually occurs at the end of the day.

20. Assessment of NPC
The near point of convergence is assessed
objectively using either a fixation target or the
fixation target on the RAF rule

21. Assessment of PFV
Base out motor fusion range is measured to find out
blur, break and recovery
N: 21/30/18
D: 8/10/6

22. Prism Cover test
Assess Latent ocular deviation such as exophoria at
distance and near
Near exophoria greater than distance exophoria
Near exophoria distance orthophoria
Vertical imbalances
Intermittent exotropia

23. Diagnosis of CI
Type I: NPC receded or Decreased PFV
Type II: NPC receded or PFV decreased and XP N> XP
D
Type III: All the clinical signs present

24. Treatment
Optical:
Proper refractive correction for any presence of
ametropia
Myopes given full correction and hyperopes
under corrected to stimulate accommodation

25. Treatment
Three approaches
Relieving symptoms
Base in prism
Plus reading glasses
Divergence exercises
Improving convergence
Brock string
Aperture rule trainer
Pencil push ups
Increase amplitude of
fusional convergence
BI/BO prism flipper
Synoptophore
Exercise
Physiological
diplopia exercise
using stereogram
Diploscope

26. Training of voluntary convergence
Prism therapy:
Base –in prism reading glasses or bifocals with
prism in the lower segment are useful as
relieving prism
Relieving prisms and bifocals should be
prescribed cautiously in young age

27. Surgical treatment
As a last resort, when all other measures fail.
When it is associated with large exophoria at near.
Medial muscle resection can be performed in one
or both eyes.

28. THANK YOU!!