convergence insufficency

Question 1

what is convergence insufficency

Answer 1

The inability to obtain or maintain binocular convergence to 10cm without undue effort

primary ci - ci is the initial defect

ci secondary to another defect e.g. significant heterphoria

Question 2

what factors are associated with onset of primary convergence insufficency

Answer 2

Predisposing Factors
Factors that risk the onset of CI
Genetic, personality and environmental factors
E.g. wide IPD, exophthalmos, occupation requiring uniocular work e.g. watch maker

Precipitating Factors (provoking factor)
Specific event or trigger causing the onset of CI
E.g. illness, increased close work, exams, stress

Question 3

what are some of the causes of secondary ci

Answer 3

Strabismus

Mechanical/neurogenic deficit of motility

Refractive error

Systemic disease

Accommodative anomalies

Strabismus/ mechanical + neurogenic

Large exophoria

SO palsy (vertical deviation makes conv difficult)

Duanes type C

Thyroid eye disease (22% - Burke et al 1993)

Question 4

how does refractive error cause secondary ci

Answer 4

Refractive Error
Uncorrected high hypermetropia
May choose not to accomm to avoid ET
Overcorrected hypermetropia
Relaxes accomm
Acquired myopia
Eliminates need to accomm at near so less accomm conv
Presbyopia
New gls reduce accomm stimulus and therefore accommodative conv
(Jenkins 1999)

Question 5

how does systemic disease cause secondary ci

Answer 5

Systemic Disease
Parkinson’s disease (31.3% - Irving et al 2016)
Progressive supranuclear palsy (PSP)
Drugs
over 100 drugs can affect accomm and therefore possibly convergence (Mazow et al 1989) – see accomm lecture
e.g. tranquilizers – Lorazepan for anxiety (Speeg-Schatz et al 2001) (but found it does not affect accommodation)

Question 6

what it is the prevalence of secondary ci

Answer 6

Age 8-91, n = 160, TBI
CI 42.5%
(41.1% accommodative dysfunction – mainly insufficiency)
Alvarez et al (2012)
Age 5-89, n = 557, TBI
CI 9% without other ocular problems
CI 23.3% all
(24.2% accomm dysfunction)

Traumatic brain injury 9 – 42%

Question 7

what are the symptoms of ci

Answer 7

Intermittent horizontal diplopia at near
Asthenopic
Frontal headaches
Eye strain/ eye ache
Photophobia
Nausea
Epiphora
Blurred near vision

Question 8

what investigations need to be done for ci

Answer 8

Case History

Symptoms?
When do symptoms occur?
When did symptoms begin?
Did anything happen at the time symptoms started?

GH
Medication
Previous treatment

Question 9

what needs to be noted about convergence

Answer 9

Convergence
How?
What’s normal?
What other factors should be considered?
What indicates a diagnosis of CI?
Fit with symptoms?

Question 10

what indicates a diagnosis of ci

Answer 10

Reduced NPC (Momeni-Moghaddam et al 2013)
124 medical students
Convergence Insufficiency Symptom Survey (CISS)
15 questions, symptoms during close work, in adults ≥ 21 = symptomatic
33.9% asymptomatic 8.4cm
61.1% symptomatic 11.7cm
NPC 9.5cm cut off for
symptoms

Question 11

how is accomodation invetsigated

Answer 11

Accommodation
Amplitude/NPA:
BEO
Monocularly
Bare in mind patient’s age
Facility:
+/- 2DS
Preferably binocularly to avoid practice effects (Horwood and Toor, 2014)
Nott dynamic retinoscopy

Question 12

how is om diagnosed

Answer 12

OM
- differentially diagnose secondary cause
mechanical (Duanes, TED) or neurogenic (SO u/a)
reading position (A exo/Veso)
Fusional amplitude
Sheard’s criterion – fusional reserve must be twice amount of heterophoria

Question 13

what additional investigations need to be done

Answer 13

Fundus and media check

Refraction
Order any significant refractive error

Question 14

what is the management of primary convergence insufficency

Answer 14

Orthoptic exercises

Prisms

Surgery

Question 15

what orthoptic exercises useful in

Answer 15

Awareness of phys dip
Underlying dev not too large (?2° CI)
No vert dev (2° CI)
good GH (2° CI)

2° CI does not prevent exercises being attempted but may limit prognosis

Question 16

what orthoptic exercises can be done

Answer 16

Smooth vergence (pen conv)
Dot card
Jump vergence (near + dist target)
BO fusional reserves (create using fresnels)
Positive relative vergence (near stereograms)

Voluntary convergence
Eliminate suppression (anti-sup exercise – if suppression when conv fails can teach awareness of dip)

Question 17

what instructions are given for orthoptic exercises

Answer 17

Demonstration
Practise in clinic
How often? Little but often
Symptoms may worsen initially
Remember…relaxation afterwards

Question 18

what is the prognosis for ci using orthoptic exercises

Answer 18

Scheiman et al (2005)
Convergence Insufficiency Treatment Trial (CITT) Study Group
47 patients aged 9 – 18
CISS (children score ≥16), symptomatic primary CI
Randomised
12 weeks office based orthoptic therapy
12 weeks home therapy (pen push-ups)
12 weeks office based placebo therapy
Significant improvement: CISS, NPC, PFR in office based orthoptic therapy group only.
CITT (2009) Long-term effectiveness

1 year follow up to CITT (2008)
Those in 12 week orthoptic home and office therapy group 84.4% remained asymptomatic 1 year after discontinuing exercises

Question 19

what indicates a diagnosis of ci

Answer 19

headaches / unconfrtabiliuty during near work , diplopia during close work, eye hurt when doing close work

Symptoms common without signs of poor convergence
Some with reduced convergence have no symptoms (recruited as normals)

Question 20

prognosis of ci using orthoptic exercises

Answer 20

Horwood et al (2014), Horwood and Toor (2014)
Most effective exercises = Simple vergence exercises
Binocular push up, binocular jump vergence, near and distance vergence facility (stress single vision) - Improved convergence and accommodation
Treatment resolving blur had no/minimal effect
Groups which exercised conv and accom were least effective than concentrating on single visual skill
‘Effort’ had greater influence on responses than any exercise groups – explains CITT findings

Question 21

what is the management for secondary ci

Answer 21

Treat cause

Orthoptic exercises may help
eg. TED (Burke, Shipman & Watts, 1993)

May need to treat associated accommodative anomaly

Prisms

Surgery

Question 22

what prisms are used to treat ci

Answer 22

Base in

Near only

Purpose
Temporary – aim to discard
Long term

Presbyopes
Teitelbaum et al (2009) found BI prisms to be effective in presbyopes with CI

Question 23

is surgery required for ci

Answer 23

Not usually required for primary CI

Appropriate if secondary CI

CI type IXT (near ≥10PD than dist)

Type Sx?
Unilateral medial rectus resection
Bilateral medial recti resections
Slanted medial rectus resections
Sx on LR muscle(s)

Question 24

what surgery can be done for ci

Answer 24

Upper edge of MR resected according to the
distance exodeviation
Lower edge of MR resected according to near
exodeviation
So lower edge resected more than upper edge.
MR reattached at its original insertion

Nemet and Stolovitch (1990) not successful in collapsing the near distance difference
Choi and Hwang (2006) resulted in undercorrection but 13/15 relief of symptoms

Question 25

compare the different surgery types

Answer 25

Farid and Abdelbaset (2018) – CI type IXT
Slanted bilat LR recession (upper edge recessed according to dist angle; lower edge to near angle)
Best at correcting dist angle (p=0.054)
Best at correcting near angle and near-dist diff (not sig)
Assoc with post-op A and V patterns
Augmented bilat LR recession (augmented to near angle)
Assoc with post-op consec ET and diplopia
Unilat MR resection (according to near angle) & LR recession (according to dist angle)
Assoc with post op undercorrections but simplest therefore recommend this