convergence insufficency Flashcards
what is convergence insufficency
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
what factors are associated with onset of primary convergence insufficency
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
what are some of the causes of secondary ci
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)
how does refractive error cause secondary ci
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)
how does systemic disease cause secondary ci
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)
what it is the prevalence of secondary ci
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%
what are the symptoms of ci
Intermittent horizontal diplopia at near
Asthenopic
Frontal headaches
Eye strain/ eye ache
Photophobia
Nausea
Epiphora
Blurred near vision
what investigations need to be done for ci
Case History
Symptoms?
When do symptoms occur?
When did symptoms begin?
Did anything happen at the time symptoms started?
GH
Medication
Previous treatment
what needs to be noted about convergence
Convergence
How?
What’s normal?
What other factors should be considered?
What indicates a diagnosis of CI?
Fit with symptoms?
what indicates a diagnosis of ci
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
how is accomodation invetsigated
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
how is om diagnosed
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
what additional investigations need to be done
Fundus and media check
Refraction
Order any significant refractive error
what is the management of primary convergence insufficency
Orthoptic exercises
Prisms
Surgery
what orthoptic exercises useful in
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
what orthoptic exercises can be done
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)
what instructions are given for orthoptic exercises
Demonstration
Practise in clinic
How often? Little but often
Symptoms may worsen initially
Remember…relaxation afterwards
what is the prognosis for ci using orthoptic exercises
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
what indicates a diagnosis of ci
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)
prognosis of ci using orthoptic exercises
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
what is the management for secondary ci
Treat cause
Orthoptic exercises may help
eg. TED (Burke, Shipman & Watts, 1993)
May need to treat associated accommodative anomaly
Prisms
Surgery
what prisms are used to treat ci
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
is surgery required for ci
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)
what surgery can be done for ci
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
compare the different surgery types
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
