Convergence insufficiency Flashcards
Normal point of convergence
6-10cm
Normal convergence fusional amplitudes (BO fusion range)
Near: 35Δ BO
Distance 15Δ BO
CI is present if…
(NPC) is less than 10 cm or if it can be maintained at this level only with effort”
Prevalence of CI
2.7% to 17.6%
Primary convergence insufficiency is when…
CI is the initial defect
Secondary convergence insufficiency is when…
CI is secondary to other defect e.g. significant heterophoria
Primary CI
No significant heterophoria/ underlying condition
Predisposing factors
Genetic- Wide IPD
Environmental: demands of occupation e.g. use of mainly distance vision and uniocular vision.
Precipitating factors- illness, stress and increased close work demands- table in pp
Secondary Convergence Insufficiency- secondary to…
Strabismus, systemic disease, drugs, mechanical or neurological deficit
refractive error, accommodative anomalies
Strabismus causing secondary CI
due to large exophoria or primary intermittent near XT
Systemic disease causing secondary CI
TED and psp
Neurological disease causing secondary CI
Parkinsons
Mechanical disease causing secondary CI
MR affected
3rd nerve or duanes
Secondary CI to mechanical and neurogenic strabismus
- Large exophoria
- SO palsy (vertical deviation makes conv difficult)
- Duanes type C
- Thyroid eye disease (22% - Burke et al, 1993)
Secondary CI to refractive error
- Uncorrected high hypermetropia – may choose not to accom to avoid ET
- Overcorrected hypermetropia- relaxes accom
- Acquired myopia- eliminates need to accom at near so less accom conv
- Presbyopia- new gls induce accom stimulus and therefore accom conv
Secondary CI to systemic disease
- Parkinson’s disease (31.3% - Irving et al, 2016)
- Progressive supranuclear palsy (PSP)
Secondary CI to 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)
*found it does not affect accommodation
Prevelance of CI
Cuiffreda et al (2007) 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%
Symptoms of CI
Intermittent horizontal diplopia at near
Asthenopic symptoms- Frontal headaches, eye strain/ eye ache, photophobia, nausea, epiphora, blurred near vision
Investigation; case history
Symptoms?- When do symptoms occur?, when did symptoms begin? Did anything happen at the time symptoms started?
GH?- Medication previous treatment
How to measure convergence?
What’s normal?
What other factors should be considered?
What indicates a diagnosis of CI?
Fit with symptoms?
Indicator of CI
Symptoms occur when NPC is greater than 10cm (studies in pp
Investigation of CI
Accommodative Amplitude/NPA: BEO, monocularly, bear in mind patient’s age
Facility: +/- 2DS, preferably binocularly to avoid practice effects (Horwood and Toor, 2014), nott dynamic retinoscopy
Ocular motility
Differentially diagnose secondary cause
* mechanical (Duanes, TED) or
* neurogenic (SO u/a)
* reading position (A exo/Veso)
Sheard’s criterion on fusional reserves and heterophoria
fusional reserve must be x2 heterophoria
Further investigation
fundus and media check, refraction
Initial management of primary convergence insufficiency
orthoptic exercises if not successful then prisms its rare to need surgery/ botox
Use of surgery
It is rare surgery or BT are done in patients with primary CI, these patients often have poor surgical prognosis as they have reduced fusional reserves and ability.
Management of secondary convergence insufficiency
initially treat underlying cause, then orthoptic exercises, prisms surgery, botox
- 2° CI does not prevent exercises being attempted but may limit prognosis
Convergence exercises
pen to nose
jump
dot card
Pen to nose (smooth vergence) The aim of these exercises is to be able to converge closer to the nose each time. Improve near point convergence. By the end the patient should be able to focus on the dot closest to nose and keep it single.
Jump exercises and dot card (jump vergence) To be able to change focusing distances more quickly whilst maintaining single vision
Near point stereograms can…
refine control, improve base out fusional reserves and positive relative convergence, can be alternative to gradual and jump convergence as NPC improves
Prism bar exercises used to…
exercise convergence using a makeshift also gradually provide patient with stronger base out prism
Patient should..
wear refractive correction and pt should have BSV at near, physiological diplopia can be used as a check if pathological diplopia is not appreciated i.e. patient suppresses at break point.
Make patient aware of
physiological diplopia if they’re not already aware, so they know they’re doing the exercises right.
When offering orthoptic exercises..
- Explain and demonstrate exercises to patient
- Allow patient to practise the exercises with you
- Check at each visit
- Give leaflet with contact details
Important- rapport, check compliance symptoms may worsen initially and having the same orthoptist each time may help
Aim of orthoptic exercises
to be able to converge closer to the nose each time. Improve near point convergence. Know patient is doing exercises correctly, check this each visit.
Method of convergence exercises
- 1 - 2 minutes per session, 3 - 4 times daily
- Relaxation
- Look at a distance target to prevent inducing convergence spasm
- See in 3-4 weeks then gradually increase length between visits
- No consensus in literature over exact duration.
- Short periods regularly.
- Emphasise that Relaxation is important
Requirements for orthoptic exercise management
✔ Symptomatic and BSV
✔ Motivated and cooperative
✔ Understands exercises
✔ Normal accommodation for age
✔ Able to attend frequently*
Prognosis of CI
- If normal NPC and normal fusional amplitudes achieved stop exercises for 4 weeks
- If symptoms re-occur patient may need maintenance exercises
- Discharge
Success rate of exercises
- Adults and children: 51.9% - 85%
- (Westman & Liinamaa, 2012; Aziz et al, 2006)
- Children: 59.5% - 97.6%
- (Westman & Liinamaa, 2012; Jenewein et al, 2022)
- Maintained to one year
- Children: 66.7% - 84.4% (CITT, 2009
Base in prisms use
- Relieve some of the effort needed to converge
- Decrease the amount of base out prism fusion range needed for comfortable vision
- Sheard’s criterion: Prism strength = 2/3 exophoria minus 1/3 near BO fusion range. (Sheard, 1930)
- Give the minimum strength allowing for comfortable near BSV
- In reality we often give the minimum strength
Base in prisms prognosis
- May be helpful in patients with TED
(Burke et al, 1993) - Found to be less effective in children
(CITT, 2005) - Found to significantly reduce symptoms in young and older adults
(Nabovati et al, 2020; Teitelbaum et al, 2009) - Effective in presbyopes with CI
(Teitelbaum et al, 2009)
Good surgical candidates
secondary convergence insufficiency, large N XP >12 dioptres
Poor surgical candidates
primary convergence insufficiency, poor response to prisms (defective motor fusion)
Surgical method - strengthen
- MR plication (of the centre of MR muscle 3 and 5 mm)
- Slanted MR resection
- Can be unilateral or bilateral
Medial rectus plication
Plication tightens the MR muscle by folding the muscle on itself, then suturing it to the sclera. No cutting or disinsertion of the muscle is required. Minimally invasive, quicker and reversible. Less risk of anterior ischaemia as the vascularisation of the eye is preserved
Has been performed under local anaesthetic. Less conjunctival swelling
Slanted MR resections
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 under correction but 13/15 relief of symptoms
Surgical comparison
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
Farid and Abdelbaset (2018) – CI type IXT
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 under corrections but simplest therefore recommend this
Hofsli et al (2023)
n = 23
Adults
57% improved at 1st follow up (median 47 days post BT)
23% improved at 2nd follow up (median 174 days post BT)
Repeat injections may be required
Surgery drawbacks
It’s a weakening and might be initially effective however repeat injections may be required
It’s not suitable for children. All patients who had previously been treated with convergence exercises, prisms, and/or surgery
TO KNOW
- Type of CI
- Previous treatment
- Patient motivation and true compliance with treatment
- Refractive error
- Type of glasses
- Accommodation status
- The pros and cons of available management options for patients with CI
- The most appropriate clinical management is for all types of CI
- How to explain management to a patient
