Convergence Insufficiency Flashcards
What’s the normal near point of convergence?
Between 6 - 10cm (Abraham et al., 2015)
What is Convergence Insufficiency?
Convergence insufficiency is present if the near point of convergence (NPC) is less than 10 cm or if it can be maintained at this level only with effort
What is the prevalence of convergence insufficiency?
2.7% to 17.6% (Ma et al., 2018)
What’s the difference between Primary & Secondary CI?
Primary CI
CI initial defect
Secondary CI
CI secondary to other defect e.g. significant heterophoria
What are some predisposing factors for Primary CI?
- Genetic: Wide interpupillary distance IPD
- Environmental: demands of occupation
e.g. use of mainly distance vision and uniocular vision.
What are some precipitating factors in Primary CI?
- Illness
- Stress
- Increased close work demands
(Jenkins, 1999)
What did Nunes et al. (2019) find about Primary CI?
Of 292 people aged 10 - 14 6.8% previously had CI, 3.1% also had AI (accommodation insufficiency) and 6.8% have AI without CI
What might CI be Secondary to?
- Strabismus e.g. large X or primary intermittent nr XT
- Systemic Disease e.g. TED
- Drugs
- Mechanical Deficit e.g. Duanes
- Neurological Disease e.g. Parkinsons, PSP
- Refractive Error
- Accommodative Anomalies
What Mechanical & Neurogenic Strabismus might CI be Secondary to?
- Large exophoria
- SO palsy (vertical deviation makes convergence difficult)
- Duanes type C
- TED
What did Burke et al. (1993) find out about TED and CI?
22% of those with active TED have secondary CI
When might CI be secondary to Rx?
- Uncorrected high hypermetropia
May choose not to accommodate to avoid ET - Overcorrected hypermetropia
Have relaxed accommodation - Acquired Myopia
Eliminates need to accommodate at near so less accommodative convergence - Presbyopia
New glasses reduces accommodation stimulus and so accommodative convergence
What did Jenkins (1999) find out about Presbyopia?
New gls reduce accomm stimulus and therefore accommodative conv
What neurological disease might CI be secondary to?
- Parkinson’s Disease
- Progressive Supranuclear Palsy (PSP)
What did Irving et al. (2016) find out about secondary CI and neurological disease?
31.3% of those with Parkinson’s Disease had secondary CI
What drugs might CI be secondary to?
- Over 100 drugs can affect accommodation and therefore possibly convergence (Mazow et al., 1989)
e.g. tranquilizers like Lorazepam for anxiety (but found it doesn’t affect accommodation Speeg-Schatz et al., 2001)
What did Cuiffreda et al. (2007) find out about Traumatic Brain Injury and Secondary CI?
Age 8-91, n = 160, TBI
CI 42.5%
(41.1% accommodative dysfunction – mainly insufficiency)
What did Alvarez et al. (2012) find out about Traumatic Brain Injury and Secondary CI?
Age 5-89, n = 557, TBI
CI 9% without other ocular problems
CI 23.3% TBI group (with and without ocular problems)
(24.2% accomm dysfunction)
What are the symptoms of CI?
Intermittent horizontal diplopia at near
Asthenopic symptoms:
- Frontal headaches
- Eye strain/eye ache
- Photophobia
- Nausea
- Epiphora
- Blurred near vision
What do we need to ask in a case history about CI?
Symptoms?
- When do symptoms occur?
- When did symptoms begin?
- Did anything happen at the time symptoms started?
GH?
- Medication
- Previous treatment
What factors should be considered in CI?
Their refractive error (& what they’re wearing)
What did Momeni-Moghaddam et al., (2013) find out about CI symptoms?
Symptoms occur when NPC (near point of convergence) is greater than 10cm
What did Momeni-Moghaddam et al., (2013) find indicates a diagnosis of CI?
- 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
What did Horwood (2014) find out about CISS (Convergence Insufficiency Symptom Score)?
- 171 students, naïve, 18 - 26 years
- Symptoms common without signs of poor convergence
- Some with reduced convergence have no symptoms
This indicates using both questionnaire and clinical judgement as part of our assessment because people will have symptoms of CI without convergence insufficiency
When investigating convergence insufficiency what do we need to consider?
- Accommodative Amplitude/NPA (BEO, Monocularly, Age)
- Facility
(+/- 2DS, binocularly, Nott dynamic RET) - OM
(for differentially diagnosing secondary cause) - Fusional amplitude
(Sheard’s criterion - fusional reserve must be twice amount of heterophoria for it to remain nicely controlled) - Fundus & media check
- Refraction
When would we say a strabismus was secondary?
If someone had a 3BI XT would say Primary CI but if someone had like 15BI XT you’d call this secondary
What is the management of Primary CI?
The first line of treatment in primary CI is orthoptic exercises, if these are not successful prisms can be trialled. 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.
More of a fusional reserve problem opposed to muscle issue so surgery and BT not needed; managed conservatively more often
What is the management of Secondary CI?
- Orthoptic exercises
- Prisms
- Surgery
- Botox
When might we want to avoid orthoptic exercises in secondary CI?
- Large underlying deviation? – surgery for more control
- Vertical deviation?
- Poor general health?
2° CI (2ndary CI) does not prevent exercises being attempted but may limit prognosis
What convergence exercises do we have as options for convergence insufficiency?
- Pen to nose (smooth vergence)
- Jump exercises & dot card (jump vergence)
What are smooth vergence exercises?
Used in convergence insufficiency with the aim 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.
e.g. pen-to-nose
What are jump vergence exercises?
To be able to change focusing distances more quickly whilst maintaining single vision
e.g. jump exercises and dot card
What are Near Position Stereograms (which is confusing because the stereogram is held at near but the pen is even closer) used for in CI?
- Refine control
- Improves BO fusional reserves and positive relative convergence
- Alternative to gradual and jump convergence as NPC improves BUT need reasonable NPC for stereograms
What do we use Prism Bar Exercises for in CI?
- Exercise convergence using a makeshift BO Fresnel prism bar
- Gradually provide patient with stronger BO Fresnel prisms
What should we consider with orthoptic exercises?
- Rx should be worn
- Pt should have BSV at Nr
- Physiological diplopia can be used as a check if pathological diplopia is not appreciated i.e. patient suppresses at break point
- Must explain the exercises and explain that symptoms may worsen initially
What’s the process for orthoptic exercises as a clinician?
Explain and demonstrate exercises to patient
Allow patient to practise the exercises with you
Check at each visit that they’re doing it right
Give leaflet with contact details
How often should orthoptic exercises be done?
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 (want to ensure no convergence spasm and that they’re on top of doing the exercises) then gradually increase length between visits
What is the checklist for orthoptic exercises?
-BSV present
- Symptomatic
- Motivated and cooperative
- Understands exercises
- Normal accommodation for age
- Able to attend frequently
Why do we need to consider age when giving orthoptic exercises in CI?
- Not suitable for young children
- Older patients can still benefit from CI exercises, however accommodation cannot be used as effectively to aid convergence
When can we move to telephone consultation in CI?
Telephone consultation or video consultant is an option for patients who cannot attend clinic, especially if you have done the 3-4 week review and know they’re not getting spasm and they’re doing the exercises correctly.
When can we stop Orthoptic Exercises?
- If normal NPC and normal fusional amplitudes achieved stop exercises for 4 weeks
- If symptoms re-occur patient may need maintenance exercises
- Discharge
What did Westman & Liinamaa (2012) find out about orthoptic exercises success rates?
Children: 59.5% - 97.6%
What did CITT (2009) find out about orthoptic exercises success rates?
Children: 66.7% - 84.4%
What did CITT-ART (2023) find out about orthoptic exercises?
Randomised control trial looking at reducing symptomatic CI through orthoptic exercises
The most improvement tends to happen within the first 4 weeks of treatment but is worth persevering and encouraging patient to 16 weeks. (65.90% asymptomatic at 4 weeks but 97.60% at 16 weeks)
What did Scheiman et al. (2005) find out about orthoptic exercises in CI?
Randomised control trial
12 week therapy:
- office-based vision therapy
- office-based placebo vision therapy
- home-based pencil push-ups
All groups reported demonstrated improvement in symptoms on CISS (including placebo patients) but NPC in office-based therapy was the only statistically significant one (even the home-based pencil push-ups didn’t have improvement so ??? to the effectiveness of these)
Significant improvement was found in NPC, PFR and CISS (questionnaire) in Orthoptic therapy group only.
= Don’t do pen push-ups alone but incorporate other exercises into the routine. Time & effort is needed
What did CITT (2008) find out about orthoptic exercises?
Significant improvement was found in the CI symptom survey and NPC in Office-based orthoptic therapy with home reinforcement only
60-minute in-office therapy visit with additional prescribed procedures to be performed at home for 15 minutes a day, 5 days per week
What did Horwood & Toor (2014) find out about the prognosis of orthoptic exercises in CI?
- Most effective exercises were simple vergence exercises
- Binocular push up, binocular jump vergence, near and distance vergence facility (stress single vision) - Improved convergence and accommodation – should give 2 to 3 exercises to each patient (usually pen push-up, stereograms or dot card)
- ‘Effort’ had greater influence on responses than any exercise groups – explains CITT (2008) findings
- Treatment resolving blur had no/minimal effect
- Groups which exercised conv and accom were the least effective than concentrating on single visual skill
What did CITT (2009) find about long-term prognosis of orthoptic exercises in CI?
- 1 year follow up
- 84.4% of those in 12-week orthoptic home and office therapy group were asymptomatic 1 year after discontinuing exercises
What did Alvarez et al. (2010) find about the mechanisms for improvement in CI?
- After 18 hours of vision therapy CI patients can fixate faster after treatment
- Before treatment CI converged slower but there was no difference in divergence speed between CI and controls
- Found increased activity in FEF, Cerebellum and the Brainstem
Why would we use BI Prisms in CI?
Relieve some of the effort needed to converge
Decrease the amount of base out prism fusion range needed for comfortable vision
How much BI Prism do we give in CI?
- 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
What did Nabovati et al. (2020) find about BI Prisms in young and older adults?
Randomly assigned 64 young adults 18 to 40 years of age to wear either base-in prism reading glasses or placebo reading glasses for all near work activities lasting more than 15 minutes for 12 weeks, with the primary outcome visit after 12 weeks prism glasses group had significantly less symptoms compared with the placebo glasses group at three months; no evidence of difference was found in NPC or PFV.
What did CITT (2005) say about BI Prisms and children with CI?
Found to be less effective in children
(CITT, 2005)
What did Teitelbaum et al. (2009) say about BI Prisms and children with CI?
Effective in presbyopes with CI
(Teitelbaum et al, 2009)
Who make good surgical candidates in CI?
- Secondary CI
- Large Nr X >12PD
What makes for a poor surgical candidate for surgery in CI?
- Primary CI
- Poor response to prisms (defective motor fusion)
What strengthening surgeries are used in CI?
- Medial rectus plication
- (Slanted) Medial rectus resection
Can be unilateral or bilateral
What is 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
What are the strengths of Medial Rectus Plication?
Rajavi et al. (2021):
- 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
What is a Slated Medial Rectus Resection?
- 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
When is the Slated Medial Rectus Resection not useful in CI’s?
Nemet and Stolovitch (1990) not successful in collapsing the near distance difference
What did Farid & Abdelbaset (2018) find about Slanted Bilateral LR recessions in CI type IXT?
Slanted bilat LR recession (upper edge recessed according to dist angle; lower edge to near angle)
- Significantly better at correcting dist angle (p=0.054) compared to Augmented bilat LR recession, Unilat MR resection & LR recession.
- Not significantly better at correcting near angle and near-dist diff
- Assoc with post-op A and V patterns
What did Farid & Abdelbaset (2018) find about Augmented Bilateral LR recessions in CI type IXT?
Augmented to near angle - associated with post-op consecutive ET & diplopia
What did Farid & Abdelbaset (2018) find about Unilateral MR Resection (according to near angle) and LR recession (according to dist angle) in CI type IXT?
Assoc with post op under corrections but simplest therefore recommend this
What did Hofsli et al. (2023) find about Lateral Rectus Botox in CI?
- 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, may not be suitable for children and botox may leak into other areas if given lying down
