Optometry case study: Evidence-based management of convergence insufficiency

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By Dr Steven Lam, Specsavers Brunswick, VIC

History

Px: 22-year-old female medical student 

Reason for visit: Following an earlier visit with a different optometrist, patient returned for a 3-month review with complaints of increasing eye strain, even while wearing glasses. She also reported intermittent headaches towards the end of the day and horizontal diplopia.

Upon her initial visit 3 months earlier, patient symptoms included trouble focussing in the distance, severe eye strain when reading, intermittent headaches, and twitching RE, with both eyes feeling irritated and watery.

There was no other relevant information regarding GH, POH or FOH.

Clinical Assessment

Screening:
Ocular motility: Full
Pupils: PERRLA DCN
NPC: 15cm
Cover test: Exophoria with mod recovery

Refraction:
R: +0.25/-0.25 x 178 = 6/6
L: Plano/-0.25 x 25 = 6/6

Additional tests:
Prism cover test
D: Orthophoric
N: 8PD Exophoria

Stereopsis: 40 sec of arc

AC/A: -2: 4exo    -1: 7exo   0: 8exo   +1:11 exo (blur)
AC/A ratio calculation: (8-4)/2 = 2:1

Prism fusional range (blur/break/recovery):
Distance: BI 6/10/6     BO 6/10/1
Near:  BI 6/20/16     BO 6/20/8

Diagnosis

Differential diagnosis:

  • Convergence insufficiency
  • Accommodative excess
  • Large phoria
  • Uncorrected refractive error
  • Dry eye
  • Supranuclear palsy
  • Demyelination
  • Myasthenia gravis
  • Old strabismus surgery

Diagnosis: Convergence insufficiency

Management

Management plan from initial visit:

  • Full time: SVD (4PD BI) + anti-reflective multicoating
  • Pencil push-up exercises
  • Systane prn
  • Review 3/12

Revised management plan after 3-month review:

  • Stop using glasses with prism
  • Vision therapy in clinic for minimum 10 visits (in place of pencil push-up exercises)
    • Stereograms at home and in clinic with prisms
    • Fusional training with prisms

Target outcome: Increase positive fusional amplitude and NPC

Discussion

Base-in prisms were initially prescribed as a short-term measure to immediately address the patient’s eye strain symptoms as they help the eye to converge less than required for binocular single vision. However, this was not practical for ongoing management as base-in prisms do not train the eyes to improve convergence or fusion. According to the Cochrane Database, base-in reading glasses were found to be no more effective than placebo reading glasses in improving clinical signs in children.

When upon review, pencil push-up exercises were found to be ineffective, office-based vision therapy was prescribed based on the Convergence Insufficiency Treatment Trial (CITT), which indicates this is more effective at managing convergence insufficiency. While pencil push-ups stimulate convergence, they do not induce diplopia or physiological diplopia to allow fusion training to occur.

According to CITT, the recommended treatment regime is as follows:

  • Home based: 15 min daily
    • Pencil push-ups
    • Computer vision therapy program
  • In clinic: 60 min → average 12-24 visits
    • Mixture of all the orthoptic therapy

Following discussion with the patient, the CITT-recommended regime was modified as follows to better fit the patient’s lifestyle and increase likelihood of compliance:

  • Home training with stereogram:
    • Interval training: 30 sec hold, 30 break for 15 min
  • In clinic once a week x12 weeks:
    • 10 min stereograms with prism
    • 10 min fusion training with prism
    • Measure PFR and NPC weekly for compliance

Outcome

After 5 weekly visits, the patient improved her near point of convergence and positive fusional range at both distance and near. The patient was then asymptomatic and was happy to cease in-clinic therapy. She did stereograms once a week for 15 min as maintenance therapy at home.

Week BO PFR (Near) NPC
1 6/25/8 17cm
5 30/40/- 7cm

Table 1. Results of PFR and NPC measured at weeks 1 and 5 (normative values – PFR near: 35-40PD BO; NPC: <10cm)


REFERENCES

  1. CITT. A Randomized Clinical Trial of Treatments for Symptomatic Convergence Insufficiency in Children. Arch Ophthal. 2008:126(10):1336-1349
  2. Ghadban R, Martinez J, Diehl N, Mohney B. The Incidence and Clinical Characteristics of Adult Onset Convergence Insufficiency. Am Ac Oph. 2015:122:1056-1059
  3. Gwiazda S. Non surgical interventions for convergence insufficiency. Cochrane Database. 2011:(3):1-53
  4. Huston P, Hoover D. Treatment of Symptomatic Convergence Insufficiency with Home Based Computerized Vergence Therapy in Children. AAPOS. 2015:19(5):417-421
  5. Lavrich J. Convergence insufficiency and its current treatment. Wills Eye Inst. 2010:7
  6. McGregor M. Convergence Insufficiency and Vision Therapy. Paed Clin NA 2014:61(3):621-630
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