WRITER Jessica Chi

While traditional thought suggests amblyopia treatment is effective only to the age of eight, Jessica Chi presents a case that shows worthwhile results can be achieved for motivated older children.

Hazel Davis,* a 10-year-old female, presented with a history of anisometropic hyperopia (R > L) and right amblyopia. This was first detected after a failed vision screening at her four-year-old maternal health check. At that time, her cycloplegic refraction was R +4.75DS, L +1.25DS, which was prescribed in full. She had worn full-time spectacles from age four to seven and underwent occlusion therapy, reporting approximately two hours of patching per day. However, following minimal improvement, and when spectacle wear and patching became difficult, these were abandoned.

There was no relevant family ocular history.

Two years prior, Hazel was reviewed by another optometrist, however they were informed that at age eight there was probably minimal improvement to be expected. Consequently, she continued unaided.

At Hazel’s initial presentation at our practice, age 10:

• Unaided visual acuity (VA): R 6/30=, L 6/6.

• Dry retinoscopy: R +6.00DS, L +1.00DS.

• Subjective refraction: R +5.50DS (6/24), L +0.75DS (6/6).

• Cycloplegic refraction: R +6.00DS, L +1.25DS.

She reported no issues with her vision and was only aware of blur in the right eye when the left was occluded. She denied any asthenopia and was performing well academically. Her near point of accommodation was R 10D, L 15D. Ocular motility was full, alignment was normal at distance and near, and there was no evidence of strabismus. Hazel had no measurable stereopsis.

Hazel’s parents were motivated to recommence therapy if there was potential improvement, especially as Hazel was now more receptive and compliant. Being a sporty and active child, Hazel was resistant to spectacles, however was open to trying contact lenses.

Given the low refractive error in the left eye, she was fitted with a contact lens only in the amblyopic right eye, leaving her hyperopia uncorrected in the left eye with the goal to keep her binocularly balanced.

• R CL Rx: Precision 1 daily disposable, 8.3/14.2/+5.50DS.

• Over-refraction: R +0.75DS.

• Subjective refraction: L +0.75DS.

• Stereoacuity: None measured.

She commenced full-time wear of the contact lens in the right eye, along with occlusion therapy for two hours daily, focussed on concentrated near tasks during patching.

Follow-Up at 10 Weeks

• R VA: improved to 6/18+.

• Stereoacuity: 80 seconds of arc.

Follow-Up at 20 Weeks

• R VA: improved to 6/15+.

• Stereoacuity: improved to 50 seconds of arc

Follow-Up at 30 Weeks

• R VA: improved to 6/12=.

• Stereoacuity: improved to 20 seconds of arc.

Hazel subjectively felt her vision had improved. She was congratulated on her progress and continued both full-time contact lens wear and occlusion therapy.

DISCUSSION

Amblyopia is a neurodevelopmental disorder that results in reduced best-corrected visual acuity. This typically results from abnormal visual input during the critical period of visual development, leading to cortical suppression of the affected eye and preferential processing by the fellow eye. Traditionally, the ‘critical period’ was believed to end around eight years of age – beyond which the visual cortex was believed to become unresponsive to amblyopia therapy.

However, more recent evidence suggests that neuroplasticity of the visual system may persist past this age.1 Although the response may be more limited and slower with older age, visual improvement can still be achieved in older children, adolescents, and even adults, particularly when appropriate therapeutic interventions are applied.

In managing amblyopia, the first step is to provide full refractive correction, to ensure a clear retinal image. Optical correction alone has been shown to improve visual acuities, even in adults.

Contact lenses were the preferred option in Hazel’s case – not only due to her resistance to wearing spectacles, which would have likely reduced compliance, but also due to the aniseikonia that would have been induced by spectacle correction.

Aniseikonia can cause visual discomfort, asthenopia, dizziness, and may impede the development of binocularity and depth perception. While Shaw lenses can help minimise aniseikonia, they often result in significant edge thickness and may be cosmetically unappealing, particularly for a self-conscious young female. Although some practitioners, parents, and guardians may be hesitant about the use of contact lenses by children, numerous studies have demonstrated that children can manage contact lenses successfully, with children in contact lenses reporting improvement in quality of life.2

Occlusion therapy or patching can provide further improvements – occluding the fellow eye forces the amblyopic eye to work harder and encourages the visual pathways for this eye in the brain to strengthen.3 Success is better with high compliance and when paired with concentrated near tasks. Pharmacological penalisation may be considered in some cases as an alternative to occlusion, particularly when there is resistance from the amblyope.

While the potential for resolving or even reducing the degree of amblyopia decreases with age, improvements can be and have been shown to occur after this so-called critical period.4 The potential is amplified in highly motivated and compliant patients, as was seen for Hazel. It is thought to be less useful for patients where occlusion therapy had been attempted in the past, however Hazel appeared to have been under-corrected by previous practitioners.

This case highlights the importance of not prematurely dismissing the potential for visual improvement in amblyopia based on patient age or history of prior treatment – particularly when previous management was undertaken elsewhere. In Hazel’s case, it was fortunate that her previous management history was available. It became evident that she had not been prescribed full cycloplegic hyperopic correction, as it is unlikely that her hyperopia would have progressed significantly over time. She had had ‘prior treatment’, but had not been prescribed appropriate prior treatment, which allowed for a reassessment of her visual potential.

While Hazel’s visual acuity improvement was modest, she achieved measurable stereoacuity – an outcome with important functional benefits, including enhanced depth perception, improved fine motor coordination, and greater visual comfort and efficiency.

Hopefully, this case will encourage clinicians to offer suitable, tailored interventions to motivated older children and adults.

*Patient name changed for anonymity.

Jessica Chi is the Director of Eyetech Optometrists, an independent specialty contact lens practice in Melbourne. She is the current Victorian, and a past National President of the Cornea and Contact Lens Society, and an invited speaker at meetings throughout Australia and beyond. She is a clinical supervisor at the University of Melbourne, a member of Optometry Victoria Optometric Sector Advisory Group, and a Fellow of the Australian College of Optometry, the British Contact Lens Association, and the International Academy of Orthokeratology and Myopia Control.

References

1. von Noorden GK, Crawford ML. The sensitive period. Trans Ophthalmol Soc UK (1962). 1979;99(3):442–6. PMID: 298829.
2. Walline JJ, Jones LA, Prinstein MJ, et al;ACHIEVE Study Group. Randomized trial of the effect of contact lens wear on self-perception in children. Optom Vis Sci. 2009 Mar;86(3):222-32. doi: 10.1097/OPX.0b013e3181971985.
3. Kavitha V, Chaitra S, Heralgi MM. Occlusion therapy in older children with amblyopia. J Clin Ophthalmol. Res. 2016;4(2):71-74. doi: 10.4103/2320-3897.183657.
4. Scheiman MM, Hertle RW, Tamkins SM; et al. Pediatric Eye Disease Investigator Group. Randomized trial of treatment of amblyopia in children aged 7 to 17 years. Arch Ophthalmol. 2005; 123(4):437-47. doi: 10.1001/archopht.123.4.437.