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NCT Number: NCT05394987

Optical Correction and Visual Functions of Adults With Amblyopia

Amblyopia is a developmental anomaly resulting from abnormal visual experiences in early life. Amblyopia causes reduced visual acuity in the absence of a pathology. Adult sensory systems are believed to be structurally invariant beyond early, critical periods of development. However, recent evidence suggest that visual functions in adults with amblyopia can be improved with optical correction alone. This study aims to investigate whether improvements in best corrected visual acuity and other visual functions can result following appropriate optical correction in adults with amblyopia. Functional measures relating to vision, binocular vision, and eye movements will be used to assess the efficacy of refractive correction for improving vision. This study will help us better understand the improvements in visual functions following optical correction, as well as the mechanisms underlying neuroplasticity in adults with amblyopia.

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Key information

Conditions

Amblyopia Brain Diseases Central Nervous System Diseases Eye Diseases Nervous System Diseases Neurologic Manifestations Pathological Conditions, Signs and Symptoms Sensation Disorders Signs and Symptoms Vision Disorders

Age range

18 year–39 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Waterloo, Waterloo, Ontario, Canada

Loading trial locations.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 18-39 (inclusive) years of age
  • Anisometropic amblyopia (difference of ≥0.50D spherical equivalent or ≥1.50D astigmatism between eyes) or mixed mechanism amblyopia (strabismus and anisometropia)
  • Best corrected visual acuity (BCVA) in the amblyopic eye of 0.3 logMAR to 1.0 logMAR (inclusive)
  • BCVA in the non-amblyopic eye of 0.1 logMAR or better, and an interocular VA difference of 2 logMAR lines or more
  • Difference of 1.00D or more between current refractive correction and study prescription
  • Good general health

Exclusion criteria

  • Other pathological ocular anomalies known to cause reduced visual acuity
  • Presbyopia (based on amplitude of accommodation)
  • Inability to tolerate prescribed refractive correction in spectacles (e.g., due to aniseikonia)
  • Contraindication to cycloplegic eye drops
  • Currently under amblyopia treatment/therapy
  • Inability to comprehend test instructions and/or provide consent
  • Eccentric fixation
  • >-6.00DS of myopia in either eye with spectacles
  • Bilateral amblyopia
  • Presence of amblyopia that is not due to strabismus and/or anisometropia
  • Presence of (current or previous) psychiatric, visual, or neurological disorders

Treatment and study plan

Spectacles

Device

Prescription of refractive error correction in spectacles. Refractive error to be determined as part of standard optometric eye exam (performed by registered optometrist).

Guidelines for optical correction for the prescription of the study spectacles (based on Pediatric Eye Disease Investigator Group [PEDIG] amblyopia clinical trial protocols): Hypermetropia: not undercorrected by >+1.50D spherical equivalent and the reduction in plus sphere must be identical between the two eyes. Anisometropia: full correction of the anisometropic difference. Astigmatism: cylinder power in each eye should be within ≤±0.50D of fully correcting the astigmatism for each eye. If cylinder power is ≥1.00D, the prescribed axis in both eyes should be within ≤±6 deg of the cycloplegic refraction axis.

Appropriate refractive error correction will be prescribed. Participants will be instructed to wear the optical correction full-time (i.e., >50% of waking hours) for the duration of the study.

Primary outcomes

  1. Best corrected visual acuity of the amblyopic eye pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    The size of the smallest line of letters read accurately on an ETDRS chart.

  2. Best corrected visual acuity of the amblyopic eye post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    The size of the smallest line of letters read accurately on an ETDRS chart.

Secondary outcomes

  1. Best corrected visual acuity of the amblyopic eye during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    The size of the smallest line of letters read accurately on an ETDRS chart.

  2. Fellow eye distance visual acuity pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    The size of the smallest line of letters read accurately on an ETDRS chart.

  3. Fellow eye distance visual acuity post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    The size of the smallest line of letters read accurately on an ETDRS chart.

  4. Fellow eye distance visual acuity during-intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    The size of the smallest line of letters read accurately on an ETDRS chart.

  5. Binocular distance visual acuity pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    The size of the smallest line of letters read accurately on an ETDRS chart.

  6. Binocular distance visual acuity post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    The size of the smallest line of letters read accurately on an ETDRS chart.

  7. Binocular distance visual acuity during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    The size of the smallest line of letters read accurately on an ETDRS chart.

  8. Near visual acuity of amblyopic eye pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  9. Near visual acuity of amblyopic eye post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  10. Near visual acuity of amblyopic eye during intervention

    Time frame: Approx. 5 mins,every 4 weeks from start of intervention

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  11. Near visual acuity of fellow eye pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  12. Near visual acuity of fellow eye post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  13. Near visual acuity of fellow eye during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  14. Near binocular visual acuity pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  15. Near binocular visual acuity post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  16. Near binocular visual acuity during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    The size of the smallest line of letters read accurately on a near ETDRS chart.

  17. Amblyopic eye contrast sensitivity pre-intervention

    Time frame: Approx. 10 mins, baseline (day 1 of spectacle wear)

    Computer-based measurement of contrast sensitivity

  18. Amblyopic eye contrast sensitivity post-intervention

    Time frame: Approx. 10 mins, on completion of study (week 24)

    Computer-based measurement of contrast sensitivity

  19. Amblyopic eye contrast sensitivity during intervention

    Time frame: Approx. 10 mins, every 4 weeks from start of intervention

    Computer-based measurement of contrast sensitivity

  20. Stereopsis pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    Smallest disparity on the Randot preschool test reported accurately.

  21. Stereopsis post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    Smallest disparity on the Randot preschool test reported accurately.

  22. Stereopsis during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    Smallest disparity on the Randot preschool test reported accurately.

  23. Angle of strabismus pre-intervention

    Time frame: Approx. 5 mins,baseline (day 1 of spectacle wear)

    Prismatic power required to neutralise the angle of deviation on alternating prism cover test.

  24. Angle of strabismus post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    Prismatic power required to neutralise the angle of deviation on alternating prism cover test.

  25. Angle of strabismus during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    Prismatic power required to neutralise the angle of deviation on alternating prism cover test.

  26. Amblyopic eye fixation stability pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).

  27. Amblyopic eye fixation stability post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).

  28. Amblyopic eye fixation stability during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).

  29. Fellow (non-amblyopic) eye fixation stability pre-intervention

    Time frame: Approx. 5 mins, baseline (day 1 of spectacle wear)

    Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).

  30. Fellow (non-amblyopic) eye fixation stability post-intervention

    Time frame: Approx. 5 mins, on completion of study (week 24)

    Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).

  31. Fellow (non-amblyopic) eye fixation stability during intervention

    Time frame: Approx. 5 mins, every 4 weeks from start of intervention

    Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).

  32. Interocular suppression pre-intervention

    Time frame: Approx. 10 mins, baseline (day 1 of spectacle wear)

    Computer-based measurement of interocular suppression.

  33. Interocular suppression post-intervention

    Time frame: Approx. 10 mins, on completion of study (week 24)

    Computer-based measurement of interocular suppression.

  34. Interocular suppression during intervention

    Time frame: Approx. 10 mins, every 4 weeks from start of intervention

    Computer-based measurement of interocular suppression.

  35. Quality of life pre-intervention

    Time frame: Approx.15-20 mins, baseline (day 1 of spectacle wear)

    Questionnaire scores for:

    • Amblyopia and Strabismus Questionnaire
    • World Health Organization Quality of Life-BREF

  36. Quality of life post-intervention

    Time frame: Approx. 15-20 mins, on completion of study (week 24)

    Questionnaire scores for:

    • Amblyopia and Strabismus Questionnaire
    • World Health Organization Quality of Life-BREF

Other outcomes

  1. Electrical potentials pre-intervention

    Time frame: Approx. 60 mins, baseline (day 1 of spectacle wear)

    Electroencephalography (EEG) measures:

    Visual evoked potentials for high and low contrast stimuli (monocular: fellow eye and amblyopic eye)

  2. Electrical potentials post-intervention

    Time frame: Approx. 60 mins, on completion of study (week 24)

    Electroencephalography (EEG) measures:

    Visual evoked potentials for high and low contrast stimuli (monocular: fellow eye and amblyopic eye)

  3. Electrical potentials during intervention

    Time frame: Approx. 60 mins, 12 weeks from baseline (day 1 of spectacle wear)

    Electroencephalography (EEG) measures:

    Visual evoked potentials for high and low contrast stimuli (monocular: fellow eye and amblyopic eye)

Study contacts

Contact information is provided by the study sponsor or research team.

Benjamin Thompson, PhD

CONTACT

[email protected]

+852-3169-9631

Ken WS Tan, PhD

CONTACT

[email protected]

+852-3169-9631

Sponsors and collaborators

Lead sponsor

Centre for Eye and Vision Research

Other

Collaborators

  • The Hong Kong Polytechnic University
  • University of Waterloo

Registry information

Official study title

Spectacle Correction for the Treatment of Amblyopia

Acronym: SPECTRA

Important dates

Study start
2022
Primary completion
2026
Study completion
2027
First posted
May 27, 2022
Registry last updated
Mar 18, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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