Optical Correction and Visual Functions of Adults With Amblyopia (SPECTRA)

Spectacle Correction for the Treatment of 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.

Study Overview

• Status: Recruiting
• Conditions: Amblyopia
• Intervention / Treatment: Device: Spectacles

• Study Type: Interventional
• Enrollment (Estimated): 36
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Benjamin Thompson, PhD; Phone Number: +852-3169-9631; Email: ben.thompson@cevr.hk
• Study Contact Backup: Name: Ken WS Tan, PhD; Phone Number: +852-3169-9631; Email: ken.tan@cevr.hk

Study Locations

• Canada
  • Ontario
    • Waterloo, Ontario, Canada, N2L 3G1
      • Recruiting
      • University of Waterloo
      • Contact: Benjamin Thompson, PhD; Phone Number: x39398 +1519-888-4567; Email: ben.thompson@uwaterloo.ca
      • Sub-Investigator: Amritha Stalin, PhD
• Hong Kong
  • Guangdong
    • Hong Kong, Guangdong, Hong Kong, 00000
      • Recruiting
      • Centre for Eye and Vision Research Limited
      • Contact: Peter CK Pang, PhD; Phone Number: +852-2766-7927; Email: csm@cevr.hk
      • Sub-Investigator: Adela SY Park, PhD
      • Sub-Investigator: Peter CK Pang, PhD
      • Sub-Investigator: Allen MY Cheong, PhD
      • Sub-Investigator: Tingni Li, PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 39 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Optical correction; Prescription of spectacles for full-time wear to correct refractive error

Device: Spectacles; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Best corrected visual acuity of the amblyopic eye pre-intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, baseline (day 1 of spectacle wear)
Best corrected visual acuity of the amblyopic eye post-intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, on completion of study (week 24)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Best corrected visual acuity of the amblyopic eye during intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, every 4 weeks from start of intervention
Fellow eye distance visual acuity pre-intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, baseline (day 1 of spectacle wear)
Fellow eye distance visual acuity post-intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, on completion of study (week 24)
Fellow eye distance visual acuity during-intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, every 4 weeks from start of intervention
Binocular distance visual acuity pre-intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, baseline (day 1 of spectacle wear)
Binocular distance visual acuity post-intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, on completion of study (week 24)
Binocular distance visual acuity during intervention	The size of the smallest line of letters read accurately on an ETDRS chart.	Approx. 5 mins, every 4 weeks from start of intervention
Near visual acuity of amblyopic eye pre-intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, baseline (day 1 of spectacle wear)
Near visual acuity of amblyopic eye post-intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, on completion of study (week 24)
Near visual acuity of amblyopic eye during intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins,every 4 weeks from start of intervention
Near visual acuity of fellow eye pre-intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, baseline (day 1 of spectacle wear)
Near visual acuity of fellow eye post-intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, on completion of study (week 24)
Near visual acuity of fellow eye during intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, every 4 weeks from start of intervention
Near binocular visual acuity pre-intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, baseline (day 1 of spectacle wear)
Near binocular visual acuity post-intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, on completion of study (week 24)
Near binocular visual acuity during intervention	The size of the smallest line of letters read accurately on a near ETDRS chart.	Approx. 5 mins, every 4 weeks from start of intervention
Amblyopic eye contrast sensitivity pre-intervention	Computer-based measurement of contrast sensitivity	Approx. 10 mins, baseline (day 1 of spectacle wear)
Amblyopic eye contrast sensitivity post-intervention	Computer-based measurement of contrast sensitivity	Approx. 10 mins, on completion of study (week 24)
Amblyopic eye contrast sensitivity during intervention	Computer-based measurement of contrast sensitivity	Approx. 10 mins, every 4 weeks from start of intervention
Stereopsis pre-intervention	Smallest disparity on the Randot preschool test reported accurately.	Approx. 5 mins, baseline (day 1 of spectacle wear)
Stereopsis post-intervention	Smallest disparity on the Randot preschool test reported accurately.	Approx. 5 mins, on completion of study (week 24)
Stereopsis during intervention	Smallest disparity on the Randot preschool test reported accurately.	Approx. 5 mins, every 4 weeks from start of intervention
Amblyopic eye fixation stability pre-intervention	Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).	Approx. 5 mins, baseline (day 1 of spectacle wear)
Amblyopic eye fixation stability post-intervention	Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).	Approx. 5 mins, on completion of study (week 24)
Amblyopic eye fixation stability during intervention	Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).	Approx. 5 mins, every 4 weeks from start of intervention
Fellow (non-amblyopic) eye fixation stability pre-intervention	Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).	Approx. 5 mins, baseline (day 1 of spectacle wear)
Fellow (non-amblyopic) eye fixation stability post-intervention	Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).	Approx. 5 mins, on completion of study (week 24)
Fellow (non-amblyopic) eye fixation stability during intervention	Eye position recorded with high-speed eye tracker during fixation as quantified by bivariate contour ellipse area (BCEA).	Approx. 5 mins, every 4 weeks from start of intervention
Interocular suppression pre-intervention	Computer-based measurement of interocular suppression.	Approx. 10 mins, baseline (day 1 of spectacle wear)
Interocular suppression post-intervention	Computer-based measurement of interocular suppression.	Approx. 10 mins, on completion of study (week 24)
Interocular suppression during intervention	Computer-based measurement of interocular suppression.	Approx. 10 mins, every 4 weeks from start of intervention
Quality of life pre-intervention	Questionnaire scores for: Amblyopia and Strabismus Questionnaire; World Health Organization Quality of Life-BREF	Approx.15-20 mins, baseline (day 1 of spectacle wear)
Quality of life post-intervention	Questionnaire scores for: Amblyopia and Strabismus Questionnaire; World Health Organization Quality of Life-BREF	Approx. 15-20 mins, on completion of study (week 24)
Angle of strabismus pre-intervention	Prismatic power required to neutralise the angle of deviation on alternating prism cover test.	Approx. 5 mins,baseline (day 1 of spectacle wear)
Angle of strabismus post-intervention	Prismatic power required to neutralise the angle of deviation on alternating prism cover test.	Approx. 5 mins, on completion of study (week 24)
Angle of strabismus during intervention	Prismatic power required to neutralise the angle of deviation on alternating prism cover test.	Approx. 5 mins, every 4 weeks from start of intervention

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Electrical potentials pre-intervention	Electroencephalography (EEG) measures: Visual evoked potentials for high and low contrast stimuli (monocular: fellow eye and amblyopic eye)	Approx. 60 mins, baseline (day 1 of spectacle wear)
Electrical potentials post-intervention	Electroencephalography (EEG) measures: Visual evoked potentials for high and low contrast stimuli (monocular: fellow eye and amblyopic eye)	Approx. 60 mins, on completion of study (week 24)
Electrical potentials during intervention	Electroencephalography (EEG) measures: Visual evoked potentials for high and low contrast stimuli (monocular: fellow eye and amblyopic eye)	Approx. 60 mins, 12 weeks from baseline (day 1 of spectacle wear)

Collaborators and Investigators

• Sponsor: Centre for Eye and Vision Research
• Collaborators: The Hong Kong Polytechnic University; University of Waterloo
• Investigators: Principal Investigator: Benjamin Thompson, PhD, Centre for Eye and Vision Research Limited; Study Director: Ken WS Tan, PhD, Centre for Eye and Vision Research Limited

Publications and helpful links

General Publications

• Tan KWS, Park ASY, Cheung BWS, Wong GHT, Thompson B; SPECTRA study team. SPEctacle Correction for the TReatment of Amblyopia (SPECTRA): study protocol for a prospective non-randomised interventional trial in adults with anisometropic/mixed mechanism amblyopia. BMJ Open. 2024 Jul 1;14(6):e080151. doi: 10.1136/bmjopen-2023-080151.

Study record dates

Study Major Dates

• Study Start (Actual): June 13, 2022
• Primary Completion (Estimated): November 30, 2026
• Study Completion (Estimated): May 31, 2027

Study Registration Dates

• First Submitted: May 19, 2022
• First Submitted That Met QC Criteria: May 26, 2022
• First Posted (Actual): May 27, 2022

Study Record Updates

• Last Update Posted (Actual): March 18, 2026
• Last Update Submitted That Met QC Criteria: March 16, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Amblyopia; Plasticity; Binocular vision; Suppression; Optical correction
• Additional Relevant MeSH Terms: Neurologic Manifestations; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Eye Diseases; Vision Disorders; Sensation Disorders; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Amblyopia; Equipment and Supplies; Optical Devices; Lenses; Eyeglasses
• Other Study ID Numbers: SPECTRA

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Anonymized data will be shared on request
• IPD Sharing Time Frame: After publication of study results for an indefinite period.
• IPD Sharing Access Criteria: Upon reasonable request and approved by the study principal investigator.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No