New Visual Acuity and Crowding Tests for Better Detection of Amblyopia

NCT03505606 | Completed Results DMC

• 1 other identifier: FST/FREP/17/739
• Study Type: interventional
• Target: 76
• Locations: 1 country
• Sites: 1

Brief Summary

Amblyopia, or 'lazy eye', is the reduction in vision usually in one eye, due to abnormal visual development without organic cause. It is a preventable and leading cause of monocular vision loss (prevalence of around 3%) and increases lifetime risk of bilateral visual impairment from 10% in the general population, to 18% in amblyopes. In the UK, vision screening in children aims to detect amblyopia and other undiagnosed visual conditions. Laboratory research suggest that amblyopia could be better detected by modifying standard clinical vision tests to enhance and quantify "crowding". Crowding is the negative effect that surrounding features have on the visibility of a target. Crowding distance and crowding magnitude are considerably greater in amblyopic eyes than in normal healthy eyes. Modifications that should lead to improved amblyopia detection are 1) place letters closer together on a vision chart, 2) define letters by contrast, rather than luminance, and 3) use a new thinner font in the form of numbers, to allow crowding distance in central vision to be measured. In this project, these modifications will be tested in amblyopic children for the first time. Amblyopic children aged 3 to 11 years (n=32) will be recruited from ACPOS (Addenbrooke's Community Paediatric Ophthalmology Service) at ARU. They will have their vision measured with the three modified tests as well as an uncrowded test. The child will view letters and numbers on a computer screen and respond (verbally or by indicating their choice on a matching card). Testing is fun and game-like with breaks for rewards. Results will be compared to standard vision measurement (SLT: Sonksen LogMAR Test) from the child's ACPOS visit. Amblyopic data will be compared to control data from normal healthy children aged 3 to 11 years (n=200), and age-matched children with normal vision (n=16) from ACPOS (false referrals from school screening).

Conditions

Amblyopia

Keywords

Amblyopia; Visual Acuity; Crowding

Outcome Measures

Primary Outcomes (2)

• Visual Acuity (LogMAR)

  Threshold visual acuity measured in LogMAR

  Visual acuities for each participant were measured at a single time point, on a single day; day one of each participants' recruitment.

• Foveal Crowding Distance (Degrees)

  Foveal critical crowding distance measured in degrees

  Crowding distances for each participant were measured at a single time point, on a single day; day one of each participants' recruitment.

Study Arms (3)

Control

ACTIVE COMPARATOR

Visual acuity tests on control participants

Diagnostic Test: Visual acuity tests

Strabismic/mixed amblyopes

EXPERIMENTAL

Visual acuity tests on strabismic/mixed amblyopic participants.

Diagnostic Test: Visual acuity tests

Anisometropic amblyopes

EXPERIMENTAL

Visual acuity tests on anisometropic amblyopic participants.

Diagnostic Test: Visual acuity tests

Interventions

Visual acuity tests DIAGNOSTIC_TEST

Participants to have visual acuity tested with the three modified vision tests.

Also known as: Contrast-modulated Cambridge Crowding test, Crowding Distance Test, Enhanced Cambridge Crowding test

Anisometropic amblyopes; Control; Strabismic/mixed amblyopes

Eligibility Criteria

• Age: 3 Years - 11 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17)

You may qualify if:

• Test participants; Male and female 3 to 11-year-old children diagnosed by ACPOS clinicians as likely having amblyopia (strabismic or anisometropic). They will be tested following 6 weeks (or more) of refractive adaption.
• Control Participants; Male and female 3 to 11-year-old children who have been falsely referred into the Hospital Eye Service (ACPOS) by the visual screening service, but have satisfactory visual functions, as per the national screening guidelines.
• All participants must be able to complete the Sonsken logMAR Test (SLT) either verbally or via use of a matching card.

You may not qualify if:

• Uncorrected refractive error.
• Any prior or existing medical history of epilepsy or seizures.

Sponsors & Collaborators

• Anglia Ruskin University: lead

Study Sites (1)

Anglia Ruskin University Eye Clinic

Cambridge, Cambridgeshire, CB11PT, United Kingdom

Location

Related Publications (12)

• Chung ST, Li RW, Levi DM. Crowding between first- and second-order letter stimuli in normal foveal and peripheral vision. J Vis. 2007 Mar 9;7(2):10.1-13. doi: 10.1167/7.2.10.

  PMID: 18217825 BACKGROUND

• Chung ST, Li RW, Levi DM. Crowding between first- and second-order letters in amblyopia. Vision Res. 2008 Mar;48(6):788-98. doi: 10.1016/j.visres.2007.12.011. Epub 2008 Jan 31.

  PMID: 18241910 BACKGROUND

• Danilova MV, Bondarko VM. Foveal contour interactions and crowding effects at the resolution limit of the visual system. J Vis. 2007 Nov 27;7(2):25.1-18. doi: 10.1167/7.2.25.

  PMID: 18217840 BACKGROUND

• FLOM MC, WEYMOUTH FW, KAHNEMAN D. VISUAL RESOLUTION AND CONTOUR INTERACTION. J Opt Soc Am. 1963 Sep;53:1026-32. doi: 10.1364/josa.53.001026. No abstract available.

  PMID: 14065335 BACKGROUND

• Formankiewicz MA, Waugh SJ. The effects of blur and eccentric viewing on adult acuity for pediatric tests: implications for amblyopia detection. Invest Ophthalmol Vis Sci. 2013 Oct 23;54(10):6934-43. doi: 10.1167/iovs.13-12543.

  PMID: 24071956 BACKGROUND

• Hairol MI, Formankiewicz MA, Waugh SJ. Foveal visual acuity is worse and shows stronger contour interaction effects for contrast-modulated than luminance-modulated Cs. Vis Neurosci. 2013 May;30(3):105-20. doi: 10.1017/S0952523813000102. Epub 2013 Apr 25.

  PMID: 23731769 BACKGROUND

• Huurneman B, Boonstra FN, Cox RF, Cillessen AH, van Rens G. A systematic review on 'Foveal Crowding' in visually impaired children and perceptual learning as a method to reduce Crowding. BMC Ophthalmol. 2012 Jul 23;12:27. doi: 10.1186/1471-2415-12-27.

  PMID: 22824242 BACKGROUND

• Lalor SJH, Formankiewicz MA, Waugh SJ. Crowding and visual acuity measured in adults using paediatric test letters, pictures and symbols. Vision Res. 2016 Apr;121:31-38. doi: 10.1016/j.visres.2016.01.007. Epub 2016 Feb 18.

  PMID: 26878696 BACKGROUND

• Siderov J, Waugh SJ, Bedell HE. Foveal contour interaction for low contrast acuity targets. Vision Res. 2013 Jan 25;77:10-3. doi: 10.1016/j.visres.2012.11.008. Epub 2012 Nov 29.

  PMID: 23200866 BACKGROUND

• Song S, Levi DM, Pelli DG. A double dissociation of the acuity and crowding limits to letter identification, and the promise of improved visual screening. J Vis. 2014 May 5;14(5):3. doi: 10.1167/14.5.3.

  PMID: 24799622 BACKGROUND

• Wong EH, Levi DM, McGraw PV. Is second-order spatial loss in amblyopia explained by the loss of first-order spatial input? Vision Res. 2001 Oct;41(23):2951-60. doi: 10.1016/s0042-6989(01)00189-4.

  PMID: 11704234 BACKGROUND

• Wong EH, Levi DM, McGraw PV. Spatial interactions reveal inhibitory cortical networks in human amblyopia. Vision Res. 2005 Oct;45(21):2810-9. doi: 10.1016/j.visres.2005.06.008.

  PMID: 16040080 BACKGROUND

MeSH Terms

Conditions

Amblyopia; Crowding

Condition Hierarchy (Ancestors)

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

Limitations and Caveats

Delays with recruitment and testing due to COVID-19 lockdowns

Results Point of Contact

• Title: Mrs Louisa Haine - Lecturer in Vision Sciences
• Organization: Anglia Ruskin University

louisa.haine@aru.ac.uk

01223695445

Study Officials

• Sarah Waugh, PhD

  University of Huddersfield

  STUDY DIRECTOR

Publication Agreements

• PI is Sponsor Employee: Yes

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: DIAGNOSTIC
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: April 4, 2018
• First Posted: April 23, 2018
• Study Start: January 1, 2019
• Primary Completion: May 31, 2021
• Study Completion: July 1, 2021
• Last Updated: October 21, 2024
• Results First Posted: October 21, 2024

Record last verified: 2024-08

Data Sharing

• IPD Sharing: Will not share

Locations

GB (1)