Exploring the Psychophysics of Keratoconus Using the Moorfields Acuity Chart (MACK)

The measurement of visual acuity is made using black letters of varying size superimposed on a uniform white background. The objective is to determine the smallest letter, or optotype, that can be correctly identified. One limitation of current tests is the variability of measurements, this making it difficult for clinicians to determine if changes in visual acuity are related to ocular disease. This variability has been attributed to the design of current optotypes, in particular their differing legibilities. Our group has recently demonstrated that a new type of letter chart (Moorfields Acuity Chart), containing letters with a black core and a white border presented on a grey background, reduces the variability of visual acuity measurements. In this study the investigators wish to determine if changes in vision owing to keratoconus, a disease that causes the cornea to adopt an irregular shape, may be detected more easily using the Moorfields Acuity Chart compared with conventional letter charts.

Study Overview

• Status: Completed
• Conditions: Keratoconic Subjects
• Intervention / Treatment: Device: Moorfields Acuity Chart

• Study Type: Interventional
• Enrollment (Actual): 80
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 35 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Keratoconic subjects (50):

• Age 18-40 years.
• The presence of keratoconus in at least one eye.
• The absence of significant media opacities (e.g. cataract, corneal scarring).
• The absence of any other ocular pathology (e.g. glaucoma, diabetic retinopathy, uveitis).
• The absence of amblyopia in the test eye.
• No previous ocular surgery (e.g. corneal crosslinking, cataract surgery, etc.)
• Best corrected visual acuity better than or equal to 6/60 (1.0 logMAR).
• Pupil diameter ≥3 mm and ≤7 mm in normal room illumination.

Healthy subjects (30):

• Age 18-35 years.
• The absence of clinically significant keratoconus.
• The absence of significant media opacities. (e.g. cataract, corneal scarring).
• The absence of any other ocular pathology (e.g. glaucoma, diabetic retinopathy, uveitis).
• The absence of amblyopia in the test eye.
• No previous ocular surgery (e.g. corneal crosslinking, cataract surgery, etc.)
• Best corrected visual acuity better than or equal to 6/9 (0.1 logMAR).
• Pupil diameter ≥3 mm and ≤7 mm in normal room illumination.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Keratoconic subjects; Short clinical interview (Questions pertaining to ocular and systemic health, medications, family history and date of birth). (approx. 2 minutes); Visual acuity measurement using EDTRS chart at 4 m (approx. 4 minutes); Refraction: retinoscopy and subjective, at 4m (approx. 10 minutes); Anterior eye examination (approx. 4 minutes); Fundus examination using binocular indirect ophthalmoscopy or a standard ophthalmoscope - to screen for eye disease that is likely to affect visual ability in this study. (approx. 5 minutes); Corneal topography measurement with an Oculus Pentacam (Oculus Gmbh., Germany). (approx. 5 minutes) Two measurements of visual acuity will be made: Standard ETDRS logMAR acuity measurement (5 minutes); Vanishing Optotype logMAR acuity measurement (5 minutes)	Device: Moorfields Acuity Chart
Experimental: Healthy subjects; Short clinical interview (Questions pertaining to ocular and systemic health, medications, family history and date of birth). (approx. 2 minutes); Visual acuity measurement using EDTRS chart at 4 m (approx. 4 minutes); Refraction: retinoscopy and subjective, at 4m (approx. 10 minutes); Anterior eye examination (approx. 4 minutes); Fundus examination using binocular indirect ophthalmoscopy or a standard ophthalmoscope - to screen for eye disease that is likely to affect visual ability in this study. (approx. 5 minutes); Corneal topography measurement with an Oculus Pentacam (Oculus Gmbh., Germany). (approx. 5 minutes) Two measurements of visual acuity will be made: Standard ETDRS logMAR acuity measurement (5 minutes); Vanishing Optotype logMAR acuity measurement (5 minutes)	Device: Moorfields Acuity Chart

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
The relative difference in visual acuity measurement between subjects with and without keratoconus when examined with different types of visual acuity chart.	9 months

Secondary Outcome Measures

Outcome Measure	Time Frame
The relationship (if any) between optical imperfections (high order aberrations) and measurements of visual acuity when measured using different test chart designs.	9 months

Collaborators and Investigators

• Sponsor: Moorfields Eye Hospital NHS Foundation Trust

Study record dates

Study Major Dates

• Study Start (Actual): April 15, 2015
• Primary Completion (Actual): April 30, 2016
• Study Completion (Actual): April 30, 2016

Study Registration Dates

• First Submitted: April 9, 2015
• First Submitted That Met QC Criteria: April 24, 2015
• First Posted (Estimate): April 29, 2015

Study Record Updates

• Last Update Posted (Actual): April 12, 2022
• Last Update Submitted That Met QC Criteria: April 4, 2022
• Last Verified: April 1, 2022

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Eye Diseases; Corneal Diseases; Keratoconus
• Other Study ID Numbers: ANDO1009