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

Moorfields Eye Hospital NHS Foundation Trust

Status: Completed

Conditions: Keratoconic Subjects

Treatments: Device: Moorfields Acuity Chart

Study type: Interventional

Funder types: Other

Identifiers

NCT02429609

ANDO1009

Details and patient eligibility

About

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.

Enrollment: 80 patients

Sex: All

Ages: 18 to 35 years old

Volunteers: Accepts Healthy Volunteers

Inclusion and exclusion criteria

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.

Trial design

Primary purpose: Basic Science

Allocation: Non-Randomized

Interventional model: Single Group Assignment

Masking: None (Open label)

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80 participants in 2 patient groups

Keratoconic subjects

Experimental group

Description:

1. Short clinical interview (Questions pertaining to ocular and systemic health, medications, family history and date of birth). (approx. 2 minutes) 2. Visual acuity measurement using EDTRS chart at 4 m (approx. 4 minutes) 3. Refraction: retinoscopy and subjective, at 4m (approx. 10 minutes) 4. Anterior eye examination (approx. 4 minutes) 5. 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) 6. Corneal topography measurement with an Oculus Pentacam (Oculus Gmbh., Germany). (approx. 5 minutes) Two measurements of visual acuity will be made: 1. Standard ETDRS logMAR acuity measurement (5 minutes) 2. Vanishing Optotype logMAR acuity measurement (5 minutes)

Treatment:

Device: Moorfields Acuity Chart

Healthy subjects

Experimental group

Description:

1. Short clinical interview (Questions pertaining to ocular and systemic health, medications, family history and date of birth). (approx. 2 minutes) 2. Visual acuity measurement using EDTRS chart at 4 m (approx. 4 minutes) 3. Refraction: retinoscopy and subjective, at 4m (approx. 10 minutes) 4. Anterior eye examination (approx. 4 minutes) 5. 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) 6. Corneal topography measurement with an Oculus Pentacam (Oculus Gmbh., Germany). (approx. 5 minutes) Two measurements of visual acuity will be made: 1. Standard ETDRS logMAR acuity measurement (5 minutes) 2. Vanishing Optotype logMAR acuity measurement (5 minutes)

Treatment:

Device: Moorfields Acuity Chart