Development of a Device to Measure Dark Adaptation

July 4, 2016 updated by: Dr Jeremiah Kelly, University of Manchester

A Study to Evaluate the Sensitivity and Specificity of a Device to Measure Dark Adaptation in Subjects With and Without Early Macular Disease

Age Related Macular Disease (AMD) is easily the leading cause of blindness in older people in developed countries. It affects between 30 and 50 million individuals worldwide, with around 30% of the over 65's showing early signs of the disease. Severe AMD has a devastating impact on the quality of life; it causes extensive visual impairment, making reading difficult and driving impossible. Patients lose their independence and become a major burden on public health systems.

Present treatment options are limited. Many new therapies are under development and all will need evaluation using a test with high specificity and sensitivity for early AMD. The present application will develop such an instrument. The prototype was funded by a previous i4i FS (feasibility study ll-FS-0110-14036). The new device measures sensitivity to a dim flickering light using the same principle as an established european conformity marked (CE marked) instrument. The original method involved lights of different wavelengths and higher intensities.

The instrument in this study assesses night vision, which is selectively damaged in early stage AMD. In low lighting, the investigators vision depends on specialized rod photoreceptors. Cone photoreceptors, which provide daytime vision, remain normal in the early stages of the disease. By the time patients complain of reduced (cone-based) visual acuity, they will have had the disease for many years and lost many thousands of photoreceptors.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Detailed Description

In a clinical environment dark adaptation (DA) is measured by exposing the patient to a brief bright light and then measuring their sensitivity to a flickering light. This sensitivity recovery has a typical appearance; an early rapid recovery mediated by the colour vision system (cone photoreceptors) and a slower recovery of the low light system (rod photoreceptors).

If the measurements are made against a black background then a bi exponential model is suitable, however if a dim luminous background is used then the recovery is better modelled by a exponential bi linear model. We will use the exponential bilinear model, which has seven parameters. The parameters are as follows; the exponential cone phase is modelled by the cone threshold, cone coefficient, and cone time constant. The S2 rod phase is modelled by its commencement time. This is the time when the rod system becomes more sensitive than the cone system, sometimes called the cone-rod break point (alpha) and the slope of the subsequent thresholds. The late rod phase (S3) is similarly modelled by a transition time or rod-rod breakpoint (beta) and its slope.

If the initial bright light is sufficiently intense then the recovery of the rod phase (S2) is termed rate limited. There is evidence that this recovery rate is a useful measure of the health of the light sensing layer of the eye an adjoining tissues, the retina, retinal pigment epithelium and choroid. It is these tissues that are thought to be affected in age related macular disease.

In this study we will measure rate of rod recovery sometimes called the S2 phase. We want to see whether this measurement can be used to identify patients with and without early macular disease.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
40

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United Kingdom
    • Greater Manchester
      • Manchester, Greater Manchester, United Kingdom, M13 9PL
        • University of Manchester

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

50 years to 80 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

Participants will be recruited from a the greater manchester area by a call for volunteers, through the local newspaper, a university email list and through the Hale Barns Macular Disease Association

Description

Inclusion Criteria:

  • They understand their rights as a research Participant and are willing and able to sign a Statement of Informed Consent.
  • They are over 50 years and less than 80 years of age.
  • They are willing and able to perform the experimental task required.
  • They are not a current participant in other studies. Lifestyle factors
  • Diet that includes animal and/or vegetable fats. Health factors
  • Good ocular health, the following will be admitted Pseudophakia, aphakic with good VA (better than 6/12), AMD with AREDS category 1,2,or 3.
  • Good systemic health, the following may be admitted Hypertension Thyroid disease Arthritis Depression
  • Medication, that is not hepatotoxic or retinotoxic directly or by treating a disease that is may be admitted. Use British National Formulary (BNF) to check if unsure.

Exclusion Criteria:

  • Unlikely to be available, willing, and able to attend
  • Unable to give consent.
  • Current participant in other studies.
  • Subject to any condition that may adversely affect fat intake (proxy for Vit A) or retinal function.

Lifestyle factors

  • Diet that excludes animal and/or vegetable fats.

Health factors

  • Ocular Any active disease, e.g. · Glaucoma, Cataract if VA worse than 6/12 · Diabetic Retinopathy · Retinal detachment · Uveitis Treatments · Laser Sx. to cornea, capsule or retina · Recent cataract extraction within 12 weeks · Drops

  • Systemic Diabetes Liver disease, Hepatitis: Past or present Digestive disorders, e.g. Crohns, irritable bowel syndrome (IBS), lactose intolerance Bowel surgery, stomach staple, ileostomy, colostomy Kidney disorder (elevated iron) Chronic alcoholism or drug abuse

    • Medication, hepatotoxic or retinotoxic directly or by treating a disease that is. If unsure use BNF and seek advice of ophthalmologist/study leader. Examples include:
  • Interferon alpha
  • Vitamin A derivatives (Chronic eczema)
  • Amiodarone (Heart disease)
  • Chloroquine/Hydrochloroquine (Plaquenil) (Rheumatoid Arthritis/ Malaria)
  • Tamoxifen (Breast Cancer)
  • Chlorpromazine (Schizophrenia)
  • Deferoxamine (Thalassemia, blood transfusions/ kidney disease)
  • Phenothiazines (Anti-psychotic/epilepsy)
  • Ethambutol (TB)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
No Maculopathy
Aged 50 to 80 with no macular disease
Early Maculopathy
Aged 50 to 80 with early AREDS defined 2,3 age related maculopathy

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
The rate of recovery of the rod phase S2
Time Frame: At participant visit only
Dark adaptation will be measured in 40 participants; 20 healthy and 20 with early macular disease. This index of retinal health will be analysed for its sensitivity and specificity for the identification participants with macular disease.
At participant visit only

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Lifestyle questionnaire
Time Frame: At participant visit only.
We have a simple questionnaire to investigate factors reported in the literature to have an effect on macular health. We will use the categorical data collected by the questionnaire to assess the influence of these lifestyle measures on the index of retinal health found from the dark adaptation measurement.
At participant visit only.
Participant Experience Questionnaire
Time Frame: Within one month of participant visit.
We will give each participant a questionnaire when they finish their visit and will ask for their experience of the process of dark adaptation measurement.
Within one month of participant visit.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
University of Manchester

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Ian J Murray, PhD, University of Manchester

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
July 1, 2014

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
February 1, 2015

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
April 1, 2015

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
March 12, 2014

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 14, 2014

First Posted (Estimate)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
March 18, 2014

Study Record Updates

Last Update Posted (Estimate)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
July 6, 2016

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 4, 2016

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
July 1, 2016

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • II-LB-0712-20001

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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