Age-Related Macular Degeneration, Scotopic Dysfunction, and Driving Performance in a Simulator


Previous work collectively suggests that rod-mediated dark adaptation (RMDA) is a promising candidate as a functional endpoint measure for evaluating interventions to slow early progression of age-related macular degeneration (AMD). However, there is no agreement among the clinical, research and regulatory communities as to what constitutes a clinically (practically) significant slowing in RMDA. Treatments for AMD are often not considered efficacious if they do not result in a criterion level of improvement in vision. But how much change in the rate of dark adaptation constitutes a clinically significant change? Until this issue is resolved, progress in developing clinical trials on early AMD are at a standstill since there is no functional endpoint to be used in the trial. One approach to establishing clinical significance is to examine how RMDA relates to the performance of an everyday visual task under low luminance conditions, such as night driving or reading. However, such data are not yet available. The purpose of this project is to examine the relationship between RMDA and night-time driving and reading under poor illumination. This information will guide the development of a definition of a clinically significant difference in RMDA that can be used in designing clinical trials on early AMD.

Study Type

  • Study Type: Observational
  • Study Design
    • Time Perspective: Cross-Sectional
  • Study Primary Completion Date: March 5, 2019

Detailed Description

The specific aims of this study are as follows:

Aim 1: To examine the association between RMDA as assessed by the rod intercept time and self reported driving difficulty and experiences during night time driving.

Aim 2: To examine the association between RMDA as assessed by rod intercept time and reading performance as assessed by the MNREAD test administered under a low light level. Reading performance will be defined in terms of maximum reading speed, critical print size (i.e., the smallest print size that supports maximum reading speed), reading acuity (i.e., the smallest print size that can be just read) and the reading accessibility index (i.e., an individual's access to text over the range of print sizes found in everyday life).

Clinical Trial Outcome Measures

Primary Measures

  • rod intercept time
    • Time Frame: measured once (1 day)
    • rate of rod-mediated dark adaptation

Secondary Measures

  • severity of age-related macular degeneration
    • Time Frame: measured once (1 day)
    • defined by grading of color fundus photos

Participating in This Clinical Trial

Inclusion Criteria

  • age-related macular degeneration in one or both eyes, ability to follow simple instructions, licensed to drive a vehicle, can read and speak English

Exclusion Criteria

  • diabetes, retinal or optic nerve conditions other than age-related macular degeneration, neurological conditions that impair vision

Gender Eligibility: All

Minimum Age: 60 Years

Maximum Age: 95 Years

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • University of Alabama at Birmingham
  • Provider of Information About this Clinical Study
    • Principal Investigator: Cynthia Owsley, Principal Investigator – University of Alabama at Birmingham
  • Overall Official(s)
    • Cynthia Owsley, PhD, Principal Investigator, University of Alabama at Birmingham
    • MiYoung Kwon, PhD, Principal Investigator, University of Alabama at Birmingham


Owsley C, McGwin G Jr, Clark ME, Jackson GR, Callahan MA, Kline LB, Witherspoon CD, Curcio CA. Delayed Rod-Mediated Dark Adaptation Is a Functional Biomarker for Incident Early Age-Related Macular Degeneration. Ophthalmology. 2016 Feb;123(2):344-351. doi: 10.1016/j.ophtha.2015.09.041. Epub 2015 Oct 30.

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