Many researchers and clinicians in the field believe that standard visual tests, such as visual acuity, may not be sensitive enough to measure changes in IRD, and hence new endpoints are required in these instances.1

This article explores new imaging, vision testing and quality of life assessment methods that are currently being developed for IRD clinical trials.  Exploring the intricacies of these tools, this article aims to shed light on what is being examined, measured, and the reasons behind these evaluations. For those who have undergone one of these tests, this information may offer a clearer understanding of the purpose and significance of the examination. 

What are novel endpoints and why are they important for clinical trials?

The selection of appropriate criteria, referred to as endpoints or outcome measures in clinical trials, is crucial for evaluating how well a treatment achieves the desired therapeutic effects for a medical condition. Ideally, the endpoint used in a clinical trial should be easy to attain, consistent and reproducible in its results, and directly related to the patient’s well-being. In the context of IRDs, regulatory authorities worldwide, such as the USA Food and Drug Administration (FDA), currently have designated four key clinically relevant endpoints to be used as primary outcome measures in evaluating the efficacy of an intervention within a clinical trial. 2 3  
The four clinically relevant endpoints focus on: 

  1. Central vision (best-corrected distance visual acuity)
  2. The sensitivity of specific parts of the retina (visual field sensitivity)
  3. The response of the entire retina in detecting minimum light levels (full-field light sensitivity threshold testing), and
  4. The confidence, speed and safety with which participants can move around (mobility testing) 

The challenge is that IRDs are generally slowly progressing, and so it is often difficult to see a difference in a measure of a clinical trial period (typically under two years). In addition, many IRD treatments being developed (such as gene therapy) have a primary goal to slow progression, not to improve vision. This means that the outcome measures used need to be able to differentiate between a slow deterioration and stable retinal function. This emphasises the importance of exploring novel, or new, advanced but non-invasive and precise ways to measure how well a treatment is working.4