ARVO 2021 Highlight: Microperimetry Emerging as a Valuable Tool in Measuring Treatment Efficacy in Clinical Trials
Precise and Sensitive Outcome Measures are Essential for Getting Vision Treatments through Clinical Trials
Vision tests typically used by eye care professionals may be useful in the initial diagnosis of a retinal disease, but they are often not well-suited for tracking disease progression or determining if a treatment is working in a clinical trial. For example, tests of visual acuity and visual fields may not change much over time, even though a condition is progressing and vision is diminishing. Also, the results from these tests can vary considerably, even from day-to-day.
At the virtual 2021 meeting of the Association for Research in Vision and Ophthalmology (ARVO), a panel of experts discussed how microperimetry is emerging as a sensitive and precise outcome measure for treatments in clinical trials for eye diseases, including retinal degenerative conditions such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP).
A microperimeter (MP) is a device that measures retinal sensitivity at multiple points (also known as loci) in the central region of the retina, including the macula. A test using an MP captures changes in the size of the area of functional vision and changes in sensitivity at various loci within that area.
Wiley Chambers, MD, director, Division of Ophthalmology, Office of Specialty Medicine, Office of New Drugs, at the US Food & Drug Administration, said that a mean change of at least 7 decibels in 5 loci or more captured by MP would be considered clinically significant.
Karl Csaky, MD, PhD, a senior scientist at the Retina Foundation of the Southwest, discussed how MP can be used to more effectively measure disease progression and potentially treatment efficacy for people with the advanced form of dry AMD known as geographic atrophy (GA).
People with GA have central vision loss caused by degeneration of photoreceptors and retinal pigment epithelial cells in their macular regions. When doctors take pictures of the back of the eyes of GA patients, the GA appears as an ominous dark spot where cells have degenerated. Disease progression has traditionally been evaluated by measuring the area of the growing atrophic tissue.
However, Dr. Csaky noted that beyond the outer edge of the GA is a transition zone where photoreceptors have lost some sensitivity but haven’t yet degenerated. Conventional pictures don’t capture retinal sensitivity or changes in the transition zone. However, MP can assess changes in sensitivity over time. Furthermore, MP can be used to evaluate the efficacy of a treatment designed to slow disease progression by capturing retinal sensitivity changes over time in a clinical trial.
Maximillian Pfau, PhD, University of Bonn, discussed a recent paper which reported that retinal sensitivity loss, as measured by microperimetry, was faster just outside of the edge of the atrophic tissue of Stargardt disease patients. That transition zone could be a sensitive measure of disease progression and the efficacy of emerging therapies in clinical trials. The paper, published in the American Journal of Ophthalmology (Schonbach, et al), was a report from ProgStar, a natural history study of Stargardt disease patients funded by the Foundation Fighting Blindness.
According to Jasleen Jolly, PhD, MCOptom, at University of Oxford, MP is being used for outcome measures in clinical trials for a variety of retinal diseases, including: choroideremia, Leber congenital amaurosis, RP, X-linked RP, and Stargardt disease.
Zhichao Wu, BAppSc(Optom), PhD, from the Centre for Eye Research Australia, presented on the spatial assessment of visual function in MP.