A recently published TVST study has investigated the reliability and repeatability of scotopic microperimetry in healthy adults.
Using the Scotopic Macular Integrity Assessment (S-MAIA) device, researchers based at the Department of Clinical Neurosciences, University of Oxford, UK, set about the goal of establishing normative data for future use in clinical trials targeting retinal diseases, such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD).
Scotopic microperimetry measures retinal sensitivity under low-light conditions, and the S-MAIA device enables two-color testing (cyan for rods, red for cones) to map photoreceptor-specific function across the macula.
Thirty-nine healthy participants underwent testing in both eyes after dark adaptation, using a 37-point radial grid. Reliability was assessed via fixation stability (BCEA), fixation losses, and identification of the rod-free foveal zone. Overall, 82 percent of tests met reliability criteria. Cyan and red mean sensitivities were ~20 dB and ~21 dB respectively, while volumetric sensitivity values were 2868–2892 dB·deg² for cyan and 3077–3126 dB·deg² for red. No significant differences were observed between right and left eyes, sexes, or age groups within this young adult cohort.
Repeatability was assessed in a subset of 12 participants. The pointwise coefficient of repeatability (CoR) was ±7.2 dB for cyan and ±7.9 dB for red, suggesting that changes smaller than this may fall within test variability. Volumetric sensitivity measures showed better repeatability, with CoRs of ±197 dB·deg² (cyan) and ±349 dB·deg² (red).
The study concludes that while scotopic microperimetry is feasible in healthy adults, it can be time-consuming, cognitively demanding, and prone to variability – particularly on a pointwise level. However, volumetric sensitivity analysis offers a more robust measure and may be better suited for clinical trial endpoints. Identifying the rod-free foveal zone and maintaining stable fixation were important reliability markers. Improvements in testing algorithms and hardware (e.g. fixation tracking) are likely needed before widespread adoption in clinical trials.
Study author questions:
How close do you think scotopic microperimetry is to being a practical clinical tool used outside of research settings?
What types of improvements are needed before it can be used as an accurate outcome measure in clinical trials?
How might the volumetric sensitivity data you generated inform clinical decision-making in retinal diseases?
Is there anything else you would like to add?
