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Microperimetry as an Outcome Measure in RPGR-associated Retinitis Pigmentosa Clinical Trials
Laura J Taylor1,2, Amandeep S Josan1,2, Jasleen K Jolly3
1Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
Purpose:
To explore which microperimetry sensitivity index (pointwise sensitivity, mean sensitivity, and volume sensitivity) is suitable as a microperimetry outcome measure in patients with X-linked RPGR-associated retinitis pigmentosa (RP).
Methods:
Microperimetry data from patients with RPGR-associated RP were collected and analyzed retrospectively. Fourteen participants completed triplicate microperimetry testing, across 2 consecutive days for the repeatability analyses. Longitudinal data was obtained from 13 participants who completed microperimetry testing at two separate visits.
Results:
The test-retest coefficients of repeatability (CoR) for pointwise sensitivity were ±9.5 dB and ±9.3 dB, in the right and left eyes, respectively. The mean sensitivity CoR for the right and left eyes was ±0.7 dB and ±1.3 dB. Volume sensitivity CoR was ±144.5 dB*deg2 and ±324.2 dB*deg2 for the right and left eyes, respectively. The mean sensitivities were positively skewed toward zero in those with a high number of nonseeing points (arbitrarily assigned to -1.0 dB) and just seen points (0.0 dB). Volume sensitivities were unaffected by the averaging effects of skewed data.
Conclusions:
Clinical trials should report population-specific test-retest variability to determine a clinically significant change. Pointwise sensitivity indices should be used with caution as outcome measures in clinical trials owing to high levels of test-retest variability. Global indices seem to be less prone to variability. Volume sensitivity indices seem to be superior for use in RPGR-associated RP clinical trials compared with mean sensitivity because they are unaffected by the averaging effects of highly skewed data.
Translational Relevance:
Careful selection of sensitivity indices (VA) is required when using microperimetry as a clinical trial outcome measure.
Insights
Volume sensitivity is a superior microperimetry outcome measure for X-linked retinitis pigmentosa clinical trials. Pointwise sensitivity shows high variability, while volume sensitivity is unaffected by skewed data, making it more reliable for RPGR-associated RP.
Area of Science:
- Ophthalmology
- Genetics
- Clinical Trials
Background:
- X-linked retinitis pigmentosa (RP) is a genetic disorder.
- RPGR gene mutations are a common cause of X-linked RP.
- Microperimetry is used to assess visual function in retinal diseases.
Purpose of the Study:
- To determine the most suitable microperimetry sensitivity index for clinical trials in X-linked RPGR-associated RP.
- To compare the test-retest variability of pointwise, mean, and volume sensitivity measures.
Main Methods:
- Retrospective analysis of microperimetry data from patients with RPGR-associated RP.
- Repeatability analysis using triplicate testing over two days.
- Longitudinal analysis of data from two separate visits.
Main Results:
- Pointwise sensitivity showed high test-retest variability (CoR ±9.5 dB right, ±9.3 dB left).
- Mean sensitivity had lower variability (CoR ±0.7 dB right, ±1.3 dB left) but was affected by skewed data.
- Volume sensitivity demonstrated low variability (CoR ±144.5 dB*deg2 right, ±324.2 dB*deg2 left) and was unaffected by skewed data.
Conclusions:
- Pointwise sensitivity indices are not recommended as outcome measures due to high variability.
- Volume sensitivity indices are superior for RPGR-associated RP clinical trials compared to mean sensitivity.
- Population-specific test-retest variability should be reported in clinical trials for accurate interpretation.
