Overview
Measuring a droopy eyelid (ptosis) by hand is experience-dependent and can vary between examiners. The authors built and tested the Digital Rulers of Ptosis (DRP), a system that reconstructs the eye in 3D from a 10-second smartphone video to automatically measure lid position and muscle function, and compared it against same-day specialist exams across 5 hospitals in 2025.
Findings
- Prospective study, 5 hospitals, 2025; participants 3 years and older.
- 952 participants, 1,904 eyes; mean age 27.9 years (range 3-86); 51.8% female, 48.2% male.
- 1,862 eyes analyzed for eyelid position (MRD1); 1,830 eyes analyzed for levator muscle function (LF), after quality control.
- Agreement with specialist measurement: mean absolute error 0.52 mm (95% CI, 0.50-0.54 mm) for MRD1; 0.95 mm (95% CI, 0.91-0.98 mm) for levator function.
- Diagnostic accuracy for ptosis: area under the curve (AUC) 0.97 (95% CI, 0.96-0.97).
- Accuracy for identifying the surgical approach needed: AUC 0.98 (95% CI, 0.97-0.98).
- Performance was consistent across sex, age and geographic region.
- Among 206 surgical participants (248 eyes), 3-month recurrence rate was 7.3% (95% CI, 4.4%-11.2%; 18 of 248 eyes), within the lower range of previously reported rates.
What it means for a patient
- A smartphone video, rather than only a specialist's hands-on measurement, can measure how droopy an eyelid is and how well its lifting muscle works, closely matching a specialist's numbers.
- This tool correctly identified ptosis and predicted the likely surgical approach with high accuracy in this study.
- Among patients who had surgery, about 7% had their ptosis come back within 3 months, a rate on the lower end of what has been reported before.
- The authors state further studies are needed to show how this changes actual clinical decisions and outcomes, not just measurement accuracy.
Why this paper matters
It validates a smartphone-based measurement tool against specialist ptosis exams in nearly 1,000 patients across 5 hospitals, with high diagnostic accuracy for both detecting ptosis and choosing a surgical approach.
Terms
- Blepharoptosis (ptosis): an eyelid that sits lower than normal, sometimes covering part of the pupil.
- Marginal reflex distance 1 (MRD1): the distance from the light reflection in the pupil to the upper eyelid margin, a standard ptosis measurement.
- Levator function (LF): how far the upper eyelid moves from looking down to looking up, reflecting how well the lifting muscle works.
- Area under the curve (AUC): a score from 0.5 to 1.0 for how well a test tells two groups apart; 1.0 is perfect.
- Mean absolute error: the average size of the difference between two measurement methods.