Sector area index: a novel supporting marker for blepharoptosis screening and grading

Purpose: To introduce a new supporting marker for discriminating different grades of ptosis called Sector Area Index (SAI) and a semi-automated technique to calculate it. Methods: In this cross-sectional comparative case series, a circle enclosing the intercanthal distance was automatically drawn after choosing two points as the medial and lateral canthus and manually selecting the palpebral fissure region. Finally, 15-degree apart sectors are applied to the enclosed circle. SAI was measured automatically by dividing the area of each 15-degree sector marked with the upper eyelid contour by the total area of the sector marked with the edge of the surrounding circle. SAI values and inter-eye SAI differences were compared between patients with different grades of ptosis as well as normal patients. Results: In the current study, 106 eyes were recruited (30, 25, 27, and 24 in the control, mild, moderate, and severe ptosis groups, respectively). Mean values of SAI in all sectors showed a decreasing trend from normal individuals toward patients with severe ptosis. The mean difference values of SAI between study eyes and fellow eyes in all four groups of patients showed a statistically significant difference (p < 0.05). In a pairwise comparison between groups, mean values of SAI in all nasal sectors from 15° to 60° showed a statistically significant difference between all groups (p < 0.05). Conclusion: The mean difference of SAI between study eyes and fellow eyes, including eyelid curvature, especially in 15°–60° and 120°–165° sectors, can demonstrate differentiating performance for detecting and discriminating varying grades of ptosis.