A new model of central lid margin apposition and tear film mixing in spontaneous blinking. Issue 3 (June 2015)

• Record Type: Journal Article
• Authors: Pult, Heiko; Korb, Donald R.; Murphy, Paul J.; Riede-Pult, Britta H.; Blackie, Caroline
• Is Part Of: Contact lens & anterior eye. Volume 38:Issue 3(2015)
• Page Start: 173
• Page End: 180
• Publication Date: 2015-06
• Subjects: Over-blink -- Spontaneous blink -- Tear film -- Tear film spreading -- Central lid position -- Spontaneous blinks -- Dry eye; Anterior segment (Eye) -- Periodicals; Contact lenses -- Periodicals; Segment antérieur (Œil) -- Périodiques; Lentilles de contact -- Périodiques; 617.752305
• DOI: 10.1016/j.clae.2015.01.012
• Languages: English
• ISSNs: 1367-0484

Abstract

Highlights: The central lid margins do not touch in spontaneous, complete blinks. The central lower lid margin over-laps during spontaneous blinking. There remains a remarkable space between posterior, central lid margins in spontaneous, complete blinks. Tear film mixing depends on building up of a capillary bridge between upper and lower tear meniscus. Abstract: Purpose: To investigate tear film spreading and central lid position in spontaneous blinks and to propose a model of the central lid position of the closed eye in such blinks. Method: In vivo: lid margin position and geometry of 15 subjects (9 female; median age = 45 years) were evaluated by high-speed video and slit-lamp microscope video in consecutive spontaneous blinks. Upper lid (UL) tear meniscus (TM) depth was observed in the open and almost closed eye. Eyelid geometry, position and UL TM depth were analysed by Image-J Software. Lid margin thicknesses were measured with a Scheimpflug camera. In vitro: tear film spreading and lipid layer formation were simulated on a lubricated glass plate and videoed by high-speed camera (JVC, GZ-GX1BE, Japan). Results: In vivo: the median central lid margin thickness was not significantly ( p = 0.258) different between UL (1.8 mm) and LL (1.7 mm) in the opened eye. During blinking, UL remained perpendicular to the corneal surface, while LL tilted in and thinned. A scaled model diagram was created and revealed an over-blink of the UL over the LL (>0.7 mm) and a height offset of the posterior lid margin of >0.7 mm. In vitro: the LL TM fused with the UL TM even before full lid touch due to capillary bridge building. Conclusions: The central UL overlaps the central LL during spontaneous blinking. This provides the appearance of complete closure. The space that results from the lack of lid margin apposition influences the fusion of the upper and lower TM and ultimately tear film mixing.