The eyelids can be divided into the following 7 structural layers:
Figure 9-10 details the anatomy of the eyelids; Activity 9-2 is an online interactive tool for self-testing knowledge of eyelid anatomy. See also BCSC Section 2, Fundamentals and Principles of Ophthalmology, for additional discussion and numerous illustrations.
Upper and lower eyelid anatomy. Illustration modified from Stewart WB.
Surgery of the Eyelid, Orbit, and Lacrimal System. Ophthalmology Monograph 8, vol 2. San Francisco: American Academy of Ophthalmology; 1994:23, 85. Illustration by Cyndie C. H. Wooley
Skin and Subcutaneous Connective Tissue
Eyelid skin is the thinnest skin of the body and is unique in having no subcutaneous fat layer. Because the thin skin of the eyelids is subjected to constant movement with each blink, the laxity that often occurs with age is not surprising. In both the upper and the lower eyelids, the pretarsal tissues are normally firmly attached to the underlying tissues, whereas the preseptal tissues are more loosely attached, creating potential spaces for fluid accumulation. The contours of the eyelid skin are defined by the eyelid crease and the eyelid fold:
The upper eyelid crease represents the attachments of the levator aponeurosis to the pretarsal orbicularis muscle and skin. In the non-Asian eyelid, this site is near or at the level of the superior tarsal border.
The upper eyelid fold consists of the loose preseptal skin and subcutaneous tissues resting above the confluence of the levator aponeurosis and orbital septum.
Figure 9-10 Upper and lower eyelid anatomy.
(Modified from Stewart WB. Surgery of the Eyelid, Orbit, and Lacrimal System. Ophthalmology Monograph 8, vol 2. San Francisco: American Academy of Ophthalmology; 1994:23, 85. Illustration by Cyndie C. H. Wooley.)
Figure 9-11 Racial variations in eyelid anatomy. Variant I (left): the orbital septum fuses with the levator aponeurosis above the tarsus. Variant II (Asian, right): the orbital septum fuses with the levator aponeurosis between the eyelid margin and the superior border of the tarsus, and there are fewer aponeurotic attachments to the skin.
(Reproduced with permission from Katowitz JA, ed. Pediatric Oculoplastic Surgery. Philadelphia: Springer-Verlag; 2002.)
Racial variation can be seen in the location of the eyelid crease and eyelid fold. The eyelid of an Asian individual normally has a relatively low upper eyelid crease because the orbital septum fuses with the levator aponeurosis between the eyelid margin and the superior border of tarsus, in contrast to a supratarsal fusion (Fig 9-11). This also allows preaponeurotic fat to occupy a position more inferior and anterior in the eyelid. Although the lower eyelid crease is less well defined than the upper eyelid crease, these differences are apparent in the lower eyelid as well.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.