EYELIDS- ANATOMY, STRUCTURE, LAYERS & EYELID GLANDS

The presentation on “Anatomy of Eyelid” provides a comprehensive overview of the structural and functional components of the human eyelid. It covers detailed information on the layers of the eyelid, including skin, subcutaneous tissue, muscular layer, tarsal plate, and conjunctiva. The slides explain the muscles of the eyelid such as the orbicularis oculi, levator palpebrae superioris, and Müller’s muscle, along with their innervation and actions.
The presentation also highlights glands of the eyelid (Meibomian, Zeis, and Moll).
Ideal for optometry, ophthalmology, and medical students, this presentation aims to simplify complex anatomy with clear diagrams, labeled structures, and concise explanations.

1. ANATOMY OF EYELIDS Ms. Reshu Yadav Assistant Professor CSJM University

2. GROSS ANATOMY The eyelids are mobile tissue curtains placed in front of the eyeballs. These act as shutters protecting the eyes from injuries and excessive light. These also perform an important function of spreading the tear film over the cornea and conjunctiva. In addition, like eyebrows, they make an important contribution to the facial features.

3. Position of eyelids- In primary position of gaze, the upper eyelid covers about one-sixth of the cornea and the lower eyelid just touches the cornea. Canthi- The two eyelids meet each other at medial and lateral angles (or inner and outer canthi). Eyelid margins- The opposing margins of the eyelids are nearly flat, some 2 mm in width. The grey line, which marks junction of skin and conjunctiva, divides the intermarginal strip into an anterior strip bearing lashes and a posterior strip which contains openings of meibomian glands.

4. STRUCTURE Each eyelid consists of following layers- Skin Layer of subcutaneous areolar tissue Layer of striated muscles Submuscular areolar tissue Fibrous layer Layer of non-striated muscle fibres Conjunctiva

5. 1. SKIN The skin covering the eyelids is elastic, having a fine texture, is thinnest in the body and folds easily thereby, contributing to the ease and in speed of mobility of the upper eyelid. Microscopic structure- The epidermis is composed of 6-7 layers of stratified squamous epithelium. The basal layer of the epidermis shows the presence of unicellular sebaceous glands and numerous typical eccrine sweat glands. The dermis is composed of a thin layer of dense connective tissue with rich network of elastic fibres, blood vessels, lymphatics and nerves.

6. 2. Subcutaneous areolar tissue It is a layer of loose areolar connective tissue, containing no fat. 3. Layer of striated muscles This layer consists of orbicularis muscle which forms a thin oval sheet across the eyelids. In addition, the upper eyelid also contains levator muscle.

7. Orbicularis oculi muscle- It is a skeletal muscle of facial expression that Surrounds the eyelids and the opening of the eye. Parts: Palpebral part – lies within the eyelids, helps in gentle closure of eyes (like blinking or sleeping). Orbital part – surrounds the orbit, helps in tight closure of eyes. Function- Closes the eyelids & Helps in blinking and protection of the eye from injury or bright light. Nerve supply: Facial nerve (cranial nerve VII).

8. Levator palpebrae superioris muscle It is a Skeletal muscle. Its location in the upper eyelid, arises from the roof of the orbit and inserts into the skin of the upper eyelid Function- Elevates (lifts) the upper eyelid, so that the eye opens & works in opposition to the orbicularis oculi. Nerve supply- Mainly by oculomotor nerve (cranial nerve III).

9. Submuscular areolar tissue It is a layer of loose connective tissue present between the orbicularis muscle and fibrous layer. The nerves and vessels of the lids lie in this layer.

10. Fibrous layer It is the framework of the lids and consists of a central thick part the tarsal plate and peripheral thin part the septum orbitale (palpebral fascia). Tarsal plate- Tarsi are firm plates of dense fibrous tissue that form the skeleton of the eyelids giving them shape and firmness. The tarsi are about 29 mm long and 1 mm thick. The upper tarsus is about 10-11 mm in height and lower tarsus is 4-5 mm in height.

11. Septum orbitale (Palpebral fascia)- It is a thin, floating membrane of connective tissue which takes part in all the movements of the eyelids. Acts as a barrier between eyelids and orbital contents & helps prevent the spread of infection from the eyelids into the orbit.

12. Layer of non-striated muscle fibres This layer consists of smooth muscle fibres of Muller which lie just deep to septum orbitale in the upper and the lower eyelids. Muller’s muscle are about 10-12 mm long and about 15 mm wide.

13. Conjunctiva The posterior most layer of the eyelid is formed by the palpebral conjunctiva, which extends from the lid margin to the conjunctival fornix. It is firmly adherent to the posterior surface of the tarsal plate and Muller's muscle

14. GLANDS OF EYELIDS The tarsal (meibomian) glands- Modified sweat glands present in the tarsal plate. They are arranged in a single row vertically parallel to each other numbering about 20-30 in each lid. It Secrete oily layer of tear film that prevents evaporation of tears.

15. 2. Glands of Zeis- These are also modified sebaceous glands, attached directly to the eyelash follicle. Usually, two glands are associated with each cilium Secretion of the Zeis gland (sebum) prevents the eyelashes from becoming dry and brittle. It also contributes towards the oily layer of tear film.

16. 3. Glands of Moll- These are modified sweat glands, which lie between the cilia . These are more numerous in the lower eyelid than the upper. 4. Accessory Lacrimal (Glands of Krause & Wolfring)- These are microscopic accessory lacrimal glands present along the upper border of superior tarsus and along the lower border of the inferior tarsus. These are about 2 to 5 in the upper lid and 2 to 3 in the lower lid.