Review of clinical anatomy and physiology of the conjunctiva

1. Review of clinical anatomy and physiology of the conjunctiva Ayesha S Abdullah 20.09.2013

2. Learning outcome By the end of this lecture the students would be able to; • Correlate the structural organization of the conjunctiva with its functions • Identify important anatomical landmarks on conjunctival photographs and histological photomicrographs. • Relate the clinical presentation of conjunctival disorders with the structural organization and physiological functions of the conjunctiva

3. Let us look at a case A 25 year old young man presented to the OPD with the complaints of watering of both the eyes with a feeling of grittiness and foreign body sensation for the last 03 years. He also had gradual visual loss of vision. His symptoms worsened over the years. He had a history of chemical injury to his eyes 03 years ago.

5. What questions come to your mind? • Why the feeling of grittiness and foreign body sensation in the eyes? • Why the gradual visual loss? • What keeps the ocular surface moistened? • When we look around in different directions why don’t we get the feeling of the ocular surface beneath the eyelids and in front of the eye rubbing against each other?

6. Some more questions • What is conjunctiva? • A mucous membrane covering the under surface of the lids and anterior part of the eyeball upto the cornea • Histologically what are the layers of the conjunctiva? • Epithelium • Submucosa/stroma/substantiapropria • What kind of epithelium should the conjunctiva have? • Stratified epithelium • Why? • Exposed ocular surface, vulnerable to subtle trauma • excessive movement of the eye and rubbing of the surfaces

7. What keeps the conjunctiva moist & lubricated? • Tear film • Which type of secretary cells and glands are responsible for this function? • Goblet cells and accessory lacrimal glands • Where are these cells located? • Throughout stratified columnar epithelium • What else is there in the submucosa? • Outer lymphoid layer; macrophages, mast cells, polmorphs, eosinophils and aggregates of lymphocytes, IgA • Inner fibrous layer; collagen fibers, blood vessels, fibroblasts and accessory lacrimal glands

8. What are follicles? • Aggregates of lymphoid tissue with in the submucosa/substantia propria • A reaction to infections or hypersensitivity response

9. What are papillae?

10. Hyperplastic conjunctival epithelium with central core vessel surrounded by infiltrate separated from each other by fibrous septa- seen in allergic & bacterial conjucntvitis

11. Topographically, what are the different parts of the conjunctiva? • Palpebral • Bulbar • Forniceal (fornix) • Plica semilunaris & caruncle

12. Limbus Bulbar conjunctiva Plica semilunaris & Caruncle 7 Forniceal conjunctiva Tarsal conjunctiva Marginal conjunctiva

15. Should the epithelium be the same or different in different parts of the conjunctiva? • It should be different • Stratified columnar epithelium 2 – 5 cells. • At limbus change into stratified squamous non keratinized epithelium. • At lid margin non keratinized stratified squamous epithelium changes into keratinized stratified squamous epithelium • Why? • Different role of each part

16. Should it be keratinized or non-keratinized? Why? • Non-keratinized to aid maintenance of smooth surface, less friction during ocular and lid movements • What keeps it non-keratinized? • Normal ocular surface environment • Vitamin A • When could it get keratinized? what would happen?

17. Tarsal conjunctiva Limbus Marginal conjunctiva Bulbar conjunctiva Forniceal conjunctiva-crypts of Henle

20. Plica semilunaris Caruncle stratified squamous epithelium with few goblet cells focal surface keratinization hair follicles (arrow 12), sebaceous glands (arrow 13) and adipose tissue (arrow 15).

21. Clincially it appears like this

24. What is the blood supply of the conjunctiva? • Why is it so richly supplied with blood vessels? • Which general physical examination draws from the rich pink colour of the palpebral conjunctiva? • What unconventional role do conjunctival blood vessels perform?

29. CILIARY CONGESTION CONJUNCTIVAL CONGESTION

30. Blood supply Arterial supply; • Posterior conjunctival arteries derived from arterial arcade of lids which is formed by palpebral branches of nasal and lacrimal arteries of the lids. • Anterior conjunctival arteries derived from the anterior ciliary arteries – muscular br. of ophthalmic artery to rectus muscles. Venous drainage; • Palpebral and Ophthalmic veins.

31. Should there be a nerve supply? • What kind? • Name the nerves? • Should there be lymphatic drainage? • Where would the lymphatics drain? • If the lymph nodes are palpable/enlarged what is it called? • What does lymphadenopathy signify?

34. PHYSIOLOGY • Smooth surface. • Secretes mucin and aqueous component of tear film. • Highly vascular: supplies nutrition to the peripheral cornea. • Aqueous veins drains from anterior chamber maintenance of IOP. • Lymphoid tissue helps in combating infections. • Basic secretion—reflex secretion.

35. Summarize • How is conjunctiva organized structurally? • What are major functions of conjunctiva? • Protection –physical, immunological • Smooth and healthy ocular surface • Nourishment for the lids and cornea • Role in aqueous drainage • Smooth, controlled and free ocular movements.

36. Summarize • How does the structure and function correlate with the clinical symptoms and signs? • Discharge, watering • Dry eyes • Follicles and papillae • Anemia • Jaundice , would you be able to see it if the conjunctiva were opaque? • Lymphadenopathy • Tumours and cysts