Anatomy and Physiology of Lacrimal system

lacrimal system embryology, anatomy, and physiology of tear formation

1. Anatomy of lacrimal system and lacrimal drainage pathway Presenter: SRISTI THAKUR 1 st year resident, L.E.I.

2. LAYOUT PRESENTATIOM Introduction to lacrimal apparatus Embryological development Anatomy -Secretory pathway -Excretory pathway Physiology- pump mechanism

3. Lacrimal apparatus. SECRETORY APPARATUS 1. Lacrimal glands The main lacrimal gland The accessory lacrimal glands EXCRETORY APPARATUS 2.Lacrimal passage Puncta Lacrimal canaliculi Lacrimal sac Nasolacrimal duct

4. DEVELOPMENT: SECRETORY APPARATUS Lacrimal gland - begins to develop between 6-7 th wks. of gestation. - Form as series of epithelial buds, which grow superolaterally from superior fornix of conjunctiva into the underlying mesenchyme. - Buds branch and canalize form ducts and alveoli

5. With the development of levator palpabrae superioris, gland divides into orbital and palpebral parts. Lacrimal gland do not function fully until 6wks after birth

6. Lacrimal sac and nasolacrimal duct By the end of 5 th wk. the nasolacrimal groove forms as a furrow between the nasal & maxillary prominence In the floor of the groove, nasolacrimal duct develops from the linear thickening of ectoderm Dilates superiorly to form the sac

7. Solid cord separates from adjacent ectoderm and sinks into mesenchyme Cords canalize forming NLD and lacrimal sac at its cranial end Canaliculi form similarly from invaginated ectoderm continuous with distal cord

8. Caudally duct extends intranasally exiting within inferior meatus Canalization is usually complete around time of birth Applied anatomy Failure of caudal end to completely canalize results in congenital NLD obstruction

9. Developmental anomalies Relate to Failure of epithelial core to completely separate from surface ectoderm from which it originates Multiple puncta Lacrimal-cutaneous fistula Incomplete patency either at eyelid ( Punctal /canalicular hypoplasia or aplasia) or Intranasally (NLD obstruction)

10. Lacimal -cutaneous fistula Multiple puncta NLDO Hypoplastic canaliculi

11. Secretory apparatus

12. MAIN LACRIMAL GLAND situated in the fossa, formed by the orbital plate of the frontal bone.

13. Gland is divided into Superior orbital part Inferior palpebral part

14. The orbital part lies in lacrimal fossa at anterolateral area of orbital roof. Almond shape Dimensions -20mm long -12 mm wide -5mm thick

15. 2 surfaces 2 borders 2 extremities

16. Superior surface : Convex Lies in contact with the periorbita. Inferior surface: concave Lies on the LPS, the lateral horn of the LPS aponeurosis and lateral rectus

17. Anterior border : Sharp Parallel to the orbital margin Upto zygomaticofrontal suture Contact with septum orbitale and preaponeurotic pad Posterior border : Round Continuous with palpebral part of gland. In contact with orbital pad of fat

18. Lateral extremity : rests on the lateral rectus muscle. Medial extremity: related to the levator palpebrae superioris

19. The paLpebral part about 1/3 rd the size of orbital part, consists of only 1 or 2 lobules. lies below the aponeurosis of LPS and extends to the upperlid . Superior surface- related to aponeurosis of levator palpebral superioris Inferior surface- lateral part of superior fornix of conjunctiva. The compressed gland can be seen through the conjuctiva when the lid is everted.

20. Ducts of lacrimal gland 10 – 12 ducts in number. All the ducts pass through the palpebral part of the gland.

21. THE ACCESSORY LACRIMAL GLANDS Glands of krause – Microscopic glands In Sub conjuctival tissue of the fornices . 40- 42 in the upper fornix and 6-8 in lower fornix.

22. Glands of wolfring Microscopic glands along the upper border of superior tarsus (2-5) and lower border of inferior tarsus(2-3) Rudimentary accessory lacrimal glands In the caruncle, plica semilunaris and infraorbital region.

23. Structure of the lacrimal gland Microscopically Glandular tissue -Acini -Ducts Stroma Septa

24. Acini are lined by single layer pyramidal cells. surrounded by flattened myoepithelial cells. pyramidal cells are serous type with eosinophilic secretory granules and nucleus.

25. Ducts - lined by 2 layers of epithelial cells -Inner lining -thick cylindrical cells -Outer – flattened cells Stroma -Connective tissue -Elastic tissue -Plasma cells -Blood vessels -Rich nerve terminals

26. Arterial supply Lacrimal artery Sometimes a branch of transverse facial artery

27. Venous and lymphatic drainage Venous drainage: Superior ophthalmic vein via the lacrimal vein. Lymphatic drainage: Joins that of conjunctiva & into preauricular nodes

28. Nerve supply

29. Higher Nervous Control Reflex control of lacrimal secretion Excessive production of tears in emotional conditions Parasympathetic lacrimatory nucleus of facial nerve receive afferent fibers from hypothalamus through descending autonomic pathway in reticular formation

30. Excessive tear production in response to olfactory stimuli Similar pathway connect olfactory system with lacrimatory nucleus

31. Reflex lacrimation secondary to cornea or conjunctival irritation Sensory nuclei of ophthalmic & maxillary division of trigeminal nerve are connected to lacrimatory nucleus by internuncial neurons

32. Applied anatomy Obstruction to secretion : Erythema multiforme Trachoma Chemical burns, Ocular cicatricial pemphigoid

33. Erythema multiforme Trachoma Chemical burns Ocular cicatricial pemphigoid

34. Drying of the conjunctiva and cornea results from the deficiency of the water component of tears in the disease of the main lacrimal gland or accessory glands.

35. Mikulicz syndrome : symmetrical enlargement of lacrimal & salivary glands

36. Dacryops : cystic swelling in upper fornix due to retention of secretion following blockade of one of the lacrimal ducts

37. Dacryoadenitis : inflammation of lacrimal gland

38. Dacryoadenitis : inflammation of lacrimal gland Dacryops : cystic swelling in upper fornix due to retention of secretion following blockade of one of the lacrimal ducts Mikulicz syndrome : symmetrical enlargement of lacrimal & salivary glands Smaller palpebral part of the lacrimal gland lies within the upper lid, damage to it may occur during surgery to the upper lid.

39. Lacrimal secretion Produced by acinar cells Duct system Lining cells of duct modify its composition Final lacrimal secretion: Lysozyme IgA Beta-lysin

40. Functions of the lacrimal secretion Keep corneal epithelium moist so that the surface epithelial cells have a medium to live First and major refractive surface of eye Lubricate apposed surface of lids and eyeball so that it moves freely beneath the lids Lysozyme (antibacterial enzyme) IgA (immunoglobin) Beta-lysin (bactericidal protein ) Secretes substance which affects ocular surface by regulating epithelial cell turnover

41. EXCRETORY APPARATUS

42. Lacrimal puncta 2 Small rounded or oval opening One each on the upper and lower eyelid Junction of ciliary and lacrimal portion of lid margin. 0.3 mm in diameter. 6mm 6.5mm lacrimal papilla

43. Applied anatomy Pallor of puncta is accentuated on applying lateral tension to lower lid – aids in finding a stenosed puncta. In the elderly the puncta become more prominent due to the atrophy of orbicularis.

44. The lacrimal canaliculi Superior and inferior canaliculi join the puncta to the lacrimal sac.

45. Each canaliculus 0.5mm diameter 2 parts- vertical(2mm) -horizontal(8mm) Lie at right angle to each other Junction of angle – ampulla Horizontal part converge toward medial canthus and pierce lacrimal fascia

46. Opening of sac lies at the middle of the lateral surface of the sac about 2.5mm from its apex. In 10% individuals, each canaliculus enters the sac separately..

47. Structure of the lacrimal canaliculus . Epithelium lining the canaliculi is of stratified squamous type. Rich in elastic tissue - wall stretchable and can be dilated about 2mm.

48. Applied anatomy Wall is so thin & elastic that it can be dilated to 3 times normal diameter. Lateral traction on the lids easily straightens them to facilitate probing.

49. Should remember the direction & length of canaliculi while passing probe. Coloured fluid injected into a canaliculi can be seen through the transluscent tissue of lid margins.

50. Lacrimal sac Membranous structure lies in the lacrimal fossa anterior part of medial orbital wall. bounded by the anterior and posterior lacrimal crests.

51. Length – 15 mm Breadth – 5 -6 mm Volume -20 cmm

52. Lacrimal sac is enclosed by lacrimal fascia, part of periorbita. Periorbita splits at posterior lacrimal crest into 2 layers, enclose the sac and meet at the anterior lacrimal crest Between lacrimal sac and fascia lie alveolar tissue and venous plexus continuous around NLD

53. Fundus (3-5mm)- portion above the opening of the canaliculi. Body (10-12mm) Neck- lower small part which is narrow and continuous with the nasolacrimal duct.

54. Relations of nasolacrimal sac Medial- anterior ethmoid sinus in upper part -middle meatus of nose in lower part -- separated by periorbita and bone Lateral- skin -part of orbicularis oculi -lacrimal fascia-attached to which are few fibes of inferior oblique

55. Anterior--medial palpebral ligament -Angular vein Applied anatomy -angular vein complicates surgical approach to lacrimal sac Cross ligament subcutaneously 8 mm from medial canthus

56. Inferior edge of medial palpeprabl ligament free but sheet of areolar tissue ascends laterally from it to blend with lacrimal fascia covering fundus of sac Explains how relatively slight blows to eye cause swelling pf lids on blown nose

57. Posterior- anterior to posterior -Lacrimal fascia and muscle -Fibres of lacrimal part of orbicularis -Septum orbitale

58. Applied anatomy Dacryocystitis : an inflammation of the lacrimal sac

59. Congenital dacryocoele

60. Anterior to medial palpebral ligament & lateral to facial artery, angular vein crosses 7- 8mm from the medial canthus Incision for removal of sac should not be more than 2-3mm medial to medial canthus.

61. The nasolacrimal duct(NLD) continuous downward from the neck of the lacrimal sac to the inferior meatus of the nose.

62. Length-15 mm Diameter-3mm Upper end narrowest part Direction- downwards, backwards and laterally Externally- location represented by line joining inner canthus with ala of nose

63. Structure of the NLD Epithelium : the NLD in lined by 2 layers of cells,the superficial is non ciliated columnar and the deep layer is of flattened cells. Subepithelial tissue : contains lymphocytes which may aggregate in pathological condition to form follicles. Plexus of vessels is well developed around the NLD forming an erectile tissue resembling the inferior concha. Engorgement of vessel cause obstruction of NLD and produce epiphora.

64. The valves Folds of mucous membrane with no valvular function.

65. Arterial supply to lacrimal sac and NLD Superior and inferior palpebral branches of ophthalmic artery Angular artery from facial Infraorbital artery from maxillary Nasal branches of Sphenopalatine artery of maxillary

66. Venous, lymphatic drainage and nerve supply Venous drainage Above: drains into angular &infraorbital vessels Below: into nasal veins Lymphatics: pass to submandibular & deep cervical nodes Nerve supply: infratrochlear branch of ophthalmic division of trigeminal nerve Anterior superior alveolar nerve, a branch of maxillary division of trigeminal nerve

67. Physiology Elimination of tear: 25% by evaporation 75% by drainage– 50% from upper and 50% from lower puncta Capillary attraction Blinking

68. With each blink, pretarsal orbicularis oculi compresses the ampulla, shortens and compresses the horizontal cannaliculi and moves puncta medially. Lacrimal part of orbicularis oculi , attached to fascia of lacrimal sac , contracts and compresses the sac creating a positive pressure which forces tear down the NLD

69. 3. Folds or valves in the duct combine to create greatest resistance to outflow of tears. However these folds form baffle that prevents air currents within the nose from invading the drainage system.

70. Physiology Physiology of tear pump : Rosengren- Doane mechanism. 70% of tear enter the lower canaliculus by capillarity and 30% enter the upper and some evaporate. In young 10% & in elderly 20% or more ,tear eliminates by evaporation. Capacity of conjunctival sac :25-30 μ l - When this volume exceeds then tearing occurs.

71. Rosengren-Doane Mechanism

72. .

73. Regurgitation test steady pressure with index finger applied over lacrimal sac area over medial palpebral ligament Reflux of mucopurulent discharge indicates chronic dacryocystitis with obstruction at lower end of sac or NLD

74. FDDT( Fluorescein Dye Disappearrance Test) One drop of fluorescein dye instilled in conjunctuctival sac of both eyes Observations after 5 min Complements Jones test and Dacryocysto - Graphy in diagnosis

75. Lacrimal syringing test

76. Probing When there is regurgitation in lacrimal syringing, probing is done to rule out level of obstruction. Probing is done as Therapeutic in case of children to open the narrow outflow.

77. Jones dye test

78. Jones dye test

79. Dacryocystography Tells exact site,nature and extent of block. Also about mucosa of sac, fistula,divertcula,stone and tumour in sac

80. Radionucleotide dacryocystography ( lacrimal scintillography ) Non-invasive technique to assess functional efficiency of lacrimal drainage A radioactive tracer( supphur colloid or technetium) instilled into conjunctival sac And its passage through lacrimal drainage system is visualised with anger gamma camera.

81. bibliography American academy of ophthalmology- 2016-17 Wolf’s anatomy of the eye and orbit- 8 th edition Clinical anatomy of eye- richard s. Snell, michael A. Lemp Adlers physiology Internet resources