Anatomy and physiology of the eyelid


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Anatomy and physiology of the eyelid

  1. 1. Speaker:Dr.Ala’ Abu Farsakh Supervised by:Dr.Amjad Younis
  2. 2. Lecture outline Eyelid anatomy • Gross anatomy • Layers of the eyelid • Eyelid arterial supply and venus and lymphatic drainage • Eyelid nerve supply Eyelid physiology • Functions of eyelids • eyelid movements: Openning,clouser,bli nking and winking,bell’s -Dynamics of eyelid openning and clouser
  3. 3. The Eyelids 4 • Each eyelid is divided by a horizontal furrow, (the superior palpebral sulcus) into: orbital & a tarsal part. • The eyelids meet at the medial & lateral angles or canthi • The lateral canthus is in direct contact with the eyeball & forms an angle of 60 when the eyes are wide open.
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  5. 5. 6 • The medial canthus : • rounded • the two eyelids are separated by lacus lacrimalis, in the centre of which is a small pinkish elevation; the caruncula lacrimalis. A semilunar fold called plica semilunaris lies on lateral side of caruncle.
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  7. 7. 8 • papilla lacrimalis: • About 5mm from the medial canthusther’s a small elevation, the • the punctum lacrimale which varies in size from 0.4 to 0.8mm in diameter. The punctum leads to canaliculus lacrimalis. • The papilla lacrimalis projects into the lacus
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  9. 9. The Eyelashes 10 • 2-3 rows • those in the upper eyelid(100-150) • those in the lower lid(50-75) • life span of 100-150 days. • The sebaceous glands of Zeis open into each follicle. • modified sweat glands, the ciliary glands of Moll, open into each follicle or into the eyelid margin.
  10. 10. 11 • (meibomian glands): • which number about 20-25 in each lid. • A gray line or sulcus can be seen running along the eyelid margin between the eyelashes & the openings of the tarsal glands.
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  12. 12. Structure of the eyelids 13 1. Skin: 2. Subcutaneous tissue 3. Striated muscle fibers of the orbicularis oculi 4. Orbital septum and tarsal plates 5. Smooth muscle 6. Conjunctiva
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  14. 14. skin 15 • Very thin and easily folds • stratified squamous epithelium keratenized. • Skin becomes continuous with conjunctiva at the posterior edge of the site of the orifices of the tarsal glands
  15. 15. Subcutaneous tissue 16 • very loose and rich in elastic fibers • Devoid of fat in whites
  16. 16. Orbicularis oculi 17 1-Orbital part: extends to the temporal region and cheek 2-Palpebral part: extends to the eyelids, divided into preseptal & pretarsal portions 3-Lacrimal part: behind the lacrimal sac 4-Ciliary part: at the lid margin --Originates from medial palpebral ligament and neighboring bones… at the lateral angle of the eye the fibers interlace at the lateral palpebral raphe
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  18. 18. 19
  19. 19. Orbicularis oculi 20 • Nerve supply Temporal and zygomatic branches of facial nerve • Action • Antagonist muscles Orbital part frontal belly of occipitofrontalis muscle Palpebral part levator palpebrae superioris
  20. 20. Orbital septum and tarsal plates 21 • Fibrous…. • attached to orbital margin • Separates eyelids from contents of orbital cavity • Stonger on lateral side than medial • Posterior to medial palpebral ligament • Anterior to lateral palpebral ligament • Tarsal plate of the upper lid: 10 mm • the lower lid: 5 mm
  21. 21. Orbital septum 22
  22. 22. Structures piercing through orbital septum 23 1. Lacrimal vessels & nerves 2. Supraorbital V. & N. 3. Supratrochlear A. & N. 4. Infratrochlear N. 5. Anastomosing vein bet angular & ophthalmic v. 6. Sup & inf palpebral A. 7. Aponeurosis of levator muscle. 8. Expantion of inf rectus muscle
  23. 23. Medial & lateral palpebral ligaments 24 • Medial palpebral ligament: is anterior to lacrimal sac • Attaches medial ends of the tarsi to lacrimal crest and frontal process of maxilla • Lateral palpebral ligament: attaches lateral ends of tarsi to marginal tubercle on the orbital margin formed by zygomatic bone
  24. 24. Smooth muscles 25 • Forms the superior and inferior tarsal muscles • Both are innervated by sympathetic nerves from the superior cervical sympathetic ggl
  25. 25. conjunctiva 26 • Subtarsal sulcus: 2 mm from post edge of lid margin, traps foreign particles • The area that covers the upper tarsal plate is strongly bound to it • That covering the lower tarsla plate is adherent only to its upper half
  26. 26. Levator palpebrae superioris 27 • From inf surface of lesser wing of sphenoid • Insertion is aponeurosis descending to upper lid post to the orbital septum • Nerve supply: occulomotor n. • Action:
  27. 27. Levator palpebrae superioris 28
  28. 28. Eyelid Arterial supply 29 • Lat and med palpebral a. Lateral: lacrimal artery: ophthalmic a. Medial: ophthalmic a. • Two arches: marginal and peripheral
  29. 29. Lids Venous and lymphatic drainage 30 Venous: • Medailly : ophth and angular v. • Laterally: superficial temporal v. lymphatic: Lat 2/3 : superficial parotid LN Medial: submandibular LN
  30. 30. Nerve supply(sensory) 31 • Upper eyelid: infratrochlear + supratrochlear + supraorbital + lacrimal nerves(V1) • Lower lid: infratrochlear + infraorbital n.
  31. 31. Lecture outline Eyelid anatomy • Gross anatomy • Layers of the eyelid • Eyelid arterial supply and venus and lymphatic drainage • Eyelid nerve supply Eyelid physiology • Functions of eyelids • eyelid movements: Openning,clouser,bli nking and winking,Bell’s phe -Dynamics of eyelid openning and clouser
  32. 32. Functions of the Eyelid 1. Reconstitution of the tear film. 2. Maintain the integrity of the corneal surface. 3. Maintain the proper position of the globe within the orbital contents. 4. Regulate the amount of light allowed to enter the eye. 5. Provide protection from airborne particles. 6. Coverage of the eye during sleep.
  34. 34. • Lid opening • Lid closure • Blinking • Voluntary blinking and winking • Bell’s phenomenon
  35. 35. Lid opening • Upper lid elevators • Lower lid retractors
  36. 36. Upper lid elevators • Levator palpebrae superioris (the primary elevator of the upper eyelid). • The superior palpebral muscle of Muller’s • Frontalis (acting as accessory elevator). Frontalis and Muller’s muscles become important when the levator is defective.
  37. 37. Muscle Attachment Nerve supply Levator palpebrae superioris (main upper lid retractor) Lesser wing of the sphenoid to the tarsal plate Superior division of the oculomotor nerve (also supplies the SRM). Muller’s muscle (minor upper lid retractor) Aponeurosis of the levator to the upper border of the tarsal plate Sympathetic Frontalis Scalp to the upper part of the orbicularis oculi
  38. 38. Eyelid excursion during opening movements: • In adults the upper eyelid is raised some 10-15 mm from extreme downward gaze to extreme upward gaze.
  39. 39. Tone of levator muscle: • In upward gaze, tone increases in both the superior rectus muscle and the levator, resulting in elevation of the visual axis and concomitant elevation and retraction of the upper lid.
  40. 40. Lower lid retractors • NO true counterpart of the levator is present, and therefore, the opening movement depends upon several factors: 1. Traction exerted by the attachment of the inferior rectus to the inferior tarsus. 2. Inferior palpebral muscle (identical to Muller’s muscle in the upper lid).
  41. 41. Dynamics of opening movement • Opening of the upper eyelid takes place against gravity. • Opening movements of the homolateral upper and lower eyelids begin in phase, although the opening movement of the lower lid is much slower than that of the upper eyelid due to lack of any direct muscular pull.
  42. 42. • During opening movement the upper lid moves vertically upwards, while the lower lid moves laterally in a horizontal direction.
  43. 43. • Bilateral coordination and their basis: • Opening movements of the eyelids are bilateral, symmetrical, and identical in direction and amplitude, although they may be voluntarily inhibited on either side. • So, the levator muscles of the two upper eyelids behave as yoke muscles in that they act as a team or pair, and like extraocular muscles, obey Hering’s law of equal innervation.
  44. 44. • This implies that the innervational energy reaching the one levator muscle is equal to that reaching the other. • When the levator on one side is weak, as in unilateral myasthenia gravis or unilateral congenital ptosis, the lid on the unaffected side may be retracted in an unconscious effort (based on Hering’s law of equal innervation) to elevate the ptotic lid.
  45. 45. Reciprocal innervation pattern • It exists between the levator muscle and the orbicularis oculi muscle, i.e. when levator receives maximum innervation during opening the orbicularis receives minimum innervation and vice versa. Thus, these muscles follow the Sherrington’s law of reciprocal innervation.
  46. 46. Lid closure
  47. 47. Orbicularis oculi controls lid closure and is supplied by the facial nerve. It is divided into three main parts:
  48. 48. Part Position Function Pretarsal fibers In front of the tarsal plate * Respond in spontaneous blinking and tactile corneal reflex. * Close lid and pull lacrimal puncta medially. Preseptal fibers In front of the orbital septum Respond to voluntary blinking and sustained activity. * Pull lacrimal fascia laterally and create a relative vacuum in lacrimal sac-improve tear drainage. Orbital fibers Surrounds the orbital rims * Respond in forceful lid closure.
  49. 49. Upper lid versus lower lid during closing movements • Upper lid moves downwards (vertically) while the lower lid moves medially (horizontally). • The rate of movement of the upper lid and lower eyelids is similar during closing movement. • Closing movements of both upper and lower eyelids occur in phase, although the movement of the lower eyelid begins some 10-20 msec. before the movement can be detected in the upper lid. • Gravity does not play any role in downward movement of the upper eyelid during closing movement.(same speed regardless of the head position).
  50. 50. The reciprocal innervation pattern: • During closing movement the orbicularis gets maximum innervation while the levator gets minimum innervation and relaxes. (Sherrington’s low ).
  51. 51. • Blinking can be divided into voluntary and involuntary types. • The involuntary blinks are further subdivided into spontaneous and reflex blinks.
  52. 52. Spontaneous blinking • It is a common form of blinking that occurs without any obvious external stimulus or voluntary willed efforts.
  53. 53. • Spontaneous blinking does not occur or is very infrequent during the first few months of life; yet the delicate infant cornea does not suffer from dryness. • Average rate: 15 times per minute (12-20). • The blink rate is increased in: 1. Extremely dry conditions. 2. Strong air currents. 3. Certain emotional stress situations (surprise, anger, or fight). • A decreased blink rate occurs during times of visual observations.
  54. 54. • Duration: 0.3-0.4 second. • Present in the blind, hence no retinal stimulation is required. • No discontinuity of visual sensation during blinking. • The upper lid begins to close with no lower lid movement. • It is followed by a zipper-like movement from the lateral canthus towards the medial canthus. • This helps the displacement of the tear film to the lacrimal puncta which are located on the medial side of the lids.
  55. 55. Mechanism • The exact stimulus for spontaneous blinking is unknown. • Spontaneous blinks occurring without gaze shifts are triggered by a timing mechanism probably located in the brainstem.
  56. 56. Course of events: • Relaxation of the levator • After about 10 msec of levator relaxation, a train of high frequency synchronous activity occurs in the pretarsal portion of the orbicularis at a frequency of about 180/ sec which lasts some 55 msec. • As the upper lid moves vertically down, the lower lid moves medially in a horizontal direction. However, when the upper eyelid touches the lower eyelid; the downward movement of the upper lid is also transmitted to the lower lid, and after contact the lower lid moves down with the upper lid.
  57. 57. • During each blink, the upper eyelid covers the center of the pupil for a period of 0.10 sec. • Due to contraction of the preseptal fibers, as the upper eyelid reaches the limit of its downward excursion, electrical activity in the orbicularis ceases and concomitantly activity reappears in the levator.
  58. 58. Reflex blinking •reflexly in a response to a stimulus.
  59. 59. Different stimuli induce a different neurological pathway. Blinking reflex Examples Afferent Efferent Central connection Tactile Corneal touch CNV CNVII Cortical Dazzle (optic) Bright light CNII CNVII Subcortical Menace (optic) Sudden presence of near object CNII CNVII Cortical Auditory Loud noise CNVIII CNVII Subcortical Orbicularis Stretching of panorbital structure (tap/blow) CNV CNVII Cortical
  60. 60. Voluntary blinking and winking is a willed coordinated closure and opening movement of the eyelids in both eyes. • The voluntary blink is under the control of the individual (rate and degree of closure and opening). • It is produced as a protective gesture.
  61. 61. Winking is unilateral voluntary lid closure. • Part of facial expression. • It is a learned activity. • Occasionally, a subject may learn to wink with one eye but not with the other. • Minimum periods between winks are 0.3 sec. • Both are voluntary blinking and winking are produced by simultaneous contraction of palpebral and orbital portions of the orbicularis.
  62. 62. BELL’S PHENOMENON • It is a highly coordinated reflex between the facial and oculomotor nuclei, whereby on closure of the eyelids, the eyeball is rotated upward and outward. • This is a protective mechanism
  63. 63. • On closure of the eyelids, all the electrical activities in the levator cease and concomitantly the activity abruptly rises in the superior rectus muscle and is inhibited in the inferior rectus muscle. • Bell’s phenomenon is NOT present in 10% of otherwise healthy persons, and therefore its absence is not necessarily a sign of disease.