Anteroposterior stability of eye ball is provided by all except:
Correct Answer: Suspensory ligament of the eye ball
Description: A. i.e. Suspensory ligament of eye Suspensory ligament of Lockwood provides inferior (not anteroposterior) stabilityQ. The posterior displacement of eye is prevented by - orbital fat, forward pull of oblique muscles and bony attachment of recto. Fascia Bulbi (Tenon's capsule) It is thin fibrous membrane that envelops the globe from margin of cornea to the optic nerve. Its inner surface is connected to sclera by fine trabeculae. Probably slight movements may take place b/w the globe and capsule but in more extensive movements the globe & capsule more together in surrounding fat. Anteriorly it merges gradually into subconjunctival tissue Posteriorly it is in contact with orbital fat and around the optic nerve it fuses with dural sheath of optic nerve Lower pa of fascia bulbi (Tenon's capsule) is thickened to form a sling or hammock on which globe rests, which is known as suspensory ligament of Lockwood. That it is effective in suppoing the eye is shown by the fact that the globe does not sink down after maxillectomy (surgical) or fractures of orbital floor, if the suspensory ligament remains intact. Fascia bulbi is pierced by optic nerve & ciliary vessels and nerve (posteriorly) Voex veins (just behind equator) and 6 extinsic ocular muscles (anteriorly) The extraocular muscles do not perforate the capsule but invaginate (pierce) it and fascia send a tubular reflection backwards which clothes muscle like fingers of a glove. This muscle expansion of lateral & medial rectus are attached to orbital tubercles on zygomatic bone and lacrimal bone respectively. These are also called lateral & medial check ligaments. These expansions are strong and to some extent limit the action of the muscles. They are there fore called check ligaments. Muscle expansion of superior rectus is attached to LPS (levator palpebrae superioris) and form superior transverse ligament of whitnall to ensure the synergic action of two muscles. Thus when the superior rectus makes the eye look upwards, the upper lid is raised as well. Expansion from inferior rectus is attached to capsulopalpebral fasciae or whitnall ligament (b/w tarsal plate & orbicularis oculi), a tissue analogue to LPS in the lower lid. Conjoint fascia of inferior rectus & oblique form suspensory ligament of Lockwood. Superior oblique expansion passes unto its trochlea & inferior oblique expansion passes to floor of orbit (lateral pa).
Category:
Ophthalmology
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