Orbit (Viva)

ORBIT


Q.1 Name the different layers of the eyelid.

  • Skin
  • Superficial fascia (has no fat).
  • Palpebral part of orbicularis oculi muscle.
  • Palpebral fascia.
  • Tarsal glands.
  • Palpebral conjunctiva

Q.2 What are the glands found in eyelid? 

  •  Zeis’s glands:
    Large sebaceous glands of cilia. Found at lid margin.
  • Ciliary glands of Moll:
    Sweat glands. Present at the lid margin.
  • Meibomian glands (Tarsal glands):
    Sebaceous glands. Present in the posterior surface of tarsi.

Q.3 What are the modifications of palpebral fascia?

  • Tarsal plates, in the lids: Tarsal plates are attached to the orbital margin by orbital septum.
  • Palpebral ligament, at the angles: Attached to walls of orbit, just inside orbital margin.

Q.4 What is the nerve supply of eyelids?

  • Upper eyelid and whole of bulbar conjunctiva:
    Supratrochlear, infratrochlear, lacrimal, and supraorbital nerves (Branches of the ophthalmic nerve).

  • Lower eyelid:
    Infraorbital and infratrochlear nerve (Branch of maxillary nerve).

Q.5 What is Chalazion?

It is chronic inflammation of the tarsal gland, causing localized swelling.

Q.6 What is Stye?

It is an infection of Zeis’s gland. The lid margin is oedematous and the gland is swollen and painful.

 Q.7 What are the constituents of the lacrimal apparatus?

  • Lacrimal gland and its ducts.
  • Conjunctival sac
  • Lacrimal puncta and lacrimal canaliculi
  • Lacrimal sac and
  • Nasolacrimal duct

Q.8 What is the nature of the lacrimal gland?

Exocrine and serous.

Q.9 What are the parts of the lacrimal gland?

  • Orbital part: Larger, in lacrimal fossa in the upper lateral part of the orbit.
  • Palpebral part: Smaller, in upper eyelid. It drains into superior conjunctival fornix through twelve ducts.

Q.9 Why the removal of palpebral part of the gland is equivalent to functional removal of the whole gland?

Because the ducts of the orbital part also pass through the palpebral part. So when palpebral part is removed the secretions of orbital part cannot be drained.

Q.10 What is the advantage of the blinking of lids?

It helps to spread the lacrimal fluid in front of the eye and deep surface of lids, thus keep the conjunctiva and cornea moist.

Q.11 What is the valve of Hasner?

It is a fold of mucous membrane at the lower end of the nasolacrimal duct.

Q.12 What is Epiphora?

Leakage of tears down the face, due to the blockade of the nasolacrimal duct.

Q.13 What is Tenon’s Sheath?

It is a thin membranous sheath around the eyeball. Extends from optic nerve to sclerocorneal junction. Eyeball can move freely within it.

Q.14 Name the structures piercing the fascial sheath of the eyeball.

  • Tendons of extra-ocular muscles
  • Ciliary vessels
  • Ciliary nerves.

Q.15 What is the suspensory ligament of Lockwood?

It is thickened Tenon’s capsule in the lower part. Formed by the union of margins of the sheath of inferior rectus and inferior oblique with medial and lateral check ligaments.

Q.16 Name the extra-ocular muscles?

 Voluntary muscles:

  • Rectus: Superior rectus Inferior rectus Medial rectus Lateral rectus
  • Oblique: Superior oblique Inferior oblique
  • Levator palpebrae superioris

Involuntary muscles:

  • Superior tarsal
  • Inferior tarsal
  • Orbitalis 

Q.17 What is the origin of rectus muscles?

They arise from the corresponding part of the common tendinous ring which surrounds the optic canal and encloses a part of the superior orbital fissure.

Q.18 What is the origin of oblique muscles?

Superior oblique: Body of sphenoid above and medial to optic canal.

Inferior oblique: Anterior and medial part of the floor of orbit from maxilla just lateral to nasolacrimal groove.

Q.19 Which muscles produce the different movements of the eyeball?

Upwards:
Superior rectus, Inferior oblique
Downwards:
Inferior rectus, Superior oblique
Inwards:
Medial rectus, Superior rectus, Inferior rectus
Outwards:
Lateral rectus, Superior oblique, Inferior oblique
Extorsion:
Inferior oblique, Inferior rectus
Intorsion:
Superior oblique, Superior rectus.


Q.20 What is the nerve supply of extraocular muscles?

Superior oblique: Trochlear nerve
Lateral rectus: Abducent nerve
Superior, inferior and medial rectus, inferior oblique and levator: Oculomotor nerve.
Involuntary muscles: By sympathetic fibers

 

Q.21 What are conjugate movements of the eye?

The normal co-ordinated movements of both eyes are called conjugate movements. These are usually horizontal and vertical.

Q.22 What is Nystagmus?

It is involuntary rhythmical oscillatory movements of the eye due to incoordination of ocular muscles.

Q.23 What is Squint?

It is the abnormal deviation of the eye due to weakness or paralysis of a muscle.