4. Embryology A-Fertilized ovum B-Morula C-Blastula Forebrain ,
midbrain and hind brain
5. Segmentation Maxillary process- lower eyelid(six weeks
gestation) Frontonasal process- upper eyelid (A) Eyelid fusion (8
to 10 weeks' gestation) (B) Development of margin structures (3 to
4 months' gestation); (C)Eyelid dysjunction (5 to 6
6. Lid fusion Lid structures gestation Lateral canthus 6 weeks
Fusion of eyelids 10 weeks Riolan muscle 12 weeks Hair bulbs of eye
lashes 12 weeks Mebomian glands 13 weeks Apocrine Molls gland 13-
16 weeks Sebaceous glands(Zeis) 13-16 weeks Levator palpebrae
superioris 10 weeks Separates from superior rectus 12-16 weeks
Desmosal adhesions are formed.
7. Lid dysjunction The epithelial adhesions break down at the
end of fifth month of gestation and completed by sixth month Causes
Holocrine production of lipids from the meibomian glands.
Keratinization of the lid margin. Pull of the developing eyelid
retractors.
8. Cryptophthalmia (ablepharon) Micro blepharia Lid
coloboma
9. Surface anatomy 8- 11mm 5mm 3mm The nasojugal fold Malar
fold Superior palpebral sulcus Inferior palpebral sulcus
10. 8-11mm 27-30mm Palpebral fissure Medial canthus Lateral
canthus 2mm 15mm The upper eyelid rests at the upper limbus in the
child and about 1 to 2 mm below the upper limbus in the adult. The
lower eyelid is generally found at the level of the lower
limbus.
11. Thyroid orbitopathy Horners syndrome
12. Structural layers Skin and sub cutaneous tissue Muscles of
protraction Orbital septum Orbital fat Muscles of retraction Tarsus
Conjunctiva Anterior lamella Posterior lamella Middle lamella
