Lecture 26 - Eye and Orbit Flashcards
What are the margins of the orbit?
Supraobital margin
- formed by the frontal bone
Infrobital margin
- zygomatic bone (laterally)
- maxilla (medially)
Why is the supraorbital notch imporatnt?
allows communication of nerves and BV going to the forehead
What bones form the orbit roof, floor, lateral and medial wall?
Roof
-Frontal bone
Floor
-maxilla
zygomatic, palatine
lateral Wall
Zygonmatic, greater wing of sphenoid
Medial wall
- maxilla, lacrimal bone, ethmoid, body of sphenoid
Which bones are likely to break in the orbit
thin and weak ones - lacrimal and part of the ethmoid
where is the optic canal located
Within the body of the sphenoid - for the optic nerve and its artery
Where is the superior orbital fissure?
in the sphenoid
Where is the inferior orbital fissure?
between sphenoid and maxilla
What are the 3 layers of the eye:
Outer coat:
cornea & sclera - strength
Middle: Uvea - nutrition
Inner: retina
describe the sclera
forms 5/6th of the eyeball
maintains the shape of the globe, offering resistance to internal and external forces
provides attachment for muscles
each collagen fibre forms in whirls - added strength than a parallel laydown like a ball of string
Describe the cornea
Anterior - 1/6th of eye
Prinicpal refrecting component of the eye
Avascular and transparent = optimum for vision
What is the structure of the cornea?
5 layers histologically
Epithelium Bowman's layer Stroma (large - collagenous) Desccment's membrane Endothelium
what percentage of light refraction occurs at the cornea?
60%
The stroma is continuous with the ..
.sclera (the collagen is continous)
the sclera and cornea(stroma) are..
pretty much the same histologically - yet one is transparent and one isn’t
What is the structure of collagen in the cornea?
uniform, evenly spaced
run in parallel - because it’s so ordered, provides transparency
Scleral opacity is affected by…
collagen fibres of different length, distribution - no order, looks white
Where is the anterior chamber
The anterior chamber (AC) is the fluid-filled space inside the eye between the iris and the cornea’s innermost surface, the endothelium.[1] Aqueous humor is the fluid that fills the anterior chamber. Hyphema and glaucoma are two main pathologies in this area. In hyphema, blood fills the anterior chamber. In glaucoma, blockage of the canal of Schlemm prevents the normal outflow of aqueous humor, resulting in accumulation of fluid, increased intraocular pressure, and eventually blindness.
