Cornea
thinnest in center
0.5 - 0.6 mm
thickest in periphery
1.2 mm
vertical diameter
10.6 mm
horizontal diameter
11.7 mm
radius of curvature
7.8 mm (anterior)
6.5 mm (posterior)
stroma thickness
90% of cornea
endothelium at birth
one million cells or
Sclera
thickest
around optic disc (1mm)
thinnest
behind recti insertion (0.3mm)
anterior ciliary artery penetrates sclera 4 mm from
limbus
vortex vein exists sclera 4 mm behind the equator
Retina
retinal pigment epithelium
1 million cells
rods
120 millions
cones
6 millions
ganglion cells
1 million
X cells
Y cells
size
smaller cells
larger cells
field
small
large
pathway
parvocellular
magnocellular
function
colour & sharp image
moving object
& flicker
Lateral geniculate body
layer 1 and 2
magnocellular pathway
layer 3 to 6
parvocellular pathway
layers 1,4 & 6
contralateral nasal retina
layers 2, 3 & 5
ipsilateral temporal retina
Extraocular muscles
longest rectus
superior rectus
rectus with longest tendon
lateral rectus
shortest rectus
inferior rectus
rectus with the shortest tendon
medial rectus
all recti receive two anterior ciliary artery except
lateral rectus which has one
all recti arise from tendinous ring but lateral recti
also has origin from the greater wing of sphenoid
Anatomy of head and neck
The section on head and neck in Snell's Textbook of Anatomy is the
recommended reading. In addition , MCQs on head and neck found in many
anatomy and primary FRCS books provide good practice. The following topics
relate to central nervous system which many candidates forget to revise