Ophthalmology Anatomy Flashcards
what is covered by the cornea?
iris
what are visible the blood vessels in the eyes called?
conjunctival vessels
where does the lacrimal fluid collect?
lacrimal lake
what are the small holes in the eyelids?
lacrimal punctum
what is the raised part of the eyelid that the punctum are on?
lacrimal papilla
junction between bulbar and palpebral conjunctiva
conjunctival cortex
what is lined by the conjunctiva?
sclera
what is the name of the corneoscleral junction?
limbus
where is the lacrimal gland located?
superolaterally
where is the nasolacrimal duct located?
inferomedially
three layers of eye
outer fibrous, middle vascular (uvea), inner retina (photosensitive)
two parts of outer fibrous layer
sclera and cornea
function of sclera
muscle attachment
function of cornea
2/3 of refractive power
three parts of uvea
iris, ciliary body, choroid
function of iris
control pupil diameter
function of ciliary body
controls iris, shape of lens, secretion of aqueous humour
function of choroid
nutrition and gas exchange
what does anterior segment contain?
aqueous humour
what is the anterior segment divided into?
anterior and posterior chambers
2 facts about posterior segment
posterior 2/3 of the eye, behind lens
what does the posterior segment of the eye secrete?
vitreous humour
what is the vitreous body?
made up of vitreous humour
path of aqueous humour
ciliary body –> posterior chamber –> anterior chamber –> canal of Schlemm –> venous system
what controls the release of aqueous humour into the venous system?
iridocorneal angle
artery that supplies the eye
ophthalmic artery
nerve that supplies the eye
optic nerve (CNII)
2 important branches of ophthalmic artery
forehead (scalp) branches and ciliary branches
what 3 veins does the orbit drain into?
superior ophthalmic vein, inferior ophthalmic vein, facial vein (anteriorly)
components of fundus
optic disc, macula, fovea,
function of fundus
posterior area where light is focussed
3 functions of optic disc
point of CNII formation, only point of entry/exit for blood vessels and axons of CNII, blind spot
what does the macula contain?
greatest density of cones
2 facts about fovea
1.5mm diameter depression, area of most acute vision
where is the fovea located?
centre of macula
3 layers of retina
photoreceptors, ganglion cells, axons of ganglion cells
are there photoreceptors in the optic disc?
no
features of fundoscopy
optic disc, central artery and vein of retina, nasal retina, temporal retina, branches of retinal vessels, macula of retina
where is light from objects in the left visual field processed?
right visual cortex
where is light from objects in the right visual field processed?
left visual cortex
transverse axis of eye movement
abduction/adduction
vertical axis of eye movement
elevation/depression
anteroposterior axis of eye movement
intorsion/extorsion
movement of lateral rectus
abduction of eyeball
nerve supply of lateral rectus
CNVI
movement of medial rectus
adduction of eyeball
nerve supply of medial rectus
CNIII
movement of superior oblique
depression of eyeball in adduction
nerve supply of superior oblique
CNIV
movement of inferior oblique
elevation of eyeball in adduction
nerve supply of inferior oblique
CNIII
movement of superior rectus
elevation of eyeball in abduction
nerve supply of superior rectus
CNIII
movement of inferior rectus
depression of eyeball in abduction
nerve supply of inferior rectus
CNIII
7 bones that make up the orbit
frontal, lacrimal, ethmoid, maxilla, zygomatic, sphenoid, palatine
is the apex of the orbital pyramid anterior or posterior?
posterior
is the base of the orbital pyramid anterior or posterior?
anterior
what are the 4 margins of the base of the orbital pyramid?
lateral, medial, superior, inferior
axis of orbit
anterolateral
axis of eyeball
anterior
blowout fractures involve…
medial wall and orbital floor
where is the outside of the orbit most likely to fracture?
suture
two parts of orbicularis oculi
palpebral and orbital
function of orbital part of orbicularis oculi
forced closing of the eye
function of palpebral part of orbicularis oculi
blinking
nerve supply of orbicularis oculi
CNVII
6 ligaments of eyelids
lateral palpebral, medial palpebral, superior tarsus, inferior tarsus, tendon of LPS, orbital septum
superior tarsus muscle aka
Mueller’s muscle
tarsal glands aka
Meibomian glands
function of Meibomian glands
lipid secretion
innervation of the lacrimal gland
CNVII (parasympathetic)
where does lacrimal fluid collect?
lacrimal lake
where does lacrimal fluid drain?
lacrimal puncta
where does lacrimal fluid go after draining through the lacrimal puncta?
lacrimal sac and nasolacrimal duct
insertion of rectus and oblique muscles
sclera
origin of rectus muscles
common tendinous ring
origin of oblique muscles
sphenoid bone
origin of LPS
lesser wing of sphenoid
insertion of LPS
skin and tarsus of superior eyelid
afferent nerve involved in blink reflex
CNV1
efferent nerve involved in blink reflex
CNVII
oculocardiac reflex
reflex bradycardia in response to tension on extraocular muscles or pressure on eyes
4 sympathetic reflexes of the eye
open eyes wider, pupillary dilatation, emotional lacrimation, focus on far objects
3 parasympathetic reflexes of the eye
pupillary constriction, reflex lacrimation, focus on near objects
innervation of LPS
CNIII (sympathetic)
muscle that constricts pupil
sphincter pupillae
muscle that dilates pupil
dilator pupillae
sphincter pupillae fibres encircle…
internal circumference of iris
origin of dilator pupillae
external circumference of iris
insertion of dilator pupillae
internal circumference of iris
which end of dilator pupillae is mobile?
internal circumference of iris
non-physiologically enlarged pupil
mydriatic pupil
non-physiologically constricted pupil
miotic pupil
fixed-dilated/blown pupil indicates…
CNIII pathology
fixed pin-point pupil indicates…
opiate drugs
sensory component of pupillary light reflex
ipsilateral CNII
motor component of pupillary light reflex
bilateral CNIII
light reflex in stimulated eye
direct
light reflex in non-stimulated eye
consensual
3 steps of first neurones in light reflex
- retinal ganglion cells pass via ipsilateral optic nerve
- decussate in optic chiasm
- synapse in pretectal nucleus in midbrain
path of second neurones in light reflex
pretectal nucleus to Edinger-Westphal nucleus
path of third neurones in light reflex
Edinger-Westphal nucleus via CNIII (inferior division) to synapse in ciliary ganglion
path of fourth neurones in light reflex
supply sphincter pupillae muscles via short ciliary nerves
what does ciliary muscle do in far vision?
relaxes
what does ciliary muscle do in near vision
contracts
innervation of ciliary muscle
CNIII
three types of tears
basal, reflex, emotional
basal tears
corneal health, clean, nourish and hydrate avascular cornea, contain lysozymes to hydrolyse bacterial walls
reflex tears
extra tears in response to mechanical or chemical stimulation
afferent nerve of reflex tears
CNV1 (from cornea/conjunctiva)
efferent nerve of reflex tears
CNVII (parasympathetic)
branch of CNVII that carries parasympathetic axons to lacrimal gland
greater petrosal nerve
3 steps of route of presynaptic sympathetic axons from CNS to head and neck
- exit spinal cord at T1
- ascend within sympathetic chain
- synapse in superior cervical ganglion
4 steps of route of postsynaptic sympathetic axons from CNS to head and neck
- enter external and internal carotid nerves
- pass onto surface of external and internal carotid arteries
- carried to organs of head and neck from branches of these arteries
- ophthalmic artery carries axons to the orbit
what do the parasympathetic ganglia in the head supply?
eye, lacrimal gland, salivary glands
what does the vagus nerve supply?
organs of neck, chest and abdomen as far as midgut
what do the sacral spinal nerves supply?
hindgut, pelvis, perineum
do parasympathetic fibres synapse in the ciliary ganglion?
yes
do sympathetic fibres synapse in the ciliary ganglion?
no
where is the ciliary ganglion located?
bony orbit
what fibres contribute to the ciliary ganglion?
CNIII
where does CNIII connect with CNS?
junction of midbrain and pons
what sinus does CNIII pass through?
cavernous sinus
what does CNIII supply?
somatic motor to majority of extraocular muscles, presynaptic parasympathetic axons to ciliary ganglion
2 divisions of CNIII
superior and inferior
4 layers of meninges
dura mater, arachnoid mater, subarachnoid space, pia mater
sensory supply of dura mater
CNV
function of dura mater
encloses venous sinuses
what does arachnoid mater contain?
arachnoid granulations
what is in the subarachnoid space?
circulating CSF and blood vessels
what does pia mater adhere to?
brain and entering/leaving vessels/nerves
how to access CSF
lumbar puncture at L3/4/5 IV disc levels
where does subarachnoid space end inferiorly?
L2
what does the subarachnoid space communicate with at specific areas in the brain?
ventricles
6 ventricles of the brain
right lateral, left lateral, midline 3rd, midline 4th, cerebral aqueduct, central canal
8 steps of CSF circulation
- secreted by choroid plexus
- through right and left lateral ventricles
- through midline 3rd ventricle
- through cerebral aqueduct
- through midline 4th ventricle
- mainly into subarachnoid space, but some into central canal
- reabsorbed in arachnoid granulations
- into dural venous sinuses
function of arachnoid granulations
reabsorb CSF
Monro-Kellie hypothesis
if one structure in the brain increases in volume, the others must decrease in volume to compensate
what percentage of patients with ICP report visual problems?
65-75%
at what ICP is intervention required?
> 20mmHg
optic discs specifically due to raised ICP
papilloedema
what can brain herniate through in raised ICP?
dural septae
4 sections of cranial cavity created by dural septae
falx cerebri, falx cerebelli, diaphragma sellae, tentorium cerebelli
what nerve is damaged in a ‘down and out’ eye?
CNIII
what nerve is damaged if the eye cannot move inferomedially?
CNIV
what nerve is damaged in medial deviation of the eye?
CNVI
which component of the blood-ocular barrier is located in the anterior segment of the eye?
blood-aqueous barrier
which component of the blood-ocular barrier is located in the posterior segment of the eye?
blood-retinal barrier
is epithelium hydrophilic or hydrophobic?
hydrophobic/lipophilic
is stroma hydrophilic or hydrophobic?
hydrophilic/lipophobic
3 major functions of CSF
mechanical protection, homeostatic function, circulation
specialised cells that secrete CSF
choroidal cells
networks of capillaries in the walls of brain ventricles
choroid plexus
what ions are transported in CSF secretion?
sodium, chloride, bicarbonate
does CSF secretion depend on other external factors?
no
where does CSF return to venous circulation?
superior sagittal sinus (SSS)
how does CSF get into SSS?
arachnoid granulations
what restricts the blood supply to the brain?
blood-brain barrier (BBB)
what is the site of the BBB?
endothelial cells of capillaries
3 components of BBB
capillary endothelium, basal membrane, perivascular astrocytes
2 parts of the brain that don’t have a BBB
circumventricular organs, pineal gland
3 types of tumours of choroid plexus, CSF and ventricles
colloid cyst, ependymomas, choroid plexus tumours
3 types of ventricular haemorrhages
epidural haematoma, subdural haematoma, subarachnoid haematoma
where is aqueous humour produced?
ciliary body
what vitamin is a powerful antioxidant in the eyes?
vitamin C (ascorbate)
two layers of ciliary epithelium
pigment epithelium of retina (PE), nonpigmented epithelium (NPE)
what ions have a net movement through PE and NPE during aqueous humour production?
Cl- and Na+
what drugs can be used to block production of aqueous humour?
carbonic anhydrase (CA) inhibitors
name 2 CA inhibitors
dorzolamide and acetazolamide
what is the scope of the visual field
150 degrees
hemiretina from fovea to nose
nasal hemiretina
hemiretina from fovea to temporal bone
temporal hemiretina
Hebb’s postulate
when an axon of cell A is near enough to excite cell B on a regular basis, its efficiency to excite cell B increases
3 steps in pathway for signal transmission
photoreceptors –> bipolar cells –> ganglion cells
receive input from photoreceptors and project to other photoreceptors and bipolar cells
horizontal cells
receive input from bipolar cells and project to ganglion cells, bipolar cells and other cells of their own type
amacrine cells
conversion of electromagnetic radiation to neural signals
transduction
4 regions of a photoreceptor cell
outer segment, inner segment, cell body, synaptic terminal
glutamate level in low light levels in dark current channel
higher
glutamate level in high light levels in dark current channel
lower
resting membrane potential of a photoreceptor
~-20mV
potential of sodium and potassium in the dark
equal
potential of sodium and potassium in response to light
potassium is higher
2 components of rhodopsin
retinal + opsin
what is retinal?
vitamin A derivative
what is opsin?
G-protein coupled receptor
what does light to do rhodopsin?
converts 11-cis-retinal to all-trans-retinal
4 steps to molecular mechanism of eyes
- rhodopsin activates transducin
- transducin activates phosphodiesterase
- phosphodiesterase hydrolyses cGMP
- reduced concentration of cGMP leads to closure of sodium channels
what is the high gain mechanism?
1 opsin activates 1000 transducin
1 PDE hydrolyses 1000 cGMP
which photoreceptor is associated with dark current channels?
rods
which photoreceptor is associated with light current channel?
cones
glutamate level in high light levels in light current channel
higher
glutamate level in low light levels in light current channel
lower
the ability to distinguish between two nearby points
visual acuity
what determines visual acuity?
photoreceptor spacing
which type of photoreceptor is concentrated at the fovea?
cones
where are rods distributed?
all over the eye
which type of photoreceptor has high convergence?
rods
which type of photoreceptor has low convergence?
cones
which type of photoreceptor has high light sensitivity?
rods
which type of photoreceptor has low light sensitivity?
cones
which type of photoreceptor has low visual acuity?
rods
which type of photoreceptor has high visual acuity?
cones
