Week 1- Science Flashcards
Name the junction between the cornea and sclera
corneoscelral junction (limbus)
Where is the lacrimal gland located?
superolateral to eye
What are the two components of the fibrous layer of the eye?
Cornea
Sclera
Name the three parts of the uvea
Iris
Ciliary body
choroid
What is the purpose of the choroid?
Nutrition and gas exchange to eye
Which part of the eye is the posterior segment and which is the anterior segment?
anterior- anterior to lens
posterior- behind the lens and contains the vitreous humour
Name the fluid secreted by the ciliary body and name the structures it supplies with nourishment. Into what chamber is the fluid reabsorbed?
Aqueous humour
scleral venous sinus in the iridocorneal angle
Name the branch of the internal carotid artery (enters through carotid canal) which is the main blood supply to the eye. Through which foramen does this pass? Which arteries emerge from this artery to supply the choroid?
Ophthalmic artery
Optic canal
ciliary artery
What is the fundus?
The posterior area surface of the eye where light is focused.
Name the three veins which drain the orbit
superior ophthalmic
inferior ophthalmic
facial vein (valve less vein)
Name the 7 bones that make up the orbit
frontal maxilla zygomatic nasal sphenoid lacrimal ethmoid
What is a blowout fracture?
Fracture of the medial wall and orbital floor
Name the muscle responsible for the closing of the eyelids. Which nerve innervates it?
orbicularis oculi
CN VII
Name the muscle responsible for the opening of the eyelid.
levator palpebrae superioris
What nerve stimulates the lacrimal gland? What vessels drain the lacrimal fluid to the lacrimal sac?
Parasympathetic division of facial nerve
Lacrimal puncta
Name the 7 extraocular muscles
superior, inferior, medial and lateral rectus
superior and inferior oblique
levator palpebrae superioris
How are the extraocular nerves innervated
LR6 SO4 AO3
Lateral Rectus CNVI
Superior Orbital CNIV
All Others CNIII
What provides parasympathetic innervation to the eye?
Ciliary ganglion
What is the conjunctival fornix?
The folds that connect the conjunctival membrane lining the inside of the eyelid to the eye itself
What is the macula and the fovea?
Macula- area of greatest density of cones
Fovea- centre of macula
light from objects in the right visual field is processed by the ____primary visual cortex.
light from objects in the lower visual field is processed by the ______ part of the primary visual cortex.
left
upper
Which of the rectus muscles depress the eyeball and which elevate the eyeball?
elevation- superior rectus and inferior oblique
depression- inferior rectus and superior oblique
Name the three nerves that supply sensory innervation to the face
CNV1- Ophthalmic
CNV2- Maxillary
CNV3- mandibular
What reflex is blinking?
The corneal reflex
Corneal Reflex: Sensory (afferent) limb : Action potentials conducted from cornea via CN \_\_\_\_\_branches to \_\_\_\_\_\_\_\_\_\_\_ ganglion, then along CN V to pons. Motor (efferent) limb: Action potentials conducted via CN \_\_\_\_ To eyelid part of \_\_\_\_\_\_\_\_\_ oculi.
V1
Trigeminal
VII
Orbicularis
What is the vestibulo-occular reflex?
Where eyes turn in the opposite direction to the movement of the head to stabilize the gaze on a particular object.
What is the occulocardiac reflex?
Reflex bradycardia when strain on extraocular muscles
What is the effect of autonomic stimulation of the eye? 1.Sympathetic 2. Parasympathetic
- Dilate pupils- more light, eyes open wider (Levator palpebrae superioris), far vision, emotional tears
- Constrict pupils- less light, short vision, reflex lacrimation
After passing through the superior cervical ganglion how does sympathetic stimulation reach the levator palpebrae superioris?
Internal carotid nerve- internal carotid plexus- on ophthalmic artery and branches
Which muscles of the iris are stimulated by parasympathetic stimulation? What effect does this have?
Sphincter pupillae
constriction of the pupil
Sympathetic innervation innervates which muscle of the iris? When may the contraction of this muscle occur?
Dilator pupillae
sick patient, low light
What is the name for a non-physiologically 1. enlarged and 2. dilated pupil
- Mydriatic pupil
2. Miotic pupil
What may result in a pin-point pupil?
Pathological sign of opiate drugs
Sensory stimulation of the pupillary light reflex is from CN ____ and action is by CN _____
CNII
CNIII
Describe the components of the accommodation of far vision and near vision
Far vision- light arrives in parallel, ciliary muscle relaxes, suspensory ligaments taut, lens flattens
Near vision- light arrives at an angle, ciliary muscle contracts, suspensory ligaments lax, lens becomes spherical
Identify the three types of tears and their purposes
Basal tears- maintain corneal health- nourish and protect with lysosymes
Reflex tears- response to chemical/mechanical stimulation
Emotional tears
What is the origin of the rectus muscles?
Common tendinous ring which is attached to the sphenoid (the origin of the superior oblique)
What are the two parts of the orbicularis oculi?
Palpebral and orbital
Into which chamber does the nasolacrimal duct drain?
Inferior meatus
What muscle that is under sympathetic control opens the eyelid?
Mullers muscle
Name the two nuclei of the midbrain that are involved in the pupillary reflex. What is the afferent nerve and what is the efferent nerves?
Pretectal nucleus
Edinger-Westphal nucleus
Afferent- CNII
Efferent- CNIII
What is meant by consensual response? What about direct response?
Shining light in one eye causes equal constriction of the pupil in both eyes. Therefore Optic and Oculomotor are working
Direct is just testing a single eyes response
What is a RAPD?
Relative Afferent Pupillary Defect
Dilation in response to light to one of the eyes indicates defect of optic nerve
What secretes cerebrospinal fluid?
The secretory epithelium of the Choroid plexus
What are the three main functions of the cerebrospinal fluid?
Shock-absorbing protection of the brain
Homeostasis- pH effects pulmonary ventilation and cerebral blood flow
Circulation- medium for exchange of nutrients and waste products between blood and brain tissue
What is the choroid plexus?
Networks of capillaries in the walls of the cranial ventricles that secrete Cerebrospinal fluid
Through which foramen does the CSF drain into the subarachnoid space? Then where does the fluid drain?
Foramen of Luschka
Foramen of Magendie
Dural venous sinuses to heart and lungs
Name the barrier that separates the blood from the CSF
Blood-Brain barrier
Name the two layers which separate enclose the subarachnoid space
Pia Mater
Dura Mater
Name the three components that make up the blood brain barrier
Capillary endothelium
basement membrane
Perivascular astrocytes
What is hydrocephalus?
Accumulation of CSF in the ventricular system of the subarachnoid space (either due to obstruction or overproduction)
What is papilloedema?
Optic disc swelling due to increased intracranial pressure transmitted to the subarachnoid space surrounding the optic nerve.
The aqueous humour is secreted by the ________ _______ then it passes between the _____ and the _____ through the pupil into the scleral venous sinuses and (the canal of _______). This is located in the __________ angle.
Ciliary body lens iris Schlem Iridocorneal angle
Describe the formation of the aqueous humour
Fluid drains from the capillaries into the pigmented ciliary epithelial cells and then into the non-pigmented epithelial cells before draining into the anterior chamber of the eye.
What enzyme is inhibited to block aqueous humour production?
Carbonic anhydrase
The right and left eye have their own __________ visual fields and the area of overlap is their ___________ visual field.
Monocular
Binocular
The retina is divided in half at the _______ into the _______ and _______ visual fields.
fovea
temporal
nasal
What nucleus does the optic nerve pass through before reaching the striate cortex?
Lateral Geniculate Cortex
In the retina signals travel from the ___________ to the ___________ and then to the ___________. __________ cells and ____________ cells bridge between them.
photoreceptors bipolar cells ganglion cells Amacrine cells horizontal cells
At rest photoreceptors have a __________ Vm (_______ ________ __________) of around -20mv. With light exposure , Vm ____________. The positive Vm is because of the dark current, a __________ ____ channel that is _____ in the dark and closed in the light.
Depolarized
resting membrane potential
Hyperpolaizes
cGMP gated Na+ channel
In the dark, Na+ influx is _____to K+ efflux. In the light, Na+ influx is reduced and so ___ ______ causes hyperpolarisation.
equal
K+ efflux
What pigment is contained within the rods? What makes up this pigment?
Rhodopsin Retinal (derivative of vitamin A) and Opsin (GPCR)
Process of hyperpolarization: Light stimulates rhodopsin. All-trans-retinal activates _________. causes a molecular cascade that decreases _____ leading to closure of ______ gated Na+ ion channel leading to ________________.
Transducin
cGMP
cGMP
Hyperpolarization
Define visual acuity? What determines this?
The ability to distinguish between two near points. Determined largely by photoreceptor spacing and refractive power.
Unlike cone cells, a number of rod cells converge on a single ganglion cell. This high __________ results in increased _________ to light but decreased __________.
Convergence
Sensitivity
Acuity
Which three types of cone cells are there?
Those that detect Red, blue and green light
What is the most commonly used topical antibiotic in ophthalmology? What is its mode of action?
Chloramphenicol
Inhibits peptidyl Transferase enzyme preventing protein synthesis
Give three possible side effects of chloramphenicol
Allergic reaction
Grey baby syndrome in neonates
irreversible aplastic anaemia
Name two types of antibiotics that inhibit cell wall synthesis and have a beta lactam ring
Penicillins
cephalosporins
Name the four layers of the meninges
Dura mater
arachnoid mater
subarachnoid space
pia mater
Which cranial nerve innervates the dura mater?
CNV Trigeminal
At what vertebral level does the subarachnoid space end?
S2
Name the septa that divides the two cerebral hemispheres
Flax cerebri
Name the septa that creates the supratentorial and infratentorial space
Tentorium cerebelli
Name the vessels enclosed by the dura mater
Dural venous sinuses
How is it best to extract a sample of the CSF from the subarachnoid space?
Lumbar puncture at L3/L4 or L4/L5 IV disc.
How many ventricles are in the cranium?
4 ventricles
Right and left lateral
3rd ventricle
4th ventricle
Name the channel that connects the 3rd ventricle to the fourth ventricle.
cerebral aqueduct
Where is the choroid plexus located?
The right and left lateral ventricles and the 3rd ventricle
How is CSF reabsorbed?
It is reabsorbed by the arachnoid granulations into the Dural venous sinuses.
Broadly speaking identify 4 possible adverse effects of raised intracranial pressure
Damage to tissues
shifts in tissues
herniation
compression of blood vessels
How come the optic nerve can be effected by increased intracranial pressure?
It is also surrounded by the meninges and so the subarachnoid space can fill with excess fluid and effect the nerve
As well as compressing the optic nerve, what else is compressed in papilloedema?
The central vein and artery of the retina
What are the effects of Oculomotor nerve compression?
Ptosis- Levator palpebrae superioris paralysis
Inferolateral gaze- extraocular muscles paralysis
dilated pupil- Sphincter pupillae paralysis
What is ptosis?
A droopy eyelid
What would a presentation of abducent nerve palsy look like?
Medial deviation of the eye
Name some of the chemical properties of the tears that make them useful in providing immune protection
Lyzozymes- anti gram - bacteria lactoferrin and transferrin- anti gram + bacteria tear lipids- antimicrobial angiogenin- antimicrobial secretory IgA interleukins complement proteins
What immune cells are found in the tears?
Neutrophils, macrophages, conjunctival mast cells Langerhans cells (principle APC of external eye)
What are Langerhans cells and where are they situated?
Antigen Presenting cells found mainly in the corneoscleral limbus
Which part of the eye possesses lymphatic drainage
Conjunctiva only
Both the lacrimal drainage system and the Conjunctiva possess _______ __________ _________ __________.
Mucosa Associated Lymphoid Tissue (MALT)
Apart from the conjunctiva, tears, lacrimal glands and lacrimal drainage system, the rest of the eye has a ______________ ________ ___________. Therefore there is the potential for severe damage
Downregulated immune environment
What is meant by immune privilege?
They are tissues that are able to tolerate the introduction of antigens without eliciting an inflammatory immune response
Which five sites in the eye are said to be immune privileged?
cornea subretinal space lens anterior chamber vitreous cavity
Identify 4 characteristics of occular immune privilege
blood-tissue barrier
lack of direct lymphatic drainage
immunosuppressive molecules
inhibitory cell surface molecules
Identify the four types of hypersensitivity reactions- what cells are used in each?
1- Immediate hypersensitivity- mast cells, B and T cells
2- cytotoxic- Macrophages, NK cells, Complement proteins
3- Immune complex mediated- Antibodies form B cells
4- delayed type hypersensitivity- T helper cells
What type of hypersensitivity is shown in the following: 1. Corneal graft melting 2. Corneal graft rejection
- Type III
2. Type IV
In what way is the lens similar to the skin?
The cell matures and its contents (nucleus etc) is replaced leaving behind a fibrous outline
Identify some factors that effect corneal penetration
It is a lipid (epithelium) : water (stroma) : lipid (epithelium)
Lipid soluble drugs penetrate lipid layer (epithelium)
Water soluble drugs penetrate water layer stroma
What makes Chloramphenicol suitable for corneal penetration?
Possess’ both hydrophilic and lipophilic properties
What is added to topical steroids to make them 1. hydrophobic and 2. Hydrophilic
- Alcohol or acetone
2. Phosphate
Name a preservative that is used to enhance corneal penetration
Benzalkonium Chloride
State a simple way of avoiding systemic absorption of topical steroids to the eye.
Occlusion of the lacrimal puncta using fingers
State 5 routes of ophthalmic drug administration
Topical (drops/ointment) subconjunctival subtenons- between capsule and sclera intravitreal- into vitreous humour intracameral- into anterior chamber
Identify three local side effects to topical steroid use in the eye
Cataracts
glaucoma
exacerbate viral infection
Identify some steroid eye drops used in ophthalmology
FML (Fluorometholone) Prednisolone phosphate prednisolone acetate betamethasone dexamethasone
How does local anaesthetic act?
Blocks sodium channels thus impeding nerve conduction
Name the main diagnostic dye used in ophthalmology
Fluorescein
Give 6 uses of fluorescein
Show corneal abrasion dendritic ulcers identify leaks tonometry angiography diagnosing nasolacrimal duct obstruction
Name two mydriatic drugs
tropicamide
cyclopentolate
Give two possible side effects of mydriatic drugs
blurring of vision
AACG
How do mydriatic drugs cause pupil dilation
Block parasympathetic supply to iris
What type of drugs result in a miotic pupil?
Sympathomimetics
