THE EYE AND THE VISUAL PATHWAYS Flashcards
The eye balls sits in the bony orbit of the skull. Using the labels below, label the bones that make up the bony orbit.
- ethmoid bone
- sphenoid bone
- lacrimal bone
- maxillary bone
- zygomatic bone
- frontal bone
1 = frontal bone 2 = sphenoid bone 3 = lacrimal bone 4 = ethmoid bone 5 = maxillary bone 6 = zygomatic bone
The eye ball is held in place by 2 ligaments, what are they called?
1 - lateral check ligament
2 - medial check ligament
The eye ball is surrounded by fatty tissue to help maintain stability. What is this tissue called?
1 - periorbital fat
2 - fat pads
3 - visceral fat
4 - subcutaneous fat
1 - periorbital fat
There are 3 layers of the eye, what are they called?
1 - fibrous, inferior and nervous tunic
2 - fibrous, peripheral and nervous tunic
3 - fibrous, vascular and nervous tunic
4 - cartilaginous, vascular and nervous tunic
3 - fibrous, vascular and nervous tunic
There are 3 layers of the eye, what is the order from the front of the eye to the back of the eye, using the labels below:
vascular tunic
fibrous tunic
nervous tunic
- front = fibrous
- middle = vascular
- back = nervous
The fibrous tunic is the front layer of the eye. This layer has 2 parts what are they?
1 - iris and sclera
2 - sclera and cornea
3 - cornea and sclera
4 - cornea and retina
3 - cornea and sclera
- sclera = white fibrous tissue
- cornea = clear part of eye protecting interior of eye
The vascular tunic is the middle layer of the eye. This layer has 3 parts, using the labels below labels numbers 1-3:
- iris
- choroid
- ciliary body
1 - iris = coloured area, controls amount of light entering the eye.
2 - choroid = connective tissue
3 - ciliary body = produces fluid in eye and contains ciliary muscle
The nervous tunic is the back layer of the eye and contains the retina. The retina has 2 parts what are they?
1 - pigmented and macula layer
2 - pigmented and neural layer
3 - fovea and neural layer
4 - pigmented and cup layer
2 - pigmented and neural layer
- pigmented layer = regeneration, nutrition and support
- neural layer = converts signals into electric signals
The sclera forms 3/5ths of the outer layer of the eye and is part of the fibrous tunic. It is fibrous tissue and is avascular. What are the 3 main functions of the sclera?
1 - attachments to muscles of the eyes, immunity, structural support
2 - attachments to muscles of the eyes, nutrition, structural support
3 - attachments to muscles of the eyes, blood supply, structural support
4 - attachments to muscles of the eyes, protection, structural support
4 - attachments to muscles of the eyes, protection, structural support
What is the name of the junction where the 3/5ths of the sclera and the cornea meet?
1 - cornea junction
2 - sclera junction
3 - corneal scleral junction
3 - corneal scleral junction
Tenons capsule sits over the sclera and covers the eyeball. What is its function?
- allows the conjunctiva to slide over the sclera
The cornea makes up 2/3rds of the outer layer of the eye the fibrous tunic, is transparent, avascular and very sensitive. It is composed of 5 layers. using the labels below, label the image:
- Epithelial layer
- Bowman’s membrane
- Stroma
- Descemet’s membrane
- Endothelium
1 = Bowman’s membrane 2 = Epithelial layer 3 = Descemet’s membrane 4 = Endothelium 5 = Stroma
The corneal reflex, also known as the blink reflex or eyelid reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), and could result from any peripheral stimulus. Which cranial nerves are involved in this reflex?
1 - CN I and V
2 - CN III and IV
3 - CN V and VI
4 - CN V and VII
4 - CN V and VII
- Afferent branch: CN V (5) region 1 (Ophthalmic) stimulus that cornea is being touched
- Efferent branch: CN VII (Facial) contracts orbicularis oculi muscle of eye to close the eye
The cornea makes up 2/3rds of the outer layer of the eye the fibrous tunic, is transparent, avascular and very sensitive. It is composed of 5 layers. Why is the cornea transparent?
- allows light to pass into the pupil
The iris is the coloured part of the eye. The muscles of the iris, namely the circular pupil muscles (contraction) and radial (dilator) pupil muscles change the size of the iris in response to light. What do these muscles do if there is too much or too little light?
- too much = circular pupil muscles contract and iris shrinks
- too little = radial (dilator) pupil muscles contract and iris grows
The iris is the coloured part of the eye. How does the iris get different colours?
- genes on chromosomes generate eye colour
- amount of pigments called melanin determine eye colour (larger amounts = darker eyes)
The eye has 3 chambers. From front to back what are they?
1 - media, posterior and vitreous (greek for glass like) chamber
2 - anterior, lateral and vitreous (greek for glass like) chamber
3 - anterior, posterior and vitreous (greek for glass like) chamber
4 - anterior, posterior and medial chamber
3 - anterior, posterior and vitreous (greek for glass like) chamber
The eye has 3 chambers. From front to back they are:
1 - anterior chamber
2 - posterior chamber
3 - vitreous (greek for glass like) chamber
What separates the anterior and posterior chambers?
- iris
The middle layer of the eye is called the vascular layer. One part is called the ciliary body, which contain ciliary muscle and the ciliary processes. What is the function of the ciliary muscles?
- contributes to changing the shape of the lens (flatter or rounder)
- involved in the accommodation reflex (lens thickening, pupillary constriction, and inward rotation of the eyes)
The middle layer of the eye, called the vascular layer. One part is called the ciliary body, which contain ciliary muscle and the ciliary processes. The ciliary muscles contribute to changing the shape of the lens, which is involved in the accommodation reflex. What is the accommodation reflex?
- a three-part reflex
- function is to bring near objects into focus through lens thickening, pupillary constriction, and inward rotation of the eyes
- essentially its cross eyes
The middle layer of the eye, called the vascular layer. One part is called the ciliary body, which contain ciliary muscle and the ciliary processes. The ciliary processes attach to the ciliary ligaments to the ciliary muscles and the other end of the ciliary ligaments attaches to what?
- the lens
- hold lens in place and help it change shape
The middle layer of the eye, called the vascular layer. One part is called the ciliary body, which contain ciliary muscle and the ciliary processes. In addition to connecting to suspensory ligaments that attach to the lens, holding the lens in place and helping it change shape, the ciliary processes also secrete what?
- aqueous humor into anterior chamber (supplies nutrients to lens and cornea)
The middle layer of the eye, called the vascular layer. There are 2 parts called the ciliary body and choroid. The choroid (greek for membrane) is a highly vascular area. What is the function of the choroid?
- contains blood vessels that provide nutrients and O2 to retina
- absorbs light preventing scattered light from reaching the retina
Once light passes through the cornea and iris, what is the next structure it will come into contact with?
- the biconvex (curved on both sides) lens
The middle layer of the eye, called the vascular layer. There are 2 parts called the ciliary body and choroid. The choroid is a highly vascular area providing nutrients and oxygen to retina and prevents scattered light from reaching the retina. Why does the choroid prevent light scattering and reaching the retina?
- it is a dark colour
- it absorbs the light
When light passes through the cornea, iris and lens it reaches retina. There are the 4 basic layers of the retina, label them in the image below:
- photoreceptors (rods and cones)
- ganglion cells
- pigmented epithelial layer
- bipolar cells
1 - ganglion cells
2 - bipolar cells
3 - photoreceptors (rods and cones)
4 - pigmented epithelial layer
When light passes through the cornea, iris and lens it reaches retina. There are the 4 basic layers of the retina,
1 - ganglion cells
2 - bipolar cells
3 - photoreceptors (rods and cones)
4 - pigmented epithelial layer
What is the function of the pigmented epithelial layer?
- absorbs light that is not detected by the photoreceptors
- ensures light does not reflect and scatter into the retina
When light passes through the cornea, iris and lens it reaches retina. There are the 4 basic layers of the retina,
1 - ganglion cells
2 - bipolar cells
3 - photoreceptors (rods and cones)
4 - pigmented epithelial layer
There are 2 types of photoreceptors, rods and cones. What is the difference between them?
- rods detect black and white
- think Cones detect Colour: red, blue and green (depending on the colour of the rod)
When light passes through the cornea, iris and lens it reaches retina. There are the 4 basic layers of the retina,
1 - ganglion cells
2 - bipolar cells
3 - photoreceptors (rods and cones)
4 - pigmented epithelial layer
There are 2 types of photoreceptors, rods and cones. Rods detect black and white and cones detect red, blue and green (depending on the colour of the rod). Where is the highest concentration of the cones and rods located in the retina?
- in the fovea, part of the macula (oval shaped disc at back of the eye)
Once light has been detected by photoreceptors (cones and rods) in the retina, what neuronal cells do they synapse with?
- bipolar neurons
Once light has been detected by photoreceptors in the retina, this information is then transmitted to bipolar neuronal cells. What do the bipolar nerve cells then synapse with?
- ganglion cells
- these transfer action potential to cranial nerve II (2) the optic nerve
Where is the highest visual acuity in the retina?
- fovea, located at the centre of the macula
The optic nerve can be seen in the image below, but what is the optic disc?
- round spot on the retina
- formed by the passage of the axons of the retinal ganglion cells that then form the optic nerve
- no photoreceptors so this is the blind spot
What is the main artery and vein supplying the eyes?
- central retinal artery
- central retinal vein
There are 3 chambers in the eyes, called:
anterior
posteror
vitreous
These are all filled with fluid. What is this fluid called in each chamber?
- anterior = aqueous humor
- posteror = aqueous humor
- vitreous = vitreous humor
What is the blind spot in the eye, and why is it a blind spot?
- portion of the visual field of each eye where we have no vision
- located where optic nerve is within the retina
- blind spot because there are no photoreceptors
What is the fundus in the eye?
- the inside, back surface of the eye
- composed of the retina, macula, optic disc, fovea and blood vessels
When the optic nerve from the left and right eye enter the brain they cross over to the opposite side forming what?
- optic chiasm
Each eye has its own visual field. This can be divided into 2 parts, what are these called?
1 - nasal field (media view and closest to the nose)
2 - temporal field (lateral view)
Each eye has its own visual field. This can be divided into 2 parts, the nasal (media view and closest to the nose) and temporal field (lateral view). These project onto the opposite sides of the retina in the eye. When the optic nerves from each eye meet at the optic chiasm, does the temporal or nasal field of view cross to the opposite side of the brain?
- temporal field of view (what we see)
- this hits the nasal retina field of view in the eye
The optic nerve developed as an out-pouching from the brain, meaning it is covered by all 3 layers of the meninges. What are the 3 layers, from outside in?
- dura mater (periosteal and meningeal)
- arachnoid mater
- pia mater
What does the optic nerve pass through before it reaches the back of the eye?
- enters the bony skull through the optic foramen in the sphenoid bone
- then travels within the optic canal of the sphenoid bone
- leaves via the optic foramen
Once the optic nerves form the optic chiasm, they then form optic tracts, which then synapse where?
- lateral geniculate nucleus of the thalamus
- able to sharpen contrast and enhance depth perception
Once the optic nerves form the optic chiasm, they then form optic tracts, and synapse with the lateral geniculate nucleus of the thalamus, which is able to sharpen contrast and enhance depth perception. The lateral geniculate nucleus then form optic radiations which travel where in the brain?
- primary visual cortex Bordmann area 17
- occipital lobe
Once the optic nerves form the optic chiasm, they then form optic tracts, and synapse with the lateral geniculate nucleus of the thalamus, which is able to sharpen contrast and enhance depth perception. The lateral geniculate nucleus then form optic radiations which then travels to the primary visual cortex Bordmann area 17 of the occipital lobe. In this process where will the action potentials be processed and form recognisable visual information?
- primary visual cortex Bordmann area 17
- electrical signal is processed in form, motion and colour
The central artery of the retina is the main blood vessel of the eye. What artery is this a branch of?
- ophthalmic artery
The central vein of the retina is the main blood vessel of the eye. What vein is this a branch of?
- ophthalmic vein
Cranial nerve II (2) the optic nerve is the main nerve that contributes to visual sight. However, what other cranial nerves are involved in the eyes that control the muscles of the eyes?
- cranial nerve III (3) occulomotor nerves
- cranial nerve IV (4) trochlear (latin for pully) nerves
- cranial nerve VI (6) the abducens nerve
The conjunctiva is a clear tissue covering the exposed sclera of the eye and the eye lids. There are 2 parts to the conjunctive, what are they called?
1 - bulbar
2 - palpebral
The conjunctiva is a clear tissue covering the exposed sclera of the eye and the eye lids. There are 2 parts to the conjunctive, called the bulbar and the palpebral. What are the characteristics of the bulbar conjunctiva?
- thin, slightly vascular, surrounds eye-ball
The conjunctiva is a clear tissue covering the exposed sclera of the eye and the eye lids. There are 2 parts to the conjunctive, called the bulbar and the palpebral. What are the characteristics of the palpebral conjunctiva?
- dense, highly vascular lines inner surface of lids
The conjunctiva is held to the underlying sclera by what fascia?
- tenons fascia
The lens is composed of proteins. As we age these proteins can change and even clump together, clouding the normally clear lens of the eye. What is this called?
- cataract
- remember by c for cataract and c for clumping proteins
Aqueous humour is a transparent water-like fluid similar to plasma, but containing low protein concentrations. It is secreted from the ciliary body, a structure supporting the lens of the eyeball from the posterior to the anterior chamber, as seen in the image below. Once into the anterior chamber it drains via the drainage angle trabecular meshwork. If this fluid does not get drained, this can increase intraoccqular pressure on the eye, specifically the optic nerve, affecting our vision. What is this condition called?
- glaucoma
- can lead to loss of vision if it’s not diagnosed and treated early
What are the eyelids of the eye?
- thin fold of skin that covers and protects an eye
Using the labels below, label the image of the lacrimal apparatus of the eye:
- Nasolacrimal duct
- Lacrimal gland
- Lacrimal sac
- Lacrimal puncta
1 = Lacrimal gland
2 = Lacrimal puncta
3 - Lacrimal sac
4 - Nasolacrimal duct
The lacrimal apparatus of the eye is composed of the Lacrimal gland, puncta, sac and nasolacrimal duct. What is the function of the lacrimal apparatus?
- formation, circulation and drainage of tears
There are 6 major muscles of the eye that arise from the back of the orbit. Label them using the labels below:
- Superior rectus
- Inferior rectus
- Medial rectus
- Lateral rectus
- Inferior oblique
- Superior oblique
1 = Superior oblique (think muscles diagonally on abs and eye) 2 = Inferior oblique 3 = Lateral rectus 4 = Inferior rectus 5 = Medial rectus 6 = Superior rectus
There are 6 major muscles of the eye that arise from the back of the orbit.
Superior rectus Inferior rectus Medial rectus Lateral rectus Inferior oblique Superior oblique
These muscles are controlled by 3 cranial nerves (CN).
CN III (3) = Oculomotor CN IV (4) = Trochlear CN VI (6) = Abducens
Which CN innervate which muscles?
- CN III (3) Occulomotor = inferior obliques, inferior, superior and medial rectus
- CN IV (4) Trochlear = superior oblique
- CN VI (6) Abducens = lateral rectus (think abduct the eye ball from medial line)
There are 6 major muscles of the eye, namely:
Superior rectus Inferior rectus Medial rectus Lateral rectus Inferior oblique Superior oblique
What movement does the superior oblique assist with?
- does opposite to what you think
- rotates eye laterally and down
There are 6 major muscles of the eye, namely:
Superior rectus Inferior rectus Medial rectus Lateral rectus Inferior oblique Superior oblique
What movement does the inferior oblique assist with?
- does opposite to what you think
- rotates eye laterally and up
The middle layer of the eye, called the vascular layer. One part is called the ciliary body, which contain ciliary muscle and the ciliary processes. The ciliary processes attach to the ciliary ligaments to the ciliary muscles and the other end of the ciliary ligaments attaches to the lens. What happens when the ciliary muscles contract?
- ciliary ligaments relax
- relaxed ciliary ligaments causes lens to bulge and shorted
- a bulged and shorter lens is for close vision (parasympathetic)
