Visual System Flashcards
How does sensory information from the eye travel to the Primary visual cortex? What is its route
Eye -> Optic nerve -> Optic chiasm -> Optic tract -> Lateral geniculate nucleus -> Optic radiation -> Primary visual cortex
Where is the primary visual cortex located? What Broadmann’s area is it?
Occipital lobe, Brodmann’s area 17, 18, 19
If a patient experiences a visual field loss which is homonymous (same side in both eyes), what does this suggest?
The lesion has occured posterior to the optic chiasm
Lesions occuring at the optic chiasm would lead to what type of partial blindness?
Heteronymous hemianopia (loss of vision in opposite fields of each eye)
Complete blindness in one visual field (left or right) would suggest a lesion were?
Optic nerve
What are the three main layers of the eye?
- Fibrous later (outermost)
- Vascular layer (middle)
- Neural layer (inner)
What two structures comprise the Fibrous layer (outer layer) of the eye?
Cornea and sclera
What three structures comprise the Vascular layer (middle layer) of the eye?
Iris, cilliary body and choroid
What one structure comprises the Neural layer (inner layer) of the eye?
Retina
What is the centre part of the retina called?
Fovea (highest resolution of vision, highest density of neurones)
What are the two main functions of eye movements?
Gaze stabilisation
Gaze shifting
Which muscle closes the eyelid?
Levator Palpebrae Superioris (LPS)
What are the 6 extrinsic muscles of the eye
Superior Oblique Inferior Oblique Medial Rectus Lateral Rectus Superior Rectus Inferior Rectus
What is the main function of the Medial Rectus muscle?
Adduction of eye
What is the main function of the Lateral Rectus muscle?
Abduction of eye
What is the main function of the Inferior Rectus muscle?
Depression of eye
What is the main function of the Superior Rectus muscle?
Elevation of eye
What is the main function of the Superior Oblique muscle?
Intorsion of eye
What is the main function of the Inferior Oblique muscle?
Extortion of eye
Cranial Nerve III (Oculomotor) innervates what Extrinsic eye muscles?
Medial Rectus
Inferior Rectus
Superior Rectus
Inferior Oblique
Cranial Nerve IV (Trochlear) innervates what Extrinstic eye muscle?
Superior Oblique (SO4)
Cranial Nerve VI (Abducens) innervates what Extrinstic eye muscle?
Lateral Rectus (LR6)
Which part of the brain controls eye movements?
Frontal Eye Field (FEF)
Which part of the brain controls planning of eye movements?
Supplementary Eye Field (SEF)
Which part of the brain is involved in maintaining visual attention?
Posterior Parietal Cortex
What is the role of Supplementary Eye Field (SEF)?
Planning of eye movements
What is the role of Posterior Parietal Cortex?
Maintaining visual attention
What is the role of Superior Colliculus with respect to eyes?
Orientation to object in the visual field
What is Anisocoria?
Unequal size of pupils in eyes
Pupil constriction is also known as..? Is the iris sphincter active or relaxed?
Miosis, sphincter active
Pupil dilation is also known as..? Is the iris sphincter active or relaxed?
Mydriasis, sphincter relaxed
Miosis and Mydriasis is under sympathetic or parasympathic control?
Miosis = Parasympathetic Mydriasis = Sympathetic
The accomodation reflex is under what control? Sympathetic or parasympthatic?
Parasympathetic control
What are Cataracts?
Clouding of lens caused by compaction and protein deposition
What are risk factors for Cataracts?
Aging, trauma, diabetes, smoking, UVB light, genetic (congenital cataracts)
What is the anterior chamber filled with?
Aqueous humour
What is the role of Cilliary epithelium of the Ciliary body in the eye?
Production of Aqueous humour for the Anterior and Posterior Chamber
How is the Aqueous humour drained from the eye?
Out of the lens, through pupil, into anterior chamber. The drain through trabecular meshwork and then Schlemm’s canal and out of the eye
What are risk factors for Glaucoma’s?
Raised intraocular pressure (normal = 12-22)
Hypertension
Long-term steroid use
Severe myopia (-6.00)
What is the most common type of Glaucoma? What is it caused by? Is it acute or chronic?
Open-angle Glaucoma, caused by blockage of Trabecular meshwork. It is chronic
What is closed-angle Glaucoma caused by?
Caused by raised intra-ocular pressure which bows the iris and closes the anterior chamber. It is an acute medical emergency
What are some treatment options for Glaucoma? 4 groups
- Beta blockers
- Alpha2 adrenoceptor agonists
- Carbonic anhydrase inhibitors
- Miotics (muscarinic agonists)
What is the mechanism of action for Acetazolamide?
Carbonic anhydrase inhibitor, preventing Sodium reabsorption and thus allowing water secretion and reduction of Intraocular pressure
What is the main blood supply to the eye?
Choroid and choriocapillaries (outer retina)
Central retinal artery and vein (inner retina)
Is the fovea vascular or avascular?
Avascular
Red/green colour blindness particularly affects which gender? Why?
Red-green colour blindness, because it is X-linked
What are the two cell types in the Lateral genicular nucleus? What do they detect?
Magnocellular (detects light / dark)
Parvocellular (detects colour)
