130 Sudden visual disturbance Flashcards
Where in the retina are cone cells predominantly found?
Centrallly - highest at the fovea
Where in the retina are rod cells predominantly found?
In the periphery
Which cells of the retina are responsible for the ‘sensor surround effect’?
Horizontal cells
Where in the brain do ganglion cells project to?
Suprachiasmatic nuclei
Which cells contain melanopsin?
Retinal ganglion cells
Which photopigment is involved with the regulation of circadian rhythm?
Melanopsin
Explain the phototransduction pathway
- light hits rhodopsin and 11-cis-retinal in the disc of rod cell
- change in conformation –> all-trans-retinal
- transducin detaches –> α subunit binds to phosphodiesterase
- phosphodiesterase changes cGMP –> GMP
- Na+ channels close as cGMP no longer bound
- no Na+ means hyperpolarisation = off –> which turns bopolar cells on
- signal transduction
What is RAPD?
Relative afferent pupil defect - lesions anterior to the chiasm eg in neuritis and MS
What is protanopia?
Red visual weakness
What is deutranopia?
Green visual weakness
What is tritanopia?
Blue visual weakness
Which nucleus in the mibrain is involved in the visual pathway?
Edinger-Westphal
Where do the oculomotor efferents synapse with short ciliary nerves?
Ciliary ganglion
Loss of vision in the right eye - where in the visual pathway is the defect?
What could cause this?
Right optic nerve
- compressive tumour
- optic neuritis
- anterior ischaemic optic neuropathy
Loss of peripheral vision - where in the visual pathway is the defect?
What could cause this?
Defect in the optic chiasm
- Parasellar mass
Loss of nasal vision in the R eye and loss of temporal vision in the L eye - where in the visual pathway is the defect?
What could cause this?
Defect in the right optic tract
- neoplasm
- inflammatory process
- arteriovenous malformation
Loss of vision in the upper left quadrant of L and R eyes - where in the visual pathway is the defect?
What could cause this?
Lesion in the upper right optic radiations
- neoplasm
- inflammatory process
- ischaemia
- infection
What protective molecules/cells are in tears?
(7 listed)
- Lactoferrin
- lysozyme
- β-lysin
- IgA
- IgG
- complement
- leukocytes
What causes primary open angle glaucoma?
Decreased outflow of aqueous humour through tebecular meshwork
What is timolol and what is it used to treat?
β- blocker used to treat primary open angle glaucoma
Where is the vision loss in age related macula degeneration?
Central
What are drusen and in which condition are they found?
Lipfuscin deposits - found in dry macula degeneration
What is the cause of wet macula degeneration?
Neovascularisation from the choroid layer which has severe impact on central vision
How does lucentis work in macular degeneration?
Binds to VEGF-A which prevents it from binding to its receptor. Normally involved with neovascularisation and angiogenesis
Which receptors does phenylephrin act on?
α1 receptors
What is the effect of topical application of phenylephrin on the eye?
Myadriasis - dilation of the pupil
Why is phenylephrin less effective in:
- diabetes
- dark irises
- elderly
- increased glucose makes the pupillary muscles less flexible
- lots of melanin which phenylephrin binds to
- lots of wear and tear
What are the SE of phenylephrin?
(5 listed)
- photophobia and blurred vision
- stinging
- acute glaucoma
- HTN
- arrhythmias
Name 3 antimuscarinics which causes myadriasis
- Atropine
- Cyclopentolate
- Tropicamide
What are the benefits of using tropicamide to cauase myadriasis?
Quick and short-acting
What are the systemic effects of tropicamide, atropine and cyclopentolate? Action on which receptors cause this?
- Dry mouth
- Flushing
- Confusion
Act to block ACh at muscarinic receptors
Which eye drugs can raise IOP?
Antimuscarinics, sympathomimetics
What drug is used in the treatment for glaucoma?
MOA?
Pilocarpine - mimics ACh on muscarinic receptors which causes miosis and opens up the drainage of the trabecular network. Reverses myadriasis in 30-60mins
Which parasympathomimetic eye drug inhibits the production of aqueous humor?
Timolol
What is the MOA of the sympathomimetic eye drug acetazolamide?
Inhibits carbonic anhydrase which is needed for the production of bicarbonate in aqueous humor
What is hypromellose the 1st line treatment for?
Artificial tears
What are the red flag symptoms suggestive of acute closed angle glaucoma?
- red, painful eye
- N&V
- blurred vision
- headache
Which antibiotic can cause orange tears?
Rifampicin
Which is the most appropriate abx for the treatment of a Pseudomonas infection of the eye + corneal ulcer?
- chloramphenicol
- gentamycin
- ciprofloxacin
Ciprofloxacin
Which is the most appropriate abx for the treatment of a *Pseudomonas *infection of the eye?
- chloramphenicol
- gentamycin
- ciprofloxacin
Gentamycin
Which is the most appropriate abx for the treatment of a Staphylococcus infection of the eye.
- chloramophenicol
- gentamycin
- ciprofloxacin
Chloramphenicol
