Common Conditions of the Eye Flashcards
What is the aetiology of cataract formation?
Lens fibres absorb harmful UV rays, preventing them from damaging the retina, but causing damage to themselves in the process. Damage to the fibres of the lens leads to opacification and cataract formation
How does the lens develop in basic terms?
Older embryological fibres are never shed from the eys and compact in the middle. They receive no blood supply, instead rely on diffusion for nutrition
Give some causes of secondary cataracts
Steroid-induced
Traumatic
Sutural & zonular - childhood
Do eye drops treat cataracts?
No
What is the treatment for cataracts?
Day case surgery, plastic lens in bag replaces damaged lens
What is the name for lens implant after cataract surgery?
Posterior Chamber Intra Ocular Lens - PCIOL
What is glaucoma?
Raised intraocular pressure
The 2nd most common global cause of blindness
Most common form is primary open angle glaucoma - POAG
What are the consequences of raised IOP?
Pressure on nerve fibres on surface of retina causes the retinal fibres to die out resulting in visual field defects
The nerve fibres die out and there is pressure on the optic nerve. When visualised the optic disc appears unhealthy, pale and cupped
The result is an altered field of vision, with the nerve fibre loss progressing until the result is total blindness
What is the ‘triad’ of signs for glaucoma diagnosis?
Raised IOP
Visual field defects
Optic disk changes on ophthalmoscopy
Management of POpenAG?
Eye drops to decrease IOP
Laser trabeculoplasty
Trabeculectomy surgery
What are the signs of angle closure glaucoma?
Sudden onset, painful, loss or blurring of vision, headaches - often confused with migraine
Red eye, cornea often opaque due to raised IOP driving fluid into cornea. Anterior chamber shallow, angle closed. Pupil mid-dilated, IOP severely raised
Management of acute angle closure glaucoma?
Decrease IOP - IV infusion with or without oral therapy, analgesics, antiemetics, constrictor eye drops, BBlockers if no contraindication, steroid eye drops
Iridotomy (laser) - both eyes, to bypass blockage
Why does the angle close and cause AC glaucoma?
- Functional blockage in a small eye - large lens
- Mid-dilated pupil -> periphery of iris crowds around angle and outflow is obstructed
- Iris sticks to the pupillary border (synechia) and fluid cannot reach AC. Iris balloons anteriorly and obstructs angle
Describe the process of POAG?
Drainage through the trabecular meshwork is impaired (in most cases). This leads to a gradual painless build up of IOP. NB: SOME FLUID CAN STILL ESCAPE SO IOP INCREASE IS GRADUAL
Describe the process of angle closure glaucoma
Some event on a predisposed eye leads to the peripheral iris blocking the angle, therefore aqueous humour cannot drain. Raised IOP is therefore sudden and leads to red eye and severe pain - usually present as emergency
What epithelium is found in the cornea?
Stratified squamous non-keratinised
Describe the layers of the cornea
Epithelium
Bowman’s membrane (basement membrane of epithelium)
Stroma - regularly arranged collagen, no blood vessels
Descemet’s layer
Endothelium - single layer
What are the two general forms of corneal pathology?
Inflammatory
Non-inflammatory
What is keratoplasty?
Corneal transplantation
Describe a corneal ulcer
Inflammatory
Infection - of the cornea via viral/bacterial/fungal. Needs aggressive treatment to stop spread and scarring
Non-infectious - due to trauma, corneal degerations, dystrophy
Describe corneal dystrophy
Non-inflammatory
Group of diseases which are all: Bilateral Opacifying Non-inflammatory Genetically determined (mostly) Sometimes due to accumulation of substances such as lipids in the cornea
Describe the clinical presentation of corneal dystrophies
First to fourth decade
Most commonly with decreased vision
Start in one layer of the cornea and spread to others
Give two examples of corneal dystrophies
Lattice (stromal) dystrophy
Fuch’s endothelial dystrophy
Describe lattice (stromal) dystrophy
The classic type is autosomal dominant
Results in deposition of amyloid material in the corneal stroma
