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
What is the clinical presentation of lattice (stromal) dystrophy?
Eye irritation, photosensitivity, pain, blurred vision
What is shown on examination of patients with lattice (stromal) dystrophy?
Bilateral criss-crossing opacities in the stroma of the cornea
What is the management for lattice (stromal) dystrophy?
Manage symptoms, in late stages keratoplasty
Describe Fuch’s endothelial dystrophy
Asymmetrical bilateral progressive oedema of the cornea
Occurs in the elderly- 60-70yrs
Due to destruction and death of the endothelial cells
When the number of functioning cells falls below the critical number required to keep the cornea clear, oedema occurs and is followed by opacification of the cornea
What special features does the cornea posses, of particular relevance to surgery?
The total lack of blood vessels makes the cornea an ‘immune-privileged’ site, greatly reducing the chance of foreign antigen recognition and subsequent rejection
What structures make up the vascular layer of the eye (uvea)
Ciliary body - suspends the lens and produces aqueous humour
Iris - controls the diameter of the pupil and thereby controls the amount of light rays entering the eyeball
Choroid - supplies blood to the outer layers of the retina
What is uveitis?
Inflammation of the uvea
What are the three of uveitis?
Anterior - iris with or without ciliary body inflamed
Intermediate - ciliary body inflamed
Posterior - choroid inflamed
What are the causes of uveitis?
Isolated illness
Non-infectious autoimmune causes
Infectious causes - chronic disease such as TB
Associated with systemnic diseases e.g. ankylosing spondylosis
What are the features of anterior uveitis?
An inflamed anterior uvea (iris) leaks plasma and white blood cells into the aqueous humour. These are seen during slit lamp examination as a hazy anterior chamber and cells deposited at the back of the cornea. The eye is red and painful with visual loss
What is hypopon?
Cells in the AC settling anteriorly, white plaque-like appearance on iris
What are the features of intermediate uveitis?
The ciliary body is inflamed and leaks cells and proteins. This leads to a hazy vitreous humour. Patients complain of hazy vision and things floating across the eye
What are the features of posterior uveitis?
The choroid is inflamed, and because the choroid sits just under the retina, the inflammation frequently spreads to the retina, causing blurred vision
What are the conjunctiva?
Thin vascular membrane that covers the inner surface of the eyelids and loops back over the sclera. It does not cover the cornea
Describe the two manifestations of a stye or hordeolum
External - affects the sebaceous glands of an eyelash
Internal - affects the meibomian glands
Both red and tender
Describe a chalazion
Sterile, chronic inflammation that arises from a blocked meibomian gland. May develop form an internal stye/hordeolum
Hard, non-tender
What is conjunctivitis?
Self-limiting bacterial or viral infection of the conjunctiva
How does conjunctivitis present?
Red, watering eyes, discharge. No loss of vision provided infection does not spread to cornea
What is the management for conjunctivitis?
Antibiotic eye drops if likely to be bacterial, eyelid hygiene
