Flashcards in Common Conditions of the Eye Deck (44)
How does nuclear sclerosis affect vision?
Makes objects appear less clear, and also makes patient see more of the red spectrum
Give an overview of some of the common conditions affecting the eye
-Glaucoma (aqueous humor outflow)
-Ulcers and dystrophies (cornea)
-Lid and conjunctivae problems
What is the epidemiology of cataract?
about 30% of people >65 had some opacity.
Estimated incidence each year of 225,000 new cases of visually impairing cataracts
Why do cataracts develop?
-Older (embryological, foetal) fibres are never shed - compacted in the middle
-No blood supply to lens, which depends entirely on diffusion for nutrition
-Absorbs harmful UV rays preventing them from damaging retina but in the process, get damaged themselves.
-Damaged lens fibres -> opaque -> CATARACT
Whats the difference between an immature cortical cataract and a mature cataract?
Immature cortical cataract:
-Seen as spoke like opacities
-Periphery of lens so only effects vision when pupil dilated
-"Struggle to drive at night"
-Centre of lens effected
Give some examples of secondary cataracts
Steroid-induced cataract (may involve lens capsule and anterior part of lens)
What causes a nuclear sclerosis type of cataract?
Age related change in the density of crystalline lens nucleus that occurs in all older animals.
It is caused by compression of older lens fibres in the nucleus by new fibre formation
What is a Sutural + Zonular cataract?
Types of childhood cataract formed due to opacification of certain zones of the lens in utero.
Maternal infection may cause.
Only centre of lens affected as the outer fibres grow later
What is the management of cataracts?
EYE DROPS DO NOT TREAT CATARACT
-(Day case) small incision
-Lens capsule opened
-Cataractous lens removed by emulsification (phacoemulsification)
-Plastic lens placed in capsular bag
Lens implant after cataract surgery (PCIOL) = Posterior Chamber Intra Ocular Lens
What is the pathway for aqueous humour from production to reabsorption?
Produced by ciliary body.
Flows between iris and lens into anterior compartment.
Filtered by trabecular meshwork and into Schlemm's canal.
Inters venous system
What is Glaucoma?
Raised intraocular pressure (IOP)
Caused by blockage of AH flow at any stage of its cycle
What is the epidemiology of Glaucoma including most common form?
2nd most common global cause of blindness
What is the most commonly seen form of primary glaucoma?
Primary Open Angle Glaucoma (POAG)
-978 per 100,000 of population aged 40-89
-Patient can be asymptomatic for a long period of time
-Picked up on routine eye exams
What are the consequences of raised IOP?
Pressure on nerve fibres on surface of retina -> die out -> visual field defects
Pressure on optic nerve head as nerve fibres die out. When seen by ophthalmoscopy - optic disc appears unhealthy, pale and cupped.
This results in altered field of vision.
Ultimately all nerve fibres are lost, which results in blindness
What is the triad of signs for the diagnosis of glaucoma?
1. Raised IOP
2. Visual field defects
3. Optic disc changes on opthalmoscopy
What is the management of POAG?
Eye drops to decrease IOP
-Carbonic anhydrase inhibitors
What is angle closure glaucoma?
Sudden onset, painful, vision lost/ blurred; HEADACHES (often confused with migraine)
Red eye, core often opaque as raised IOP drives fluid into cornea
AC shallow, and angle is closed
IOP severely raised
How do you manage an acute episode of angle closure glaucoma?
1. Decrease IOP
---IV infusion with or without oral therapy (carbonic anhydrase inhibitors)
---Consider eye drops (pilocarpine)
---If no contraindication beta-blocker drops such as timolol
---Steroid eye drops (dexamethasone)
2. Iridotomy (laser) BOTH EYES to bypass blockage
Give an example of a carbonic anhydrase inhibitor
Why does the angle close in angle closure glaucoma
1. functional block in a small eye (large lens)
2. Mid dilated pupil -> periphery of iris crowds around angle and outflow is obstructed
3. Iris sticks to pupillary border (synechia) which prevents reaching AC. Leads to iris ballooning anteriorly and obstructing angle
What is Iridotomy?
Tiny hole in iris of BOTH EYES.
(both eyes will be larger compared to size of lens)
Allows AH to drain through iris
Summarise open angle glaucoma
In open angle glaucoma the drainage through the trabecular meshwork is blocked (in most cases).
This leads to gradual, painless build up of IOP.
This type of glaucoma is called Primary Open Angle Glaucoma (POAG)
Summarise Angle Closure Glaucoma
In angle closure glaucoma, some event on a predisposed eye leads to the peripheral iris blocking the angle therefore AH can't drain.
So the increase in IOP is SUDDEN leading to a red eye and severe pain.
Patient usually presents as an emergency
What are the two types of cornea pathology?
-e.g. corneal ulcers
Management of some corneal pathologies that cause opacification of the cornea are by corneal transplantation.
What is this procedure called?
What are the causes of corneal ulcer (corneal inflammatory pathology)?
-Viral/ bacterial/ fungal infection of cornea
-Adenovirus is a very common cause (start with conjunctivitis which spreads to cornea)
-Needs aggressive management to prevent spread, scarring
What are corneal dystrophies?
Group of diseases affecting the cornea which are:
-Mostly genetically determined
-Sometimes due to accumulation of substances such as lipids within the cornea
What is the clinical presentation of corneal dystrophies?
First to fourth decade
Most commonly - decreased vision
Start in one of the layers of the cornea and spread to the others
Describe lattice (stromal) dystrophy
Type of corneal dystrophy
-The classic type is autosomal dominant
-Deposition of amyloid material in corneal stroma
-Patient presents with eye irritation, photosensitivity, pain, blurred vision
Examination shows bilateral criss-crossing opacities in the storm of the cornea
Treatment = manage symptoms, in late stages corneal transplant