Week 2 - E - Ophthamology 4 - Gradual vision loss causes Flashcards
What is the mnemonic to remember the causes of gradual vision loss?
C - cataracts
A - age related macular degeneration (dry)
R - refractive error
D - iabetetic retinopathy
I - inheritied diseases (retinitis pigmentosa)
G - glaucoma (open angle)
Access to clinical and
Non urgent
Is gradual visual loss usually unilateral or bilateral?
Usually bilateral but can be unilateral often as well
What is age related clouding of the lens known as?
This is cataracts
How does cataracts present?
Gradual deterioration of vision in both eyes
Sight is blurred and worse in bright lights
Absent red reflexes
Why is it important to check red reflexes in children?
Because children can have congenital cataracts if there had been an intrauterine infection
What is the most common intrauterine infection causing congenital cataracts?
Rubella
What is the most common type of cataract and what happens?
Nuclear cataracts
gradual hardening and yellowing of the central zone of the lens, also known as the nucleus.
Over time, this hardening and yellowing will expand to the other layers of the lens
What is the treatment of cataracts?
Surgical removal of lens and replacement with intraocular lens
Gradual distortion of central vision and an abnormal macula on examination What is this?
This is dry age related macular degeneration
What are the build up of waste products below the retinal pigment epithelium in dry ARMD known as?
Drusen depsoits - these are a build up of fat showing as yellow on fundoscopy
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What is the treatment for dry age related macular degeneration as there is no cure?
Prevention is the best - stop smoking
The use of magnifying glasses to help with vision
Antioxidant vitamins and mineral supplements are also advised - vitamin A, C, E and zinc
Refractive error is when the lens shape of the eye is not correct and therefore rays to not focus on the retina What are the four types of refractive error?
Myopia - near sightedness
Hypermetropia - far sightedness
Astigmatism - irregular corneal curvature
Presbyopia
What is presbyopia?
Presbyopia is an ageing condition of the eyes where the lens hardens and is therefore unable to fatten for near sight objects as the ray focus behind the eyes (age related long sightedness causing loss of accomodation)
What does it mean to have loss of accomodation in presbyopia?
This means when changing from looking at a distant object to a close one, the lens is too hard and wont change in size to accommodate causing blurred vision
What type of lens is required to fix myopic eyes? Describe what happens to the rays in myopia?
require a concave lens to diverge the rays as the rays focus in front of the retina in myopia
What type of lens is required in hypermetropia? What type of lens is required in astigmatism?
In hypermetropia - a convex lens to increase refraction so light rays can focus on the retina
In astigmatism - a cylindrical lens is reuired
What happens in astigmatism?
There is irregular curvature of the cornea causing the light to not focus on one pooint but instead can be refracted in front and / or behind the retina
This causes the image to be blurring both longitudinally and vertically
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What are the two names for the ligaments attaching the ciliary body to the lens of the eye?
Zonules of Zinn
Suspensory ligaments of the lens
What causes the lens to shorten and fatten in a normal circumstances? What type of sight is this in?
This is due to ciliary muscles contracting, relaxing the suspensory ligaments of the lens allowing the lens to shorten and fatten
this is for seeing near objects
What causes the lens to elongate and narrow? What type of sight is this in?
This is when the ciliary muscles relax, the suspensory ligaments of the lens contract causing the lens to elongate
This is for far sightedness
What is the nerve supply to the ciliary muscles?
Parasympathetic nerve supply from the oculomotor nerve (CN III)
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What type of sight is acute angle closure glaucoma associated with?
Associated with perople who have long sight - wide lens can close uveoscleral tract
Is the prescription for long or short sighted people a negative dioptre?
Near sighted people have a negative dioptre
Far sighted people have a positive dioptre
Poor diabetic control can lead to diabetic retinopathy due to the hyperglycaemia What are the signs of non proliferative diabetic retinopathy?
Cotton wool patches hard exudates
Microaneusyms (dot/blot hemorrhages)
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What is the main sign of proliferative diabetic retinopathy?
Neovasuclarisation of the disc and retina
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What can happen due to the neovasuclarisation?
The vessels are weak and can burst causing vitreous haemorrhage and therefore affecting vision due to floaters
What are the cotton wool spots in diabetic retinopathy a sign of?
These are signs of areas of ischaemia
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What is the treatment of diabetic retinopathy?
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Usually try Pan retinal photocoagulation (PRP)
to stop the vessels leaking and reduces oxygen requirment therefore stopping formation of new blood vessels
Patient must get hyperglycaemia under control
What are the potential side effects of pan retinal photocoagulation?
- Decreased night vision and dark adaptation
- Decreased visual field / peripheral vision
- Peripheral and night vision mainly affected as rods are burnt
- Central vision usually less affected than peripheral
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in both CRVO and Proliferative diabetic retinopathy, vessel growth can occur in the iris due to VEGF, What is this known as?
Rubeosis iridis is a medical condition of the iris of the eye in which new abnormal blood vessels (i.e. neovascularization) are found on the surface of the iris.
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What is an example of inherited condition hat leads to loss of vision and blindness?
Retinitis pigmentosa intially due to the progressive degeneration of the rod photoreceptor cells in the retina. and later followed by loss of cone receptors
What are the features of retintiis pigmentosa? What is seen on fundoscopy in retinitis pigmentosa?
Features night blindness is often the initial sign tunnel vision due to loss of the peripheral retina
Fundoscopy: black bone spicule-shaped pigmentation in the peripheral retina, mottling of the retinal pigment epithelium
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To drive a car You must be able to read (with glasses or contact lenses, if necessary) a car number plate made after 1 September 2001 from 20 metres. What is the minimal visual acuity that you must have in order to drive a car?
You must also meet the minimum eyesight standard for driving by having a visual acuity of at least decimal 6/12 in one of the eyes (can read from 6 metres away what somebody with perfect vision can read from 12 metres away)
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What standards must both eyes meet for a lorry and bus drivers?
You must have a visual acuity at least 6/7.5 (basically 6/6 vision on snellen) measured on the Snellen scale in your best eye and at least 6/60 on the Snellen scale in the other eye.