gradual loss of vision macular degeneration Flashcards
what is the Macula
macula lutea is the part of the retina where the visual acuity is the highest
it is located 3mm temporal to the optic disc (equivalent of 2 disc diametres)
what is the centre of the macula
In the centre of the macula is the fovea centralis
Here the retina just consists of cone photoreceptors
what is good visual acuity depenedent on
Functioning photoreceptors
Cones (abundant at macula)
Rods
Healthy Retinal Pigment Epithelium (RPE)
Perfusion by the capillary layer of the choroid-the choriocapillaris
All work together as a single unit
Problems with one lead to changes in all
what are the types of macular degeneration
The first sign of aging in the retina is the development of drusen
This may progress to atrophy of the retina (dry AMD), or
Lead to new vessel growth under the retina (wet AMD)
what is retinal drusen
Waste material from the photoreceptors accumulates in and below the RPE
There are several different types of drusen
Small white drusen
Larger more confluent soft drusen
Crystalline hard drusen
Drusen represent a poorly functioning RPE
what is dry AMD
The features of ‘dry’ AMD are
Atrophy of RPE, choroid and retina can be seen using the ophthalmoscope
The patient develops a central scotoma
The patient retains good peripheral vision
Frequently the vision deteriorates so that the patient is eligible for blind registration (this is the commonest reason in the UK)
Low Vision Aids can assist patients with reading
Recent evidence suggests there may some benefit by nutritional treatment with anti-oxidants and vitamin supplements
what would you see happen to the RPE in dry AMD
atrophy of RPE and choroid
what is wed AMD
The features of ‘wet’ AMD are:
Choroidal neovascular membrane (CNVM)
Leaking vessels below retina
Localised retinal detachment which leads to distorted central vision and eventually a central scotoma
Exudates and haemorrhage seen using the ophthalmosocope
Retinal scarring
what will pts with wet AMD notice
Patients with wet AMD notice a more rapid change in vision
Objects may become distorted or smaller in size (micropsia)
Rapid referral for assessment is important
wet amd management
Wet AMD has some potential for treatment
Photodynamic laser after intravenous injection of a photsensitive drug (verteporfin) is used for some CNVM that are under the fovea
Intravitreal injections of anti TNF beta (macugen, lucentis) can be effective for some patients
why can wet AMD happen in young peoplem
Myopia (extreme short-sightedness)
Choroidal rupture after blunt trauma
Angioid streaks associated with pseudoxanthoma elasticum
