Week 1.07 AMD Flashcards
What are the structures within the macula
Macula - widest possible region
Fovea - similar size to optic nerve head
Foveola- photoreceptor cells
Umbo - light reflex in opthalmoscope
What is the size of the macula
Approx 5.5mm
Why is the macula darker than the rest of the retina
RPE cells taller and contain more pigment here than elsewhere
What are the yellow hue pigments in the macula
- Lutein & zeaxanthin concentration greatest here – thought to play a protective role – highly metabolic active tissue so really susceptible to damage
- Absorb short light
- Protection from UV damage
What is the fovea
• 1.5mm diameter
• Highest conc of cones
• Shrinking down and thinning of the retina in this region
• Depression created by sweeping of neurons
• Floor of this depression = foveola
• Cones only in central 0.57mm
• Bordered by para-fovea region then peri-fovea
What is the function of the RPE
Transportation of nutrients to the PR & phagocytosis of PR outer segment
o Lipofusion is produced during this process – really important aging pigment, build up of lipofusion tells you which areas on the back of the eye are affected
• Loss of RPE causes death of photoreceptors and loss of vision
Burch’s membrane
2 to 4 micrometres thick
Thickens with age - waste products usually transported across so if gets thick that stops it from doing this
How does the retina age
• Bruchs membrane thickens
• RPE metabolism becomes inefficient
• allowing waste products build up in RPE cells – lipofusion
• Collagen / lipid deposit on bruchs membrane
= drusen – yellow dots on back of eye in macula diseases
What’s the main reason drusen forms
Thickening of bruchs membrane so drusen forms between RPE and bruchs membrane
What are the 2 types of drusen
Soft - typically bigger
Hard - typically smaller
Hard drusen
Small scattered
Yellow
Round
Well defined
Normal ageing process
Soft drusen
Larger and less well defined
Overlying RPE changes soften appearance - RPE detachment
Confluent drusen
Soft drusen that gradually coalesces
Increases risk of AMD
How to differentiate between exudates and drusen
Exudate is more brighter and easier to see, more superficial in the retina. Closer to the optom
What’s the difference between exudates and hard drusen
Exudates are intraretinal and hard drusen is subretinal
Exudates are ring patterns, hard drusen random pattern
Exudates - vascular changes (microaneurysms, dot and blot haemorrhage, cotton wool spots)
hard drusen - no vascular changes
Two main types of AMD
Dry - 90% of cases - 10% cases causing blindness
Wet - 10% of cases - 90% cause blindness
Dry - untreatable
Wet - treatable if URGENT referral
Dry is slowly progressing
Wet quickly progressing
Dry AMD
Geographic atrophy - Choroidal blood vessels are visible. Very few or no photoreceptors in this area
What happens in wet amd
- Things start in the same way as the dry type
- Brunch’s membrane thickens
- Drusen forms
- RPE detachment occurs
- New vessels grow out from the choroid
- Leakage and haemorrhage occur – causes blood to leak into the retina
- Scarring without treatment
What is Choroidal neovascularisation
New blood vessels growing up from choroid through spilts in bruchs membrane into the retina. Start to leak and disrupt photoreceptors.
Also known as choroidal neovascularisation – new blood vessels from choroid although there can be other causes of this such as high myopia, other conditions where u get splits in the retina.
What are the risk factors for AMD
Older age
Presence of AMD in the other eye
FH of AMD
Smoking
Hypertension
High BMI
Diet low in omega 3 and 6, vitamins
Edit high in fat
Lack of exercise
How to investigate AMD
Case hx - sxs
VA
Amsler grid
Volk
Maddox rod
Photo stress recovery test
OCT
FFA (hospital)
What might a person with AMD say in case hx
Distortion especially centrally
Reduced reading vision
Shimmering
Difficulty recognising faces
Central scotoma
Family history
AMD in other eye
Amsler chart
- Chart at 30cms
- Wearing appropriate reading spectacles (+3.25 add)
- Occlude each eye individually
- Full room illumination
- Covers central 20 degrees – 10 degrees either side of fixation
Maddox rod
Px may report breaks or distortion in the image
Photo stress recovery test
Basically bleaching vision and then checking how long it takes for vision to come back
Measure DV VA
Occlude one eye
Look light 10 secs
Replace specs back on
Direct px to line above VA
Ask them to read line immediately the after image disappears
Time how long it takes for px top read 2/3rd of line correctly
Repeat for other eye if necessary
Normal recovery 0-30 seconds
30-60 seconds possible maculopathy not definite
>60 seconds maculopathy
What is shown in late AMD
Scare tissue
How to manage dry amd
Monitor and be aware wet could develop
Counsel
Advice
Refer
Eat foods that contain more leutein and zeaxanthin - kale, sweetcorn, orange, peppers, eggs
How to manage wet AMD
Urgent referral from primary care within 2 weeks
Anti-VEGF injections
Smoking advice
Registration - blind
What is the NICE guidelines for referral of amd
In order for eye to be treated:
- Best corrected VA between 6/12 and 6/96
- no permanent structural damage to central fovea
- lesion size is less than or equal to 12 disc areas in greatest linear dimension
