OHA2 sem 1 age related macular degeneration 1.09

macula size

approx 5.5mm in diameter

where does the macula stretch

stretches all the way from superior to inferior temporal arcades

yellow hue in macula

bc of macula pigment. Lutein and zeaxanthin concentration greatest here. Absorb short light. Protection from UV damage

what is the diameter of the fovea

1.5mm

where is the concentration of cones the highest

fovea

why is there a depression in the fovea

due to the sweeping of neurons

term for floor of depression

foveola

diameter of foveola

0.35mm

foveal avascular zone (FAZ) diameter

0.4-0.5mm

how can FAZ only be identified

fluorescein angiography

what does lack of blood vessels in the foveal avascular zone allow

allows light to reach photoreceptors unhindered

functions of RPE

transportation of nutrients to the photoreceptors and phagocytosis of photoreceptor outer segment. lipofuscin is produced during this process

loss of RPE causes what

death of photoreceptors and loss of vision

thickness of bruchs membrane

between 2 to 4 micrometres thick

layers of bruchs membrane

basement membranes for both RPE and choriocapillaris, along with collagenous and elastic layers

Metabolic waste from the RPE is transported across BM into the choroid

how is bruchs membrane related to AMD

Thickens with age, hampering transmission of waste products

Reduces efficiency of its job bc things build up. Key driver of AMD

ageing retina- what happens

Bruchs membrane thickens

RPE metabolism becomes inefficient

Waste products build up in RPE cells - lipofuscin

Collagen/lipid deposit on bruchs membrane

Drusen- term for deposits

how can the RPE change

changing pigmentation

Hyperpigmentation - more pigmented

Hypopigmentation - less pigmented

another term for drusen

colloid bodies

first clinically detectable sign of AMD

drusen

two types of drusen

hard, soft

hard drusen - properties

Small

Yellow, round

Well defined

Normal ageing process

Accompanying pigmentary changes may be seen - not much here

Extracellular hyaline deposits on inner layer of bruchs membrane

soft drusen - properties

Larger and less well defined

Less distinct edges

Overlying RPE changes soften appearance - RPE detachment

confluent drusen

Soft drusen can graduallly coalese

If it joins together

>risk of AMD progression

differentiating between exudate and drusen

exudates

Intraretinal

Tend to be in certain patterns - usually around a leak

Ring pattern

Usually accompanied by vascular changes - microaneurysms, dot and blot haemorrhages, cotton wool spots

Hard drusen - deeper

Subretinal

Random pattern

No vascular changes initially

types of AMD

wet and dry

what % of cases are wet? wb dry?

AMD

dry AMD 90%

wet AMD 10%

process of Dry AMD

Drusen formation -----> RPE atrophy (lose RPE. Death of RPE) ------> geographic atrophy (loss of photoreceptors)

geographic atrophy of RPE

Sharply demarcated area of partial or complete depigmentation

Atrophic RPE

Scalloped margins

Large choroidal vessels visible (no RPE in front so can see them)

what things happen with wet AMD

Bruchs membrane thickens

Drusen form (both wet and dry early sign)

RPE dtachment occurs

New vessels grow out from the choroid - choroidal neovasc CNV. New vessels are very leaky

Leakage and haemorrhage occur

Scarring without treatment - if wet AMD left untreated

non modifiable risk factors of AMD

Older age

Presence of AMD in the other eye

Family history of AMD

modifiable risk factors of AMD

Smoking

Hypertension

BMI of 30kg/m2 or higher

Diet low in omega 3 and 6, vitamins, cartenoid and minerals

Diet high in fat

Lack of exercise

parts of an AMD investigation

Case history, symptoms

VA

Amsler grid

Binocular indirect ophthalmoscopy - volk or bio headset

Maddox rod

Photostress recovery test

OCT

FFA (hospital)

case history AMD - what symptoms is the px likely to report?

Distortion, especially centrally

Reduced reading vision

"Shimmering"

Difficulty in recognising faces

Scotoma

investigation - VA AMD

High contrast VA

Monocular measures- binocular is useless

Distance and near

Pinhole VA

No improvement with pinhole

with a pinhole- taking the option away to use peripheral area- forcing them to use eye damaged

Reduced vision if patient has been viewing the chart eccentrically

investigation - Amsler, AMD

Chart at 30cms

Wearing reading specs - not varifocals

Occlude each eye individually - monocular test

Full room illumination

Covers central 20 degrees - 10 degrees either side of fixation

Sensitivity 78% - how good at correctly picking up px with the disease. Specificity 97%

investigation AMD , Maddox rod

Spotlight on test chart

Red lens

One eye will see vertical line

Other eye will see spotlight

If have distortion - put maddox lens in front of eye with problem. May see distortion

investigation AMD: photo stress recovery test

what does it rely on,

when do we do it

Photo stress recovery test relies on measuring the speed of regenration of the visual pigments

Done if we have no oct

Shine bright light in front of eye for certain length of time - will bleach their vision

Wait and see how many seconds takes for fusion to occur again

method for photo stress recovery test and recovery time results

Measure monocular VA with distance acuity

Remove spectacles if worn and occlude one eye

Ask the px to view the light from ophthalmoscope for ten secs then replace specs

Direct px to line of acuity one above their habitual best VA

Ask px to read line immediately after not bleached

Time how long it takes for px to read 2/3rds of line correctly

Repeat to other eye if necessary

Recovery time results

<50 secs - normal

>50 secs- indicates abnormality

wet AMD pigment epithelium detachment

results from disruption of the junction between the RPE basement membrane and the inner collagenous layer of BM

serous fluid from the choriocapillaris enters the sub RPE space

what does wet AMD pigment epithelium detachment look like on oct

dome shaped elevation

classification of AMD

normal'

No signs of age related macular degeneration (AMD)

Small ("hard") drusen (less than 63 micrometres) only

classification of AMD

'early AMD(I) - low risk of progression)

Medium drusen (63 micrometres or more and less than 125 micrometres) OR

Pigmentary abnormalities

classification of AMD

'early AMD(ii) - medium risk of progression

Large drusen (125 micrometres or more) OR

Reticular drusen OR

Medium drusen with pigmentary abnormalities

Reticular drusen is a network of small fine drusen

classification of AMD

'early AMD(iii) - high risk of progression

Large drusen (125 micrometres or more) with pigmentary abnormalities or

Reticular drusen with pigmentary abnormalities or

Vitelliform lesion without significant visual loss OR

Atrophy smaller than 175 micrometres and not involving the fovea

classification - late AMD (indeterminate)

serous pigment epithelial detachment (PED) without neovascularisation- late AMD. no obvious cause. can't see any drusen

dry AMD management optometrist

Monitor

Counsel

Advise

Refer - low vision assessment?

Registration - sight impaired?

wet AMD management optometrist

If recent onset/progression and VA 6/96 or better, refer urgently - not via GP

Urgent referral from primary eye care

Smoking advice

Anti - VEGF injections