Macula Flashcards
Key features of macula:
• Densely packed cone photoreceptors
- absence of rods at the fovea
• Fovea is avascular and in this area the retina is supplied with oxygen which diffuses from the choroid to the foveal retina
• Fovea 1.5mm across
• Foveola 0.15mm diameter - cones most densely packed in this area
• Avascular zone 0.5mm diameter
•Half of the retinal nerves in the optic nerve serve the fovea
Common macular diseases:
• Age Related Macular Degeneration
- Dry AMD
- Wet AMD
• Diabetic Maculopathy
• Cystoid Macular Oedema
Describe AMD:
• Changes that occur with aging, without obvious cause, in central area of retina ages 50 and over
• Wet AMD - may also be called exudative
• Dry AMD - may also be called non-exudative
- Patients can progress from Dry to Wet AMD
AMD: Symptoms
• A positive scotoma: photoreceptor loss.
• Metamorphopsia - Disorganisation of the photoreceptor layer
• Charles Bonnet syndrome: visual hallucinations
• Colour discrimination: Due to conditions affecting the macula where cones abundant, But less evident than even relatively mild optic neuropathy
• Micropsia: Spreading apart of foveal cones
• Macropsia: Crowding together of foveal cones
AMD: Risk factors
• Age
• Race - More common in caucasians
• Family history - Hereditary element 3x if 1st degree relative
• Smoking - 2x
• Hypertension/ other cardiovascular
• Hypercholesteraemia
• Dietary factors - High fat intake and obesity may promote AMD
ARMD: Drusen
• Can be a sign of early ARMD
• Diferent types of drusen
- Small/hard Drusen: less than 1/2 a vein
- Intermediate Drusen: 1/2 to 1 vein width
- Large/soft Drusen: more than 1 vein width
• All drusen are yellow white retinal lesions, small drusen; defined edges, large drusen; less well defined edges
• Drusen become calcified
- Pigmentary abnormalities - hyper and hypopigmentation of RPE
• Drusen (especially large drusen) and pigmentary changes in the RPE are = increased risk of developing ARMD
Dry AMD: Symptoms
• Symptoms
- GRADUAL asymmetric but bilateral impairment of central VA
- Vision is often better in bright light and may fluctuate
- Metamorphopsia occurs in more advanced cases as atroony progresses
Dry AMD: Pathogenesis
• Degenerative changes in the retinal structure caused by oxidative stress, inflammatory processes and dysregulation of lipid metabolism
Dry AMD: Signs
• Reduced VA: 6/7.5 - 6/60
• Intermediate/large drusen which may become coalescent
• Focalised hyper and hypopigmentation of the RPE
• RPE atrophy, loss of overlying retina and underlying choriocapillaris
• Drusenoid retinal pigment epithelial detachment
• Enlargement of areas of atrophy with underlying choroidal vessels visible - geographic atrophy - severely reduced VA at this stage if overlying fovea
Dry AMD: Signs on OCT
• Drusen - hyperflurescent and elevations of the with less reflective material beneath them
• Outer retinal tubulations
• Hyper and hypopigmentation of RPE
• Loss of RPE, atrophic changes in overlying retina as geographic atrophy progresses
Dry AMD: Management
(life style)
• Prophylactic use of antioxidant supplements in at risk patients with at least one of the following features:
- Extensive intermediate drusen
- At least one large drusen
- Geographic atrophy in one or both eyes
- Late AMD in one eye
• Addressing modifiable lifestyle factors
- Smoking
- Ocular sun protection
- Improved diet - high im antioxidants, lower cholesterol
Dry AMD: Management
(Grid)
• Issue an Amsler grid
- Central 20 degree subjective visual field test
- Picks up metamorphopsia, micropsia and macropsia
- Monitors for progression from Dry to Wet ARMD
• Make sure patient instructions are correct
- View monocularly, Fixate on central dot, Report any waviness or distortion in the grid
Dry AMD: Management
(Monitor)
• Monitor at regular intervals to determine if progressing to Wet AMD
• Refer for registration as partially sighted/blind in advanced disease
• No effective treatment options
• Nutritional and lifestyle advice
Wet AMD: Pathogenesis
• Degenerative changes in retina; oxidative stress, inflammatory processes, dysregulation of lipid metabolism
- Oxidative stress leads to VEGF, forming new leaky BVs at macula
• Build up of fluid due to leaky BVs, or due to thickened dysfunctional bruchs membrane preventing fluid leaving retina
Wet AMD: Symptoms
• Sudden onset reduced vision generally
unilateral
• Metamorphopsia - may be noticed particularly at near
• Positive scotoma - especially if extensive haemorrhage is present
Wet AMD: General and types of WET AMD
• Reduced VA - 6/12-HM
• Metamorphopsia on amsler grid
• Serous Pigment Epithelium detachment (PED) - detachment of the RE from Bruch’s membrane with a fluid filled void
• Choroidal Neovascularisation (CNV) - blood vessels complex which extends from the choriocapillaris thru Bruch’s membrane into the sub-RPE space or sub-retinal space.
WET ARMD WITH SEROUS PED : SIGNS
• Drusen
• Induced hyperopia; Elevation of inner retinal layers
• Dome shaped elevation of macula with sharply defined edges, pale margin caused by subretinal fluid
• band of pigment at edge of lesion may indicate that lesion is longstanding
• OCT will show separation between RPE and Bruch’s membrane filled by optically clear fluid
• Haemorrhage, lipid exudates and chorioretinal folds may be present if there is an underlying CNV
Wet ARMD with CNV: Signs
• Intermediate and large drusen
• CNV may be visible as a green/grey or pink/yellow lesion
• Localised sub-retinal fluid (may take the form of CMO)
• Intra and subretinal lipid depostion - exudates
• Haemorrhages
• Associated pigment epithelium detachment
• Disciform scar in late stage lesion
• OCT useful in monitoring treatment outcomes and progression but less useful in diagnosis of CNV
• Fluorescein Angiography used for definitive diagnesis
AMD : Management
• Most health boards have a rapid access
scheme for urgent referral if:
- The patient has noticed a recent sudden change in vision
- Vision is less than 6/12 or 6/18
- Signs of WET ARMD are present
• Rapid access form is send electronically and is separate to other referrals
- rapid access patients should be seen within 2 weeks of referral date
- Anti-VEGF at ophthalmology
Diabetic Maculopathy: Describe and Symptoms
• Diabetic retinopathy which occurs at the
macula
• Symptoms
- Acute or subacute reduction in VA
- Distortion of vision
- May be asymptomatic if early stage and away from central fovea
Diabetic Maculopathy - Signs
> Caused by leakage
• Microaneurysms
• Retinal haemorrhages (dot-blot and flame-shaped)
• Oedema - Cystoid macular oedema
• Hard exudates
> Signs caused by retinal ischaemia:
• Cotton wool spots
• Non-perfusion of the macula on FA
• IRMA
> Signs caused by hypoxia: new blood vessels
Diabetic Maculopathy: Management
• If VA reduced and signs of
- Oedema within 500m of foveola
- Exudates within 500m of foveola
- Oedema 1500m in diameter within 1 disc diameter of foveal centre
Then refer for further investigation
Cystoid macular oedema: Describe + caused by:
• Accumulation of fluid in the outer plexiform and inner nuclear layers with the formation of cystic spaces
• Can be caused by various factors:
- CNV in ARMD
- Diabetic maculopathy
- Ocular surgery e.g. phacoemulsification, pan retinal photocoagulation
Cystoid macular oedema: Symptoms
• Blurred vision
• Metamorphopsia
• Micropsia
