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