Gradual vision loss Flashcards
ARMD : Anatomy
- Macula : area of the retina,
Responsible for central vision - Fovea centralis : a small depression within the macula which contains a high concentration of ‘Cone cells’
- Cone cells : Photoreceptor cells responsible for colour vision
ARMD : Layers of the macula
Layers of the Macula
1. Photoreceptor cells (cone cells)
2. Retinal pigment epithelium
3. Bruch’s membrane
4. Choroid layer - base which contains the blood vessels that supply the macula
Dry age related macular degeneration : Pathophysiology
-
Drusen accumulation ;
* Deposit of lipids and potions
Between the retinal pigment epithelium and Bruch’s membrane
* Thinning and dysfunction of the Retinal pigment epithelium -
Retinal pigment epithelium dysfunction
* RPE provides support and nourishment for the cone cells
* Accumulation of Drusen reduces nutrient exchange -
Atrophy of Photoreceptor cells
* Gradual loss leads to decline in central vision
Wet age related macular degeneration: Pathophysiology
-
Over-expression of vascular endothelial growth factor
* stimulate formation of new abnormal blood vessels from the choroid -
Neovascularisation :
* New vessels develop from choroid layer and travel up to the retina -
Increased Permeability:
* The abnormal blood vessels in wet AMD are very permeable
* Allow fluids, proteins, and blood to leak into the retinal tissue and the subretinal space
Age related macular degeneration: Complications
-
Macular Edema:
* Macula swelling caused by the leakage of fluid into the macula * Disrupts the macula, affecting vision -
RPE Detachment:
* The growth of abnormal blood vessels can lead to
* Detachment of the retinal pigment epithelium (RPE) from the underlying Bruch’s membrane. -
Vison loss
* Photoreceptor Damage
* The accumulation of fluid, blood, and other materials in the macula can damage the photoreceptor cells, which are essential for vision. - Macular scarring - fibrous tissue can develop in advanced stages
Age related macular degeneration: Risk factors
- Older age > 75 years
- Smoking > 2x
- Family history
- Cardiovascular disease (e.g., hypertension)
- Obesity
- Poor diet (low in vitamins and high in fat)
ARMD : Clinical features
- Unilateral
- Onset : Gradual loss of Central vision - macula has high metabolic demand thus accumulates more oxidative stress
- Reduced visual acuity :
- Deterioration of vision at night, worsening ability to read small text
- Crooked or wavy appearance to straight lines (metamorphopsia) - cones are responsible for detailed vision
- Flickering lights
Wet ARMD : Clinical features
Onset : More acutely
- Develops within days - complete loss within 2-3 years
- Often progresses to bilateral disease.
ARMD : Clinical signs on examination
- Snellen chart : Reduced visual acuity
* Scotoma (an enlarged central area of vision loss)* - Amsler grid test : assess for the distortion of straight lines seen in AMD
- Fundoscopy :
* Drusen, yellow areas of pigment deposition
* Wet ARMD : show red patches of sub retinal haemorrhage*
ARMD : Investigations
Initial investigation
1 . Slit lamp examination
* gives a detailed view of the retina and macula.
2 . Optical coherence tomography
* gives 3D view of the layers of the retina and is used for diagnosing and monitoring AMD.
3 . Fluorescein angiography
* if wet ARMD is suspected
fluorescein contrast and photographing the retina to assess the blood supply,
* showing oedema and neovascularisation in wet AMD.
ARMD : Management
- General advice : Avoid smoking, control BP
- First line : combination of zinc with anti-oxidant vitamins A,C and E reduced progression of the disease by around one third
- Wet ARMD
1. Intravitral injection of anti-VEGF medications : Ranibizumab
2. Laser photocoagulation : slows progression of ARMD when there is a new vessel formation
Diabetic retinopathy : Definition
Diabetic retinopathy involves damage to the retinal blood vessels due to prolonged high blood sugar levels.
Diabetic retinopathy : Pathophysiology
1 . Hyperglycaemia :
High blood sugar damages the retinal small vessels and endothelial cells.
2 . Increased vascular permeability :
* leads to leaking blood vessels
* Leaking of blood, lipid and proteins : Blot haemorrhages and hard exudates
3 . Blood vessel damage
* Microaneurysms are small bulges in the blood vessel walls.
* Venous beading veins become tortuous
4 . Damage to nerve fibres
Cotton wool spots : fluffy white patches on the retina
5 . Neovascularisation
involves the release of growth factors in the retina, stimulating new blood vessel development.
Diabetic retinopathy : Grading
- Background – microaneurysms, retinal haemorrhages, hard exudates and cotton wool spots
- Pre-proliferative – venous beading, multiple blot haemorrhages, cotton wool spots
- Proliferative – neovascularisation
Diabetic maculopathy may show
* Exudates within the macula
* Macular oedema
Diabetic retinopathy : Complications
- Vision loss
- Retinal detachment
- Vitreous haemorrhage (bleeding into the vitreous humour)
- Rubeosis iridis (new blood vessel formation in the iris) – this can lead to neovascular glaucoma
- Optic neuropathy
Diabetic retinopathy : Management
- Maculopathy - If changes in visual acuity - ANTIVGEF inhibitor
-
Non-proliferative
* diabetic retinopathy requires close monitoring and careful diabetic control.
3 . Proliferative diabetic retinopathy :
* Pan-retinal photocoagulation– extensive laser treatment across the retina to suppress new vessels
* Anti-VEGF medications by intravitreal injection
* Surgery (e.g., vitrectomy) may be required in severe disease
Hypertensive Retinopathy : Definition
- Hypertensive retinopathy involves damage to the small blood vessels in the retina relating to hypertension (high blood pressure).
- Changes can happen slowly with chronic hypertension or develop quickly in response to malignant hypertension.
Hypertensive Retinopathy : Clinical features
1 . Copper wiring
* walls of the arterioles become thickened and sclerosed and reflect more light on examination.
2 . Arteriovenous nipping (AV nipping)
* arterioles cause compression of the veins where they cross due to sclerosis and hardening of the arterioles.
3 . Cotton wool spots
* are caused by ischaemia and infarction in the retina, causing damage to nerve fibres.
4 . Hard exudates
* caused by damaged vessels leaking lipids onto the retina.
5 . Retinal haemorrhages
* caused by damaged vessels rupturing and releasing blood in the retina.
6 . Papilloedema :
* caused by ischaemia to the optic nerve, resulting in optic nerve swelling (oedema).
Hypertensive Retinopathy : Classification
- Stage 1: Mild narrowing of the arterioles, + light reflex - silver wiring
- Stage 2: AV nicking
- Stage 3: Cotton-wool patches, exudates and haemorrhages
- Stage 4: Papilloedema
Hypertensive Retinopathy : Management
Management is focused on controlling blood pressure and managing risk factors (e.g., smoking and blood lipids).
Cataracts : Definition
Cataracts describe a progressively opaque eye lens, which reduces the light entering the eye and visual acuity.
Cataracts : Anatomy of lens
- Role : lens is to focus light on the retina.
- Supply : no blood supply and is nourished by the aqueous humour.
3. It is held in place by suspensory ligaments
4. Suspensory ligaments attached to the ciliary body.
5. Ciliary body contracts -> releases tension on the suspensory ligaments ->
lens thickens
6. Ciliary body relaxes -> the suspensory ligaments tension -> lens narrow
Cataracts : Pathophysiology
1 . Aggregations of lens protein
* Due to ageing, proteins clump together interfering with the normal arrangement of lung fibres
2 . Changes in Lens fiber cells
* Changes in the structure of organised elongated fibre cells - disrupts transparency of the lens
Cataracts : Risk factors
- Increasing age
- Smoking
- Alcohol
- Diabetes
- Steroids
- Hypocalcaemia
Cataracts : Clinical presentation
Asymmetrical
Onset: Slow reduction in visual acuity
1. Progressive blurring of the vision
2. Colours becoming more faded, brown or yellow
3. Starbursts can appear around lights, particularly at night
Cataracts : Clinical signs
-
Loss of the red reflex is a key examination finding.
* The lens can appear grey or white using an ophthalmoscope
Cataracts : Management
- Cataract surgery : involves drilling and breaking the lens to pieces, removing the pieces and implanting an artificial lens
Retinitis Pigmentosa : Definition
A genetic condition causing degeneration of the photoreceptors in the retina, particularly the rods cells > cone cells
*Rod cells : peripheral retina, low light and non colour perception
Retinitis Pigmentosa : Clinical presentation
Rods degenerate more than the cones.
Rods are responsible for night vision and peripheral vision. Therefore, there is:
- Night blindness (often the first symptom)
- Peripheral vision loss (before the central vision is affected)
Retinitis Pigmentosa : Fundoscopy
‘Bone-Spicule appearance : sharp pointed appearance similar to bone matrix
* Concentrated at ‘Peripheral retina’
