AMD and Primary Open Angle Glaucoma Flashcards
What is age-related macular degeneration?
Age-related macular degeneration (AMD, or AMRD) is the term applied to ageing changes without any other obvious precipitating cause that occur in the central area of the retina (macula) in people aged 55 years and older.
AMD is a progressive chronic disease of the central retina and a leading cause of vision loss worldwide. Most visual loss occurs in the late stages of the disease.
What is the pathophysiology of dry AMD?
Dry AMD/geographic atrophy (GA)
- The characteristic lesions of dry AMD are soft drusen and changes in pigmentation (hypopigmentation and/or hyperpigmentation) of the retinal pigment epithelium (RPE).
- Atrophy of the RPE becomes more extensive with time. The dry form can advance and cause vision loss without turning into the wet form. The end stage of the dry form involves the whole macula becoming affected as the GA evolves.
- Dry AMD is the most common form of AMD, occurring in 90% of cases.
- Progression to visual loss is usually gradual.
- Eventually there is an area of partial or complete atrophy of the RPE. This may or may not involve the fovea.
- Those with dry AMD have a 4-12% chance per year of developing choroidal neovascularisation (wet AMD).
What is the pathophysiology of wet AMD?
In the wet type of AMD, new blood vessels grow in from the choriocapillaris under the retina. They spread under or above the RPE or both.
They are fragile and easily leak. Blood vessels don’t initially grow under the macula - they start off to the side of the retina and grow towards the centre.
For some, it can take only days to grow under the macula; for others it will take weeks. They can reoccur, sometimes many years later. The consequences of abnormal vessel growth are haemorrhage and scar formation (disciform scarring).
Wet AMD accounts for 10% of all cases of AMD but about 60% of advanced cases. Wet AMD is by definition considered advanced at presentation.
Progression varies from a few months to three years. Untreated, most will become severely visually impaired within approximately two years.
The end point of this type of AMD is scar formation known as disciform macular degeneration.
Approximately 50% of patients who have wet AMD in one eye will also develop this condition in their second eye within five years.
What is idiopathic polypoidal choroidopathy?
This is a variant of AMD, consisting of neovascularisation, primarily located within the choroid. It shares some features with AMD - it involves the macula, it is seen in the same age-group, it shares common non-genetic risk factors, such as smoking and hypertension, and it shares common genetic risk factors.
However, in contrast to AMD, polypoidal choroidopathy is seen in a younger age group than AMD, it more often occurs in the nasal macula and the polypoidal neovascular complexes may leak and bleed but are less likely to invade the retina.
What is the classification of AMD?
No AMD: none or a few small drusen.
Early AMD: multiple small or a few intermediate drusen +/- abnormalities of the RPE.
Intermediate AMD: extensive intermediate or one or more large drusen +/- GA not involving the fovea.
Advanced AMD: GA involving the fovea +/- any features of wet AMD.
What are the risk factors for AMD?
AMD is a multi-factorial disease. Increasing age (main RF) Smoking- both for onset and progression Family history Obesity Most common in white people Diets high in fat, cholesterol and high glycaemic index foods.
What is the general presentation of AMD?
AMD causes painless deterioration of central vision, typically in a person aged 55 or more.
Patients may initially be asymptomatic and retinal signs may be detected incidentally during a routine eye test.
General symptoms
- Reduction in visual acuity, noticed particularly for near vision.
- Loss of (or decreased) contrast sensitivity (the ability to discern between different shades).
- Size or colour of objects appearing different with each eye.
- Abnormal dark adaptation (difficulty adjusting from bright to dim lighting). There may be a central dark patch in the visual field noticed at night, which clears within a few minutes as the eyes adapt.
- Photopsia (a perception of flickering or flashing lights).
- Light glare.
- Visual hallucinations (Charles Bonnet syndrome). These can occur with severe visual loss of any cause. Visual hallucinations are often not reported unless specifically asked about.
What are the features of dry AMD?
Visual deterioration tends to be gradual. A common presentation is difficulty with reading, initially with the smallest sizes of print and then later with larger print.
People may not notice visual deterioration when only one eye is affected, so that the visual loss only becomes apparent when the second eye becomes affected.
When GA is bilateral and involves both foveae, patients may complain of deterioration of central vision.
Scotoma - the person may describe a black or grey patch affecting their central field of vision.
What are the features of wet AMD?
The most common symptoms typical of onset of exudative AMD are central visual blurring and distortion. Most patients will complain that straight lines appear crooked or wavy.
Visual deterioration may develop quickly. A person may suddenly become unable to read, drive, or see fine detail such as facial features and expressions.
Vision may suddenly deteriorate to profound central visual loss in the event of a bleed. This may be preceded or accompanied by a shower of floaters.
As for dry AMD, when exudative AMD occurs in the second eye, patients may suddenly become aware of their visual loss.
What is seen in the eye examination of a px with AMD?
Normal or decreased visual acuity with distortion on the Amsler grid.
Fundus examination reveals drusen (discrete yellow deposits) in the macular area, which may become paler, larger and confluent.
Macular scar may develop,
Well-demarcated red patches representing intraretinal, subretinal or sub-RPE haemorrhages or fluid.
What are the differentials for AMD?
Refractive errors
Cataracts
Corneal diseases
Posterior vitreous detachment or retinal detachment
Retinal artery occlusion or retinal vein occlusion
Central serous retinopathy
Cerebrovascular disease
Pituitary tumour, CNS tumour and papillodema
Macular hole
Glaucoma
Optic atrophy
What are the investigations for AMD?
Secondary care investigations are aimed at confirming the diagnosis, assessing the extent of the disease and the possibilities for intervention, and keeping a record in order to measure treatment effects and disease progression:
- Slit-lamp biomicroscopy to identify drusen and any pigmentary, exudative, haemorrhagic, or atrophic changes affecting the macula (looking for the characteristic area or areas of pallor with sharply defined and scalloped edges). This also helps to detect retinal thickening or elevation due to neovascular AMD.
- Colour fundus photography is used to record the appearance of the retina.
- Fluorescein angiography is used if neovascular AMD is suspected, in order to confirm the diagnosis and assess the lesions. Fluorescein dye is injected intravenously and photographs of the retina are taken serially to detect abnormal vasculature or leakage from capillaries.
- Indocyanine green angiography may be used to visualise the choroidal circulation, which provides additional information to fluorescein angiography.
- Ocular coherence tomography produces high-resolution cross-sectional and three-dimensional images of the retina. The guideline from The Royal College of Ophthalmologists states that this test is mandatory for diagnosis and that monitoring response to therapy can reveal areas of GA that may not be clinically visible on biomicroscopy.
What are the general measures of the management of AMD?
If AMD is suspected, refer the person urgently for further assessment, ideally to be seen within one week of referral.
Urgent referral is particularly important in people who present with distortion or with rapid-onset visual loss, as these suggest wet AMD.
Advise the person that if there is either a delay of more than one week in being seen by an ophthalmologist or symptoms are worsening whilst they are waiting to be seen, they should attend Eye Casualty as soon as possible, or seek other immediate medical attention to expedite urgent specialist assessment.
What is the management of dry AMD?
There is no treatment which prevents progression of dry AMD, although lifestyle adjustments may slow progression.
Management consists mainly of counselling, smoking cessation, visual rehabilitation and nutritional supplements in those expected to benefit.
Co-existing visual impairments such as cataract and refractory error should be appropriately managed
Advice and support from secondary care such as:
- Seeking urgent care as they develop worsening symptoms.
- What can be done to slow progression
Lifestyle advice: -Smoking cessation -Healthy balanced diet rich in leafy green vegtables -Visual rehabilitation: Mainstay of treatment Maximises remaining visual function Refraction check Use of optical aids Low visual aid clinic referral
What is the management of wet AMD?
Intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents are the current standard of care. Treatment is carried out by ophthalmologists with a special interest in retinal and macular problems
VEGF is a pro-angiogenic growth factor that also stimulates vascular permeability and has a major role in the pathology of neovascular AMD. Since anti-VEGF therapy has become available there has been a substantial improvement in the prognosis of people affected by neovascular AMD
Anti-VEGF drugs include ranibizumab, bevacizumab and aflibercept.
Older treatments include laser photocoagulation, photodynamic therapy with verteporfin and macular translocation.
