Classic age related macular degeneration (ARMD)
blood vessel growth
leakage..blood and fluid
give anti-VEGF drug
leakage stops for a while
In wet ARMD, new vessels grow under the central retina in the macular area, causing retinal leakage and swelling. (CNV..choroidal neovascularisation). The blood vessel frowth seems to be part of the eye's 'healiing' response to ack of oxggen/damage. The damaged retina releases a chemical VEGF (Vascular endothelial growth factor). The VEGF stimulates blood vessel growth, to produce the different types of wet ARMD. In addition, the new blood vessels leak, causing fluid under the retina in these condition.
The network of blood vessels usually progresses to cause a scar in the macular area. If the scar is small, sight is reasonable; but if large, the sight can be very poor. It is very difficult to predict whose dry ARMD will progress, but the risk factors include those mentioned above (soft drusen, high blood pressure, smoking, poor diet, lack of exercise). This is described below.
There are different types of wet ARMD
- Classic CNV
- Occult CNV type 2 (no 'PED')
- Occult CNV type 1, vascularised PED
- RAP type 3 (separate page)
- Myopic (separate page, not really ARMD)
- Peripapillary (separate page)
When blood vessels grow under the macula, this is termed choroidal neovascularisation (CNV). When the new vessels are seen easily on a fluorescein angiogram, they are called 'classic CNV': they look like a net of blood vessels.
When a doctor looks in the retina looks elevated, there may be tiny haemorrhages, a grey area, or exudates. Severe . In milder cases vision may still be good. The condition may develop over days or weeks, with increasing distortion or blurred central vision. If this process is early you can still read, but if it becomes severe reading with any magnifier is impossible. Treatment is based on anti-VEGF drugs, although other treatment are available
This is usually a serious type of macular degeneration, serious because it can cause very poor central vision. It never blinds in the sense that you cannot see light and dark, but in its serious form it can damage the central vision so you can only see fingers or even the movements of hands. Once again, the side vision will normally be good, so you should always be able to walk around the house.
- CNV grow at 20µ/day, reaching 3000 µ in 6 month, difficult to see in early stages.
- OCT scans are essential to diagnose this early.
- Small membranes gain ~5 lines of vision with anti-VEGF, 10% unresponsive to treatment.
- The biggest problem is detecting them early, and much work ('Replacing the Amsler Grid") is being carried out to detect early membranes.
- photos.... ffa same patient 3 months after pdt another classic same patient other eye...disciform scar CNV due to sarcoid membrane other healthy eye Ajith Kumar/BMEC)
- treatment with PDT
|ARMD progression rate and relative risk of smoking||geographic||neovascular|
|active smoking||x 3.4||x 2.5|
|passive smoking||x 2|