Wet Age Related Macular Degeneration
Wet Age Related Macular Degeneration occurs when new abnormal blood vessels arise from part of the eye which lies behind the retina and is called choroid.
These abnormal vessels will start to grow under the macula and these abnormal blood vessels are called CNV which stands for choroidal neovascularization.
Any abnormal blood vessels are fragile and easy to be ruptured and also they will be weak so they will leak fluid and lipid which is called exudates.
This fluid leakage and bleeding will accumulate under the retina or macula and it will destroy photoreceptors and retinal functions with the formation of retinal scar.
As we said before, this form is responsible for 20 % of cases with age related macular degeneration but it is responsible for 80% of cases with severe visual impairment.
All cases of Wet type were Dry AMD at first and almost always show signs of Dry AMD like drusens and atrophy of RPEs. The main reasons behind this change are unknown and no one can tell when the dry form will change to wet form.
One possibility behind this change is that large drusens lead to a decrease in the blood supply to the RPE and photoreceptor cells, resulting in hypoxia or decrease in oxygen supply.
In an attempt to overcome this hypoxia, These cells that suffer from hypoxia will release growth factors called VEGF which will stimulate the formation of new abnormal blood vessels(NeoVascularization) leading to wet AMD. That is why all patients with dry form should be in regular ocular examinations.
Wet degeneration has no stages as Dry degeneration but it has two types according to the type of CNV which can be occult CNV or classic CNV.