AMD – Age-related Macular DegenerationRPE – retinal pigment epithelium Age-related Macular Degeneration – alsoreferred to as AMD – can be divided into dry AMD and wet AMD.
Maculardegeneration is defined as the loss of macular function from the degenerativechanges of ageing and so mainly affects the central vision. 80-90% of all AMD cases are of the dry form1and 10-15% are wet, however 80% of severe vision loss relating to AMD is due tothe wet form2. Due to wet AMD having such a severe impacton vision it is important to prevent dry AMD developing into the wet form andso prevention of this is key.
Pathogenesis Dry AMD develops slowly and in stages. Thefirst initial pathological change is basal laminar and basal linear depositsbetween the plasma membrane and basal lamina of the RPE. These start of verysmall and can often be undetectable with an ophthalmoscope4.These deposits then develop and increase toform drusen between the retinal pigment epithelium and Bruch’s membrane.
These deposits and drusen that form are dueto oxidative stress throughout the patient’s life through UV light exposure andageing that causes the accumulation of Advanced Glycation end-products andphoto-oxidation end products, with inflammation and hypoxia playing a majorrole3. Along with this hyper/hypo pigmentation of the RPE resultsand also thickening of Bruch’s membrane occurs with age3.The blood vessels in the choroid show anarrowing of the lumens and decrease in the vessel density. Atrophy of the RPEcan also occur showing the absence and death of RPE cells leading to the lossof photoreceptors.
This can cause vision loss whilst the AMD is still in thedry phase4. 1 – (Mitchell J, Bradley C.http://www.hqlo.com/content/pdf/1477-7525-4-97.pdf ) 2 – (Jager RD et al.
N Engl J Med 2008; 358(24):2606–2617) 3 – (Ocular Disease University ofManchester Macular lecture)4 – (Age-Related Macular Degeneration:Etiology, Pathogenesis, and Therapeutic Strategies Jayakrishna Ambati, MD,1,2Balamurali K. Ambati, MD,2,3 Sonia H. Yoo, MD,2,4 Sean Ianchulev, MD,2 andAnthony P. Adamis, MD2,5,6 – SURVEY OF OPHTHALMOLOGY VOLUME 48 • NUMBER 3 •MAY–JUNE 2003) RiskFactors There are many risk factors, which can leadto the formation of dry AMD.
The main one is being elderly as AMD increaseswith age. Having a family history of the condition increases the chances thatother family members will also get it with the gene variant Y402H being linkedto drusen formation. Smoking increases the risk by two times andalso having other conditions such as cardiovascular disease and hypertension isalso a risk factors. Having a diet that lacks fruits and vegetables and consistingof high amounts of unsaturated fats can increase the risk. Dry AMD is morelikely in those with light hair, light skin and light eyes and also in individualswho have had more UV light exposure and is also known to pose more risk forfemales. 2