CHOROID
The changes that occur in AMD occur throughout the choroid with advancing age. However, only those occurring in the macula significantly affect visual acuity and the patient's daily life. Bruch's membrane increases in thickness with age. Various substances and particles accumulate, decreasing the membrane's permeability to serum proteins, and its capacity to facilitate metabolite exchange with the retina decreases.Calcification 21. s and deposits in the inner collagenous layer are responsible for the clinical appearance of drusen, which increase in number with age. As lysosomal activity in the RPE decreases with age, atypical material(including lipofuscin) may accumulate in Bruch's membrane.The choriocapillaris decreases in density and diameter, resulting in a decrease in choroidal blood flow, and choroidal thickness decreases in the normal aging macula.