We would like to thank Dr Hayreh for his comments regarding our article and his seminal contributions to the field of ocular hemodynamics and the role of ischemia in different ocular diseases.

We agree with Dr Hayreh’s comment that the possible role of ischemia in the development of age-related macular degeneration (AMD) has received little attention. Most probably, the fact that the choroidal circulation has such a high blood flow rate has led people to believe that decreases in choroidal blood flow may not be of consequence. Because of the unique anatomic conditions of the fovea, where the photoreceptors are relatively far from the blood supply provided by the choriocapillaries, even a small decrease in choroidal blood flow may be deleterious to the normal retinal function. Moreover, as Dr Hayreh points out, the unique anatomic features of the foveolar choroidal circulation may put this particular area of the retina at greater risk.

We previously reported evidence suggesting that the choroidal circulation is impaired in AMD. We indeed showed, using the laser Doppler flowmetry technique, that choroidal circulation decreases with age in normal subjects and that in patients with AMD, choroidal circulation is diminished further. Moreover, AMD patients with lower choroidal blood flow have a higher risk of developing choroidal neovascularization and decreases in vision. Finally, we also showed evidence of decreases in choroidal blood flow preceding the appearance of CNV. All these reports, together with our recent article showing that several risk factors for ARMD are associated with decreased choroidal blood flow, strongly suggest that ischemia and hypoxia may have a role in the development of AMD.

Dr Hayreh mentions that choroidal watershed zones, which are prominent in the fovea, are areas particularly vulnerable to ischemia. This is supported by his work and the report of Ross and associates showing that CNV often occurs in proximity to watershed zones detected by indocyanine green angiography, as we previously mentioned in our article.

We again thank Dr Hayreh for his illuminating comments and apologize for failing to acknowledge his work.