Abstract
Abstract: :
Purpose: There is increasing support to the hypothesis that AMD is a vascular disorder. There is evidence that lipids in drusen and Bruch's membrane are lipoproteins processed by the retinal pigment epithelium. A key proposition of the vascular model is that the lipids accumulate in these tissues because choriocapillaris cannot clear them. While it is known that eyes with neovascular AMD are characterized by impaired choroidal blood flow, it is less clear whether this is also true of eyes with non–neovascular AMD. In order to clarify this question a study of choroidal blood flow was carried out on patients with either or both forms. Methods: 54 patients with AMD were recruited from the clinics of the Massachusetts Eye and Ear Infirmary along with 30 patients without retinal disease, matched for age. All patients had the following procedures performed: ocular and medical history, visual acuity, intra–ocular pressure, axial length, scleral rigidity, Color Doppler Imaging, fundus photography, and blood pressure. Results: The mean Pourcelot's Ratio (PR) of the temporal and nasal short posterior ciliary arteries of both eyes of 30 patients without retinal disease (controls) was 0.69 (SD: 0.04). The same measurements performed on the eyes of 21 patients with bilateral neovascular AMD yielded a mean value of 0.77 (SD: 0.06). The differences from controls had a p–value of <0001. The same measurements performed on patients with bilateral non–neovascular AMD yielded a mean value of 0.73 (SD: 0.07). The difference from controls had a range of p–values between 0.03 and .001. The difference in the mean PR between the eyes with bilateral neovascular AMD and those with bilateral non–neovascular AMD had a p–value that ranged from0.05 to 0.11. The same measurements performed on 15 eyes with unilateral neovascular AMD yielded mean PRs of 0.75 (SD: 0.04) and 0.74 (SD: 0.04) for the neovascular and non–neovascular eyes respectively. The p–values for the differences from controls were <0.0001 in all cases. Conclusions: The resistance to the flow of blood in the choroid of eyes with neovascular AMD may be higher than that of eyes with non–neovascular AMD. Both appear to be significantly higher than age–matched controls. Further analysis may be necessary to control for potential confounders such as age in order to confirm these differences.
Keywords: age–related macular degeneration • choroid: neovascularization • blood supply