Abstract
Purpose :
We have recently demonstrated an association between the subretinal drusenoid deposit (SDD) form of age-related macular degeneration (AMD) and cardiovascular disease and stroke. Our hypothesis for the mechanism driving the SDDs in these cases is reduced choroidal perfusion and photoreceptor (PR) ischemic damage. Other investigators have found decreased reflectivity of the ellipsoid zone (EZ) in AMD subjects with SDDs relative to those without, also consistent with PR damage, especially mitochondrial damage in the EZ. Herein we propose reduced physical thickness of the EZ as another surrogate for mitochondrial damage, and investigate EZ thickness in subjects with SDDs versus those without.
Methods :
We measured EZ thickness in five locations on spectral domain optical coherence tomography (SD-OCT) images of two hundred AMD patients (400 eyes). Eyes were classified as having SDD (with or without drusen) or controls (no SDDs). Measurements were taken at the fovea and 2000 µm nasal, temporal, superior, and inferior to the fovea. Statistical analysis with two tailed t-tests was performed in Microsoft Excel.
Results :
The mean EZ thicknesses in the SDD group at the foveal, nasal, temporal, superior, and inferior locations were 13.41, 12.41, 12.14, 12.72, and 12.80 µm, and in the control group were 15.52, 13.87, 14.03, 14.22, and 13.73 µm. The mean differences were 2.12, 1.46, 1.88, 1.50, and 0.93 µm. Mean EZ thicknesses were significantly thinner in all regions in the SDD group versus controls after Bonferroni correction (p<0.01).
Conclusions :
Ellipsoid zones were significantly thinner at 5 cardinal locations in patients with SDDs than in controls without SDDs. This is consistent with loss of very reflective mitochondria in the EZ in subjects with SDDs. Given the great oxygen consumption by mitochondria, this is also consistent with our hypothesis of ischemic photoreceptor damage from systemic vascular disease. In particular, ischemic damage appears to be least in the inferior macula, whose perfusion would be relatively spared by the influence of gravity directing more flow inferiorly. This is also consistent with the well-known observed higher prevalence of SDD in the superior macula, another argument for inadequate perfusion as a mechanism.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.