Purpose
To improve our understanding of Stargardt disease by comparing structural changes seen on spectral domain optical coherence tomography (SD-OCT) to those visible on fundus autofluorescence (FAF).
Methods
FAF and SD-OCT were obtained on 22 eyes of 11 patients with Stargardt disease. SD-OCT images were obtained at the fovea and at the eccentric preferred retinal locus (PRL). The diameters of “absent” (hypo-autofluorescent) and “abnormal” FAF areas were measured. The extent of the transverse defect of the junction between the inner and outer segments of the photoreceptors (IS-OS) was measured in the foveal area. The PRL was evaluated with fundus photography and microperimetry.
Results
Twenty-one of 22 eyes showed defective FAF. For 17 eyes, FAF was absent in the fovea and for 4 eyes the FAF was abnormal. All eyes showed disorganization and/or loss of the IS-OS junction in the foveal area on SD-OCT. The diameter of the absent FAF area was smaller than the measurement of the IS-OS junction loss; the latter was closer to the diameter of the abnormal FAF area. Seventeen eyes had an eccentric PRL associated with a retinal area with no defects on FAF.
Conclusions
For the majority of eyes changes on SD-OCT correlated well with changes on FAF. However for 3 patients, photoreceptor abnormalities were seen in the fovea on SD-OCT without an equivalent abnormality on FAF. This suggests that for these patients, the structural integrity of the photoreceptors may be affected earlier than changes in the RPE at least as detected by FAF.
Purpose
To evaluate Stargardt disease (STGD) progression & relative lipofuscin levels via autofluorescence image analysis.
Methods
We analyzed the relationship between focally increased autofluorescence (FIAF), geographic atrophy (GA) and focally decreased autofluorescence (FDAF) in serial, registered autofluorescence (AF) scans of 10 patients with STGD (20 eyes, 40 scans, mean follow-up 2.0 years) using automated techniques.
Results
GA progressed uniformly in a transition zone with minimal FIAF. Only 4.3% of FIAF progressed to GA or FDAF, despite significant progression of GA (median 30%/yr) and FDAF (mean 29%/yr). As a spatial predictor, the mean chance of FIAF for progression to FDAF was 4.3 ± 4.4%, significantly less than that of random areas (6.7 ± 4.0%, p = 0.029, Mann-Whitney test). For the seven eyes with GA, the mean chance of FIAF in the transition zone for transition to GA was 12 ± 8.9%, significantly less than that of random areas (33 ± 3.6%, p = 0.026, Mann-Whitney test).
Conclusions
Autofluorescent flecks and FIAF deposits with AF levels elevated above the initial macular background were less likely in the short term (2 years) to transform to GA and FDAF (AF levels below the final background) than random areas, suggesting additional mechanisms beyond direct lipofuscin toxicity. FIAF/FDAF levels were observed to fluctuate, with focal remodeling of FIAF and FDAF, or rarely, even transition of FDAF to FIAF. FDAF tended to develop, not coincident with, but adjacent to initial FIAF. Because AF identifies these characteristic biologic markers so specifically, autofluorescence metrics merit consideration in the study of Stargardt disease.
Recovery of IS/OS line integrity after surgery, in patients with preoperative IS/OS disruption and normal fov.AF, can be explained by the presence of a functional retinal pigment epithelium-photoreceptor complex, supporting normal photoreceptor activity. Autofluorescence imaging provides a functional component to the study of epiretinal membranes, complementing the structural information obtained with optical coherence tomography.
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